Adding upstream version 110.0.1.upstream/110.0.1upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

21 files changed, 16977 insertions, 0 deletions

diff --git a/js/src/shell/Makefile.in b/js/src/shell/Makefile.in
new file mode 100644
index 0000000000..3ce017a08d
--- /dev/null
+++ b/js/src/shell/Makefile.in
@@ -0,0 +1,16 @@
+# -*- Mode: makefile -*-
+#
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+ifdef QEMU_EXE
+MOZ_POST_PROGRAM_COMMAND = $(topsrcdir)/build/qemu-wrap --qemu $(QEMU_EXE) --libdir $(CROSS_LIB)
+endif
+
+include $(topsrcdir)/config/rules.mk
+
+# Install versioned binary for parallel installability in Linux distributions
+install:: $(PROGRAM)
+	cp $^ $(basename $^)$(MOZJS_MAJOR_VERSION)$(suffix $^)
+	$(SYSINSTALL) $(basename $^)$(MOZJS_MAJOR_VERSION)$(suffix $^) $(DESTDIR)$(bindir)
diff --git a/js/src/shell/ModuleLoader.cpp b/js/src/shell/ModuleLoader.cpp
new file mode 100644
index 0000000000..5b22a6d3f0
--- /dev/null
+++ b/js/src/shell/ModuleLoader.cpp
@@ -0,0 +1,672 @@
+/* -*- Mode: javascript; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4
+ * -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "shell/ModuleLoader.h"
+
+#include "mozilla/DebugOnly.h"
+#include "mozilla/TextUtils.h"
+
+#include "jsapi.h"
+#include "NamespaceImports.h"
+
+#include "builtin/TestingUtility.h"  // js::CreateScriptPrivate
+#include "js/Conversions.h"
+#include "js/MapAndSet.h"
+#include "js/Modules.h"
+#include "js/PropertyAndElement.h"  // JS_DefineProperty, JS_GetProperty
+#include "js/SourceText.h"
+#include "js/StableStringChars.h"
+#include "shell/jsshell.h"
+#include "shell/OSObject.h"
+#include "shell/StringUtils.h"
+#include "util/Text.h"
+#include "vm/JSAtom.h"
+#include "vm/JSContext.h"
+#include "vm/StringType.h"
+
+using namespace js;
+using namespace js::shell;
+
+static constexpr char16_t JavaScriptScheme[] = u"javascript:";
+
+static bool IsJavaScriptURL(Handle<JSLinearString*> path) {
+  return StringStartsWith(path, JavaScriptScheme);
+}
+
+static JSString* ExtractJavaScriptURLSource(JSContext* cx,
+                                            Handle<JSLinearString*> path) {
+  MOZ_ASSERT(IsJavaScriptURL(path));
+
+  const size_t schemeLength = js_strlen(JavaScriptScheme);
+  return SubString(cx, path, schemeLength);
+}
+
+bool ModuleLoader::init(JSContext* cx, HandleString loadPath) {
+  loadPathStr = AtomizeString(cx, loadPath);
+  if (!loadPathStr || !PinAtom(cx, loadPathStr)) {
+    return false;
+  }
+
+  MOZ_ASSERT(IsAbsolutePath(loadPathStr));
+
+  char16_t sep = PathSeparator;
+  pathSeparatorStr = AtomizeChars(cx, &sep, 1);
+  if (!pathSeparatorStr || !PinAtom(cx, pathSeparatorStr)) {
+    return false;
+  }
+
+  JSRuntime* rt = cx->runtime();
+  JS::SetModuleResolveHook(rt, ModuleLoader::ResolveImportedModule);
+  JS::SetModuleMetadataHook(rt, ModuleLoader::GetImportMetaProperties);
+  JS::SetModuleDynamicImportHook(rt, ModuleLoader::ImportModuleDynamically);
+
+  JS::ImportAssertionVector assertions;
+  MOZ_ALWAYS_TRUE(assertions.reserve(1));
+  assertions.infallibleAppend(JS::ImportAssertion::Type);
+  JS::SetSupportedImportAssertions(rt, assertions);
+
+  return true;
+}
+
+// static
+JSObject* ModuleLoader::ResolveImportedModule(
+    JSContext* cx, JS::HandleValue referencingPrivate,
+    JS::HandleObject moduleRequest) {
+  ShellContext* scx = GetShellContext(cx);
+  return scx->moduleLoader->resolveImportedModule(cx, referencingPrivate,
+                                                  moduleRequest);
+}
+
+// static
+bool ModuleLoader::GetImportMetaProperties(JSContext* cx,
+                                           JS::HandleValue privateValue,
+                                           JS::HandleObject metaObject) {
+  ShellContext* scx = GetShellContext(cx);
+  return scx->moduleLoader->populateImportMeta(cx, privateValue, metaObject);
+}
+
+bool ModuleLoader::ImportMetaResolve(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+  RootedValue modulePrivate(
+      cx, js::GetFunctionNativeReserved(&args.callee(), ModulePrivateSlot));
+
+  // https://html.spec.whatwg.org/#hostgetimportmetaproperties
+  // Step 4.1. Set specifier to ? ToString(specifier).
+  //
+  // https://tc39.es/ecma262/#sec-tostring
+  RootedValue v(cx, args.get(ImportMetaResolveSpecifierArg));
+  RootedString specifier(cx, JS::ToString(cx, v));
+  if (!specifier) {
+    return false;
+  }
+
+  // Step 4.2, 4.3 are implemented in importMetaResolve.
+  ShellContext* scx = GetShellContext(cx);
+  RootedString url(cx);
+  if (!scx->moduleLoader->importMetaResolve(cx, modulePrivate, specifier,
+                                            &url)) {
+    return false;
+  }
+
+  // Step 4.4. Return the serialization of url.
+  args.rval().setString(url);
+  return true;
+}
+
+// static
+bool ModuleLoader::ImportModuleDynamically(JSContext* cx,
+                                           JS::HandleValue referencingPrivate,
+                                           JS::HandleObject moduleRequest,
+                                           JS::HandleObject promise) {
+  ShellContext* scx = GetShellContext(cx);
+  return scx->moduleLoader->dynamicImport(cx, referencingPrivate, moduleRequest,
+                                          promise);
+}
+
+// static
+bool ModuleLoader::GetSupportedImportAssertions(
+    JSContext* cx, JS::ImportAssertionVector& values) {
+  MOZ_ASSERT(values.empty());
+
+  if (!values.reserve(1)) {
+    ReportOutOfMemory(cx);
+    return false;
+  }
+
+  values.infallibleAppend(JS::ImportAssertion::Type);
+
+  return true;
+}
+
+bool ModuleLoader::loadRootModule(JSContext* cx, HandleString path) {
+  RootedValue rval(cx);
+  if (!loadAndExecute(cx, path, &rval)) {
+    return false;
+  }
+
+  RootedObject evaluationPromise(cx, &rval.toObject());
+  if (evaluationPromise == nullptr) {
+    return false;
+  }
+
+  return JS::ThrowOnModuleEvaluationFailure(cx, evaluationPromise);
+}
+
+bool ModuleLoader::registerTestModule(JSContext* cx, HandleObject moduleRequest,
+                                      Handle<ModuleObject*> module) {
+  Rooted<JSLinearString*> path(
+      cx, resolve(cx, moduleRequest, UndefinedHandleValue));
+  if (!path) {
+    return false;
+  }
+
+  path = normalizePath(cx, path);
+  if (!path) {
+    return false;
+  }
+
+  return addModuleToRegistry(cx, path, module);
+}
+
+void ModuleLoader::clearModules(JSContext* cx) {
+  Handle<GlobalObject*> global = cx->global();
+  global->setReservedSlot(GlobalAppSlotModuleRegistry, UndefinedValue());
+}
+
+bool ModuleLoader::loadAndExecute(JSContext* cx, HandleString path,
+                                  MutableHandleValue rval) {
+  RootedObject module(cx, loadAndParse(cx, path));
+  if (!module) {
+    return false;
+  }
+
+  if (!JS::ModuleLink(cx, module)) {
+    return false;
+  }
+
+  return JS::ModuleEvaluate(cx, module, rval);
+}
+
+JSObject* ModuleLoader::resolveImportedModule(
+    JSContext* cx, JS::HandleValue referencingPrivate,
+    JS::HandleObject moduleRequest) {
+  Rooted<JSLinearString*> path(cx,
+                               resolve(cx, moduleRequest, referencingPrivate));
+  if (!path) {
+    return nullptr;
+  }
+
+  return loadAndParse(cx, path);
+}
+
+bool ModuleLoader::populateImportMeta(JSContext* cx,
+                                      JS::HandleValue privateValue,
+                                      JS::HandleObject metaObject) {
+  Rooted<JSLinearString*> path(cx);
+  if (!privateValue.isUndefined()) {
+    if (!getScriptPath(cx, privateValue, &path)) {
+      return false;
+    }
+  }
+
+  if (!path) {
+    path = NewStringCopyZ<CanGC>(cx, "(unknown)");
+    if (!path) {
+      return false;
+    }
+  }
+
+  RootedValue pathValue(cx, StringValue(path));
+  if (!JS_DefineProperty(cx, metaObject, "url", pathValue, JSPROP_ENUMERATE)) {
+    return false;
+  }
+
+  JSFunction* resolveFunc = js::DefineFunctionWithReserved(
+      cx, metaObject, "resolve", ImportMetaResolve, ImportMetaResolveNumArgs,
+      JSPROP_ENUMERATE);
+  if (!resolveFunc) {
+    return false;
+  }
+
+  RootedObject resolveFuncObj(cx, JS_GetFunctionObject(resolveFunc));
+  js::SetFunctionNativeReserved(resolveFuncObj, ModulePrivateSlot,
+                                privateValue);
+
+  return true;
+}
+
+bool ModuleLoader::importMetaResolve(JSContext* cx,
+                                     JS::Handle<JS::Value> referencingPrivate,
+                                     JS::Handle<JSString*> specifier,
+                                     JS::MutableHandle<JSString*> urlOut) {
+  Rooted<JSLinearString*> path(cx, resolve(cx, specifier, referencingPrivate));
+  if (!path) {
+    return false;
+  }
+
+  urlOut.set(path);
+  return true;
+}
+
+bool ModuleLoader::dynamicImport(JSContext* cx,
+                                 JS::HandleValue referencingPrivate,
+                                 JS::HandleObject moduleRequest,
+                                 JS::HandleObject promise) {
+  // To make this more realistic, use a promise to delay the import and make it
+  // happen asynchronously. This method packages up the arguments and creates a
+  // resolved promise, which on fullfillment calls doDynamicImport with the
+  // original arguments.
+
+  MOZ_ASSERT(promise);
+  RootedValue moduleRequestValue(cx, ObjectValue(*moduleRequest));
+  RootedValue promiseValue(cx, ObjectValue(*promise));
+  RootedObject closure(cx, JS_NewObjectWithGivenProto(cx, nullptr, nullptr));
+  if (!closure ||
+      !JS_DefineProperty(cx, closure, "referencingPrivate", referencingPrivate,
+                         JSPROP_ENUMERATE) ||
+      !JS_DefineProperty(cx, closure, "moduleRequest", moduleRequestValue,
+                         JSPROP_ENUMERATE) ||
+      !JS_DefineProperty(cx, closure, "promise", promiseValue,
+                         JSPROP_ENUMERATE)) {
+    return false;
+  }
+
+  RootedFunction onResolved(
+      cx, NewNativeFunction(cx, DynamicImportDelayFulfilled, 1, nullptr));
+  if (!onResolved) {
+    return false;
+  }
+
+  RootedFunction onRejected(
+      cx, NewNativeFunction(cx, DynamicImportDelayRejected, 1, nullptr));
+  if (!onRejected) {
+    return false;
+  }
+
+  RootedObject delayPromise(cx);
+  RootedValue closureValue(cx, ObjectValue(*closure));
+  delayPromise = PromiseObject::unforgeableResolve(cx, closureValue);
+  if (!delayPromise) {
+    return false;
+  }
+
+  return JS::AddPromiseReactions(cx, delayPromise, onResolved, onRejected);
+}
+
+bool ModuleLoader::DynamicImportDelayFulfilled(JSContext* cx, unsigned argc,
+                                               Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+  RootedObject closure(cx, &args[0].toObject());
+
+  RootedValue referencingPrivate(cx);
+  RootedValue moduleRequestValue(cx);
+  RootedValue promiseValue(cx);
+  if (!JS_GetProperty(cx, closure, "referencingPrivate", &referencingPrivate) ||
+      !JS_GetProperty(cx, closure, "moduleRequest", &moduleRequestValue) ||
+      !JS_GetProperty(cx, closure, "promise", &promiseValue)) {
+    return false;
+  }
+
+  RootedObject moduleRequest(cx, &moduleRequestValue.toObject());
+  RootedObject promise(cx, &promiseValue.toObject());
+
+  ShellContext* scx = GetShellContext(cx);
+  return scx->moduleLoader->doDynamicImport(cx, referencingPrivate,
+                                            moduleRequest, promise);
+}
+
+bool ModuleLoader::DynamicImportDelayRejected(JSContext* cx, unsigned argc,
+                                              Value* vp) {
+  MOZ_CRASH("This promise should never be rejected");
+}
+
+bool ModuleLoader::doDynamicImport(JSContext* cx,
+                                   JS::HandleValue referencingPrivate,
+                                   JS::HandleObject moduleRequest,
+                                   JS::HandleObject promise) {
+  // Exceptions during dynamic import are handled by calling
+  // FinishDynamicModuleImport with a pending exception on the context.
+  RootedValue rval(cx);
+  bool ok =
+      tryDynamicImport(cx, referencingPrivate, moduleRequest, promise, &rval);
+  JSObject* evaluationObject = ok ? &rval.toObject() : nullptr;
+  RootedObject evaluationPromise(cx, evaluationObject);
+  return JS::FinishDynamicModuleImport(
+      cx, evaluationPromise, referencingPrivate, moduleRequest, promise);
+}
+
+bool ModuleLoader::tryDynamicImport(JSContext* cx,
+                                    JS::HandleValue referencingPrivate,
+                                    JS::HandleObject moduleRequest,
+                                    JS::HandleObject promise,
+                                    JS::MutableHandleValue rval) {
+  Rooted<JSLinearString*> path(cx,
+                               resolve(cx, moduleRequest, referencingPrivate));
+  if (!path) {
+    return false;
+  }
+
+  return loadAndExecute(cx, path, rval);
+}
+
+JSLinearString* ModuleLoader::resolve(JSContext* cx,
+                                      HandleObject moduleRequestArg,
+                                      HandleValue referencingInfo) {
+  ModuleRequestObject* moduleRequest =
+      &moduleRequestArg->as<ModuleRequestObject>();
+  if (moduleRequest->specifier()->length() == 0) {
+    JS_ReportErrorASCII(cx, "Invalid module specifier");
+    return nullptr;
+  }
+
+  Rooted<JSLinearString*> name(
+      cx, JS_EnsureLinearString(cx, moduleRequest->specifier()));
+  if (!name) {
+    return nullptr;
+  }
+
+  return resolve(cx, name, referencingInfo);
+}
+
+JSLinearString* ModuleLoader::resolve(JSContext* cx, HandleString specifier,
+                                      HandleValue referencingInfo) {
+  Rooted<JSLinearString*> name(cx, JS_EnsureLinearString(cx, specifier));
+  if (!name) {
+    return nullptr;
+  }
+
+  if (IsJavaScriptURL(name) || IsAbsolutePath(name)) {
+    return name;
+  }
+
+  // Treat |name| as a relative path if it starts with either "./" or "../".
+  bool isRelative =
+      StringStartsWith(name, u"./") || StringStartsWith(name, u"../")
+#ifdef XP_WIN
+      || StringStartsWith(name, u".\\") || StringStartsWith(name, u"..\\")
+#endif
+      ;
+
+  RootedString path(cx, loadPathStr);
+
+  if (isRelative) {
+    if (referencingInfo.isUndefined()) {
+      JS_ReportErrorASCII(cx, "No referencing module for relative import");
+      return nullptr;
+    }
+
+    Rooted<JSLinearString*> refPath(cx);
+    if (!getScriptPath(cx, referencingInfo, &refPath)) {
+      return nullptr;
+    }
+
+    if (!refPath) {
+      JS_ReportErrorASCII(cx, "No path set for referencing module");
+      return nullptr;
+    }
+
+    int32_t sepIndex = LastIndexOf(refPath, u'/');
+#ifdef XP_WIN
+    sepIndex = std::max(sepIndex, LastIndexOf(refPath, u'\\'));
+#endif
+    if (sepIndex >= 0) {
+      path = SubString(cx, refPath, 0, sepIndex);
+      if (!path) {
+        return nullptr;
+      }
+    }
+  }
+
+  RootedString result(cx);
+  RootedString pathSep(cx, pathSeparatorStr);
+  result = JS_ConcatStrings(cx, path, pathSep);
+  if (!result) {
+    return nullptr;
+  }
+
+  result = JS_ConcatStrings(cx, result, name);
+  if (!result) {
+    return nullptr;
+  }
+
+  Rooted<JSLinearString*> linear(cx, JS_EnsureLinearString(cx, result));
+  if (!linear) {
+    return nullptr;
+  }
+  return normalizePath(cx, linear);
+}
+
+JSObject* ModuleLoader::loadAndParse(JSContext* cx, HandleString pathArg) {
+  Rooted<JSLinearString*> path(cx, JS_EnsureLinearString(cx, pathArg));
+  if (!path) {
+    return nullptr;
+  }
+
+  path = normalizePath(cx, path);
+  if (!path) {
+    return nullptr;
+  }
+
+  RootedObject module(cx);
+  if (!lookupModuleInRegistry(cx, path, &module)) {
+    return nullptr;
+  }
+
+  if (module) {
+    return module;
+  }
+
+  UniqueChars filename = JS_EncodeStringToLatin1(cx, path);
+  if (!filename) {
+    return nullptr;
+  }
+
+  JS::CompileOptions options(cx);
+  options.setFileAndLine(filename.get(), 1);
+
+  RootedString source(cx, fetchSource(cx, path));
+  if (!source) {
+    return nullptr;
+  }
+
+  JS::AutoStableStringChars linearChars(cx);
+  if (!linearChars.initTwoByte(cx, source)) {
+    return nullptr;
+  }
+
+  JS::SourceText<char16_t> srcBuf;
+  if (!srcBuf.initMaybeBorrowed(cx, linearChars)) {
+    return nullptr;
+  }
+
+  module = JS::CompileModule(cx, options, srcBuf);
+  if (!module) {
+    return nullptr;
+  }
+
+  RootedObject info(cx, js::CreateScriptPrivate(cx, path));
+  if (!info) {
+    return nullptr;
+  }
+
+  JS::SetModulePrivate(module, ObjectValue(*info));
+
+  if (!addModuleToRegistry(cx, path, module)) {
+    return nullptr;
+  }
+
+  return module;
+}
+
+bool ModuleLoader::lookupModuleInRegistry(JSContext* cx, HandleString path,
+                                          MutableHandleObject moduleOut) {
+  moduleOut.set(nullptr);
+
+  RootedObject registry(cx, getOrCreateModuleRegistry(cx));
+  if (!registry) {
+    return false;
+  }
+
+  RootedValue pathValue(cx, StringValue(path));
+  RootedValue moduleValue(cx);
+  if (!JS::MapGet(cx, registry, pathValue, &moduleValue)) {
+    return false;
+  }
+
+  if (!moduleValue.isUndefined()) {
+    moduleOut.set(&moduleValue.toObject());
+  }
+
+  return true;
+}
+
+bool ModuleLoader::addModuleToRegistry(JSContext* cx, HandleString path,
+                                       HandleObject module) {
+  RootedObject registry(cx, getOrCreateModuleRegistry(cx));
+  if (!registry) {
+    return false;
+  }
+
+  RootedValue pathValue(cx, StringValue(path));
+  RootedValue moduleValue(cx, ObjectValue(*module));
+  return JS::MapSet(cx, registry, pathValue, moduleValue);
+}
+
+JSObject* ModuleLoader::getOrCreateModuleRegistry(JSContext* cx) {
+  Handle<GlobalObject*> global = cx->global();
+  RootedValue value(cx, global->getReservedSlot(GlobalAppSlotModuleRegistry));
+  if (!value.isUndefined()) {
+    return &value.toObject();
+  }
+
+  JSObject* registry = JS::NewMapObject(cx);
+  if (!registry) {
+    return nullptr;
+  }
+
+  global->setReservedSlot(GlobalAppSlotModuleRegistry, ObjectValue(*registry));
+  return registry;
+}
+
+bool ModuleLoader::getScriptPath(JSContext* cx, HandleValue privateValue,
+                                 MutableHandle<JSLinearString*> pathOut) {
+  pathOut.set(nullptr);
+
+  RootedObject infoObj(cx, &privateValue.toObject());
+  RootedValue pathValue(cx);
+  if (!JS_GetProperty(cx, infoObj, "path", &pathValue)) {
+    return false;
+  }
+
+  if (pathValue.isUndefined()) {
+    return true;
+  }
+
+  RootedString path(cx, pathValue.toString());
+  pathOut.set(JS_EnsureLinearString(cx, path));
+  return pathOut;
+}
+
+JSLinearString* ModuleLoader::normalizePath(JSContext* cx,
+                                            Handle<JSLinearString*> pathArg) {
+  Rooted<JSLinearString*> path(cx, pathArg);
+
+  if (IsJavaScriptURL(path)) {
+    return path;
+  }
+
+#ifdef XP_WIN
+  // Replace all forward slashes with backward slashes.
+  path = ReplaceCharGlobally(cx, path, u'/', PathSeparator);
+  if (!path) {
+    return nullptr;
+  }
+
+  // Remove the drive letter, if present.
+  Rooted<JSLinearString*> drive(cx);
+  if (path->length() > 2 && mozilla::IsAsciiAlpha(CharAt(path, 0)) &&
+      CharAt(path, 1) == u':' && CharAt(path, 2) == u'\\') {
+    drive = SubString(cx, path, 0, 2);
+    path = SubString(cx, path, 2);
+    if (!drive || !path) {
+      return nullptr;
+    }
+  }
+#endif  // XP_WIN
+
+  // Normalize the path by removing redundant path components.
+  Rooted<GCVector<JSLinearString*>> components(cx, cx);
+  size_t lastSep = 0;
+  while (lastSep < path->length()) {
+    int32_t i = IndexOf(path, PathSeparator, lastSep);
+    if (i < 0) {
+      i = path->length();
+    }
+
+    Rooted<JSLinearString*> part(cx, SubString(cx, path, lastSep, i));
+    if (!part) {
+      return nullptr;
+    }
+
+    lastSep = i + 1;
+
+    // Remove "." when preceded by a path component.
+    if (StringEquals(part, u".") && !components.empty()) {
+      continue;
+    }
+
+    if (StringEquals(part, u"..") && !components.empty()) {
+      // Replace "./.." with "..".
+      if (StringEquals(components.back(), u".")) {
+        components.back() = part;
+        continue;
+      }
+
+      // When preceded by a non-empty path component, remove ".." and the
+      // preceding component, unless the preceding component is also "..".
+      if (!StringEquals(components.back(), u"") &&
+          !StringEquals(components.back(), u"..")) {
+        components.popBack();
+        continue;
+      }
+    }
+
+    if (!components.append(part)) {
+      return nullptr;
+    }
+  }
+
+  Rooted<JSLinearString*> pathSep(cx, pathSeparatorStr);
+  RootedString normalized(cx, JoinStrings(cx, components, pathSep));
+  if (!normalized) {
+    return nullptr;
+  }
+
+#ifdef XP_WIN
+  if (drive) {
+    normalized = JS_ConcatStrings(cx, drive, normalized);
+    if (!normalized) {
+      return nullptr;
+    }
+  }
+#endif
+
+  return JS_EnsureLinearString(cx, normalized);
+}
+
+JSString* ModuleLoader::fetchSource(JSContext* cx,
+                                    Handle<JSLinearString*> path) {
+  if (IsJavaScriptURL(path)) {
+    return ExtractJavaScriptURLSource(cx, path);
+  }
+
+  RootedString resolvedPath(cx, ResolvePath(cx, path, RootRelative));
+  if (!resolvedPath) {
+    return nullptr;
+  }
+
+  return FileAsString(cx, resolvedPath);
+}
diff --git a/js/src/shell/ModuleLoader.h b/js/src/shell/ModuleLoader.h
new file mode 100644
index 0000000000..c8f0147356
--- /dev/null
+++ b/js/src/shell/ModuleLoader.h
@@ -0,0 +1,94 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef shell_ModuleLoader_h
+#define shell_ModuleLoader_h
+
+#include "builtin/ModuleObject.h"
+#include "js/RootingAPI.h"
+
+namespace js {
+namespace shell {
+
+class ModuleLoader {
+ public:
+  bool init(JSContext* cx, HandleString loadPath);
+  bool loadRootModule(JSContext* cx, HandleString path);
+
+  // Testing hook to register a module that wasn't loaded by the module loader.
+  bool registerTestModule(JSContext* cx, HandleObject moduleRequest,
+                          Handle<ModuleObject*> module);
+
+  // Testing hook to clear all loaded modules.
+  void clearModules(JSContext* cx);
+
+ private:
+  static JSObject* ResolveImportedModule(JSContext* cx,
+                                         HandleValue referencingPrivate,
+                                         HandleObject moduleRequest);
+  static bool GetImportMetaProperties(JSContext* cx, HandleValue privateValue,
+                                      HandleObject metaObject);
+  static bool ImportMetaResolve(JSContext* cx, unsigned argc, Value* vp);
+  static bool ImportModuleDynamically(JSContext* cx,
+                                      HandleValue referencingPrivate,
+                                      HandleObject moduleRequest,
+                                      HandleObject promise);
+  static bool GetSupportedImportAssertions(JSContext* cx,
+                                           JS::ImportAssertionVector& values);
+
+  static bool DynamicImportDelayFulfilled(JSContext* cx, unsigned argc,
+                                          Value* vp);
+  static bool DynamicImportDelayRejected(JSContext* cx, unsigned argc,
+                                         Value* vp);
+
+  bool loadAndExecute(JSContext* cx, HandleString path, MutableHandleValue);
+  JSObject* resolveImportedModule(JSContext* cx, HandleValue referencingPrivate,
+                                  HandleObject moduleRequest);
+  bool populateImportMeta(JSContext* cx, HandleValue privateValue,
+                          HandleObject metaObject);
+  bool importMetaResolve(JSContext* cx,
+                         JS::Handle<JS::Value> referencingPrivate,
+                         JS::Handle<JSString*> specifier,
+                         JS::MutableHandle<JSString*> urlOut);
+  bool dynamicImport(JSContext* cx, HandleValue referencingPrivate,
+                     HandleObject moduleRequest, HandleObject promise);
+  bool doDynamicImport(JSContext* cx, HandleValue referencingPrivate,
+                       HandleObject moduleRequest, HandleObject promise);
+  bool tryDynamicImport(JSContext* cx, HandleValue referencingPrivate,
+                        HandleObject moduleRequest, HandleObject promise,
+                        MutableHandleValue rval);
+  JSObject* loadAndParse(JSContext* cx, HandleString path);
+  bool lookupModuleInRegistry(JSContext* cx, HandleString path,
+                              MutableHandleObject moduleOut);
+  bool addModuleToRegistry(JSContext* cx, HandleString path,
+                           HandleObject module);
+  JSLinearString* resolve(JSContext* cx, HandleObject moduleRequestArg,
+                          HandleValue referencingInfo);
+  JSLinearString* resolve(JSContext* cx, HandleString specifier,
+                          HandleValue referencingInfo);
+  bool getScriptPath(JSContext* cx, HandleValue privateValue,
+                     MutableHandle<JSLinearString*> pathOut);
+  JSLinearString* normalizePath(JSContext* cx, Handle<JSLinearString*> path);
+  JSObject* getOrCreateModuleRegistry(JSContext* cx);
+  JSString* fetchSource(JSContext* cx, Handle<JSLinearString*> path);
+
+  // The following are used for pinned atoms which do not need rooting.
+  JSAtom* loadPathStr = nullptr;
+  JSAtom* pathSeparatorStr = nullptr;
+
+  // The slot stored in ImportMetaResolve function.
+  enum { ModulePrivateSlot = 0, SlotCount };
+
+  // The number of args in ImportMetaResolve.
+  static const uint32_t ImportMetaResolveNumArgs = 1;
+  // The index of the 'specifier' argument in ImportMetaResolve.
+  static const uint32_t ImportMetaResolveSpecifierArg = 0;
+} JS_HAZ_NON_GC_POINTER;
+
+}  // namespace shell
+}  // namespace js
+
+#endif  // shell_ModuleLoader_h
diff --git a/js/src/shell/OSObject.cpp b/js/src/shell/OSObject.cpp
new file mode 100644
index 0000000000..deaba8b44a
--- /dev/null
+++ b/js/src/shell/OSObject.cpp
@@ -0,0 +1,1215 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+// OSObject.h - os object for exposing posix system calls in the JS shell
+
+#include "shell/OSObject.h"
+
+#include "mozilla/ScopeExit.h"
+#include "mozilla/TextUtils.h"
+
+#include <errno.h>
+#include <stdlib.h>
+#ifdef XP_WIN
+#  include <direct.h>
+#  include <process.h>
+#  include <string.h>
+#  include <windows.h>
+#elif __wasi__
+#  include <dirent.h>
+#  include <sys/types.h>
+#  include <unistd.h>
+#else
+#  include <dirent.h>
+#  include <sys/types.h>
+#  include <sys/wait.h>
+#  include <unistd.h>
+#endif
+
+#include "jsapi.h"
+// For JSFunctionSpecWithHelp
+#include "jsfriendapi.h"
+
+#include "gc/GCContext.h"
+#include "js/CharacterEncoding.h"
+#include "js/Conversions.h"
+#include "js/experimental/TypedData.h"  // JS_NewUint8Array
+#include "js/Object.h"                  // JS::GetReservedSlot
+#include "js/PropertyAndElement.h"      // JS_DefineProperty
+#include "js/PropertySpec.h"
+#include "js/Value.h"  // JS::Value
+#include "js/Wrapper.h"
+#include "shell/jsshell.h"
+#include "shell/StringUtils.h"
+#include "util/GetPidProvider.h"  // getpid()
+#include "util/StringBuffer.h"
+#include "util/Text.h"
+#include "util/WindowsWrapper.h"
+#include "vm/JSObject.h"
+#include "vm/TypedArrayObject.h"
+
+#include "vm/JSObject-inl.h"
+
+#ifdef XP_WIN
+#  ifndef PATH_MAX
+#    define PATH_MAX (MAX_PATH > _MAX_DIR ? MAX_PATH : _MAX_DIR)
+#  endif
+#  define getcwd _getcwd
+#elif defined(__wasi__)
+// Nothing.
+#else
+#  include <libgen.h>
+#endif
+
+using js::shell::RCFile;
+
+namespace js {
+namespace shell {
+
+bool IsAbsolutePath(JSLinearString* filename) {
+  size_t length = filename->length();
+
+#ifdef XP_WIN
+  // On Windows there are various forms of absolute paths (see
+  // http://msdn.microsoft.com/en-us/library/windows/desktop/aa365247%28v=vs.85%29.aspx
+  // for details):
+  //
+  //   "\..."
+  //   "\\..."
+  //   "C:\..."
+  //
+  // The first two cases are handled by the common test below so we only need a
+  // specific test for the last one here.
+
+  if (length > 3 && mozilla::IsAsciiAlpha(CharAt(filename, 0)) &&
+      CharAt(filename, 1) == u':' && CharAt(filename, 2) == u'\\') {
+    return true;
+  }
+#endif
+
+  return length > 0 && CharAt(filename, 0) == PathSeparator;
+}
+
+/*
+ * Resolve a (possibly) relative filename to an absolute path. If
+ * |scriptRelative| is true, then the result will be relative to the directory
+ * containing the currently-running script, or the current working directory if
+ * the currently-running script is "-e" (namely, you're using it from the
+ * command line.) Otherwise, it will be relative to the current working
+ * directory.
+ */
+JSString* ResolvePath(JSContext* cx, HandleString filenameStr,
+                      PathResolutionMode resolveMode) {
+  if (!filenameStr) {
+#ifdef XP_WIN
+    return JS_NewStringCopyZ(cx, "nul");
+#elif defined(__wasi__)
+    MOZ_CRASH("NYI for WASI");
+    return nullptr;
+#else
+    return JS_NewStringCopyZ(cx, "/dev/null");
+#endif
+  }
+
+  Rooted<JSLinearString*> str(cx, JS_EnsureLinearString(cx, filenameStr));
+  if (!str) {
+    return nullptr;
+  }
+
+  if (IsAbsolutePath(str)) {
+    return str;
+  }
+
+  UniqueChars filename = JS_EncodeStringToLatin1(cx, str);
+  if (!filename) {
+    return nullptr;
+  }
+
+  JS::AutoFilename scriptFilename;
+  if (resolveMode == ScriptRelative) {
+    // Get the currently executing script's name.
+    if (!DescribeScriptedCaller(cx, &scriptFilename)) {
+      return nullptr;
+    }
+
+    if (!scriptFilename.get()) {
+      return nullptr;
+    }
+
+    if (strcmp(scriptFilename.get(), "-e") == 0 ||
+        strcmp(scriptFilename.get(), "typein") == 0) {
+      resolveMode = RootRelative;
+    }
+  }
+
+  char buffer[PATH_MAX + 1];
+  if (resolveMode == ScriptRelative) {
+#ifdef XP_WIN
+    // The docs say it can return EINVAL, but the compiler says it's void
+    _splitpath(scriptFilename.get(), nullptr, buffer, nullptr, nullptr);
+#else
+    strncpy(buffer, scriptFilename.get(), PATH_MAX);
+    if (buffer[PATH_MAX - 1] != '\0') {
+      return nullptr;
+    }
+
+#  ifdef __wasi__
+    // dirname() seems not to behave properly with wasi-libc; so we do our own
+    // simple thing here.
+    char* p = buffer + strlen(buffer);
+    while (p > buffer) {
+      if (*p == '/') {
+        *p = '\0';
+        break;
+      }
+      p--;
+    }
+#  else
+    // dirname(buffer) might return buffer, or it might return a
+    // statically-allocated string
+    memmove(buffer, dirname(buffer), strlen(buffer) + 1);
+#  endif
+#endif
+  } else {
+    const char* cwd = getcwd(buffer, PATH_MAX);
+    if (!cwd) {
+      return nullptr;
+    }
+  }
+
+  size_t len = strlen(buffer);
+  buffer[len] = '/';
+  strncpy(buffer + len + 1, filename.get(), sizeof(buffer) - (len + 1));
+  if (buffer[PATH_MAX] != '\0') {
+    return nullptr;
+  }
+
+  return JS_NewStringCopyZ(cx, buffer);
+}
+
+JSObject* FileAsTypedArray(JSContext* cx, JS::HandleString pathnameStr) {
+  UniqueChars pathname = JS_EncodeStringToLatin1(cx, pathnameStr);
+  if (!pathname) {
+    return nullptr;
+  }
+
+  FILE* file = fopen(pathname.get(), "rb");
+  if (!file) {
+    /*
+     * Use Latin1 variant here because the encoding of the return value of
+     * strerror function can be non-UTF-8.
+     */
+    JS_ReportErrorLatin1(cx, "can't open %s: %s", pathname.get(),
+                         strerror(errno));
+    return nullptr;
+  }
+  AutoCloseFile autoClose(file);
+
+  RootedObject obj(cx);
+  if (fseek(file, 0, SEEK_END) != 0) {
+    pathname = JS_EncodeStringToUTF8(cx, pathnameStr);
+    if (!pathname) {
+      return nullptr;
+    }
+    JS_ReportErrorUTF8(cx, "can't seek end of %s", pathname.get());
+  } else {
+    size_t len = ftell(file);
+    if (fseek(file, 0, SEEK_SET) != 0) {
+      pathname = JS_EncodeStringToUTF8(cx, pathnameStr);
+      if (!pathname) {
+        return nullptr;
+      }
+      JS_ReportErrorUTF8(cx, "can't seek start of %s", pathname.get());
+    } else {
+      if (len > ArrayBufferObject::MaxByteLength) {
+        JS_ReportErrorUTF8(cx, "file %s is too large for a Uint8Array",
+                           pathname.get());
+        return nullptr;
+      }
+      obj = JS_NewUint8Array(cx, len);
+      if (!obj) {
+        return nullptr;
+      }
+      js::TypedArrayObject& ta = obj->as<js::TypedArrayObject>();
+      if (ta.isSharedMemory()) {
+        // Must opt in to use shared memory.  For now, don't.
+        //
+        // (It is incorrect to read into the buffer without
+        // synchronization since that can create a race.  A
+        // lock here won't fix it - both sides must
+        // participate.  So what one must do is to create a
+        // temporary buffer, read into that, and use a
+        // race-safe primitive to copy memory into the
+        // buffer.)
+        pathname = JS_EncodeStringToUTF8(cx, pathnameStr);
+        if (!pathname) {
+          return nullptr;
+        }
+        JS_ReportErrorUTF8(cx, "can't read %s: shared memory buffer",
+                           pathname.get());
+        return nullptr;
+      }
+      char* buf = static_cast<char*>(ta.dataPointerUnshared());
+      size_t cc = fread(buf, 1, len, file);
+      if (cc != len) {
+        if (ptrdiff_t(cc) < 0) {
+          /*
+           * Use Latin1 variant here because the encoding of the return
+           * value of strerror function can be non-UTF-8.
+           */
+          JS_ReportErrorLatin1(cx, "can't read %s: %s", pathname.get(),
+                               strerror(errno));
+        } else {
+          pathname = JS_EncodeStringToUTF8(cx, pathnameStr);
+          if (!pathname) {
+            return nullptr;
+          }
+          JS_ReportErrorUTF8(cx, "can't read %s: short read", pathname.get());
+        }
+        obj = nullptr;
+      }
+    }
+  }
+  return obj;
+}
+
+/**
+ * Return the current working directory or |null| on failure.
+ */
+UniqueChars GetCWD() {
+  char buffer[PATH_MAX + 1];
+  const char* cwd = getcwd(buffer, PATH_MAX);
+  if (!cwd) {
+    return UniqueChars();
+  }
+  return js::DuplicateString(buffer);
+}
+
+static bool ReadFile(JSContext* cx, unsigned argc, Value* vp,
+                     bool scriptRelative) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  if (args.length() < 1 || args.length() > 2) {
+    JS_ReportErrorNumberASCII(
+        cx, js::shell::my_GetErrorMessage, nullptr,
+        args.length() < 1 ? JSSMSG_NOT_ENOUGH_ARGS : JSSMSG_TOO_MANY_ARGS,
+        "snarf");
+    return false;
+  }
+
+  if (!args[0].isString() || (args.length() == 2 && !args[1].isString())) {
+    JS_ReportErrorNumberASCII(cx, js::shell::my_GetErrorMessage, nullptr,
+                              JSSMSG_INVALID_ARGS, "snarf");
+    return false;
+  }
+
+  RootedString givenPath(cx, args[0].toString());
+  RootedString str(
+      cx, js::shell::ResolvePath(
+              cx, givenPath, scriptRelative ? ScriptRelative : RootRelative));
+  if (!str) {
+    return false;
+  }
+
+  if (args.length() > 1) {
+    JSString* opt = JS::ToString(cx, args[1]);
+    if (!opt) {
+      return false;
+    }
+    bool match;
+    if (!JS_StringEqualsLiteral(cx, opt, "binary", &match)) {
+      return false;
+    }
+    if (match) {
+      JSObject* obj;
+      if (!(obj = FileAsTypedArray(cx, str))) {
+        return false;
+      }
+      args.rval().setObject(*obj);
+      return true;
+    }
+  }
+
+  if (!(str = FileAsString(cx, str))) {
+    return false;
+  }
+  args.rval().setString(str);
+  return true;
+}
+
+static bool osfile_readFile(JSContext* cx, unsigned argc, Value* vp) {
+  return ReadFile(cx, argc, vp, false);
+}
+
+static bool osfile_readRelativeToScript(JSContext* cx, unsigned argc,
+                                        Value* vp) {
+  return ReadFile(cx, argc, vp, true);
+}
+
+static bool ListDir(JSContext* cx, unsigned argc, Value* vp,
+                    PathResolutionMode resolveMode) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  if (args.length() != 1) {
+    JS_ReportErrorASCII(cx, "os.file.listDir requires 1 argument");
+    return false;
+  }
+
+  if (!args[0].isString()) {
+    JS_ReportErrorNumberASCII(cx, js::shell::my_GetErrorMessage, nullptr,
+                              JSSMSG_INVALID_ARGS, "os.file.listDir");
+    return false;
+  }
+
+  RootedString givenPath(cx, args[0].toString());
+  RootedString str(cx, ResolvePath(cx, givenPath, resolveMode));
+  if (!str) {
+    return false;
+  }
+
+  UniqueChars pathname = JS_EncodeStringToLatin1(cx, str);
+  if (!pathname) {
+    JS_ReportErrorASCII(cx, "os.file.listDir cannot convert path to Latin1");
+    return false;
+  }
+
+  RootedValueVector elems(cx);
+  auto append = [&](const char* name) -> bool {
+    if (!(str = JS_NewStringCopyZ(cx, name))) {
+      return false;
+    }
+    if (!elems.append(StringValue(str))) {
+      js::ReportOutOfMemory(cx);
+      return false;
+    }
+    return true;
+  };
+
+#if defined(XP_UNIX)
+  {
+    DIR* dir = opendir(pathname.get());
+    if (!dir) {
+      JS_ReportErrorASCII(cx, "os.file.listDir is unable to open: %s",
+                          pathname.get());
+      return false;
+    }
+    auto close = mozilla::MakeScopeExit([&] {
+      if (closedir(dir) != 0) {
+        MOZ_CRASH("Could not close dir");
+      }
+    });
+
+    while (struct dirent* entry = readdir(dir)) {
+      if (!append(entry->d_name)) {
+        return false;
+      }
+    }
+  }
+#elif defined(XP_WIN)
+  {
+    const size_t pathlen = strlen(pathname.get());
+    Vector<char> pattern(cx);
+    if (!pattern.append(pathname.get(), pathlen) ||
+        !pattern.append(PathSeparator) || !pattern.append("*", 2)) {
+      js::ReportOutOfMemory(cx);
+      return false;
+    }
+
+    WIN32_FIND_DATA FindFileData;
+    HANDLE hFind = FindFirstFile(pattern.begin(), &FindFileData);
+    auto close = mozilla::MakeScopeExit([&] {
+      if (!FindClose(hFind)) {
+        MOZ_CRASH("Could not close Find");
+      }
+    });
+    for (bool found = (hFind != INVALID_HANDLE_VALUE); found;
+         found = FindNextFile(hFind, &FindFileData)) {
+      if (!append(FindFileData.cFileName)) {
+        return false;
+      }
+    }
+  }
+#endif
+
+  JSObject* array = JS::NewArrayObject(cx, elems);
+  if (!array) {
+    return false;
+  }
+
+  args.rval().setObject(*array);
+  return true;
+}
+
+static bool osfile_listDir(JSContext* cx, unsigned argc, Value* vp) {
+  return ListDir(cx, argc, vp, RootRelative);
+}
+
+static bool osfile_listDirRelativeToScript(JSContext* cx, unsigned argc,
+                                           Value* vp) {
+  return ListDir(cx, argc, vp, ScriptRelative);
+}
+
+static bool osfile_writeTypedArrayToFile(JSContext* cx, unsigned argc,
+                                         Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  if (args.length() != 2 || !args[0].isString() || !args[1].isObject() ||
+      !args[1].toObject().is<TypedArrayObject>()) {
+    JS_ReportErrorNumberASCII(cx, my_GetErrorMessage, nullptr,
+                              JSSMSG_INVALID_ARGS, "writeTypedArrayToFile");
+    return false;
+  }
+
+  RootedString givenPath(cx, args[0].toString());
+  RootedString str(cx, ResolvePath(cx, givenPath, RootRelative));
+  if (!str) {
+    return false;
+  }
+
+  UniqueChars filename = JS_EncodeStringToLatin1(cx, str);
+  if (!filename) {
+    return false;
+  }
+
+  FILE* file = fopen(filename.get(), "wb");
+  if (!file) {
+    /*
+     * Use Latin1 variant here because the encoding of the return value of
+     * strerror function can be non-UTF-8.
+     */
+    JS_ReportErrorLatin1(cx, "can't open %s: %s", filename.get(),
+                         strerror(errno));
+    return false;
+  }
+  AutoCloseFile autoClose(file);
+
+  TypedArrayObject* obj = &args[1].toObject().as<TypedArrayObject>();
+
+  if (obj->isSharedMemory()) {
+    // Must opt in to use shared memory.  For now, don't.
+    //
+    // See further comments in FileAsTypedArray, above.
+    filename = JS_EncodeStringToUTF8(cx, str);
+    if (!filename) {
+      return false;
+    }
+    JS_ReportErrorUTF8(cx, "can't write %s: shared memory buffer",
+                       filename.get());
+    return false;
+  }
+  void* buf = obj->dataPointerUnshared();
+  size_t length = obj->length();
+  if (fwrite(buf, obj->bytesPerElement(), length, file) != length ||
+      !autoClose.release()) {
+    filename = JS_EncodeStringToUTF8(cx, str);
+    if (!filename) {
+      return false;
+    }
+    JS_ReportErrorUTF8(cx, "can't write %s", filename.get());
+    return false;
+  }
+
+  args.rval().setUndefined();
+  return true;
+}
+
+/* static */
+RCFile* RCFile::create(JSContext* cx, const char* filename, const char* mode) {
+  FILE* fp = fopen(filename, mode);
+  if (!fp) {
+    return nullptr;
+  }
+
+  RCFile* file = cx->new_<RCFile>(fp);
+  if (!file) {
+    fclose(fp);
+    return nullptr;
+  }
+
+  return file;
+}
+
+void RCFile::close() {
+  if (fp) {
+    fclose(fp);
+  }
+  fp = nullptr;
+}
+
+bool RCFile::release() {
+  if (--numRefs) {
+    return false;
+  }
+  this->close();
+  return true;
+}
+
+class FileObject : public NativeObject {
+  enum : uint32_t { FILE_SLOT = 0, NUM_SLOTS };
+
+ public:
+  static const JSClass class_;
+
+  static FileObject* create(JSContext* cx, RCFile* file) {
+    FileObject* obj = js::NewBuiltinClassInstance<FileObject>(cx);
+    if (!obj) {
+      return nullptr;
+    }
+
+    InitReservedSlot(obj, FILE_SLOT, file, MemoryUse::FileObjectFile);
+    file->acquire();
+    return obj;
+  }
+
+  static void finalize(JS::GCContext* gcx, JSObject* obj) {
+    FileObject* fileObj = &obj->as<FileObject>();
+    RCFile* file = fileObj->rcFile();
+    gcx->removeCellMemory(obj, sizeof(*file), MemoryUse::FileObjectFile);
+    if (file->release()) {
+      gcx->deleteUntracked(file);
+    }
+  }
+
+  bool isOpen() {
+    RCFile* file = rcFile();
+    return file && file->isOpen();
+  }
+
+  void close() {
+    if (!isOpen()) {
+      return;
+    }
+    rcFile()->close();
+  }
+
+  RCFile* rcFile() {
+    return reinterpret_cast<RCFile*>(
+        JS::GetReservedSlot(this, FILE_SLOT).toPrivate());
+  }
+};
+
+static const JSClassOps FileObjectClassOps = {
+    nullptr,               // addProperty
+    nullptr,               // delProperty
+    nullptr,               // enumerate
+    nullptr,               // newEnumerate
+    nullptr,               // resolve
+    nullptr,               // mayResolve
+    FileObject::finalize,  // finalize
+    nullptr,               // call
+    nullptr,               // construct
+    nullptr,               // trace
+};
+
+const JSClass FileObject::class_ = {
+    "File",
+    JSCLASS_HAS_RESERVED_SLOTS(FileObject::NUM_SLOTS) |
+        JSCLASS_FOREGROUND_FINALIZE,
+    &FileObjectClassOps};
+
+static FileObject* redirect(JSContext* cx, HandleString relFilename,
+                            RCFile** globalFile) {
+  RootedString filename(cx, ResolvePath(cx, relFilename, RootRelative));
+  if (!filename) {
+    return nullptr;
+  }
+  UniqueChars filenameABS = JS_EncodeStringToLatin1(cx, filename);
+  if (!filenameABS) {
+    return nullptr;
+  }
+  RCFile* file = RCFile::create(cx, filenameABS.get(), "wb");
+  if (!file) {
+    /*
+     * Use Latin1 variant here because the encoding of the return value of
+     * strerror function can be non-UTF-8.
+     */
+    JS_ReportErrorLatin1(cx, "cannot redirect to %s: %s", filenameABS.get(),
+                         strerror(errno));
+    return nullptr;
+  }
+
+  // Grant the global gOutFile ownership of the new file, release ownership
+  // of its old file, and return a FileObject owning the old file.
+  file->acquire();  // Global owner of new file
+
+  FileObject* fileObj =
+      FileObject::create(cx, *globalFile);  // Newly created owner of old file
+  if (!fileObj) {
+    file->release();
+    return nullptr;
+  }
+
+  (*globalFile)->release();  // Release (global) ownership of old file.
+  *globalFile = file;
+
+  return fileObj;
+}
+
+static bool Redirect(JSContext* cx, const CallArgs& args, RCFile** outFile) {
+  if (args.length() > 1) {
+    JS_ReportErrorNumberASCII(cx, js::shell::my_GetErrorMessage, nullptr,
+                              JSSMSG_INVALID_ARGS, "redirect");
+    return false;
+  }
+
+  RCFile* oldFile = *outFile;
+  RootedObject oldFileObj(cx, FileObject::create(cx, oldFile));
+  if (!oldFileObj) {
+    return false;
+  }
+
+  if (args.get(0).isUndefined()) {
+    args.rval().setObject(*oldFileObj);
+    return true;
+  }
+
+  if (args[0].isObject()) {
+    Rooted<FileObject*> fileObj(cx,
+                                args[0].toObject().maybeUnwrapIf<FileObject>());
+    if (!fileObj) {
+      JS_ReportErrorNumberASCII(cx, js::shell::my_GetErrorMessage, nullptr,
+                                JSSMSG_INVALID_ARGS, "redirect");
+      return false;
+    }
+
+    // Passed in a FileObject. Create a FileObject for the previous
+    // global file, and set the global file to the passed-in one.
+    *outFile = fileObj->rcFile();
+    (*outFile)->acquire();
+    oldFile->release();
+
+    args.rval().setObject(*oldFileObj);
+    return true;
+  }
+
+  RootedString filename(cx);
+  if (!args[0].isNull()) {
+    filename = JS::ToString(cx, args[0]);
+    if (!filename) {
+      return false;
+    }
+  }
+
+  if (!redirect(cx, filename, outFile)) {
+    return false;
+  }
+
+  args.rval().setObject(*oldFileObj);
+  return true;
+}
+
+static bool osfile_redirectOutput(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+  ShellContext* scx = GetShellContext(cx);
+  return Redirect(cx, args, scx->outFilePtr);
+}
+
+static bool osfile_redirectError(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+  ShellContext* scx = GetShellContext(cx);
+  return Redirect(cx, args, scx->errFilePtr);
+}
+
+static bool osfile_close(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  Rooted<FileObject*> fileObj(cx);
+  if (args.get(0).isObject()) {
+    fileObj = args[0].toObject().maybeUnwrapIf<FileObject>();
+  }
+
+  if (!fileObj) {
+    JS_ReportErrorNumberASCII(cx, js::shell::my_GetErrorMessage, nullptr,
+                              JSSMSG_INVALID_ARGS, "close");
+    return false;
+  }
+
+  fileObj->close();
+
+  args.rval().setUndefined();
+  return true;
+}
+
+// clang-format off
+static const JSFunctionSpecWithHelp osfile_functions[] = {
+    JS_FN_HELP("readFile", osfile_readFile, 1, 0,
+"readFile(filename, [\"binary\"])",
+"  Read entire contents of filename. Returns a string, unless \"binary\" is passed\n"
+"  as the second argument, in which case it returns a Uint8Array. Filename is\n"
+"  relative to the current working directory."),
+
+    JS_FN_HELP("readRelativeToScript", osfile_readRelativeToScript, 1, 0,
+"readRelativeToScript(filename, [\"binary\"])",
+"  Read filename into returned string. Filename is relative to the directory\n"
+"  containing the current script."),
+
+    JS_FN_HELP("listDir", osfile_listDir, 1, 0,
+"listDir(dirname)",
+"  Read entire contents of a directory. The \"dirname\" parameter is relate to the\n"
+"  current working directory. Returns a list of filenames within the given directory.\n"
+"  Note that \".\" and \"..\" are also listed."),
+
+    JS_FN_HELP("listDirRelativeToScript", osfile_listDirRelativeToScript, 1, 0,
+"listDirRelativeToScript(dirname)",
+"  Same as \"listDir\" except that the \"dirname\" is relative to the directory\n"
+"  containing the current script."),
+
+    JS_FS_HELP_END
+};
+// clang-format on
+
+// clang-format off
+static const JSFunctionSpecWithHelp osfile_unsafe_functions[] = {
+    JS_FN_HELP("writeTypedArrayToFile", osfile_writeTypedArrayToFile, 2, 0,
+"writeTypedArrayToFile(filename, data)",
+"  Write the contents of a typed array to the named file."),
+
+    JS_FN_HELP("redirect", osfile_redirectOutput, 1, 0,
+"redirect([path-or-object])",
+"  Redirect print() output to the named file.\n"
+"   Return an opaque object representing the previous destination, which\n"
+"   may be passed into redirect() later to restore the output."),
+
+    JS_FN_HELP("redirectErr", osfile_redirectError, 1, 0,
+"redirectErr([path-or-object])",
+"  Same as redirect(), but for printErr"),
+
+    JS_FN_HELP("close", osfile_close, 1, 0,
+"close(object)",
+"  Close the file returned by an earlier redirect call."),
+
+    JS_FS_HELP_END
+};
+// clang-format on
+
+static bool ospath_isAbsolute(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  if (args.length() != 1 || !args[0].isString()) {
+    JS_ReportErrorNumberASCII(cx, my_GetErrorMessage, nullptr,
+                              JSSMSG_INVALID_ARGS, "isAbsolute");
+    return false;
+  }
+
+  Rooted<JSLinearString*> str(cx,
+                              JS_EnsureLinearString(cx, args[0].toString()));
+  if (!str) {
+    return false;
+  }
+
+  args.rval().setBoolean(IsAbsolutePath(str));
+  return true;
+}
+
+static bool ospath_join(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  if (args.length() < 1) {
+    JS_ReportErrorNumberASCII(cx, my_GetErrorMessage, nullptr,
+                              JSSMSG_INVALID_ARGS, "join");
+    return false;
+  }
+
+  // This function doesn't take into account some aspects of Windows paths,
+  // e.g. the drive letter is always reset when an absolute path is appended.
+
+  JSStringBuilder buffer(cx);
+
+  for (unsigned i = 0; i < args.length(); i++) {
+    if (!args[i].isString()) {
+      JS_ReportErrorASCII(cx, "join expects string arguments only");
+      return false;
+    }
+
+    Rooted<JSLinearString*> str(cx,
+                                JS_EnsureLinearString(cx, args[i].toString()));
+    if (!str) {
+      return false;
+    }
+
+    if (IsAbsolutePath(str)) {
+      MOZ_ALWAYS_TRUE(buffer.resize(0));
+    } else if (i != 0) {
+      UniqueChars path = JS_EncodeStringToLatin1(cx, str);
+      if (!path) {
+        return false;
+      }
+
+      if (!buffer.append(PathSeparator)) {
+        return false;
+      }
+    }
+
+    if (!buffer.append(args[i].toString())) {
+      return false;
+    }
+  }
+
+  JSString* result = buffer.finishString();
+  if (!result) {
+    return false;
+  }
+
+  args.rval().setString(result);
+  return true;
+}
+
+// clang-format off
+static const JSFunctionSpecWithHelp ospath_functions[] = {
+    JS_FN_HELP("isAbsolute", ospath_isAbsolute, 1, 0,
+"isAbsolute(path)",
+"  Return whether the given path is absolute."),
+
+    JS_FN_HELP("join", ospath_join, 1, 0,
+"join(paths...)",
+"  Join one or more path components in a platform independent way."),
+
+    JS_FS_HELP_END
+};
+// clang-format on
+
+static bool os_getenv(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+  if (args.length() < 1) {
+    JS_ReportErrorASCII(cx, "os.getenv requires 1 argument");
+    return false;
+  }
+  RootedString key(cx, ToString(cx, args[0]));
+  if (!key) {
+    return false;
+  }
+  UniqueChars keyBytes = JS_EncodeStringToUTF8(cx, key);
+  if (!keyBytes) {
+    return false;
+  }
+
+  if (const char* valueBytes = getenv(keyBytes.get())) {
+    RootedString value(cx, JS_NewStringCopyZ(cx, valueBytes));
+    if (!value) {
+      return false;
+    }
+    args.rval().setString(value);
+  } else {
+    args.rval().setUndefined();
+  }
+  return true;
+}
+
+static bool os_getpid(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+  if (args.length() != 0) {
+    JS_ReportErrorASCII(cx, "os.getpid takes no arguments");
+    return false;
+  }
+  args.rval().setInt32(getpid());
+  return true;
+}
+
+#ifndef __wasi__
+#  if !defined(XP_WIN)
+
+// There are two possible definitions of strerror_r floating around. The GNU
+// one returns a char* which may or may not be the buffer you passed in. The
+// other one returns an integer status code, and always writes the result into
+// the provided buffer.
+
+inline char* strerror_message(int result, char* buffer) {
+  return result == 0 ? buffer : nullptr;
+}
+
+inline char* strerror_message(char* result, char* buffer) { return result; }
+
+#  endif
+
+static void ReportSysError(JSContext* cx, const char* prefix) {
+  char buffer[200];
+
+#  if defined(XP_WIN)
+  strerror_s(buffer, sizeof(buffer), errno);
+  const char* errstr = buffer;
+#  else
+  const char* errstr =
+      strerror_message(strerror_r(errno, buffer, sizeof(buffer)), buffer);
+#  endif
+
+  if (!errstr) {
+    errstr = "unknown error";
+  }
+
+  /*
+   * Use Latin1 variant here because the encoding of the return value of
+   * strerror_s and strerror_r function can be non-UTF-8.
+   */
+  JS_ReportErrorLatin1(cx, "%s: %s", prefix, errstr);
+}
+
+static bool os_system(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  if (args.length() == 0) {
+    JS_ReportErrorASCII(cx, "os.system requires 1 argument");
+    return false;
+  }
+
+  JSString* str = JS::ToString(cx, args[0]);
+  if (!str) {
+    return false;
+  }
+
+  UniqueChars command = JS_EncodeStringToLatin1(cx, str);
+  if (!command) {
+    return false;
+  }
+
+  int result = system(command.get());
+  if (result == -1) {
+    ReportSysError(cx, "system call failed");
+    return false;
+  }
+
+  args.rval().setInt32(result);
+  return true;
+}
+
+#  ifndef XP_WIN
+static bool os_spawn(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  if (args.length() == 0) {
+    JS_ReportErrorASCII(cx, "os.spawn requires 1 argument");
+    return false;
+  }
+
+  JSString* str = JS::ToString(cx, args[0]);
+  if (!str) {
+    return false;
+  }
+
+  UniqueChars command = JS_EncodeStringToLatin1(cx, str);
+  if (!command) {
+    return false;
+  }
+
+  int32_t childPid = fork();
+  if (childPid == -1) {
+    ReportSysError(cx, "fork failed");
+    return false;
+  }
+
+  if (childPid) {
+    args.rval().setInt32(childPid);
+    return true;
+  }
+
+  // We are in the child
+
+  const char* cmd[] = {"sh", "-c", nullptr, nullptr};
+  cmd[2] = command.get();
+
+  execvp("sh", (char* const*)cmd);
+  exit(1);
+}
+
+static bool os_kill(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+  int32_t pid;
+  if (args.length() < 1) {
+    JS_ReportErrorASCII(cx, "os.kill requires 1 argument");
+    return false;
+  }
+  if (!JS::ToInt32(cx, args[0], &pid)) {
+    return false;
+  }
+
+  // It is too easy to kill yourself accidentally with os.kill("goose").
+  if (pid == 0 && !args[0].isInt32()) {
+    JS_ReportErrorASCII(cx, "os.kill requires numeric pid");
+    return false;
+  }
+
+  int signal = SIGINT;
+  if (args.length() > 1) {
+    if (!JS::ToInt32(cx, args[1], &signal)) {
+      return false;
+    }
+  }
+
+  int status = kill(pid, signal);
+  if (status == -1) {
+    ReportSysError(cx, "kill failed");
+    return false;
+  }
+
+  args.rval().setUndefined();
+  return true;
+}
+
+static bool os_waitpid(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  int32_t pid;
+  if (args.length() == 0) {
+    pid = -1;
+  } else {
+    if (!JS::ToInt32(cx, args[0], &pid)) {
+      return false;
+    }
+  }
+
+  bool nohang = false;
+  if (args.length() >= 2) {
+    nohang = JS::ToBoolean(args[1]);
+  }
+
+  int status = 0;
+  pid_t result = waitpid(pid, &status, nohang ? WNOHANG : 0);
+  if (result == -1) {
+    ReportSysError(cx, "os.waitpid failed");
+    return false;
+  }
+
+  RootedObject info(cx, JS_NewPlainObject(cx));
+  if (!info) {
+    return false;
+  }
+
+  RootedValue v(cx);
+  if (result != 0) {
+    v.setInt32(result);
+    if (!JS_DefineProperty(cx, info, "pid", v, JSPROP_ENUMERATE)) {
+      return false;
+    }
+    if (WIFEXITED(status)) {
+      v.setInt32(WEXITSTATUS(status));
+      if (!JS_DefineProperty(cx, info, "exitStatus", v, JSPROP_ENUMERATE)) {
+        return false;
+      }
+    }
+  }
+
+  args.rval().setObject(*info);
+  return true;
+}
+#  endif  // !__wasi__
+#endif
+
+// clang-format off
+static const JSFunctionSpecWithHelp os_functions[] = {
+    JS_FN_HELP("getenv", os_getenv, 1, 0,
+"getenv(variable)",
+"  Get the value of an environment variable."),
+
+    JS_FN_HELP("getpid", os_getpid, 0, 0,
+"getpid()",
+"  Return the current process id."),
+
+#ifndef __wasi__
+    JS_FN_HELP("system", os_system, 1, 0,
+"system(command)",
+"  Execute command on the current host, returning result code or throwing an\n"
+"  exception on failure."),
+
+#  ifndef XP_WIN
+    JS_FN_HELP("spawn", os_spawn, 1, 0,
+"spawn(command)",
+"  Start up a separate process running the given command. Returns the pid."),
+
+    JS_FN_HELP("kill", os_kill, 1, 0,
+"kill(pid[, signal])",
+"  Send a signal to the given pid. The default signal is SIGINT. The signal\n"
+"  passed in must be numeric, if given."),
+
+    JS_FN_HELP("waitpid", os_waitpid, 1, 0,
+"waitpid(pid[, nohang])",
+"  Calls waitpid(). 'nohang' is a boolean indicating whether to pass WNOHANG.\n"
+"  The return value is an object containing a 'pid' field, if a process was waitable\n"
+"  and an 'exitStatus' field if a pid exited."),
+#  endif
+#endif  // !__wasi__
+
+    JS_FS_HELP_END
+};
+// clang-format on
+
+bool DefineOS(JSContext* cx, HandleObject global, bool fuzzingSafe,
+              RCFile** shellOut, RCFile** shellErr) {
+  RootedObject obj(cx, JS_NewPlainObject(cx));
+  if (!obj || !JS_DefineProperty(cx, global, "os", obj, 0)) {
+    return false;
+  }
+
+  if (!fuzzingSafe) {
+    if (!JS_DefineFunctionsWithHelp(cx, obj, os_functions)) {
+      return false;
+    }
+  }
+
+  RootedObject osfile(cx, JS_NewPlainObject(cx));
+  if (!osfile || !JS_DefineFunctionsWithHelp(cx, osfile, osfile_functions) ||
+      !JS_DefineProperty(cx, obj, "file", osfile, 0)) {
+    return false;
+  }
+
+  if (!fuzzingSafe) {
+    if (!JS_DefineFunctionsWithHelp(cx, osfile, osfile_unsafe_functions)) {
+      return false;
+    }
+  }
+
+  if (!GenerateInterfaceHelp(cx, osfile, "os.file")) {
+    return false;
+  }
+
+  RootedObject ospath(cx, JS_NewPlainObject(cx));
+  if (!ospath || !JS_DefineFunctionsWithHelp(cx, ospath, ospath_functions) ||
+      !JS_DefineProperty(cx, obj, "path", ospath, 0) ||
+      !GenerateInterfaceHelp(cx, ospath, "os.path")) {
+    return false;
+  }
+
+  if (!GenerateInterfaceHelp(cx, obj, "os")) {
+    return false;
+  }
+
+  ShellContext* scx = GetShellContext(cx);
+  scx->outFilePtr = shellOut;
+  scx->errFilePtr = shellErr;
+
+  // For backwards compatibility, expose various os.file.* functions as
+  // direct methods on the global.
+  struct Export {
+    const char* src;
+    const char* dst;
+  };
+
+  const Export osfile_exports[] = {
+      {"readFile", "read"},
+      {"readFile", "snarf"},
+      {"readRelativeToScript", "readRelativeToScript"},
+  };
+
+  for (auto pair : osfile_exports) {
+    if (!CreateAlias(cx, pair.dst, osfile, pair.src)) {
+      return false;
+    }
+  }
+
+  if (!fuzzingSafe) {
+    const Export unsafe_osfile_exports[] = {{"redirect", "redirect"},
+                                            {"redirectErr", "redirectErr"}};
+
+    for (auto pair : unsafe_osfile_exports) {
+      if (!CreateAlias(cx, pair.dst, osfile, pair.src)) {
+        return false;
+      }
+    }
+  }
+
+  return true;
+}
+
+}  // namespace shell
+}  // namespace js
diff --git a/js/src/shell/OSObject.h b/js/src/shell/OSObject.h
new file mode 100644
index 0000000000..48c075b9cd
--- /dev/null
+++ b/js/src/shell/OSObject.h
@@ -0,0 +1,46 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+// OSObject.h - os object for exposing posix system calls in the JS shell
+
+#ifndef shell_OSObject_h
+#define shell_OSObject_h
+
+#include "js/TypeDecls.h"
+#include "js/Utility.h"
+
+class JSLinearString;
+
+namespace js {
+namespace shell {
+
+#ifdef XP_WIN
+constexpr char PathSeparator = '\\';
+#else
+constexpr char PathSeparator = '/';
+#endif
+
+struct RCFile;
+
+/* Define an os object on the given global object. */
+bool DefineOS(JSContext* cx, JS::HandleObject global, bool fuzzingSafe,
+              RCFile** shellOut, RCFile** shellErr);
+
+enum PathResolutionMode { RootRelative, ScriptRelative };
+
+bool IsAbsolutePath(JSLinearString* filename);
+
+JSString* ResolvePath(JSContext* cx, JS::HandleString filenameStr,
+                      PathResolutionMode resolveMode);
+
+JSObject* FileAsTypedArray(JSContext* cx, JS::HandleString pathnameStr);
+
+JS::UniqueChars GetCWD();
+
+}  // namespace shell
+}  // namespace js
+
+#endif /* shell_OSObject_h */
diff --git a/js/src/shell/ShellModuleObjectWrapper.cpp b/js/src/shell/ShellModuleObjectWrapper.cpp
new file mode 100644
index 0000000000..4bc10d846d
--- /dev/null
+++ b/js/src/shell/ShellModuleObjectWrapper.cpp
@@ -0,0 +1,469 @@
+/* -*- Mode: javascript; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4
+ * -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "shell/ShellModuleObjectWrapper.h"
+
+#include "mozilla/Maybe.h"
+#include "mozilla/Span.h"
+
+#include "jsapi.h"  // JS_GetProperty, JS::Call, JS_NewPlainObject, JS_DefineProperty
+
+#include "builtin/ModuleObject.h"     // js::ModuleObject
+#include "js/CallAndConstruct.h"      // JS::Call
+#include "js/CallArgs.h"              // JS::CallArgs
+#include "js/CallNonGenericMethod.h"  // CallNonGenericMethod
+#include "js/Class.h"                 // JSClass, JSCLASS_*
+#include "js/ErrorReport.h"           // JS_ReportErrorASCII
+#include "js/PropertyAndElement.h"    // JS_GetProperty
+#include "js/PropertySpec.h"  // JSPropertySpec, JS_PSG, JS_PS_END, JSFunctionSpec, JS_FN, JS_FN_END
+#include "js/RootingAPI.h"    // JS::Rooted, JS::Handle, JS::MutableHandle
+#include "js/Value.h"         // JS::Value
+#include "vm/ArrayObject.h"   // ArrayObject, NewDenseFullyAllocatedArray
+#include "vm/GlobalObject.h"  // DefinePropertiesAndFunctions
+#include "vm/JSFunction.h"    // JSFunction
+#include "vm/JSObject.h"      // JSObject
+#include "vm/List.h"          // ListObject
+#include "vm/NativeObject.h"  // NativeObject
+#include "vm/Stack.h"         // FixedInvokeArgs
+
+#include "vm/NativeObject-inl.h"  // NativeObject::ensureDenseInitializedLength
+
+using namespace js;
+using namespace js::shell;
+
+using mozilla::Span;
+
+#define DEFINE_CLASS_IMPL(CLASS)                                            \
+  CLASS* Shell##CLASS##Wrapper::get() {                                     \
+    return &getReservedSlot(TargetSlot).toObject().as<CLASS>();             \
+  }                                                                         \
+  /* static */ const JSClass Shell##CLASS##Wrapper::class_ = {              \
+      "Shell" #CLASS "Wrapper",                                             \
+      JSCLASS_HAS_RESERVED_SLOTS(Shell##CLASS##Wrapper::SlotCount)};        \
+  MOZ_ALWAYS_INLINE bool IsShell##CLASS##Wrapper(JS::Handle<JS::Value> v) { \
+    return v.isObject() && v.toObject().is<Shell##CLASS##Wrapper>();        \
+  }
+
+#define DEFINE_CLASS(CLASS)                                       \
+  class Shell##CLASS##Wrapper : public js::NativeObject {         \
+   public:                                                        \
+    using Target = CLASS;                                         \
+    enum ModuleSlot { TargetSlot = 0, SlotCount };                \
+    static const JSClass class_;                                  \
+    static Shell##CLASS##Wrapper* create(JSContext* cx,           \
+                                         JS::Handle<CLASS*> obj); \
+    CLASS* get();                                                 \
+  };                                                              \
+  DEFINE_CLASS_IMPL(CLASS)
+
+#define DEFINE_NATIVE_CLASS_IMPL(CLASS)                                     \
+  CLASS* Shell##CLASS##Wrapper::get() {                                     \
+    return static_cast<CLASS*>(getReservedSlot(TargetSlot).toPrivate());    \
+  }                                                                         \
+  /* static */ const JSClass Shell##CLASS##Wrapper::class_ = {              \
+      "Shell" #CLASS "Wrapper",                                             \
+      JSCLASS_HAS_RESERVED_SLOTS(Shell##CLASS##Wrapper::SlotCount)};        \
+  MOZ_ALWAYS_INLINE bool IsShell##CLASS##Wrapper(JS::Handle<JS::Value> v) { \
+    return v.isObject() && v.toObject().is<Shell##CLASS##Wrapper>();        \
+  }
+
+#define DEFINE_NATIVE_CLASS(CLASS)                                    \
+  class Shell##CLASS##Wrapper : public js::NativeObject {             \
+   public:                                                            \
+    using Target = CLASS;                                             \
+    enum ModuleSlot { OwnerSlot = 0, TargetSlot, SlotCount };         \
+    static const JSClass class_;                                      \
+    static Shell##CLASS##Wrapper* create(JSContext* cx,               \
+                                         JS::Handle<JSObject*> owner, \
+                                         CLASS* obj);                 \
+    CLASS* get();                                                     \
+  };                                                                  \
+  DEFINE_NATIVE_CLASS_IMPL(CLASS)
+
+DEFINE_CLASS(ModuleRequestObject)
+DEFINE_NATIVE_CLASS(ImportEntry)
+DEFINE_NATIVE_CLASS(ExportEntry)
+DEFINE_NATIVE_CLASS(RequestedModule)
+// NOTE: We don't need wrapper for IndirectBindingMap and ModuleNamespaceObject
+DEFINE_CLASS_IMPL(ModuleObject)
+
+#undef DEFINE_CLASS
+#undef DEFINE_CLASS_IMPL
+#undef DEFINE_NATIVE_CLASS
+#undef DEFINE_NATIVE_CLASS_IMPL
+
+bool IdentFilter(JSContext* cx, JS::Handle<JS::Value> from,
+                 JS::MutableHandle<JS::Value> to) {
+  to.set(from);
+  return true;
+}
+
+template <class T>
+bool SingleFilter(JSContext* cx, JS::Handle<JS::Value> from,
+                  JS::MutableHandle<JS::Value> to) {
+  using TargetT = typename T::Target;
+
+  if (!from.isObject() || !from.toObject().is<TargetT>()) {
+    to.set(from);
+    return true;
+  }
+
+  JS::Rooted<TargetT*> obj(cx, &from.toObject().as<TargetT>());
+  JS::Rooted<T*> filtered(cx, T::create(cx, obj));
+  if (!filtered) {
+    return false;
+  }
+  to.setObject(*filtered);
+  return true;
+}
+
+template <class T>
+bool ArrayFilter(JSContext* cx, JS::Handle<JS::Value> from,
+                 JS::MutableHandle<JS::Value> to) {
+  using TargetT = typename T::Target;
+
+  if (!from.isObject() || !from.toObject().is<ArrayObject>()) {
+    to.set(from);
+    return true;
+  }
+
+  JS::Rooted<ArrayObject*> fromArray(cx, &from.toObject().as<ArrayObject>());
+  uint32_t length = fromArray->length();
+  JS::Rooted<ArrayObject*> toArray(cx, NewDenseFullyAllocatedArray(cx, length));
+  if (!toArray) {
+    return false;
+  }
+
+  toArray->ensureDenseInitializedLength(0, length);
+
+  for (uint32_t i = 0; i < length; i++) {
+    JS::Rooted<JS::Value> item(cx, fromArray->getDenseElement(i));
+    JS::Rooted<TargetT*> req(cx, &item.toObject().as<TargetT>());
+    JS::Rooted<T*> filtered(cx, T::create(cx, req));
+    if (!filtered) {
+      return false;
+    }
+    toArray->initDenseElement(i, ObjectValue(*filtered));
+  }
+  to.setObject(*toArray);
+  return true;
+}
+
+template <class T>
+bool ListToArrayFilter(JSContext* cx, JS::Handle<JS::Value> from,
+                       JS::MutableHandle<JS::Value> to) {
+  using TargetT = typename T::Target;
+
+  if (!from.isObject() || !from.toObject().is<ListObject>()) {
+    to.set(from);
+    return true;
+  }
+
+  JS::Rooted<ListObject*> fromList(cx, &from.toObject().as<ListObject>());
+  uint32_t length = fromList->length();
+  JS::Rooted<ArrayObject*> toArray(cx, NewDenseFullyAllocatedArray(cx, length));
+  if (!toArray) {
+    return false;
+  }
+
+  toArray->ensureDenseInitializedLength(0, length);
+
+  for (uint32_t i = 0; i < length; i++) {
+    JS::Rooted<JS::Value> item(cx, fromList->get(i));
+    JS::Rooted<TargetT*> req(cx, &item.toObject().as<TargetT>());
+    JS::Rooted<T*> filtered(cx, T::create(cx, req));
+    if (!filtered) {
+      return false;
+    }
+    toArray->initDenseElement(i, ObjectValue(*filtered));
+  }
+  to.setObject(*toArray);
+  return true;
+}
+
+static Value StringOrNullValue(JSString* maybeString) {
+  if (!maybeString) {
+    return NullValue();
+  }
+
+  return StringValue(maybeString);
+}
+
+static Value Uint32Value(uint32_t x) {
+  MOZ_ASSERT(x <= INT32_MAX);
+  return Int32Value(x);
+}
+
+static Value Uint32OrUndefinedValue(mozilla::Maybe<uint32_t> x) {
+  if (x.isNothing()) {
+    return UndefinedValue();
+  }
+
+  return Uint32Value(x.value());
+}
+
+static Value StatusValue(ModuleStatus status) {
+  return Int32Value(int32_t(status));
+}
+
+static Value ObjectOrUndefinedValue(JSObject* object) {
+  if (!object) {
+    return UndefinedValue();
+  }
+
+  return ObjectValue(*object);
+}
+
+template <class T, typename RawGetterT, typename FilterT>
+bool ShellModuleWrapperGetter(JSContext* cx, const JS::CallArgs& args,
+                              RawGetterT rawGetter, FilterT filter) {
+  JS::Rooted<T*> wrapper(cx, &args.thisv().toObject().as<T>());
+  JS::Rooted<JS::Value> raw(cx, rawGetter(wrapper->get()));
+
+  JS::Rooted<JS::Value> filtered(cx);
+  if (!filter(cx, raw, &filtered)) {
+    return false;
+  }
+
+  args.rval().set(filtered);
+  return true;
+}
+
+#define DEFINE_GETTER_FUNCTIONS(CLASS, PROP, TO_VALUE, FILTER)                 \
+  static Value Shell##CLASS##Wrapper_##PROP##Getter_raw(CLASS* obj) {          \
+    return TO_VALUE(obj->PROP());                                              \
+  }                                                                            \
+  static bool Shell##CLASS##Wrapper_##PROP##Getter_impl(                       \
+      JSContext* cx, const JS::CallArgs& args) {                               \
+    return ShellModuleWrapperGetter<Shell##CLASS##Wrapper>(                    \
+        cx, args, Shell##CLASS##Wrapper_##PROP##Getter_raw, FILTER);           \
+  }                                                                            \
+  static bool Shell##CLASS##Wrapper_##PROP##Getter(JSContext* cx,              \
+                                                   unsigned argc, Value* vp) { \
+    JS::CallArgs args = JS::CallArgsFromVp(argc, vp);                          \
+    return CallNonGenericMethod<IsShell##CLASS##Wrapper,                       \
+                                Shell##CLASS##Wrapper_##PROP##Getter_impl>(    \
+        cx, args);                                                             \
+  }
+
+template <class T>
+bool SpanToArrayFilter(JSContext* cx, JS::Handle<JSObject*> owner,
+                       Span<const typename T::Target> from,
+                       JS::MutableHandle<JS::Value> to) {
+  size_t length = from.Length();
+  JS::Rooted<ArrayObject*> toArray(cx, NewDenseFullyAllocatedArray(cx, length));
+  if (!toArray) {
+    return false;
+  }
+
+  toArray->ensureDenseInitializedLength(0, length);
+
+  for (uint32_t i = 0; i < length; i++) {
+    auto* element = const_cast<typename T::Target*>(&from[i]);
+    JS::Rooted<T*> filtered(cx, T::create(cx, owner, element));
+    if (!filtered) {
+      return false;
+    }
+    toArray->initDenseElement(i, ObjectValue(*filtered));
+  }
+
+  to.setObject(*toArray);
+  return true;
+}
+
+template <class T, typename RawGetterT, typename FilterT>
+bool ShellModuleNativeWrapperGetter(JSContext* cx, const JS::CallArgs& args,
+                                    RawGetterT rawGetter, FilterT filter) {
+  JS::Rooted<T*> wrapper(cx, &args.thisv().toObject().as<T>());
+  JS::Rooted<typename T::Target*> owner(cx, wrapper->get());
+
+  JS::Rooted<JS::Value> filtered(cx);
+  if (!filter(cx, owner, rawGetter(owner), &filtered)) {
+    return false;
+  }
+
+  args.rval().set(filtered);
+  return true;
+}
+
+#define DEFINE_NATIVE_GETTER_FUNCTIONS(CLASS, PROP, FILTER)                    \
+  static auto Shell##CLASS##Wrapper_##PROP##Getter_raw(CLASS* obj) {           \
+    return obj->PROP();                                                        \
+  }                                                                            \
+  static bool Shell##CLASS##Wrapper_##PROP##Getter_impl(                       \
+      JSContext* cx, const JS::CallArgs& args) {                               \
+    return ShellModuleNativeWrapperGetter<Shell##CLASS##Wrapper>(              \
+        cx, args, Shell##CLASS##Wrapper_##PROP##Getter_raw, FILTER);           \
+  }                                                                            \
+  static bool Shell##CLASS##Wrapper_##PROP##Getter(JSContext* cx,              \
+                                                   unsigned argc, Value* vp) { \
+    JS::CallArgs args = JS::CallArgsFromVp(argc, vp);                          \
+    return CallNonGenericMethod<IsShell##CLASS##Wrapper,                       \
+                                Shell##CLASS##Wrapper_##PROP##Getter_impl>(    \
+        cx, args);                                                             \
+  }
+
+DEFINE_GETTER_FUNCTIONS(ModuleRequestObject, specifier, StringOrNullValue,
+                        IdentFilter)
+DEFINE_GETTER_FUNCTIONS(ModuleRequestObject, assertions, ObjectOrNullValue,
+                        IdentFilter)
+
+static const JSPropertySpec ShellModuleRequestObjectWrapper_accessors[] = {
+    JS_PSG("specifier", ShellModuleRequestObjectWrapper_specifierGetter, 0),
+    JS_PSG("assertions", ShellModuleRequestObjectWrapper_assertionsGetter, 0),
+    JS_PS_END};
+
+DEFINE_GETTER_FUNCTIONS(ImportEntry, moduleRequest, ObjectOrNullValue,
+                        SingleFilter<ShellModuleRequestObjectWrapper>)
+DEFINE_GETTER_FUNCTIONS(ImportEntry, importName, StringOrNullValue, IdentFilter)
+DEFINE_GETTER_FUNCTIONS(ImportEntry, localName, StringValue, IdentFilter)
+DEFINE_GETTER_FUNCTIONS(ImportEntry, lineNumber, Uint32Value, IdentFilter)
+DEFINE_GETTER_FUNCTIONS(ImportEntry, columnNumber, Uint32Value, IdentFilter)
+
+static const JSPropertySpec ShellImportEntryWrapper_accessors[] = {
+    JS_PSG("moduleRequest", ShellImportEntryWrapper_moduleRequestGetter, 0),
+    JS_PSG("importName", ShellImportEntryWrapper_importNameGetter, 0),
+    JS_PSG("localName", ShellImportEntryWrapper_localNameGetter, 0),
+    JS_PSG("lineNumber", ShellImportEntryWrapper_lineNumberGetter, 0),
+    JS_PSG("columnNumber", ShellImportEntryWrapper_columnNumberGetter, 0),
+    JS_PS_END};
+
+DEFINE_GETTER_FUNCTIONS(ExportEntry, exportName, StringOrNullValue, IdentFilter)
+DEFINE_GETTER_FUNCTIONS(ExportEntry, moduleRequest, ObjectOrNullValue,
+                        SingleFilter<ShellModuleRequestObjectWrapper>)
+DEFINE_GETTER_FUNCTIONS(ExportEntry, importName, StringOrNullValue, IdentFilter)
+DEFINE_GETTER_FUNCTIONS(ExportEntry, localName, StringOrNullValue, IdentFilter)
+DEFINE_GETTER_FUNCTIONS(ExportEntry, lineNumber, Uint32Value, IdentFilter)
+DEFINE_GETTER_FUNCTIONS(ExportEntry, columnNumber, Uint32Value, IdentFilter)
+
+static const JSPropertySpec ShellExportEntryWrapper_accessors[] = {
+    JS_PSG("exportName", ShellExportEntryWrapper_exportNameGetter, 0),
+    JS_PSG("moduleRequest", ShellExportEntryWrapper_moduleRequestGetter, 0),
+    JS_PSG("importName", ShellExportEntryWrapper_importNameGetter, 0),
+    JS_PSG("localName", ShellExportEntryWrapper_localNameGetter, 0),
+    JS_PSG("lineNumber", ShellExportEntryWrapper_lineNumberGetter, 0),
+    JS_PSG("columnNumber", ShellExportEntryWrapper_columnNumberGetter, 0),
+    JS_PS_END};
+
+DEFINE_GETTER_FUNCTIONS(RequestedModule, moduleRequest, ObjectOrNullValue,
+                        SingleFilter<ShellModuleRequestObjectWrapper>)
+DEFINE_GETTER_FUNCTIONS(RequestedModule, lineNumber, Uint32Value, IdentFilter)
+DEFINE_GETTER_FUNCTIONS(RequestedModule, columnNumber, Uint32Value, IdentFilter)
+
+static const JSPropertySpec ShellRequestedModuleWrapper_accessors[] = {
+    JS_PSG("moduleRequest", ShellRequestedModuleWrapper_moduleRequestGetter, 0),
+    JS_PSG("lineNumber", ShellRequestedModuleWrapper_lineNumberGetter, 0),
+    JS_PSG("columnNumber", ShellRequestedModuleWrapper_columnNumberGetter, 0),
+    JS_PS_END};
+
+DEFINE_GETTER_FUNCTIONS(ModuleObject, namespace_, ObjectOrNullValue,
+                        IdentFilter)
+DEFINE_GETTER_FUNCTIONS(ModuleObject, status, StatusValue, IdentFilter)
+DEFINE_GETTER_FUNCTIONS(ModuleObject, maybeEvaluationError, Value, IdentFilter)
+DEFINE_NATIVE_GETTER_FUNCTIONS(ModuleObject, requestedModules,
+                               SpanToArrayFilter<ShellRequestedModuleWrapper>)
+DEFINE_NATIVE_GETTER_FUNCTIONS(ModuleObject, importEntries,
+                               SpanToArrayFilter<ShellImportEntryWrapper>)
+DEFINE_NATIVE_GETTER_FUNCTIONS(ModuleObject, localExportEntries,
+                               SpanToArrayFilter<ShellExportEntryWrapper>)
+DEFINE_NATIVE_GETTER_FUNCTIONS(ModuleObject, indirectExportEntries,
+                               SpanToArrayFilter<ShellExportEntryWrapper>)
+DEFINE_NATIVE_GETTER_FUNCTIONS(ModuleObject, starExportEntries,
+                               SpanToArrayFilter<ShellExportEntryWrapper>)
+DEFINE_GETTER_FUNCTIONS(ModuleObject, maybeDfsIndex, Uint32OrUndefinedValue,
+                        IdentFilter)
+DEFINE_GETTER_FUNCTIONS(ModuleObject, maybeDfsAncestorIndex,
+                        Uint32OrUndefinedValue, IdentFilter)
+DEFINE_GETTER_FUNCTIONS(ModuleObject, hasTopLevelAwait, BooleanValue,
+                        IdentFilter)
+DEFINE_GETTER_FUNCTIONS(ModuleObject, maybeTopLevelCapability,
+                        ObjectOrUndefinedValue, IdentFilter)
+DEFINE_GETTER_FUNCTIONS(ModuleObject, isAsyncEvaluating, BooleanValue,
+                        IdentFilter)
+DEFINE_GETTER_FUNCTIONS(ModuleObject, maybeAsyncEvaluatingPostOrder,
+                        Uint32OrUndefinedValue, IdentFilter)
+DEFINE_GETTER_FUNCTIONS(ModuleObject, asyncParentModules, ObjectOrNullValue,
+                        ListToArrayFilter<ShellModuleObjectWrapper>)
+DEFINE_GETTER_FUNCTIONS(ModuleObject, maybePendingAsyncDependencies,
+                        Uint32OrUndefinedValue, IdentFilter)
+
+static const JSPropertySpec ShellModuleObjectWrapper_accessors[] = {
+    JS_PSG("namespace", ShellModuleObjectWrapper_namespace_Getter, 0),
+    JS_PSG("status", ShellModuleObjectWrapper_statusGetter, 0),
+    JS_PSG("evaluationError",
+           ShellModuleObjectWrapper_maybeEvaluationErrorGetter, 0),
+    JS_PSG("requestedModules", ShellModuleObjectWrapper_requestedModulesGetter,
+           0),
+    JS_PSG("importEntries", ShellModuleObjectWrapper_importEntriesGetter, 0),
+    JS_PSG("localExportEntries",
+           ShellModuleObjectWrapper_localExportEntriesGetter, 0),
+    JS_PSG("indirectExportEntries",
+           ShellModuleObjectWrapper_indirectExportEntriesGetter, 0),
+    JS_PSG("starExportEntries",
+           ShellModuleObjectWrapper_starExportEntriesGetter, 0),
+    JS_PSG("dfsIndex", ShellModuleObjectWrapper_maybeDfsIndexGetter, 0),
+    JS_PSG("dfsAncestorIndex",
+           ShellModuleObjectWrapper_maybeDfsAncestorIndexGetter, 0),
+    JS_PSG("hasTopLevelAwait", ShellModuleObjectWrapper_hasTopLevelAwaitGetter,
+           0),
+    JS_PSG("topLevelCapability",
+           ShellModuleObjectWrapper_maybeTopLevelCapabilityGetter, 0),
+    JS_PSG("isAsyncEvaluating",
+           ShellModuleObjectWrapper_isAsyncEvaluatingGetter, 0),
+    JS_PSG("asyncEvaluatingPostOrder",
+           ShellModuleObjectWrapper_maybeAsyncEvaluatingPostOrderGetter, 0),
+    JS_PSG("asyncParentModules",
+           ShellModuleObjectWrapper_asyncParentModulesGetter, 0),
+    JS_PSG("pendingAsyncDependencies",
+           ShellModuleObjectWrapper_maybePendingAsyncDependenciesGetter, 0),
+    JS_PS_END};
+
+#undef DEFINE_GETTER_FUNCTIONS
+#undef DEFINE_NATIVE_GETTER_FUNCTIONS
+
+#define DEFINE_CREATE(CLASS, ACCESSORS, FUNCTIONS)                      \
+  /* static */                                                          \
+  Shell##CLASS##Wrapper* Shell##CLASS##Wrapper::create(                 \
+      JSContext* cx, JS::Handle<CLASS*> target) {                       \
+    JS::Rooted<JSObject*> obj(cx, JS_NewObject(cx, &class_));           \
+    if (!obj) {                                                         \
+      return nullptr;                                                   \
+    }                                                                   \
+    if (!DefinePropertiesAndFunctions(cx, obj, ACCESSORS, FUNCTIONS)) { \
+      return nullptr;                                                   \
+    }                                                                   \
+    auto* wrapper = &obj->as<Shell##CLASS##Wrapper>();                  \
+    wrapper->initReservedSlot(TargetSlot, ObjectValue(*target));        \
+    return wrapper;                                                     \
+  }
+
+#define DEFINE_NATIVE_CREATE(CLASS, ACCESSORS, FUNCTIONS)               \
+  /* static */                                                          \
+  Shell##CLASS##Wrapper* Shell##CLASS##Wrapper::create(                 \
+      JSContext* cx, JS::Handle<JSObject*> owner, CLASS* target) {      \
+    JS::Rooted<JSObject*> obj(cx, JS_NewObject(cx, &class_));           \
+    if (!obj) {                                                         \
+      return nullptr;                                                   \
+    }                                                                   \
+    if (!DefinePropertiesAndFunctions(cx, obj, ACCESSORS, FUNCTIONS)) { \
+      return nullptr;                                                   \
+    }                                                                   \
+    auto* wrapper = &obj->as<Shell##CLASS##Wrapper>();                  \
+    wrapper->initReservedSlot(OwnerSlot, ObjectValue(*owner));          \
+    wrapper->initReservedSlot(TargetSlot, PrivateValue(target));        \
+    return wrapper;                                                     \
+  }
+
+DEFINE_CREATE(ModuleRequestObject, ShellModuleRequestObjectWrapper_accessors,
+              nullptr)
+DEFINE_NATIVE_CREATE(ImportEntry, ShellImportEntryWrapper_accessors, nullptr)
+DEFINE_NATIVE_CREATE(ExportEntry, ShellExportEntryWrapper_accessors, nullptr)
+DEFINE_NATIVE_CREATE(RequestedModule, ShellRequestedModuleWrapper_accessors,
+                     nullptr)
+DEFINE_CREATE(ModuleObject, ShellModuleObjectWrapper_accessors, nullptr)
+
+#undef DEFINE_CREATE
+#undef DEFINE_NATIVE_CREATE
diff --git a/js/src/shell/ShellModuleObjectWrapper.h b/js/src/shell/ShellModuleObjectWrapper.h
new file mode 100644
index 0000000000..8e0fd20987
--- /dev/null
+++ b/js/src/shell/ShellModuleObjectWrapper.h
@@ -0,0 +1,36 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef shell_ShellModuleObjectWrapper_h
+#define shell_ShellModuleObjectWrapper_h
+
+#include "builtin/ModuleObject.h"  // js::ModuleObject
+#include "js/Class.h"              // JSClass
+#include "js/RootingAPI.h"         // JS::Handle
+#include "vm/NativeObject.h"       // js::NativeObject
+
+namespace js {
+
+namespace shell {
+
+// ModuleObject's accessors and methods are only for internal usage in
+// js/src/builtin/Module.js, and they don't check arguments types.
+//
+// To use ModuleObject in tests, add a wrapper that checks arguments types.
+class ShellModuleObjectWrapper : public js::NativeObject {
+ public:
+  using Target = ModuleObject;
+  enum ModuleSlot { TargetSlot = 0, SlotCount };
+  static const JSClass class_;
+  static ShellModuleObjectWrapper* create(JSContext* cx,
+                                          JS::Handle<ModuleObject*> moduleObj);
+  ModuleObject* get();
+};
+
+}  // namespace shell
+}  // namespace js
+
+#endif /* shell_ShellModuleObjectWrapper_h */
diff --git a/js/src/shell/StringUtils.h b/js/src/shell/StringUtils.h
new file mode 100644
index 0000000000..1267c81eee
--- /dev/null
+++ b/js/src/shell/StringUtils.h
@@ -0,0 +1,146 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* String utility functions used by the module loader. */
+
+#ifndef shell_StringUtils_h
+#define shell_StringUtils_h
+
+#include "js/StableStringChars.h"
+#include "js/String.h"
+
+namespace js {
+namespace shell {
+
+inline char16_t CharAt(JSLinearString* str, size_t index) {
+  return str->latin1OrTwoByteChar(index);
+}
+
+inline JSLinearString* SubString(JSContext* cx, JSLinearString* str,
+                                 size_t start, size_t end) {
+  MOZ_ASSERT(start <= str->length());
+  MOZ_ASSERT(end >= start && end <= str->length());
+  return NewDependentString(cx, str, start, end - start);
+}
+
+inline JSLinearString* SubString(JSContext* cx, JSLinearString* str,
+                                 size_t start) {
+  return SubString(cx, str, start, str->length());
+}
+
+template <size_t NullTerminatedLength>
+bool StringStartsWith(JSLinearString* str,
+                      const char16_t (&chars)[NullTerminatedLength]) {
+  MOZ_ASSERT(NullTerminatedLength > 0);
+  const size_t length = NullTerminatedLength - 1;
+  MOZ_ASSERT(chars[length] == '\0');
+
+  if (str->length() < length) {
+    return false;
+  }
+
+  for (size_t i = 0; i < length; i++) {
+    if (CharAt(str, i) != chars[i]) {
+      return false;
+    }
+  }
+
+  return true;
+}
+
+template <size_t NullTerminatedLength>
+bool StringEquals(JSLinearString* str,
+                  const char16_t (&chars)[NullTerminatedLength]) {
+  MOZ_ASSERT(NullTerminatedLength > 0);
+  const size_t length = NullTerminatedLength - 1;
+  MOZ_ASSERT(chars[length] == '\0');
+
+  return str->length() == length && StringStartsWith(str, chars);
+}
+
+inline int32_t IndexOf(Handle<JSLinearString*> str, char16_t target,
+                       size_t start = 0) {
+  int32_t length = str->length();
+  for (int32_t i = start; i < length; i++) {
+    if (CharAt(str, i) == target) {
+      return i;
+    }
+  }
+
+  return -1;
+}
+
+inline int32_t LastIndexOf(Handle<JSLinearString*> str, char16_t target) {
+  int32_t length = str->length();
+  for (int32_t i = length - 1; i >= 0; i--) {
+    if (CharAt(str, i) == target) {
+      return i;
+    }
+  }
+
+  return -1;
+}
+
+inline JSLinearString* ReplaceCharGlobally(JSContext* cx,
+                                           Handle<JSLinearString*> str,
+                                           char16_t target,
+                                           char16_t replacement) {
+  int32_t i = IndexOf(str, target);
+  if (i == -1) {
+    return str;
+  }
+
+  JS::AutoStableStringChars chars(cx);
+  if (!chars.initTwoByte(cx, str)) {
+    return nullptr;
+  }
+
+  Vector<char16_t> buf(cx);
+  if (!buf.append(chars.twoByteChars(), str->length())) {
+    return nullptr;
+  }
+
+  for (; i < int32_t(buf.length()); i++) {
+    if (buf[i] == target) {
+      buf[i] = replacement;
+    }
+  }
+
+  RootedString result(cx, JS_NewUCStringCopyN(cx, buf.begin(), buf.length()));
+  if (!result) {
+    return nullptr;
+  }
+
+  return JS_EnsureLinearString(cx, result);
+}
+
+inline JSString* JoinStrings(JSContext* cx,
+                             Handle<GCVector<JSLinearString*>> strings,
+                             Handle<JSLinearString*> separator) {
+  RootedString result(cx, JS_GetEmptyString(cx));
+
+  for (size_t i = 0; i < strings.length(); i++) {
+    HandleString str = strings[i];
+    if (i != 0) {
+      result = JS_ConcatStrings(cx, result, separator);
+      if (!result) {
+        return nullptr;
+      }
+    }
+
+    result = JS_ConcatStrings(cx, result, str);
+    if (!result) {
+      return nullptr;
+    }
+  }
+
+  return result;
+}
+
+}  // namespace shell
+}  // namespace js
+
+#endif  // shell_StringUtils_h
diff --git a/js/src/shell/WasmTesting.cpp b/js/src/shell/WasmTesting.cpp
new file mode 100644
index 0000000000..a6e97e5ec1
--- /dev/null
+++ b/js/src/shell/WasmTesting.cpp
@@ -0,0 +1,81 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ *
+ * Copyright 2015 Mozilla Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "shell/WasmTesting.h"
+
+#include <inttypes.h>
+#include <stdbool.h>
+#include <stddef.h>
+
+#include "js/Printf.h"
+#include "wasm/WasmTypeDecls.h"
+
+using namespace js;
+using namespace js::wasm;
+
+extern "C" {
+bool wasm_text_to_binary(const char16_t* text, size_t text_len,
+                         uint8_t** out_bytes, size_t* out_bytes_len,
+                         uint8_t** out_error, size_t* out_error_len);
+void wasm_code_offsets(const uint8_t* bytes, size_t bytes_len,
+                       uint32_t** out_offsets, size_t* out_offset_len);
+}  // extern "C"
+
+bool wasm::TextToBinary(const char16_t* text, size_t textLen, Bytes* bytes,
+                        UniqueChars* error) {
+  uint8_t* outBytes = nullptr;
+  size_t outBytesLength = 0;
+
+  uint8_t* outError = nullptr;
+  size_t outErrorLength = 0;
+
+  bool result = wasm_text_to_binary(text, textLen, &outBytes, &outBytesLength,
+                                    &outError, &outErrorLength);
+
+  if (result) {
+    if (outBytesLength == 0) {
+      *error = JS_smprintf("missing bytes");
+      return false;
+    }
+
+    MOZ_ASSERT(outBytes);
+    MOZ_ASSERT(outBytesLength > 0);
+    bytes->replaceRawBuffer(outBytes, outBytesLength);
+    return true;
+  }
+
+  MOZ_ASSERT(outError);
+  MOZ_ASSERT(outErrorLength > 0);
+  *error = UniqueChars{(char*)outError};
+  return false;
+}
+
+void wasm::CodeOffsets(const uint8_t* bytes, size_t bytesLen,
+                       Uint32Vector* offsets) {
+  uint32_t* outOffsets = nullptr;
+  size_t outOffsetsLength = 0;
+
+  wasm_code_offsets(bytes, bytesLen, &outOffsets, &outOffsetsLength);
+
+  if (outOffsets) {
+    MOZ_ASSERT(outOffsetsLength > 0);
+    offsets->replaceRawBuffer(outOffsets, outOffsetsLength);
+  } else {
+    offsets->clear();
+  }
+}
diff --git a/js/src/shell/WasmTesting.h b/js/src/shell/WasmTesting.h
new file mode 100644
index 0000000000..d669466c13
--- /dev/null
+++ b/js/src/shell/WasmTesting.h
@@ -0,0 +1,46 @@
+/* -*- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ *
+ * Copyright 2020 Mozilla Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef shell_wasm_h
+#define shell_wasm_h
+
+#include "wasm/WasmTypeDecls.h"
+
+namespace js {
+namespace wasm {
+
+// Translate the textual representation of a wasm module (given by a
+// char16_t array + length) into serialized bytes. If there is an error
+// other than out-of-memory an error message string will be stored in 'error'.
+
+[[nodiscard]] extern bool TextToBinary(const char16_t* text, size_t textLen,
+                                       Bytes* bytes, UniqueChars* error);
+
+// Decode the binary wasm module given and return the offsets of all
+// instructions inside of the the code section.
+//
+// This function is used exclusively for testing and handles errors by
+// returning an empty offset array.
+
+extern void CodeOffsets(const uint8_t* bytes, size_t bytesLen,
+                        Uint32Vector* offsets);
+
+}  // namespace wasm
+}  // namespace js
+
+#endif  // shell_wasm_h
diff --git a/js/src/shell/fuzz-flags.txt b/js/src/shell/fuzz-flags.txt
new file mode 100644
index 0000000000..abff845ca6
--- /dev/null
+++ b/js/src/shell/fuzz-flags.txt
@@ -0,0 +1,90 @@
+# This lists all the possible flags we'd like to see tested out in the shell by
+# fuzzers. A non-empty line not starting with # should be considered a valid
+# one. Note the following flag is recommended in ALL the cases: --fuzzing-safe
+
+# general jit flags
+--baseline-eager
+--blinterp
+--no-blinterp
+--blinterp-eager
+--cache-ir-stubs=off
+--cache-ir-stubs=on
+--ion-check-range-analysis
+--ion-eager
+--ion-edgecase-analysis=off
+--ion-edgecase-analysis=on
+--ion-extra-checks
+--ion-gvn=off
+--ion-gvn=on
+--ion-inlining=off
+--ion-inlining=on
+--ion-instruction-reordering=off
+--ion-instruction-reordering=on
+--ion-licm=off
+--ion-licm=on
+--ion-limit-script-size=off
+--ion-limit-script-size=on
+--ion-offthread-compile=off
+--ion-optimize-shapeguards=off
+--ion-optimize-shapeguards=on
+--ion-osr=off
+--ion-osr=on
+--ion-pruning=off
+--ion-pruning=on
+--ion-range-analysis=off
+--ion-range-analysis=on
+--ion-regalloc=testbed
+--ion-scalar-replacement=off
+--ion-scalar-replacement=on
+--ion-warmup-threshold=0
+--ion-warmup-threshold=10
+--ion-warmup-threshold=100
+--no-native-regexp
+--nursery-strings=off
+--nursery-strings=on
+--nursery-bigints=off
+--nursery-bigints=on
+--spectre-mitigations=off
+--spectre-mitigations=on
+--more-compartments
+--fast-warmup
+--no-jit-backend
+--enable-watchtower
+--disable-watchtower
+
+# GC-related
+# These 2 flags can cause the shell to slow down
+# --gc-zeal=2
+# --gc-zeal=10
+--no-cgc
+--no-ggc
+--no-incremental-gc
+
+# wasm flags
+--wasm-gc
+--wasm-compiler=baseline
+--wasm-compiler=optimizing
+--wasm-compiler=baseline+optimizing
+--test-wasm-await-tier2
+--wasm-disable-huge-memory
+
+# CPU instruction set-related
+--no-sse3
+--no-ssse3
+--no-sse41
+--no-sse42
+
+# arm specific, no-ops on other platforms.
+--arm-sim-icache-checks
+--arm-asm-nop-fill=1
+--arm-hwcap=vfp
+
+# Profiling, code coverage, and debugging
+# --dump-bytecode option implies --code-coverage
+--dump-bytecode
+
+# Shadow Realms
+--enable-shadow-realms
+
+# Array.fromAsync
+--enable-array-from-async
diff --git a/js/src/shell/js-gdb.py b/js/src/shell/js-gdb.py
new file mode 100644
index 0000000000..72d73508d6
--- /dev/null
+++ b/js/src/shell/js-gdb.py
@@ -0,0 +1,21 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+""" GDB Python customization auto-loader for JS shell binary """
+
+# This script will be installed into $objdir/dist/bin. Add $objdir to gdb's
+# source search path and load in the Gecko+JS init file.
+
+import os
+import re
+from os.path import abspath, dirname
+
+import gdb
+
+devel_objdir = abspath(os.path.join(dirname(__file__), "..", ".."))
+m = re.search(r"[\w ]+: (.*)", gdb.execute("show dir", False, True))
+if m and devel_objdir not in m.group(1).split(":"):
+    gdb.execute("set dir {}:{}".format(devel_objdir, m.group(1)))
+
+gdb.execute("source -s build/.gdbinit.loader")
diff --git a/js/src/shell/js.cpp b/js/src/shell/js.cpp
new file mode 100644
index 0000000000..a909393c99
--- /dev/null
+++ b/js/src/shell/js.cpp
@@ -0,0 +1,12410 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* JS shell. */
+
+#include "mozilla/ArrayUtils.h"
+#include "mozilla/Atomics.h"
+#include "mozilla/Attributes.h"
+#include "mozilla/DebugOnly.h"
+#include "mozilla/EnumSet.h"
+#include "mozilla/IntegerPrintfMacros.h"
+#include "mozilla/mozalloc.h"
+#include "mozilla/PodOperations.h"
+#include "mozilla/RandomNum.h"
+#include "mozilla/RefPtr.h"
+#include "mozilla/ScopeExit.h"
+#include "mozilla/Sprintf.h"
+#include "mozilla/TimeStamp.h"
+#include "mozilla/UniquePtrExtensions.h"  // UniqueFreePtr
+#include "mozilla/Utf8.h"
+#include "mozilla/Variant.h"
+
+#include <algorithm>
+#include <chrono>
+#ifdef XP_WIN
+#  include <direct.h>
+#  include <process.h>
+#endif
+#include <errno.h>
+#include <fcntl.h>
+#if defined(XP_WIN)
+#  include <io.h> /* for isatty() */
+#endif
+#include <locale.h>
+#if defined(MALLOC_H)
+#  include MALLOC_H /* for malloc_usable_size, malloc_size, _msize */
+#endif
+#include <ctime>
+#include <math.h>
+#ifndef __wasi__
+#  include <signal.h>
+#endif
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <utility>
+#ifdef XP_UNIX
+#  ifndef __wasi__
+#    include <sys/mman.h>
+#    include <sys/wait.h>
+#  endif
+#  include <sys/stat.h>
+#  include <unistd.h>
+#endif
+#ifdef XP_LINUX
+#  include <sys/prctl.h>
+#endif
+
+#include "jsapi.h"
+#include "jsfriendapi.h"
+#include "jstypes.h"
+#ifndef JS_WITHOUT_NSPR
+#  include "prerror.h"
+#  include "prlink.h"
+#endif
+
+#include "builtin/Array.h"
+#include "builtin/MapObject.h"
+#include "builtin/ModuleObject.h"
+#include "builtin/RegExp.h"
+#include "builtin/TestingFunctions.h"
+#include "builtin/TestingUtility.h"  // js::ParseCompileOptions, js::ParseDebugMetadata, js::CreateScriptPrivate
+#include "debugger/DebugAPI.h"
+#include "frontend/BytecodeCompilation.h"
+#include "frontend/BytecodeCompiler.h"
+#include "frontend/CompilationStencil.h"
+#ifdef JS_ENABLE_SMOOSH
+#  include "frontend/Frontend2.h"
+#endif
+#include "frontend/FrontendContext.h"  // AutoReportFrontendContext
+#include "frontend/ModuleSharedContext.h"
+#include "frontend/Parser.h"
+#include "frontend/ScopeBindingCache.h"  // js::frontend::ScopeBindingCache
+#include "frontend/SourceNotes.h"  // SrcNote, SrcNoteType, SrcNoteIterator
+#include "gc/PublicIterators.h"
+#ifdef DEBUG
+#  include "irregexp/RegExpAPI.h"
+#endif
+#include "gc/GC-inl.h"  // ZoneCellIter
+
+#ifdef JS_SIMULATOR_ARM
+#  include "jit/arm/Simulator-arm.h"
+#endif
+#ifdef JS_SIMULATOR_MIPS32
+#  include "jit/mips32/Simulator-mips32.h"
+#endif
+#ifdef JS_SIMULATOR_MIPS64
+#  include "jit/mips64/Simulator-mips64.h"
+#endif
+#ifdef JS_SIMULATOR_LOONG64
+#  include "jit/loong64/Simulator-loong64.h"
+#endif
+#include "jit/CacheIRHealth.h"
+#include "jit/InlinableNatives.h"
+#include "jit/Ion.h"
+#include "jit/JitcodeMap.h"
+#include "jit/shared/CodeGenerator-shared.h"
+#include "js/Array.h"        // JS::NewArrayObject
+#include "js/ArrayBuffer.h"  // JS::{CreateMappedArrayBufferContents,NewMappedArrayBufferWithContents,IsArrayBufferObject,GetArrayBufferLengthAndData}
+#include "js/BuildId.h"      // JS::BuildIdCharVector, JS::SetProcessBuildIdOp
+#include "js/CallAndConstruct.h"  // JS::Call, JS::IsCallable, JS_CallFunction, JS_CallFunctionValue
+#include "js/CharacterEncoding.h"  // JS::StringIsASCII
+#include "js/CompilationAndEvaluation.h"
+#include "js/CompileOptions.h"
+#include "js/ContextOptions.h"  // JS::ContextOptions{,Ref}
+#include "js/Debug.h"
+#include "js/Equality.h"                   // JS::SameValue
+#include "js/ErrorReport.h"                // JS::PrintError
+#include "js/Exception.h"                  // JS::StealPendingExceptionStack
+#include "js/experimental/CodeCoverage.h"  // js::EnableCodeCoverage
+#include "js/experimental/CTypes.h"        // JS::InitCTypesClass
+#include "js/experimental/Intl.h"  // JS::AddMoz{DateTimeFormat,DisplayNames}Constructor
+#include "js/experimental/JitInfo.h"  // JSJit{Getter,Setter,Method}CallArgs, JSJitGetterInfo, JSJit{Getter,Setter}Op, JSJitInfo
+#include "js/experimental/JSStencil.h"  // JS::Stencil, JS::CompileToStencilOffThread, JS::FinishCompileToStencilOffThread
+#include "js/experimental/SourceHook.h"  // js::{Set,Forget,}SourceHook
+#include "js/experimental/TypedData.h"   // JS_NewUint8Array
+#include "js/friend/DumpFunctions.h"     // JS::FormatStackDump
+#include "js/friend/ErrorMessages.h"     // js::GetErrorMessage, JSMSG_*
+#include "js/friend/StackLimits.h"       // js::AutoCheckRecursionLimit
+#include "js/friend/WindowProxy.h"  // js::IsWindowProxy, js::SetWindowProxyClass, js::ToWindowProxyIfWindow, js::ToWindowIfWindowProxy
+#include "js/GCAPI.h"               // JS::AutoCheckCannotGC
+#include "js/GCVector.h"
+#include "js/GlobalObject.h"
+#include "js/Initialization.h"
+#include "js/Interrupt.h"
+#include "js/JSON.h"
+#include "js/MemoryCallbacks.h"
+#include "js/MemoryFunctions.h"
+#include "js/Modules.h"  // JS::GetModulePrivate, JS::SetModule{DynamicImport,Metadata,Resolve}Hook, JS::SetModulePrivate
+#include "js/Object.h"  // JS::GetClass, JS::GetCompartment, JS::GetReservedSlot, JS::SetReservedSlot
+#include "js/Principals.h"
+#include "js/Printf.h"
+#include "js/PropertyAndElement.h"  // JS_DefineElement, JS_DefineFunction, JS_DefineFunctions, JS_DefineProperties, JS_DefineProperty, JS_GetElement, JS_GetProperty, JS_GetPropertyById, JS_HasProperty, JS_SetElement, JS_SetProperty, JS_SetPropertyById
+#include "js/PropertySpec.h"
+#include "js/Realm.h"
+#include "js/RegExp.h"  // JS::ObjectIsRegExp
+#include "js/ScriptPrivate.h"
+#include "js/SourceText.h"
+#include "js/StableStringChars.h"
+#include "js/Stack.h"
+#include "js/StreamConsumer.h"
+#include "js/StructuredClone.h"
+#include "js/SweepingAPI.h"
+#include "js/Transcoding.h"  // JS::TranscodeBuffer, JS::TranscodeRange
+#include "js/Warnings.h"     // JS::SetWarningReporter
+#include "js/WasmModule.h"   // JS::WasmModule
+#include "js/Wrapper.h"
+#include "proxy/DeadObjectProxy.h"  // js::IsDeadProxyObject
+#include "shell/jsoptparse.h"
+#include "shell/jsshell.h"
+#include "shell/OSObject.h"
+#include "shell/ShellModuleObjectWrapper.h"
+#include "shell/WasmTesting.h"
+#include "threading/ConditionVariable.h"
+#include "threading/ExclusiveData.h"
+#include "threading/LockGuard.h"
+#include "threading/Thread.h"
+#include "util/CompleteFile.h"  // js::FileContents, js::ReadCompleteFile
+#include "util/DifferentialTesting.h"
+#include "util/StringBuffer.h"
+#include "util/Text.h"
+#include "util/WindowsWrapper.h"
+#include "vm/ArgumentsObject.h"
+#include "vm/Compression.h"
+#include "vm/ErrorObject.h"
+#include "vm/ErrorReporting.h"
+#include "vm/HelperThreads.h"
+#include "vm/JSAtom.h"
+#include "vm/JSContext.h"
+#include "vm/JSFunction.h"
+#include "vm/JSObject.h"
+#include "vm/JSScript.h"
+#include "vm/ModuleBuilder.h"  // js::ModuleBuilder
+#include "vm/Modules.h"
+#include "vm/Monitor.h"
+#include "vm/MutexIDs.h"
+#include "vm/Printer.h"        // QuoteString
+#include "vm/PromiseObject.h"  // js::PromiseObject
+#include "vm/Shape.h"
+#include "vm/SharedArrayObject.h"
+#include "vm/StencilObject.h"  // js::StencilObject
+#include "vm/Time.h"
+#include "vm/ToSource.h"  // js::ValueToSource
+#include "vm/TypedArrayObject.h"
+#include "vm/WrapperObject.h"
+#include "wasm/WasmJS.h"
+
+#include "vm/Compartment-inl.h"
+#include "vm/ErrorObject-inl.h"
+#include "vm/Interpreter-inl.h"
+#include "vm/JSObject-inl.h"
+#include "vm/Realm-inl.h"
+#include "vm/Stack-inl.h"
+
+using namespace js;
+using namespace js::cli;
+using namespace js::shell;
+
+using JS::AutoStableStringChars;
+using JS::CompileOptions;
+
+using js::shell::RCFile;
+
+using mozilla::ArrayEqual;
+using mozilla::AsVariant;
+using mozilla::Atomic;
+using mozilla::MakeScopeExit;
+using mozilla::Maybe;
+using mozilla::Nothing;
+using mozilla::NumberEqualsInt32;
+using mozilla::TimeDuration;
+using mozilla::TimeStamp;
+using mozilla::Utf8Unit;
+using mozilla::Variant;
+
+#ifdef FUZZING_JS_FUZZILLI
+#  define REPRL_CRFD 100
+#  define REPRL_CWFD 101
+#  define REPRL_DRFD 102
+#  define REPRL_DWFD 103
+
+#  define SHM_SIZE 0x100000
+#  define MAX_EDGES ((SHM_SIZE - 4) * 8)
+
+struct shmem_data {
+  uint32_t num_edges;
+  unsigned char edges[];
+};
+
+struct shmem_data* __shmem;
+
+uint32_t *__edges_start, *__edges_stop;
+void __sanitizer_cov_reset_edgeguards() {
+  uint64_t N = 0;
+  for (uint32_t* x = __edges_start; x < __edges_stop && N < MAX_EDGES; x++)
+    *x = ++N;
+}
+
+extern "C" void __sanitizer_cov_trace_pc_guard_init(uint32_t* start,
+                                                    uint32_t* stop) {
+  // Avoid duplicate initialization
+  if (start == stop || *start) return;
+
+  if (__edges_start != NULL || __edges_stop != NULL) {
+    fprintf(stderr,
+            "Coverage instrumentation is only supported for a single module\n");
+    _exit(-1);
+  }
+
+  __edges_start = start;
+  __edges_stop = stop;
+
+  // Map the shared memory region
+  const char* shm_key = getenv("SHM_ID");
+  if (!shm_key) {
+    puts("[COV] no shared memory bitmap available, skipping");
+    __shmem = (struct shmem_data*)malloc(SHM_SIZE);
+  } else {
+    int fd = shm_open(shm_key, O_RDWR, S_IREAD | S_IWRITE);
+    if (fd <= -1) {
+      fprintf(stderr, "Failed to open shared memory region: %s\n",
+              strerror(errno));
+      _exit(-1);
+    }
+
+    __shmem = (struct shmem_data*)mmap(0, SHM_SIZE, PROT_READ | PROT_WRITE,
+                                       MAP_SHARED, fd, 0);
+    if (__shmem == MAP_FAILED) {
+      fprintf(stderr, "Failed to mmap shared memory region\n");
+      _exit(-1);
+    }
+  }
+
+  __sanitizer_cov_reset_edgeguards();
+
+  __shmem->num_edges = stop - start;
+  printf("[COV] edge counters initialized. Shared memory: %s with %u edges\n",
+         shm_key, __shmem->num_edges);
+}
+
+extern "C" void __sanitizer_cov_trace_pc_guard(uint32_t* guard) {
+  // There's a small race condition here: if this function executes in two
+  // threads for the same edge at the same time, the first thread might disable
+  // the edge (by setting the guard to zero) before the second thread fetches
+  // the guard value (and thus the index). However, our instrumentation ignores
+  // the first edge (see libcoverage.c) and so the race is unproblematic.
+  uint32_t index = *guard;
+  // If this function is called before coverage instrumentation is properly
+  // initialized we want to return early.
+  if (!index) return;
+  __shmem->edges[index / 8] |= 1 << (index % 8);
+  *guard = 0;
+}
+#endif /* FUZZING_JS_FUZZILLI */
+
+enum JSShellExitCode {
+  EXITCODE_RUNTIME_ERROR = 3,
+  EXITCODE_FILE_NOT_FOUND = 4,
+  EXITCODE_OUT_OF_MEMORY = 5,
+  EXITCODE_TIMEOUT = 6
+};
+
+/*
+ * Limit the timeout to 30 minutes to prevent an overflow on platfoms
+ * that represent the time internally in microseconds using 32-bit int.
+ */
+static const double MAX_TIMEOUT_SECONDS = 1800.0;
+
+// Not necessarily in sync with the browser
+#ifdef ENABLE_SHARED_MEMORY
+#  define SHARED_MEMORY_DEFAULT 1
+#else
+#  define SHARED_MEMORY_DEFAULT 0
+#endif
+
+// Fuzzing support for JS runtime fuzzing
+#ifdef FUZZING_INTERFACES
+#  include "shell/jsrtfuzzing/jsrtfuzzing.h"
+static bool fuzzDoDebug = !!getenv("MOZ_FUZZ_DEBUG");
+static bool fuzzHaveModule = !!getenv("FUZZER");
+#endif  // FUZZING_INTERFACES
+
+// Code to support GCOV code coverage measurements on standalone shell
+#ifdef MOZ_CODE_COVERAGE
+#  if defined(__GNUC__) && !defined(__clang__)
+extern "C" void __gcov_dump();
+extern "C" void __gcov_reset();
+
+void counters_dump(int) { __gcov_dump(); }
+
+void counters_reset(int) { __gcov_reset(); }
+#  else
+void counters_dump(int) { /* Do nothing */
+}
+
+void counters_reset(int) { /* Do nothing */
+}
+#  endif
+
+static void InstallCoverageSignalHandlers() {
+#  ifndef XP_WIN
+  fprintf(stderr, "[CodeCoverage] Setting handlers for process %d.\n",
+          getpid());
+
+  struct sigaction dump_sa;
+  dump_sa.sa_handler = counters_dump;
+  dump_sa.sa_flags = SA_RESTART;
+  sigemptyset(&dump_sa.sa_mask);
+  mozilla::DebugOnly<int> r1 = sigaction(SIGUSR1, &dump_sa, nullptr);
+  MOZ_ASSERT(r1 == 0, "Failed to install GCOV SIGUSR1 handler");
+
+  struct sigaction reset_sa;
+  reset_sa.sa_handler = counters_reset;
+  reset_sa.sa_flags = SA_RESTART;
+  sigemptyset(&reset_sa.sa_mask);
+  mozilla::DebugOnly<int> r2 = sigaction(SIGUSR2, &reset_sa, nullptr);
+  MOZ_ASSERT(r2 == 0, "Failed to install GCOV SIGUSR2 handler");
+#  endif
+}
+#endif
+
+// An off-thread parse or decode job.
+class js::shell::OffThreadJob {
+  enum State {
+    RUNNING,   // Working; no token.
+    DONE,      // Finished; have token.
+    CANCELLED  // Cancelled due to error.
+  };
+
+ public:
+  using Source = mozilla::Variant<JS::UniqueTwoByteChars, JS::TranscodeBuffer>;
+
+  OffThreadJob(ShellContext* sc, Source&& source);
+  ~OffThreadJob();
+
+  void cancel();
+  void markDone(JS::OffThreadToken* newToken);
+  JS::OffThreadToken* waitUntilDone(JSContext* cx);
+
+  char16_t* sourceChars() { return source.as<UniqueTwoByteChars>().get(); }
+  JS::TranscodeBuffer& xdrBuffer() { return source.as<JS::TranscodeBuffer>(); }
+
+ public:
+  const int32_t id;
+
+ private:
+  js::Monitor& monitor;
+  State state;
+  JS::OffThreadToken* token;
+  Source source;
+};
+
+static OffThreadJob* NewOffThreadJob(JSContext* cx, CompileOptions& options,
+                                     OffThreadJob::Source&& source) {
+  ShellContext* sc = GetShellContext(cx);
+  UniquePtr<OffThreadJob> job(cx->new_<OffThreadJob>(sc, std::move(source)));
+  if (!job) {
+    return nullptr;
+  }
+
+  if (!sc->offThreadJobs.append(job.get())) {
+    job->cancel();
+    JS_ReportErrorASCII(cx, "OOM adding off-thread job");
+    return nullptr;
+  }
+
+  return job.release();
+}
+
+static OffThreadJob* GetSingleOffThreadJob(JSContext* cx) {
+  ShellContext* sc = GetShellContext(cx);
+  const auto& jobs = sc->offThreadJobs;
+  if (jobs.empty()) {
+    JS_ReportErrorASCII(cx, "No off-thread jobs are pending");
+    return nullptr;
+  }
+
+  if (jobs.length() > 1) {
+    JS_ReportErrorASCII(
+        cx, "Multiple off-thread jobs are pending: must specify job ID");
+    return nullptr;
+  }
+
+  return jobs[0];
+}
+
+static OffThreadJob* LookupOffThreadJobByID(JSContext* cx, int32_t id) {
+  if (id <= 0) {
+    JS_ReportErrorASCII(cx, "Bad off-thread job ID");
+    return nullptr;
+  }
+
+  ShellContext* sc = GetShellContext(cx);
+  const auto& jobs = sc->offThreadJobs;
+  if (jobs.empty()) {
+    JS_ReportErrorASCII(cx, "No off-thread jobs are pending");
+    return nullptr;
+  }
+
+  OffThreadJob* job = nullptr;
+  for (auto someJob : jobs) {
+    if (someJob->id == id) {
+      job = someJob;
+      break;
+    }
+  }
+
+  if (!job) {
+    JS_ReportErrorASCII(cx, "Off-thread job not found");
+    return nullptr;
+  }
+
+  return job;
+}
+
+static OffThreadJob* LookupOffThreadJobForArgs(JSContext* cx,
+                                               const CallArgs& args,
+                                               size_t arg) {
+  // If the optional ID argument isn't present, get the single pending job.
+  if (args.length() <= arg) {
+    return GetSingleOffThreadJob(cx);
+  }
+
+  // Lookup the job using the specified ID.
+  int32_t id = 0;
+  RootedValue value(cx, args[arg]);
+  if (!ToInt32(cx, value, &id)) {
+    return nullptr;
+  }
+
+  return LookupOffThreadJobByID(cx, id);
+}
+
+static void DeleteOffThreadJob(JSContext* cx, OffThreadJob* job) {
+  ShellContext* sc = GetShellContext(cx);
+  for (size_t i = 0; i < sc->offThreadJobs.length(); i++) {
+    if (sc->offThreadJobs[i] == job) {
+      sc->offThreadJobs.erase(&sc->offThreadJobs[i]);
+      js_delete(job);
+      return;
+    }
+  }
+
+  MOZ_CRASH("Off-thread job not found");
+}
+
+static void CancelOffThreadJobsForContext(JSContext* cx) {
+  // Parse jobs may be blocked waiting on GC.
+  gc::FinishGC(cx);
+
+  // Wait for jobs belonging to this context.
+  ShellContext* sc = GetShellContext(cx);
+  while (!sc->offThreadJobs.empty()) {
+    OffThreadJob* job = sc->offThreadJobs.popCopy();
+    job->waitUntilDone(cx);
+    js_delete(job);
+  }
+}
+
+static void CancelOffThreadJobsForRuntime(JSContext* cx) {
+  // Parse jobs may be blocked waiting on GC.
+  gc::FinishGC(cx);
+
+  // Cancel jobs belonging to this runtime.
+  CancelOffThreadParses(cx->runtime());
+  ShellContext* sc = GetShellContext(cx);
+  while (!sc->offThreadJobs.empty()) {
+    js_delete(sc->offThreadJobs.popCopy());
+  }
+}
+
+mozilla::Atomic<int32_t> gOffThreadJobSerial(1);
+
+OffThreadJob::OffThreadJob(ShellContext* sc, Source&& source)
+    : id(gOffThreadJobSerial++),
+      monitor(sc->offThreadMonitor),
+      state(RUNNING),
+      token(nullptr),
+      source(std::move(source)) {
+  MOZ_RELEASE_ASSERT(id > 0, "Off-thread job IDs exhausted");
+}
+
+OffThreadJob::~OffThreadJob() { MOZ_ASSERT(state != RUNNING); }
+
+void OffThreadJob::cancel() {
+  MOZ_ASSERT(state == RUNNING);
+  MOZ_ASSERT(!token);
+
+  state = CANCELLED;
+}
+
+void OffThreadJob::markDone(JS::OffThreadToken* newToken) {
+  AutoLockMonitor alm(monitor);
+  MOZ_ASSERT(state == RUNNING);
+  MOZ_ASSERT(!token);
+  MOZ_ASSERT(newToken);
+
+  token = newToken;
+  state = DONE;
+  alm.notifyAll();
+}
+
+JS::OffThreadToken* OffThreadJob::waitUntilDone(JSContext* cx) {
+  AutoLockMonitor alm(monitor);
+  MOZ_ASSERT(state != CANCELLED);
+
+  while (state != DONE) {
+    alm.wait();
+  }
+
+  MOZ_ASSERT(token);
+  return token;
+}
+
+struct ShellCompartmentPrivate {
+  GCPtr<JSObject*> grayRoot;
+};
+
+struct MOZ_STACK_CLASS EnvironmentPreparer
+    : public js::ScriptEnvironmentPreparer {
+  explicit EnvironmentPreparer(JSContext* cx) {
+    js::SetScriptEnvironmentPreparer(cx, this);
+  }
+  void invoke(JS::HandleObject global, Closure& closure) override;
+};
+
+const char* shell::selfHostedXDRPath = nullptr;
+bool shell::encodeSelfHostedCode = false;
+bool shell::enableCodeCoverage = false;
+bool shell::enableDisassemblyDumps = false;
+bool shell::offthreadCompilation = false;
+JS::DelazificationOption shell::defaultDelazificationMode =
+    JS::DelazificationOption::OnDemandOnly;
+bool shell::enableAsmJS = false;
+bool shell::enableWasm = false;
+bool shell::enableSharedMemory = SHARED_MEMORY_DEFAULT;
+bool shell::enableWasmBaseline = false;
+bool shell::enableWasmOptimizing = false;
+
+#define WASM_DEFAULT_FEATURE(NAME, ...) bool shell::enableWasm##NAME = true;
+#define WASM_EXPERIMENTAL_FEATURE(NAME, ...) \
+  bool shell::enableWasm##NAME = false;
+JS_FOR_WASM_FEATURES(WASM_DEFAULT_FEATURE, WASM_DEFAULT_FEATURE,
+                     WASM_EXPERIMENTAL_FEATURE);
+#undef WASM_DEFAULT_FEATURE
+#undef WASM_EXPERIMENTAL_FEATURE
+
+bool shell::enableWasmVerbose = false;
+bool shell::enableTestWasmAwaitTier2 = false;
+bool shell::enableSourcePragmas = true;
+bool shell::enableAsyncStacks = false;
+bool shell::enableAsyncStackCaptureDebuggeeOnly = false;
+bool shell::enableWeakRefs = false;
+bool shell::enableToSource = false;
+bool shell::enablePropertyErrorMessageFix = false;
+bool shell::enableIteratorHelpers = false;
+bool shell::enableShadowRealms = false;
+#ifdef NIGHTLY_BUILD
+bool shell::enableArrayGrouping = false;
+bool shell::enableArrayFromAsync = false;
+#endif
+#ifdef ENABLE_CHANGE_ARRAY_BY_COPY
+bool shell::enableChangeArrayByCopy = false;
+#endif
+#ifdef ENABLE_NEW_SET_METHODS
+bool shell::enableNewSetMethods = true;
+#endif
+bool shell::enableImportAssertions = false;
+#ifdef JS_GC_ZEAL
+uint32_t shell::gZealBits = 0;
+uint32_t shell::gZealFrequency = 0;
+#endif
+bool shell::printTiming = false;
+RCFile* shell::gErrFile = nullptr;
+RCFile* shell::gOutFile = nullptr;
+bool shell::reportWarnings = true;
+bool shell::compileOnly = false;
+bool shell::disableOOMFunctions = false;
+bool shell::defaultToSameCompartment = true;
+
+bool shell::useFdlibmForSinCosTan = false;
+
+#ifdef DEBUG
+bool shell::dumpEntrainedVariables = false;
+bool shell::OOM_printAllocationCount = false;
+#endif
+
+UniqueChars shell::processWideModuleLoadPath;
+
+static bool SetTimeoutValue(JSContext* cx, double t);
+
+static void KillWatchdog(JSContext* cx);
+
+static bool ScheduleWatchdog(JSContext* cx, double t);
+
+static void CancelExecution(JSContext* cx);
+
+enum class ShellGlobalKind {
+  GlobalObject,
+  WindowProxy,
+};
+
+static JSObject* NewGlobalObject(JSContext* cx, JS::RealmOptions& options,
+                                 JSPrincipals* principals, ShellGlobalKind kind,
+                                 bool immutablePrototype);
+
+/*
+ * A toy WindowProxy class for the shell. This is intended for testing code
+ * where global |this| is a WindowProxy. All requests are forwarded to the
+ * underlying global and no navigation is supported.
+ */
+const JSClass ShellWindowProxyClass =
+    PROXY_CLASS_DEF("ShellWindowProxy", JSCLASS_HAS_RESERVED_SLOTS(1));
+
+JSObject* NewShellWindowProxy(JSContext* cx, JS::HandleObject global) {
+  MOZ_ASSERT(global->is<GlobalObject>());
+
+  js::WrapperOptions options;
+  options.setClass(&ShellWindowProxyClass);
+
+  JSAutoRealm ar(cx, global);
+  JSObject* obj =
+      js::Wrapper::New(cx, global, &js::Wrapper::singleton, options);
+  MOZ_ASSERT_IF(obj, js::IsWindowProxy(obj));
+  return obj;
+}
+
+/*
+ * A toy principals type for the shell.
+ *
+ * In the shell, a principal is simply a 32-bit mask: P subsumes Q if the
+ * set bits in P are a superset of those in Q. Thus, the principal 0 is
+ * subsumed by everything, and the principal ~0 subsumes everything.
+ *
+ * As a special case, a null pointer as a principal is treated like 0xffff.
+ *
+ * The 'newGlobal' function takes an option indicating which principal the
+ * new global should have; 'evaluate' does for the new code.
+ */
+class ShellPrincipals final : public JSPrincipals {
+  uint32_t bits;
+
+  static uint32_t getBits(JSPrincipals* p) {
+    if (!p) {
+      return 0xffff;
+    }
+    return static_cast<ShellPrincipals*>(p)->bits;
+  }
+
+ public:
+  explicit ShellPrincipals(uint32_t bits, int32_t refcount = 0) : bits(bits) {
+    this->refcount = refcount;
+  }
+
+  bool write(JSContext* cx, JSStructuredCloneWriter* writer) override {
+    // The shell doesn't have a read principals hook, so it doesn't really
+    // matter what we write here, but we have to write something so the
+    // fuzzer is happy.
+    return JS_WriteUint32Pair(writer, bits, 0);
+  }
+
+  bool isSystemOrAddonPrincipal() override { return true; }
+
+  static void destroy(JSPrincipals* principals) {
+    MOZ_ASSERT(principals != &fullyTrusted);
+    MOZ_ASSERT(principals->refcount == 0);
+    js_delete(static_cast<const ShellPrincipals*>(principals));
+  }
+
+  static bool subsumes(JSPrincipals* first, JSPrincipals* second) {
+    uint32_t firstBits = getBits(first);
+    uint32_t secondBits = getBits(second);
+    return (firstBits | secondBits) == firstBits;
+  }
+
+  static JSSecurityCallbacks securityCallbacks;
+
+  // Fully-trusted principals singleton.
+  static ShellPrincipals fullyTrusted;
+};
+
+JSSecurityCallbacks ShellPrincipals::securityCallbacks = {
+    nullptr,  // contentSecurityPolicyAllows
+    subsumes};
+
+// The fully-trusted principal subsumes all other principals.
+ShellPrincipals ShellPrincipals::fullyTrusted(-1, 1);
+
+#ifdef EDITLINE
+extern "C" {
+extern MOZ_EXPORT char* readline(const char* prompt);
+extern MOZ_EXPORT void add_history(char* line);
+}  // extern "C"
+#endif
+
+ShellContext::ShellContext(JSContext* cx)
+    : isWorker(false),
+      lastWarningEnabled(false),
+      trackUnhandledRejections(true),
+      timeoutInterval(-1.0),
+      startTime(PRMJ_Now()),
+      serviceInterrupt(false),
+      haveInterruptFunc(false),
+      interruptFunc(cx, NullValue()),
+      lastWarning(cx, NullValue()),
+      promiseRejectionTrackerCallback(cx, NullValue()),
+      unhandledRejectedPromises(cx),
+      watchdogLock(mutexid::ShellContextWatchdog),
+      exitCode(0),
+      quitting(false),
+      readLineBufPos(0),
+      errFilePtr(nullptr),
+      outFilePtr(nullptr),
+      offThreadMonitor(mutexid::ShellOffThreadState),
+      finalizationRegistryCleanupCallbacks(cx) {}
+
+ShellContext::~ShellContext() { MOZ_ASSERT(offThreadJobs.empty()); }
+
+ShellContext* js::shell::GetShellContext(JSContext* cx) {
+  ShellContext* sc = static_cast<ShellContext*>(JS_GetContextPrivate(cx));
+  MOZ_ASSERT(sc);
+  return sc;
+}
+
+static bool TraceGrayRoots(JSTracer* trc, SliceBudget& budget, void* data) {
+  JSRuntime* rt = trc->runtime();
+  for (ZonesIter zone(rt, SkipAtoms); !zone.done(); zone.next()) {
+    for (CompartmentsInZoneIter comp(zone); !comp.done(); comp.next()) {
+      auto priv = static_cast<ShellCompartmentPrivate*>(
+          JS_GetCompartmentPrivate(comp.get()));
+      if (priv) {
+        TraceNullableEdge(trc, &priv->grayRoot, "test gray root");
+      }
+    }
+  }
+
+  return true;
+}
+
+static mozilla::UniqueFreePtr<char[]> GetLine(FILE* file, const char* prompt) {
+#ifdef EDITLINE
+  /*
+   * Use readline only if file is stdin, because there's no way to specify
+   * another handle.  Are other filehandles interactive?
+   */
+  if (file == stdin) {
+    mozilla::UniqueFreePtr<char[]> linep(readline(prompt));
+    /*
+     * We set it to zero to avoid complaining about inappropriate ioctl
+     * for device in the case of EOF. Looks like errno == 251 if line is
+     * finished with EOF and errno == 25 (EINVAL on Mac) if there is
+     * nothing left to read.
+     */
+    if (errno == 251 || errno == 25 || errno == EINVAL) {
+      errno = 0;
+    }
+    if (!linep) {
+      return nullptr;
+    }
+    if (linep[0] != '\0') {
+      add_history(linep.get());
+    }
+    return linep;
+  }
+#endif
+
+  size_t len = 0;
+  if (*prompt != '\0' && gOutFile->isOpen()) {
+    fprintf(gOutFile->fp, "%s", prompt);
+    fflush(gOutFile->fp);
+  }
+
+  size_t size = 80;
+  mozilla::UniqueFreePtr<char[]> buffer(static_cast<char*>(malloc(size)));
+  if (!buffer) {
+    return nullptr;
+  }
+
+  char* current = buffer.get();
+  do {
+    while (true) {
+      if (fgets(current, size - len, file)) {
+        break;
+      }
+      if (errno != EINTR) {
+        return nullptr;
+      }
+    }
+
+    len += strlen(current);
+    char* t = buffer.get() + len - 1;
+    if (*t == '\n') {
+      /* Line was read. We remove '\n' and exit. */
+      *t = '\0';
+      break;
+    }
+
+    if (len + 1 == size) {
+      size = size * 2;
+      char* raw = buffer.release();
+      char* tmp = static_cast<char*>(realloc(raw, size));
+      if (!tmp) {
+        free(raw);
+        return nullptr;
+      }
+      buffer.reset(tmp);
+    }
+    current = buffer.get() + len;
+  } while (true);
+  return buffer;
+}
+
+static bool ShellInterruptCallback(JSContext* cx) {
+  ShellContext* sc = GetShellContext(cx);
+  if (!sc->serviceInterrupt) {
+    return true;
+  }
+
+  // Reset serviceInterrupt. CancelExecution or InterruptIf will set it to
+  // true to distinguish watchdog or user triggered interrupts.
+  // Do this first to prevent other interrupts that may occur while the
+  // user-supplied callback is executing from re-entering the handler.
+  sc->serviceInterrupt = false;
+
+  bool result;
+  if (sc->haveInterruptFunc) {
+    bool wasAlreadyThrowing = cx->isExceptionPending();
+    JS::AutoSaveExceptionState savedExc(cx);
+    JSAutoRealm ar(cx, &sc->interruptFunc.toObject());
+    RootedValue rval(cx);
+
+    // Report any exceptions thrown by the JS interrupt callback, but do
+    // *not* keep it on the cx. The interrupt handler is invoked at points
+    // that are not expected to throw catchable exceptions, like at
+    // JSOp::RetRval.
+    //
+    // If the interrupted JS code was already throwing, any exceptions
+    // thrown by the interrupt handler are silently swallowed.
+    {
+      Maybe<AutoReportException> are;
+      if (!wasAlreadyThrowing) {
+        are.emplace(cx);
+      }
+      result = JS_CallFunctionValue(cx, nullptr, sc->interruptFunc,
+                                    JS::HandleValueArray::empty(), &rval);
+    }
+    savedExc.restore();
+
+    if (rval.isBoolean()) {
+      result = rval.toBoolean();
+    } else {
+      result = false;
+    }
+  } else {
+    result = false;
+  }
+
+  if (!result && sc->exitCode == 0) {
+    static const char msg[] = "Script terminated by interrupt handler.\n";
+    fputs(msg, stderr);
+
+    sc->exitCode = EXITCODE_TIMEOUT;
+  }
+
+  return result;
+}
+
+/*
+ * Some UTF-8 files, notably those written using Notepad, have a Unicode
+ * Byte-Order-Mark (BOM) as their first character. This is useless (byte-order
+ * is meaningless for UTF-8) but causes a syntax error unless we skip it.
+ */
+static void SkipUTF8BOM(FILE* file) {
+  int ch1 = fgetc(file);
+  int ch2 = fgetc(file);
+  int ch3 = fgetc(file);
+
+  // Skip the BOM
+  if (ch1 == 0xEF && ch2 == 0xBB && ch3 == 0xBF) {
+    return;
+  }
+
+  // No BOM - revert
+  if (ch3 != EOF) {
+    ungetc(ch3, file);
+  }
+  if (ch2 != EOF) {
+    ungetc(ch2, file);
+  }
+  if (ch1 != EOF) {
+    ungetc(ch1, file);
+  }
+}
+
+void EnvironmentPreparer::invoke(HandleObject global, Closure& closure) {
+  MOZ_ASSERT(JS_IsGlobalObject(global));
+
+  JSContext* cx = TlsContext.get();
+  MOZ_ASSERT(!JS_IsExceptionPending(cx));
+
+  AutoRealm ar(cx, global);
+  AutoReportException are(cx);
+  if (!closure(cx)) {
+    return;
+  }
+}
+
+static bool RegisterScriptPathWithModuleLoader(JSContext* cx,
+                                               HandleScript script,
+                                               const char* filename) {
+  // Set the private value associated with a script to a object containing the
+  // script's filename so that the module loader can use it to resolve
+  // relative imports.
+
+  RootedString path(cx, JS_NewStringCopyZ(cx, filename));
+  if (!path) {
+    return false;
+  }
+
+  MOZ_ASSERT(JS::GetScriptPrivate(script).isUndefined());
+  RootedObject infoObject(cx, js::CreateScriptPrivate(cx, path));
+  if (!infoObject) {
+    return false;
+  }
+
+  JS::SetScriptPrivate(script, ObjectValue(*infoObject));
+  return true;
+}
+
+enum class CompileUtf8 {
+  InflateToUtf16,
+  DontInflate,
+};
+
+[[nodiscard]] static bool RunFile(JSContext* cx, const char* filename,
+                                  FILE* file, CompileUtf8 compileMethod,
+                                  bool compileOnly, bool fullParse) {
+  SkipUTF8BOM(file);
+
+  int64_t t1 = PRMJ_Now();
+  RootedScript script(cx);
+
+  {
+    CompileOptions options(cx);
+    options.setIntroductionType("js shell file")
+        .setFileAndLine(filename, 1)
+        .setIsRunOnce(true)
+        .setNoScriptRval(true);
+
+    if (fullParse) {
+      options.setForceFullParse();
+    } else {
+      options.setEagerDelazificationStrategy(defaultDelazificationMode);
+    }
+
+    if (compileMethod == CompileUtf8::DontInflate) {
+      script = JS::CompileUtf8File(cx, options, file);
+    } else {
+      fprintf(stderr, "(compiling '%s' after inflating to UTF-16)\n", filename);
+
+      FileContents buffer(cx);
+      if (!ReadCompleteFile(cx, file, buffer)) {
+        return false;
+      }
+
+      size_t length = buffer.length();
+      auto chars = UniqueTwoByteChars(
+          UTF8CharsToNewTwoByteCharsZ(
+              cx,
+              JS::UTF8Chars(reinterpret_cast<const char*>(buffer.begin()),
+                            buffer.length()),
+              &length, js::MallocArena)
+              .get());
+      if (!chars) {
+        return false;
+      }
+
+      JS::SourceText<char16_t> source;
+      if (!source.init(cx, std::move(chars), length)) {
+        return false;
+      }
+
+      script = JS::Compile(cx, options, source);
+    }
+
+    if (!script) {
+      return false;
+    }
+  }
+
+  if (!RegisterScriptPathWithModuleLoader(cx, script, filename)) {
+    return false;
+  }
+
+#ifdef DEBUG
+  if (dumpEntrainedVariables) {
+    AnalyzeEntrainedVariables(cx, script);
+  }
+#endif
+  if (!compileOnly) {
+    if (!JS_ExecuteScript(cx, script)) {
+      return false;
+    }
+    int64_t t2 = PRMJ_Now() - t1;
+    if (printTiming) {
+      printf("runtime = %.3f ms\n", double(t2) / PRMJ_USEC_PER_MSEC);
+    }
+  }
+  return true;
+}
+
+[[nodiscard]] static bool RunModule(JSContext* cx, const char* filename,
+                                    bool compileOnly) {
+  ShellContext* sc = GetShellContext(cx);
+
+  RootedString path(cx, JS_NewStringCopyZ(cx, filename));
+  if (!path) {
+    return false;
+  }
+
+  path = ResolvePath(cx, path, RootRelative);
+  if (!path) {
+    return false;
+  }
+
+  return sc->moduleLoader->loadRootModule(cx, path);
+}
+
+static void ShellCleanupFinalizationRegistryCallback(JSFunction* doCleanup,
+                                                     JSObject* incumbentGlobal,
+                                                     void* data) {
+  // In the browser this queues a task. Shell jobs correspond to microtasks so
+  // we arrange for cleanup to happen after all jobs/microtasks have run. The
+  // incumbent global is ignored in the shell.
+
+  auto sc = static_cast<ShellContext*>(data);
+  AutoEnterOOMUnsafeRegion oomUnsafe;
+  if (!sc->finalizationRegistryCleanupCallbacks.append(doCleanup)) {
+    oomUnsafe.crash("ShellCleanupFinalizationRegistryCallback");
+  }
+}
+
+// Run any FinalizationRegistry cleanup tasks and return whether any ran.
+static bool MaybeRunFinalizationRegistryCleanupTasks(JSContext* cx) {
+  ShellContext* sc = GetShellContext(cx);
+  MOZ_ASSERT(!sc->quitting);
+
+  Rooted<ShellContext::FunctionVector> callbacks(cx);
+  std::swap(callbacks.get(), sc->finalizationRegistryCleanupCallbacks.get());
+
+  bool ranTasks = false;
+
+  RootedFunction callback(cx);
+  for (JSFunction* f : callbacks) {
+    callback = f;
+
+    AutoRealm ar(cx, f);
+
+    {
+      AutoReportException are(cx);
+      RootedValue unused(cx);
+      (void)JS_CallFunction(cx, nullptr, callback, HandleValueArray::empty(),
+                            &unused);
+    }
+
+    ranTasks = true;
+
+    if (sc->quitting) {
+      break;
+    }
+  }
+
+  return ranTasks;
+}
+
+static bool EnqueueJob(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  if (!IsFunctionObject(args.get(0))) {
+    JS_ReportErrorASCII(cx, "EnqueueJob's first argument must be a function");
+    return false;
+  }
+
+  args.rval().setUndefined();
+
+  RootedObject job(cx, &args[0].toObject());
+  return js::EnqueueJob(cx, job);
+}
+
+static void RunShellJobs(JSContext* cx) {
+  ShellContext* sc = GetShellContext(cx);
+  if (sc->quitting) {
+    return;
+  }
+
+  while (true) {
+    // Run microtasks.
+    js::RunJobs(cx);
+    if (sc->quitting) {
+      return;
+    }
+
+    // Run tasks (only finalization registry clean tasks are possible).
+    bool ranTasks = MaybeRunFinalizationRegistryCleanupTasks(cx);
+    if (!ranTasks) {
+      break;
+    }
+  }
+}
+
+static bool DrainJobQueue(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  if (GetShellContext(cx)->quitting) {
+    JS_ReportErrorASCII(
+        cx, "Mustn't drain the job queue when the shell is quitting");
+    return false;
+  }
+
+  RunShellJobs(cx);
+
+  if (GetShellContext(cx)->quitting) {
+    return false;
+  }
+
+  args.rval().setUndefined();
+  return true;
+}
+
+static bool GlobalOfFirstJobInQueue(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  RootedObject job(cx, cx->internalJobQueue->maybeFront());
+  if (!job) {
+    JS_ReportErrorASCII(cx, "Job queue is empty");
+    return false;
+  }
+
+  RootedObject global(cx, &job->nonCCWGlobal());
+  if (!cx->compartment()->wrap(cx, &global)) {
+    return false;
+  }
+
+  args.rval().setObject(*global);
+  return true;
+}
+
+static bool TrackUnhandledRejections(JSContext* cx, JS::HandleObject promise,
+                                     JS::PromiseRejectionHandlingState state) {
+  ShellContext* sc = GetShellContext(cx);
+  if (!sc->trackUnhandledRejections) {
+    return true;
+  }
+
+#if defined(DEBUG) || defined(JS_OOM_BREAKPOINT)
+  if (cx->runningOOMTest) {
+    // When OOM happens, we cannot reliably track the set of unhandled
+    // promise rejections. Throw error only when simulated OOM is used
+    // *and* promises are used in the test.
+    JS_ReportErrorASCII(
+        cx,
+        "Can't track unhandled rejections while running simulated OOM "
+        "test. Call ignoreUnhandledRejections before using oomTest etc.");
+    return false;
+  }
+#endif
+
+  if (!sc->unhandledRejectedPromises) {
+    sc->unhandledRejectedPromises = SetObject::create(cx);
+    if (!sc->unhandledRejectedPromises) {
+      return false;
+    }
+  }
+
+  RootedValue promiseVal(cx, ObjectValue(*promise));
+
+  AutoRealm ar(cx, sc->unhandledRejectedPromises);
+  if (!cx->compartment()->wrap(cx, &promiseVal)) {
+    return false;
+  }
+
+  switch (state) {
+    case JS::PromiseRejectionHandlingState::Unhandled:
+      if (!SetObject::add(cx, sc->unhandledRejectedPromises, promiseVal)) {
+        return false;
+      }
+      break;
+    case JS::PromiseRejectionHandlingState::Handled:
+      bool deleted = false;
+      if (!SetObject::delete_(cx, sc->unhandledRejectedPromises, promiseVal,
+                              &deleted)) {
+        return false;
+      }
+      // We can't MOZ_ASSERT(deleted) here, because it's possible we failed to
+      // add the promise in the first place, due to OOM.
+      break;
+  }
+
+  return true;
+}
+
+static void ForwardingPromiseRejectionTrackerCallback(
+    JSContext* cx, bool mutedErrors, JS::HandleObject promise,
+    JS::PromiseRejectionHandlingState state, void* data) {
+  AutoReportException are(cx);
+
+  if (!TrackUnhandledRejections(cx, promise, state)) {
+    return;
+  }
+
+  RootedValue callback(cx,
+                       GetShellContext(cx)->promiseRejectionTrackerCallback);
+  if (callback.isNull()) {
+    return;
+  }
+
+  AutoRealm ar(cx, &callback.toObject());
+
+  FixedInvokeArgs<2> args(cx);
+  args[0].setObject(*promise);
+  args[1].setInt32(static_cast<int32_t>(state));
+
+  if (!JS_WrapValue(cx, args[0])) {
+    return;
+  }
+
+  RootedValue rval(cx);
+  (void)Call(cx, callback, UndefinedHandleValue, args, &rval);
+}
+
+static bool SetPromiseRejectionTrackerCallback(JSContext* cx, unsigned argc,
+                                               Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  if (!IsFunctionObject(args.get(0))) {
+    JS_ReportErrorASCII(
+        cx,
+        "setPromiseRejectionTrackerCallback expects a function as its sole "
+        "argument");
+    return false;
+  }
+
+  GetShellContext(cx)->promiseRejectionTrackerCallback = args[0];
+
+  args.rval().setUndefined();
+  return true;
+}
+
+// clang-format off
+static const char* telemetryNames[static_cast<int>(JSMetric::Count)] = {
+#define LIT(NAME, _) #NAME,
+  FOR_EACH_JS_METRIC(LIT)
+#undef LIT
+};
+// clang-format on
+
+// Telemetry can be executed from multiple threads, and the callback is
+// responsible to avoid contention on the recorded telemetry data.
+static Mutex* telemetryLock = nullptr;
+class MOZ_RAII AutoLockTelemetry : public LockGuard<Mutex> {
+  using Base = LockGuard<Mutex>;
+
+ public:
+  AutoLockTelemetry() : Base(*telemetryLock) { MOZ_ASSERT(telemetryLock); }
+};
+
+using TelemetryData = uint32_t;
+using TelemetryVec = Vector<TelemetryData, 0, SystemAllocPolicy>;
+static mozilla::Array<TelemetryVec, size_t(JSMetric::Count)> telemetryResults;
+static void AccumulateTelemetryDataCallback(JSMetric id, uint32_t sample) {
+  AutoLockTelemetry alt;
+  // We ignore OOMs while writting teleemtry data.
+  if (telemetryResults[static_cast<int>(id)].append(sample)) {
+    return;
+  }
+}
+
+static void WriteTelemetryDataToDisk(const char* dir) {
+  const int pathLen = 260;
+  char fileName[pathLen];
+  Fprinter output;
+  auto initOutput = [&](const char* name) -> bool {
+    if (SprintfLiteral(fileName, "%s%s.csv", dir, name) >= pathLen) {
+      return false;
+    }
+    FILE* file = fopen(fileName, "a");
+    if (!file) {
+      return false;
+    }
+    output.init(file);
+    return true;
+  };
+
+  for (size_t id = 0; id < size_t(JSMetric::Count); id++) {
+    auto clear = MakeScopeExit([&] { telemetryResults[id].clearAndFree(); });
+    if (!initOutput(telemetryNames[id])) {
+      continue;
+    }
+    for (uint32_t data : telemetryResults[id]) {
+      output.printf("%u\n", data);
+    }
+    output.finish();
+  }
+}
+
+#undef MAP_TELEMETRY
+
+static bool BoundToAsyncStack(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  RootedValue function(cx, GetFunctionNativeReserved(&args.callee(), 0));
+  RootedObject options(
+      cx, &GetFunctionNativeReserved(&args.callee(), 1).toObject());
+
+  Rooted<SavedFrame*> stack(cx, nullptr);
+  bool isExplicit;
+
+  RootedValue v(cx);
+
+  if (!JS_GetProperty(cx, options, "stack", &v)) {
+    return false;
+  }
+  if (!v.isObject() || !v.toObject().is<SavedFrame>()) {
+    JS_ReportErrorASCII(cx,
+                        "The 'stack' property must be a SavedFrame object.");
+    return false;
+  }
+  stack = &v.toObject().as<SavedFrame>();
+
+  if (!JS_GetProperty(cx, options, "cause", &v)) {
+    return false;
+  }
+  RootedString causeString(cx, ToString(cx, v));
+  if (!causeString) {
+    MOZ_ASSERT(cx->isExceptionPending());
+    return false;
+  }
+
+  UniqueChars cause = JS_EncodeStringToUTF8(cx, causeString);
+  if (!cause) {
+    MOZ_ASSERT(cx->isExceptionPending());
+    return false;
+  }
+
+  if (!JS_GetProperty(cx, options, "explicit", &v)) {
+    return false;
+  }
+  isExplicit = v.isUndefined() ? true : ToBoolean(v);
+
+  auto kind =
+      (isExplicit ? JS::AutoSetAsyncStackForNewCalls::AsyncCallKind::EXPLICIT
+                  : JS::AutoSetAsyncStackForNewCalls::AsyncCallKind::IMPLICIT);
+
+  JS::AutoSetAsyncStackForNewCalls asasfnckthxbye(cx, stack, cause.get(), kind);
+  return Call(cx, UndefinedHandleValue, function, JS::HandleValueArray::empty(),
+              args.rval());
+}
+
+static bool BindToAsyncStack(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  if (args.length() != 2) {
+    JS_ReportErrorASCII(cx, "bindToAsyncStack takes exactly two arguments.");
+    return false;
+  }
+
+  if (!args[0].isObject() || !IsCallable(args[0])) {
+    JS_ReportErrorASCII(
+        cx, "bindToAsyncStack's first argument should be a function.");
+    return false;
+  }
+
+  if (!args[1].isObject()) {
+    JS_ReportErrorASCII(
+        cx, "bindToAsyncStack's second argument should be an object.");
+    return false;
+  }
+
+  RootedFunction bound(cx, NewFunctionWithReserved(cx, BoundToAsyncStack, 0, 0,
+                                                   "bindToAsyncStack thunk"));
+  if (!bound) {
+    return false;
+  }
+  SetFunctionNativeReserved(bound, 0, args[0]);
+  SetFunctionNativeReserved(bound, 1, args[1]);
+
+  args.rval().setObject(*bound);
+  return true;
+}
+
+#ifdef JS_HAS_INTL_API
+static bool AddIntlExtras(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+  if (!args.get(0).isObject()) {
+    JS_ReportErrorASCII(cx, "addIntlExtras must be passed an object");
+    return false;
+  }
+  JS::RootedObject intl(cx, &args[0].toObject());
+
+  static const JSFunctionSpec funcs[] = {
+      JS_SELF_HOSTED_FN("getCalendarInfo", "Intl_getCalendarInfo", 1, 0),
+      JS_FS_END};
+
+  if (!JS_DefineFunctions(cx, intl, funcs)) {
+    return false;
+  }
+
+  if (!JS::AddMozDateTimeFormatConstructor(cx, intl)) {
+    return false;
+  }
+
+  if (!JS::AddMozDisplayNamesConstructor(cx, intl)) {
+    return false;
+  }
+
+  args.rval().setUndefined();
+  return true;
+}
+#endif  // JS_HAS_INTL_API
+
+[[nodiscard]] static bool EvalUtf8AndPrint(JSContext* cx, const char* bytes,
+                                           size_t length, int lineno,
+                                           bool compileOnly) {
+  // Eval.
+  JS::CompileOptions options(cx);
+  options.setIntroductionType("js shell interactive")
+      .setIsRunOnce(true)
+      .setFileAndLine("typein", lineno)
+      .setEagerDelazificationStrategy(defaultDelazificationMode);
+
+  JS::SourceText<Utf8Unit> srcBuf;
+  if (!srcBuf.init(cx, bytes, length, JS::SourceOwnership::Borrowed)) {
+    return false;
+  }
+
+  RootedScript script(cx, JS::Compile(cx, options, srcBuf));
+  if (!script) {
+    return false;
+  }
+  if (compileOnly) {
+    return true;
+  }
+  RootedValue result(cx);
+  if (!JS_ExecuteScript(cx, script, &result)) {
+    return false;
+  }
+
+  if (!result.isUndefined() && gOutFile->isOpen()) {
+    // Print.
+    RootedString str(cx, JS_ValueToSource(cx, result));
+    if (!str) {
+      return false;
+    }
+
+    UniqueChars utf8chars = JS_EncodeStringToUTF8(cx, str);
+    if (!utf8chars) {
+      return false;
+    }
+    fprintf(gOutFile->fp, "%s\n", utf8chars.get());
+  }
+  return true;
+}
+
+[[nodiscard]] static bool ReadEvalPrintLoop(JSContext* cx, FILE* in,
+                                            bool compileOnly) {
+  ShellContext* sc = GetShellContext(cx);
+  int lineno = 1;
+  bool hitEOF = false;
+
+  do {
+    /*
+     * Accumulate lines until we get a 'compilable unit' - one that either
+     * generates an error (before running out of source) or that compiles
+     * cleanly.  This should be whenever we get a complete statement that
+     * coincides with the end of a line.
+     */
+    int startline = lineno;
+    typedef Vector<char, 32> CharBuffer;
+    RootedObject globalLexical(cx, &cx->global()->lexicalEnvironment());
+    CharBuffer buffer(cx);
+    do {
+      ScheduleWatchdog(cx, -1);
+      sc->serviceInterrupt = false;
+      errno = 0;
+
+      mozilla::UniqueFreePtr<char[]> line =
+          GetLine(in, startline == lineno ? "js> " : "");
+      if (!line) {
+        if (errno) {
+          /*
+           * Use Latin1 variant here because strerror(errno)'s
+           * encoding depends on the user's C locale.
+           */
+          JS_ReportErrorLatin1(cx, "%s", strerror(errno));
+          return false;
+        }
+        hitEOF = true;
+        break;
+      }
+
+      if (!buffer.append(line.get(), strlen(line.get())) ||
+          !buffer.append('\n')) {
+        return false;
+      }
+
+      lineno++;
+      if (!ScheduleWatchdog(cx, sc->timeoutInterval)) {
+        hitEOF = true;
+        break;
+      }
+    } while (!JS_Utf8BufferIsCompilableUnit(cx, cx->global(), buffer.begin(),
+                                            buffer.length()));
+
+    if (hitEOF && buffer.empty()) {
+      break;
+    }
+
+    {
+      // Report exceptions but keep going.
+      AutoReportException are(cx);
+      (void)EvalUtf8AndPrint(cx, buffer.begin(), buffer.length(), startline,
+                             compileOnly);
+    }
+
+    // If a let or const fail to initialize they will remain in an unusable
+    // without further intervention. This call cleans up the global scope,
+    // setting uninitialized lexicals to undefined so that they may still
+    // be used. This behavior is _only_ acceptable in the context of the repl.
+    if (JS::ForceLexicalInitialization(cx, globalLexical) &&
+        gErrFile->isOpen()) {
+      fputs(
+          "Warning: According to the standard, after the above exception,\n"
+          "Warning: the global bindings should be permanently uninitialized.\n"
+          "Warning: We have non-standard-ly initialized them to `undefined`"
+          "for you.\nWarning: This nicety only happens in the JS shell.\n",
+          stderr);
+    }
+
+    RunShellJobs(cx);
+  } while (!hitEOF && !sc->quitting);
+
+  if (gOutFile->isOpen()) {
+    fprintf(gOutFile->fp, "\n");
+  }
+
+  return true;
+}
+
+enum FileKind {
+  PreludeScript,    // UTF-8 script, fully-parsed, to avoid conflicting
+                    // configurations.
+  FileScript,       // UTF-8, directly parsed as such
+  FileScriptUtf16,  // FileScript, but inflate to UTF-16 before parsing
+  FileModule,
+};
+
+static void ReportCantOpenErrorUnknownEncoding(JSContext* cx,
+                                               const char* filename) {
+  /*
+   * Filenames are in some random system encoding.  *Probably* it's UTF-8,
+   * but no guarantees.
+   *
+   * strerror(errno)'s encoding, in contrast, depends on the user's C locale.
+   *
+   * Latin-1 is possibly wrong for both of these -- but at least if it's
+   * wrong it'll produce mojibake *safely*.  Run with Latin-1 til someone
+   * complains.
+   */
+  JS_ReportErrorNumberLatin1(cx, my_GetErrorMessage, nullptr, JSSMSG_CANT_OPEN,
+                             filename, strerror(errno));
+}
+
+[[nodiscard]] static bool Process(JSContext* cx, const char* filename,
+                                  bool forceTTY, FileKind kind) {
+  FILE* file;
+  if (forceTTY || !filename || strcmp(filename, "-") == 0) {
+    file = stdin;
+  } else {
+    file = fopen(filename, "rb");
+    if (!file) {
+      ReportCantOpenErrorUnknownEncoding(cx, filename);
+      return false;
+    }
+  }
+  AutoCloseFile autoClose(file);
+
+  bool fullParse = false;
+  if (!forceTTY && !isatty(fileno(file))) {
+    // It's not interactive - just execute it.
+    switch (kind) {
+      case PreludeScript:
+        fullParse = true;
+        if (!RunFile(cx, filename, file, CompileUtf8::DontInflate, compileOnly,
+                     fullParse)) {
+          return false;
+        }
+        break;
+      case FileScript:
+        if (!RunFile(cx, filename, file, CompileUtf8::DontInflate, compileOnly,
+                     fullParse)) {
+          return false;
+        }
+        break;
+      case FileScriptUtf16:
+        if (!RunFile(cx, filename, file, CompileUtf8::InflateToUtf16,
+                     compileOnly, fullParse)) {
+          return false;
+        }
+        break;
+      case FileModule:
+        if (!RunModule(cx, filename, compileOnly)) {
+          return false;
+        }
+        break;
+      default:
+        MOZ_CRASH("Impossible FileKind!");
+    }
+  } else {
+    // It's an interactive filehandle; drop into read-eval-print loop.
+    MOZ_ASSERT(kind == FileScript);
+    if (!ReadEvalPrintLoop(cx, file, compileOnly)) {
+      return false;
+    }
+  }
+#ifdef FUZZING_JS_FUZZILLI
+  fprintf(stderr, "executionHash is 0x%x with %d inputs\n", cx->executionHash,
+          cx->executionHashInputs);
+#endif
+  return true;
+}
+
+#ifdef XP_WIN
+#  define GET_FD_FROM_FILE(a) int(_get_osfhandle(fileno(a)))
+#else
+#  define GET_FD_FROM_FILE(a) fileno(a)
+#endif
+
+static void freeExternalCallback(void* contents, void* userData) {
+  MOZ_ASSERT(!userData);
+  js_free(contents);
+}
+
+static bool CreateExternalArrayBuffer(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+  if (args.length() != 1) {
+    JS_ReportErrorNumberASCII(
+        cx, my_GetErrorMessage, nullptr,
+        args.length() < 1 ? JSSMSG_NOT_ENOUGH_ARGS : JSSMSG_TOO_MANY_ARGS,
+        "createExternalArrayBuffer");
+    return false;
+  }
+
+  int32_t bytes = 0;
+  if (!ToInt32(cx, args[0], &bytes)) {
+    return false;
+  }
+
+  if (bytes < 0) {
+    JS_ReportErrorASCII(cx, "Size must be non-negative");
+    return false;
+  }
+
+  void* buffer = js_malloc(bytes);
+  if (!buffer) {
+    JS_ReportOutOfMemory(cx);
+    return false;
+  }
+
+  RootedObject arrayBuffer(
+      cx, JS::NewExternalArrayBuffer(cx, bytes, buffer, &freeExternalCallback));
+  if (!arrayBuffer) {
+    return false;
+  }
+
+  args.rval().setObject(*arrayBuffer);
+  return true;
+}
+
+static bool CreateMappedArrayBuffer(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  if (args.length() < 1 || args.length() > 3) {
+    JS_ReportErrorNumberASCII(
+        cx, my_GetErrorMessage, nullptr,
+        args.length() < 1 ? JSSMSG_NOT_ENOUGH_ARGS : JSSMSG_TOO_MANY_ARGS,
+        "createMappedArrayBuffer");
+    return false;
+  }
+
+  RootedString rawFilenameStr(cx, JS::ToString(cx, args[0]));
+  if (!rawFilenameStr) {
+    return false;
+  }
+  // It's a little bizarre to resolve relative to the script, but for testing
+  // I need a file at a known location, and the only good way I know of to do
+  // that right now is to include it in the repo alongside the test script.
+  // Bug 944164 would introduce an alternative.
+  JSString* filenameStr = ResolvePath(cx, rawFilenameStr, ScriptRelative);
+  if (!filenameStr) {
+    return false;
+  }
+  UniqueChars filename = JS_EncodeStringToLatin1(cx, filenameStr);
+  if (!filename) {
+    return false;
+  }
+
+  uint32_t offset = 0;
+  if (args.length() >= 2) {
+    if (!JS::ToUint32(cx, args[1], &offset)) {
+      return false;
+    }
+  }
+
+  bool sizeGiven = false;
+  uint32_t size;
+  if (args.length() >= 3) {
+    if (!JS::ToUint32(cx, args[2], &size)) {
+      return false;
+    }
+    sizeGiven = true;
+    if (size == 0) {
+      JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                                JSMSG_BAD_ARRAY_LENGTH);
+      return false;
+    }
+  }
+
+  FILE* file = fopen(filename.get(), "rb");
+  if (!file) {
+    ReportCantOpenErrorUnknownEncoding(cx, filename.get());
+    return false;
+  }
+  AutoCloseFile autoClose(file);
+
+  struct stat st;
+  if (fstat(fileno(file), &st) < 0) {
+    JS_ReportErrorASCII(cx, "Unable to stat file");
+    return false;
+  }
+
+  if ((st.st_mode & S_IFMT) != S_IFREG) {
+    JS_ReportErrorASCII(cx, "Path is not a regular file");
+    return false;
+  }
+
+  if (!sizeGiven) {
+    if (off_t(offset) >= st.st_size) {
+      JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                                JSMSG_OFFSET_LARGER_THAN_FILESIZE);
+      return false;
+    }
+    size = st.st_size - offset;
+  }
+
+  void* contents =
+      JS::CreateMappedArrayBufferContents(GET_FD_FROM_FILE(file), offset, size);
+  if (!contents) {
+    JS_ReportErrorASCII(cx,
+                        "failed to allocate mapped array buffer contents "
+                        "(possibly due to bad alignment)");
+    return false;
+  }
+
+  RootedObject obj(cx,
+                   JS::NewMappedArrayBufferWithContents(cx, size, contents));
+  if (!obj) {
+    return false;
+  }
+
+  args.rval().setObject(*obj);
+  return true;
+}
+
+#undef GET_FD_FROM_FILE
+
+static bool AddPromiseReactions(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  if (args.length() != 3) {
+    JS_ReportErrorNumberASCII(
+        cx, my_GetErrorMessage, nullptr,
+        args.length() < 3 ? JSSMSG_NOT_ENOUGH_ARGS : JSSMSG_TOO_MANY_ARGS,
+        "addPromiseReactions");
+    return false;
+  }
+
+  RootedObject promise(cx);
+  if (args[0].isObject()) {
+    promise = &args[0].toObject();
+  }
+
+  if (!promise || !JS::IsPromiseObject(promise)) {
+    JS_ReportErrorNumberASCII(cx, my_GetErrorMessage, nullptr,
+                              JSSMSG_INVALID_ARGS, "addPromiseReactions");
+    return false;
+  }
+
+  RootedObject onResolve(cx);
+  if (args[1].isObject()) {
+    onResolve = &args[1].toObject();
+  }
+
+  RootedObject onReject(cx);
+  if (args[2].isObject()) {
+    onReject = &args[2].toObject();
+  }
+
+  if (!onResolve || !onResolve->is<JSFunction>() || !onReject ||
+      !onReject->is<JSFunction>()) {
+    JS_ReportErrorNumberASCII(cx, my_GetErrorMessage, nullptr,
+                              JSSMSG_INVALID_ARGS, "addPromiseReactions");
+    return false;
+  }
+
+  return JS::AddPromiseReactions(cx, promise, onResolve, onReject);
+}
+
+static bool IgnoreUnhandledRejections(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  ShellContext* sc = GetShellContext(cx);
+  sc->trackUnhandledRejections = false;
+
+  args.rval().setUndefined();
+  return true;
+}
+
+static bool Options(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  JS::ContextOptions oldContextOptions = JS::ContextOptionsRef(cx);
+  for (unsigned i = 0; i < args.length(); i++) {
+    RootedString str(cx, JS::ToString(cx, args[i]));
+    if (!str) {
+      return false;
+    }
+
+    Rooted<JSLinearString*> opt(cx, str->ensureLinear(cx));
+    if (!opt) {
+      return false;
+    }
+
+    if (StringEqualsLiteral(opt, "throw_on_asmjs_validation_failure")) {
+      JS::ContextOptionsRef(cx).toggleThrowOnAsmJSValidationFailure();
+    } else if (StringEqualsLiteral(opt, "strict_mode")) {
+      JS::ContextOptionsRef(cx).toggleStrictMode();
+    } else {
+      UniqueChars optChars = QuoteString(cx, opt, '"');
+      if (!optChars) {
+        return false;
+      }
+
+      JS_ReportErrorASCII(cx,
+                          "unknown option name %s."
+                          " The valid names are "
+                          "throw_on_asmjs_validation_failure and strict_mode.",
+                          optChars.get());
+      return false;
+    }
+  }
+
+  UniqueChars names = DuplicateString("");
+  bool found = false;
+  if (names && oldContextOptions.throwOnAsmJSValidationFailure()) {
+    names = JS_sprintf_append(std::move(names), "%s%s", found ? "," : "",
+                              "throw_on_asmjs_validation_failure");
+    found = true;
+  }
+  if (names && oldContextOptions.strictMode()) {
+    names = JS_sprintf_append(std::move(names), "%s%s", found ? "," : "",
+                              "strict_mode");
+    found = true;
+  }
+  if (!names) {
+    JS_ReportOutOfMemory(cx);
+    return false;
+  }
+
+  JSString* str = JS_NewStringCopyZ(cx, names.get());
+  if (!str) {
+    return false;
+  }
+  args.rval().setString(str);
+  return true;
+}
+
+static bool LoadScript(JSContext* cx, unsigned argc, Value* vp,
+                       bool scriptRelative) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  RootedString str(cx);
+  for (unsigned i = 0; i < args.length(); i++) {
+    str = JS::ToString(cx, args[i]);
+    if (!str) {
+      JS_ReportErrorNumberASCII(cx, my_GetErrorMessage, nullptr,
+                                JSSMSG_INVALID_ARGS, "load");
+      return false;
+    }
+
+    str = ResolvePath(cx, str, scriptRelative ? ScriptRelative : RootRelative);
+    if (!str) {
+      JS_ReportErrorASCII(cx, "unable to resolve path");
+      return false;
+    }
+
+    UniqueChars filename = JS_EncodeStringToLatin1(cx, str);
+    if (!filename) {
+      return false;
+    }
+
+    errno = 0;
+
+    CompileOptions opts(cx);
+    opts.setIntroductionType("js shell load")
+        .setIsRunOnce(true)
+        .setNoScriptRval(true)
+        .setEagerDelazificationStrategy(defaultDelazificationMode);
+
+    RootedValue unused(cx);
+    if (!(compileOnly
+              ? JS::CompileUtf8Path(cx, opts, filename.get()) != nullptr
+              : JS::EvaluateUtf8Path(cx, opts, filename.get(), &unused))) {
+      return false;
+    }
+  }
+
+  args.rval().setUndefined();
+  return true;
+}
+
+static bool Load(JSContext* cx, unsigned argc, Value* vp) {
+  return LoadScript(cx, argc, vp, false);
+}
+
+static bool LoadScriptRelativeToScript(JSContext* cx, unsigned argc,
+                                       Value* vp) {
+  return LoadScript(cx, argc, vp, true);
+}
+
+static void my_LargeAllocFailCallback() {
+  JSContext* cx = TlsContext.get();
+  if (!cx || cx->isHelperThreadContext()) {
+    return;
+  }
+
+  MOZ_ASSERT(!JS::RuntimeHeapIsBusy());
+
+  JS::PrepareForFullGC(cx);
+  cx->runtime()->gc.gc(JS::GCOptions::Shrink,
+                       JS::GCReason::SHARED_MEMORY_LIMIT);
+}
+
+static const uint32_t CacheEntry_SOURCE = 0;
+static const uint32_t CacheEntry_BYTECODE = 1;
+static const uint32_t CacheEntry_OPTIONS = 2;
+
+// Some compile options can't be combined differently between save and load.
+//
+// CacheEntries store a CacheOption set, and on load an exception is thrown
+// if the entries are incompatible.
+
+enum CacheOptions : uint32_t {
+  IsRunOnce,
+  NoScriptRval,
+  Global,
+  NonSyntactic,
+  SourceIsLazy,
+  ForceFullParse,
+};
+
+struct CacheOptionSet : public mozilla::EnumSet<CacheOptions> {
+  using mozilla::EnumSet<CacheOptions>::EnumSet;
+
+  explicit CacheOptionSet(const CompileOptions& options) : EnumSet() {
+    initFromOptions(options);
+  }
+
+  void initFromOptions(const CompileOptions& options) {
+    if (options.noScriptRval) {
+      *this += CacheOptions::NoScriptRval;
+    }
+    if (options.isRunOnce) {
+      *this += CacheOptions::IsRunOnce;
+    }
+    if (options.sourceIsLazy) {
+      *this += CacheOptions::SourceIsLazy;
+    }
+    if (options.forceFullParse()) {
+      *this += CacheOptions::ForceFullParse;
+    }
+    if (options.nonSyntacticScope) {
+      *this += CacheOptions::NonSyntactic;
+    }
+  }
+};
+
+static bool CacheOptionsCompatible(const CacheOptionSet& a,
+                                   const CacheOptionSet& b) {
+  // If the options are identical, they are trivially compatible.
+  return a == b;
+}
+
+static const JSClass CacheEntry_class = {"CacheEntryObject",
+                                         JSCLASS_HAS_RESERVED_SLOTS(3)};
+
+static bool CacheEntry(JSContext* cx, unsigned argc, JS::Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  if (args.length() != 1 || !args[0].isString()) {
+    JS_ReportErrorNumberASCII(cx, my_GetErrorMessage, nullptr,
+                              JSSMSG_INVALID_ARGS, "CacheEntry");
+    return false;
+  }
+
+  RootedObject obj(cx, JS_NewObject(cx, &CacheEntry_class));
+  if (!obj) {
+    return false;
+  }
+
+  JS::SetReservedSlot(obj, CacheEntry_SOURCE, args[0]);
+  JS::SetReservedSlot(obj, CacheEntry_BYTECODE, UndefinedValue());
+
+  // Fill in empty option set.
+  CacheOptionSet defaultOptions;
+  JS::SetReservedSlot(obj, CacheEntry_OPTIONS,
+                      Int32Value(defaultOptions.serialize()));
+
+  args.rval().setObject(*obj);
+  return true;
+}
+
+static bool CacheEntry_isCacheEntry(JSObject* cache) {
+  return cache->hasClass(&CacheEntry_class);
+}
+
+static JSString* CacheEntry_getSource(JSContext* cx, HandleObject cache) {
+  MOZ_ASSERT(CacheEntry_isCacheEntry(cache));
+  Value v = JS::GetReservedSlot(cache, CacheEntry_SOURCE);
+  if (!v.isString()) {
+    JS_ReportErrorASCII(
+        cx, "CacheEntry_getSource: Unexpected type of source reserved slot.");
+    return nullptr;
+  }
+
+  return v.toString();
+}
+
+static bool CacheEntry_compatible(JSContext* cx, HandleObject cache,
+                                  const CacheOptionSet& currentOptionSet) {
+  CacheOptionSet cacheEntryOptions;
+  MOZ_ASSERT(CacheEntry_isCacheEntry(cache));
+  Value v = JS::GetReservedSlot(cache, CacheEntry_OPTIONS);
+  cacheEntryOptions.deserialize(v.toInt32());
+  if (!CacheOptionsCompatible(cacheEntryOptions, currentOptionSet)) {
+    JS_ReportErrorASCII(cx,
+                        "CacheEntry_compatible: Incompatible cache contents");
+    return false;
+  }
+  return true;
+}
+
+static uint8_t* CacheEntry_getBytecode(JSContext* cx, HandleObject cache,
+                                       size_t* length) {
+  MOZ_ASSERT(CacheEntry_isCacheEntry(cache));
+  Value v = JS::GetReservedSlot(cache, CacheEntry_BYTECODE);
+  if (!v.isObject() || !v.toObject().is<ArrayBufferObject>()) {
+    JS_ReportErrorASCII(
+        cx,
+        "CacheEntry_getBytecode: Unexpected type of bytecode reserved slot.");
+    return nullptr;
+  }
+
+  ArrayBufferObject* arrayBuffer = &v.toObject().as<ArrayBufferObject>();
+  *length = arrayBuffer->byteLength();
+  return arrayBuffer->dataPointer();
+}
+
+static bool CacheEntry_setBytecode(JSContext* cx, HandleObject cache,
+                                   const CacheOptionSet& cacheOptions,
+                                   uint8_t* buffer, uint32_t length) {
+  MOZ_ASSERT(CacheEntry_isCacheEntry(cache));
+
+  using BufferContents = ArrayBufferObject::BufferContents;
+
+  BufferContents contents = BufferContents::createMalloced(buffer);
+  Rooted<ArrayBufferObject*> arrayBuffer(
+      cx, ArrayBufferObject::createForContents(cx, length, contents));
+  if (!arrayBuffer) {
+    return false;
+  }
+
+  JS::SetReservedSlot(cache, CacheEntry_BYTECODE, ObjectValue(*arrayBuffer));
+  JS::SetReservedSlot(cache, CacheEntry_OPTIONS,
+                      Int32Value(cacheOptions.serialize()));
+  return true;
+}
+
+static bool ConvertTranscodeResultToJSException(JSContext* cx,
+                                                JS::TranscodeResult rv) {
+  switch (rv) {
+    case JS::TranscodeResult::Ok:
+      return true;
+
+    default:
+      [[fallthrough]];
+    case JS::TranscodeResult::Failure:
+      MOZ_ASSERT(!cx->isExceptionPending());
+      JS_ReportErrorASCII(cx, "generic warning");
+      return false;
+    case JS::TranscodeResult::Failure_BadBuildId:
+      MOZ_ASSERT(!cx->isExceptionPending());
+      JS_ReportErrorASCII(cx, "the build-id does not match");
+      return false;
+    case JS::TranscodeResult::Failure_AsmJSNotSupported:
+      MOZ_ASSERT(!cx->isExceptionPending());
+      JS_ReportErrorASCII(cx, "Asm.js is not supported by XDR");
+      return false;
+    case JS::TranscodeResult::Failure_BadDecode:
+      MOZ_ASSERT(!cx->isExceptionPending());
+      JS_ReportErrorASCII(cx, "XDR data corruption");
+      return false;
+
+    case JS::TranscodeResult::Throw:
+      MOZ_ASSERT(cx->isExceptionPending());
+      return false;
+  }
+}
+
+static bool Evaluate(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  if (args.length() < 1 || args.length() > 2) {
+    JS_ReportErrorNumberASCII(
+        cx, my_GetErrorMessage, nullptr,
+        args.length() < 1 ? JSSMSG_NOT_ENOUGH_ARGS : JSSMSG_TOO_MANY_ARGS,
+        "evaluate");
+    return false;
+  }
+
+  RootedString code(cx, nullptr);
+  RootedObject cacheEntry(cx, nullptr);
+  if (args[0].isString()) {
+    code = args[0].toString();
+  } else if (args[0].isObject() &&
+             CacheEntry_isCacheEntry(&args[0].toObject())) {
+    cacheEntry = &args[0].toObject();
+    code = CacheEntry_getSource(cx, cacheEntry);
+    if (!code) {
+      return false;
+    }
+  }
+
+  if (!code || (args.length() == 2 && args[1].isPrimitive())) {
+    JS_ReportErrorNumberASCII(cx, my_GetErrorMessage, nullptr,
+                              JSSMSG_INVALID_ARGS, "evaluate");
+    return false;
+  }
+
+  RootedObject opts(cx);
+  if (args.length() == 2) {
+    if (!args[1].isObject()) {
+      JS_ReportErrorASCII(cx, "evaluate: The 2nd argument must be an object");
+      return false;
+    }
+
+    opts = &args[1].toObject();
+  }
+
+  RootedObject global(cx, JS::CurrentGlobalOrNull(cx));
+  MOZ_ASSERT(global);
+
+  // Check "global" property before everything to use the given global's
+  // option as the default value.
+  Maybe<CompileOptions> maybeOptions;
+  if (opts) {
+    RootedValue v(cx);
+    if (!JS_GetProperty(cx, opts, "global", &v)) {
+      return false;
+    }
+    if (!v.isUndefined()) {
+      if (v.isObject()) {
+        global = js::CheckedUnwrapDynamic(&v.toObject(), cx,
+                                          /* stopAtWindowProxy = */ false);
+        if (!global) {
+          return false;
+        }
+      }
+      if (!global || !(JS::GetClass(global)->flags & JSCLASS_IS_GLOBAL)) {
+        JS_ReportErrorNumberASCII(
+            cx, GetErrorMessage, nullptr, JSMSG_UNEXPECTED_TYPE,
+            "\"global\" passed to evaluate()", "not a global object");
+        return false;
+      }
+
+      JSAutoRealm ar(cx, global);
+      maybeOptions.emplace(cx);
+    }
+  }
+  if (!maybeOptions) {
+    // If "global" property is not given, use the current global's option as
+    // the default value.
+    maybeOptions.emplace(cx);
+  }
+
+  CompileOptions& options = maybeOptions.ref();
+  UniqueChars fileNameBytes;
+  RootedString displayURL(cx);
+  RootedString sourceMapURL(cx);
+  bool catchTermination = false;
+  bool loadBytecode = false;
+  bool saveIncrementalBytecode = false;
+  bool execute = true;
+  bool assertEqBytecode = false;
+  JS::RootedObjectVector envChain(cx);
+  RootedObject callerGlobal(cx, cx->global());
+
+  options.setIntroductionType("js shell evaluate")
+      .setFileAndLine("@evaluate", 1)
+      .setDeferDebugMetadata();
+
+  RootedValue privateValue(cx);
+  RootedString elementAttributeName(cx);
+
+  if (opts) {
+    if (!js::ParseCompileOptions(cx, options, opts, &fileNameBytes)) {
+      return false;
+    }
+    if (!ParseDebugMetadata(cx, opts, &privateValue, &elementAttributeName)) {
+      return false;
+    }
+    if (!ParseSourceOptions(cx, opts, &displayURL, &sourceMapURL)) {
+      return false;
+    }
+
+    RootedValue v(cx);
+    if (!JS_GetProperty(cx, opts, "catchTermination", &v)) {
+      return false;
+    }
+    if (!v.isUndefined()) {
+      catchTermination = ToBoolean(v);
+    }
+
+    if (!JS_GetProperty(cx, opts, "loadBytecode", &v)) {
+      return false;
+    }
+    if (!v.isUndefined()) {
+      loadBytecode = ToBoolean(v);
+    }
+
+    if (!JS_GetProperty(cx, opts, "saveIncrementalBytecode", &v)) {
+      return false;
+    }
+    if (!v.isUndefined()) {
+      saveIncrementalBytecode = ToBoolean(v);
+    }
+
+    if (!JS_GetProperty(cx, opts, "execute", &v)) {
+      return false;
+    }
+    if (!v.isUndefined()) {
+      execute = ToBoolean(v);
+    }
+
+    if (!JS_GetProperty(cx, opts, "assertEqBytecode", &v)) {
+      return false;
+    }
+    if (!v.isUndefined()) {
+      assertEqBytecode = ToBoolean(v);
+    }
+
+    if (!JS_GetProperty(cx, opts, "envChainObject", &v)) {
+      return false;
+    }
+    if (!v.isUndefined()) {
+      if (!v.isObject()) {
+        JS_ReportErrorNumberASCII(
+            cx, GetErrorMessage, nullptr, JSMSG_UNEXPECTED_TYPE,
+            "\"envChainObject\" passed to evaluate()", "not an object");
+        return false;
+      } else if (v.toObject().is<GlobalObject>()) {
+        JS_ReportErrorASCII(
+            cx,
+            "\"envChainObject\" passed to evaluate() should not be a global");
+        return false;
+      } else if (!envChain.append(&v.toObject())) {
+        return false;
+      }
+    }
+
+    // We cannot load or save the bytecode if we have no object where the
+    // bytecode cache is stored.
+    if (loadBytecode || saveIncrementalBytecode) {
+      if (!cacheEntry) {
+        JS_ReportErrorNumberASCII(cx, my_GetErrorMessage, nullptr,
+                                  JSSMSG_INVALID_ARGS, "evaluate");
+        return false;
+      }
+    }
+  }
+
+  if (envChain.length() != 0) {
+    // Wrap the envChainObject list into target realm.
+    JSAutoRealm ar(cx, global);
+    for (size_t i = 0; i < envChain.length(); ++i) {
+      if (!JS_WrapObject(cx, envChain[i])) {
+        return false;
+      }
+    }
+
+    options.setNonSyntacticScope(true);
+  }
+
+  // The `loadBuffer` we use below outlives the Stencil we generate so we can
+  // use its contents directly in the Stencil.
+  options.borrowBuffer = true;
+
+  // We need to track the options used to generate bytecode for a CacheEntry to
+  // avoid mismatches. This is primarily a concern when fuzzing the jsshell.
+  CacheOptionSet cacheOptions;
+  cacheOptions.initFromOptions(options);
+
+  JS::TranscodeBuffer loadBuffer;
+  JS::TranscodeBuffer saveBuffer;
+
+  if (loadBytecode) {
+    size_t loadLength = 0;
+    uint8_t* loadData = nullptr;
+
+    if (!CacheEntry_compatible(cx, cacheEntry, cacheOptions)) {
+      return false;
+    }
+
+    loadData = CacheEntry_getBytecode(cx, cacheEntry, &loadLength);
+    if (!loadData) {
+      return false;
+    }
+    if (!loadBuffer.append(loadData, loadLength)) {
+      JS_ReportOutOfMemory(cx);
+      return false;
+    }
+  }
+
+  {
+    JSAutoRealm ar(cx, global);
+    RefPtr<JS::Stencil> stencil;
+
+    if (loadBytecode) {
+      JS::TranscodeRange range(loadBuffer.begin(), loadBuffer.length());
+      JS::DecodeOptions decodeOptions(options);
+
+      JS::TranscodeResult rv =
+          JS::DecodeStencil(cx, decodeOptions, range, getter_AddRefs(stencil));
+      if (!ConvertTranscodeResultToJSException(cx, rv)) {
+        return false;
+      }
+    } else {
+      AutoStableStringChars linearChars(cx);
+      if (!linearChars.initTwoByte(cx, code)) {
+        return false;
+      }
+
+      JS::SourceText<char16_t> srcBuf;
+      if (!srcBuf.initMaybeBorrowed(cx, linearChars)) {
+        return false;
+      }
+
+      stencil = JS::CompileGlobalScriptToStencil(cx, options, srcBuf);
+      if (!stencil) {
+        return false;
+      }
+    }
+
+    JS::InstantiateOptions instantiateOptions(options);
+    RootedScript script(
+        cx, JS::InstantiateGlobalStencil(cx, instantiateOptions, stencil));
+    if (!script) {
+      return false;
+    }
+
+    AutoReportFrontendContext fc(cx);
+    if (!SetSourceOptions(cx, &fc, script->scriptSource(), displayURL,
+                          sourceMapURL)) {
+      return false;
+    }
+
+    if (!JS::UpdateDebugMetadata(cx, script, instantiateOptions, privateValue,
+                                 elementAttributeName, nullptr, nullptr)) {
+      return false;
+    }
+
+    if (saveIncrementalBytecode) {
+      if (!JS::StartIncrementalEncoding(cx, std::move(stencil))) {
+        return false;
+      }
+    }
+
+    if (execute) {
+      if (!(envChain.empty()
+                ? JS_ExecuteScript(cx, script, args.rval())
+                : JS_ExecuteScript(cx, envChain, script, args.rval()))) {
+        if (catchTermination && !JS_IsExceptionPending(cx)) {
+          JSAutoRealm ar1(cx, callerGlobal);
+          JSString* str = JS_NewStringCopyZ(cx, "terminated");
+          if (!str) {
+            return false;
+          }
+          args.rval().setString(str);
+          return true;
+        }
+        return false;
+      }
+    }
+
+    // Serialize the encoded bytecode, recorded before the execution, into a
+    // buffer which can be deserialized linearly.
+    if (saveIncrementalBytecode) {
+      if (!FinishIncrementalEncoding(cx, script, saveBuffer)) {
+        return false;
+      }
+    }
+  }
+
+  if (saveIncrementalBytecode) {
+    // If we are both loading and saving, we assert that we are going to
+    // replace the current bytecode by the same stream of bytes.
+    if (loadBytecode && assertEqBytecode) {
+      if (saveBuffer.length() != loadBuffer.length()) {
+        char loadLengthStr[16];
+        SprintfLiteral(loadLengthStr, "%zu", loadBuffer.length());
+        char saveLengthStr[16];
+        SprintfLiteral(saveLengthStr, "%zu", saveBuffer.length());
+
+        JS_ReportErrorNumberASCII(cx, my_GetErrorMessage, nullptr,
+                                  JSSMSG_CACHE_EQ_SIZE_FAILED, loadLengthStr,
+                                  saveLengthStr);
+        return false;
+      }
+
+      if (!ArrayEqual(loadBuffer.begin(), saveBuffer.begin(),
+                      loadBuffer.length())) {
+        JS_ReportErrorNumberASCII(cx, my_GetErrorMessage, nullptr,
+                                  JSSMSG_CACHE_EQ_CONTENT_FAILED);
+        return false;
+      }
+    }
+
+    size_t saveLength = saveBuffer.length();
+    if (saveLength >= INT32_MAX) {
+      JS_ReportErrorASCII(cx, "Cannot save large cache entry content");
+      return false;
+    }
+    uint8_t* saveData = saveBuffer.extractOrCopyRawBuffer();
+    if (!CacheEntry_setBytecode(cx, cacheEntry, cacheOptions, saveData,
+                                saveLength)) {
+      js_free(saveData);
+      return false;
+    }
+  }
+
+  return JS_WrapValue(cx, args.rval());
+}
+
+JSString* js::shell::FileAsString(JSContext* cx, JS::HandleString pathnameStr) {
+  UniqueChars pathname = JS_EncodeStringToLatin1(cx, pathnameStr);
+  if (!pathname) {
+    return nullptr;
+  }
+
+  FILE* file;
+
+  file = fopen(pathname.get(), "rb");
+  if (!file) {
+    ReportCantOpenErrorUnknownEncoding(cx, pathname.get());
+    return nullptr;
+  }
+
+  AutoCloseFile autoClose(file);
+
+  struct stat st;
+  if (fstat(fileno(file), &st) != 0) {
+    JS_ReportErrorUTF8(cx, "can't stat %s", pathname.get());
+    return nullptr;
+  }
+
+  if ((st.st_mode & S_IFMT) != S_IFREG) {
+    JS_ReportErrorUTF8(cx, "can't read non-regular file %s", pathname.get());
+    return nullptr;
+  }
+
+  if (fseek(file, 0, SEEK_END) != 0) {
+    pathname = JS_EncodeStringToUTF8(cx, pathnameStr);
+    if (!pathname) {
+      return nullptr;
+    }
+    JS_ReportErrorUTF8(cx, "can't seek end of %s", pathname.get());
+    return nullptr;
+  }
+
+  long endPos = ftell(file);
+  if (endPos < 0) {
+    JS_ReportErrorUTF8(cx, "can't read length of %s", pathname.get());
+    return nullptr;
+  }
+
+  size_t len = endPos;
+  if (fseek(file, 0, SEEK_SET) != 0) {
+    pathname = JS_EncodeStringToUTF8(cx, pathnameStr);
+    if (!pathname) {
+      return nullptr;
+    }
+    JS_ReportErrorUTF8(cx, "can't seek start of %s", pathname.get());
+    return nullptr;
+  }
+
+  UniqueChars buf(js_pod_malloc<char>(len + 1));
+  if (!buf) {
+    JS_ReportErrorUTF8(cx, "out of memory reading %s", pathname.get());
+    return nullptr;
+  }
+
+  size_t cc = fread(buf.get(), 1, len, file);
+  if (cc != len) {
+    if (ptrdiff_t(cc) < 0) {
+      ReportCantOpenErrorUnknownEncoding(cx, pathname.get());
+    } else {
+      pathname = JS_EncodeStringToUTF8(cx, pathnameStr);
+      if (!pathname) {
+        return nullptr;
+      }
+      JS_ReportErrorUTF8(cx, "can't read %s: short read", pathname.get());
+    }
+    return nullptr;
+  }
+
+  UniqueTwoByteChars ucbuf(
+      JS::LossyUTF8CharsToNewTwoByteCharsZ(cx, JS::UTF8Chars(buf.get(), len),
+                                           &len, js::MallocArena)
+          .get());
+  if (!ucbuf) {
+    pathname = JS_EncodeStringToUTF8(cx, pathnameStr);
+    if (!pathname) {
+      return nullptr;
+    }
+    JS_ReportErrorUTF8(cx, "Invalid UTF-8 in file '%s'", pathname.get());
+    return nullptr;
+  }
+
+  return JS_NewUCStringCopyN(cx, ucbuf.get(), len);
+}
+
+/*
+ * Function to run scripts and return compilation + execution time. Semantics
+ * are closely modelled after the equivalent function in WebKit, as this is used
+ * to produce benchmark timings by SunSpider.
+ */
+static bool Run(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+  if (args.length() != 1) {
+    JS_ReportErrorNumberASCII(cx, my_GetErrorMessage, nullptr,
+                              JSSMSG_INVALID_ARGS, "run");
+    return false;
+  }
+
+  RootedString str(cx, JS::ToString(cx, args[0]));
+  if (!str) {
+    return false;
+  }
+  args[0].setString(str);
+
+  str = FileAsString(cx, str);
+  if (!str) {
+    return false;
+  }
+
+  AutoStableStringChars linearChars(cx);
+  if (!linearChars.initTwoByte(cx, str)) {
+    return false;
+  }
+
+  JS::SourceText<char16_t> srcBuf;
+  if (!srcBuf.initMaybeBorrowed(cx, linearChars)) {
+    return false;
+  }
+
+  RootedScript script(cx);
+  int64_t startClock = PRMJ_Now();
+  {
+    /* FIXME: This should use UTF-8 (bug 987069). */
+    UniqueChars filename = JS_EncodeStringToLatin1(cx, str);
+    if (!filename) {
+      return false;
+    }
+
+    JS::CompileOptions options(cx);
+    options.setIntroductionType("js shell run")
+        .setFileAndLine(filename.get(), 1)
+        .setIsRunOnce(true)
+        .setNoScriptRval(true)
+        .setEagerDelazificationStrategy(defaultDelazificationMode);
+
+    script = JS::Compile(cx, options, srcBuf);
+    if (!script) {
+      return false;
+    }
+  }
+
+  if (!JS_ExecuteScript(cx, script)) {
+    return false;
+  }
+
+  int64_t endClock = PRMJ_Now();
+
+  args.rval().setDouble((endClock - startClock) / double(PRMJ_USEC_PER_MSEC));
+  return true;
+}
+
+static int js_fgets(char* buf, int size, FILE* file) {
+  int n, i, c;
+  bool crflag;
+
+  n = size - 1;
+  if (n < 0) {
+    return -1;
+  }
+
+  // Use the fastest available getc.
+  auto fast_getc =
+#if defined(HAVE_GETC_UNLOCKED)
+      getc_unlocked
+#elif defined(HAVE__GETC_NOLOCK)
+      _getc_nolock
+#else
+      getc
+#endif
+      ;
+
+  crflag = false;
+  for (i = 0; i < n && (c = fast_getc(file)) != EOF; i++) {
+    buf[i] = c;
+    if (c == '\n') {  // any \n ends a line
+      i++;            // keep the \n; we know there is room for \0
+      break;
+    }
+    if (crflag) {  // \r not followed by \n ends line at the \r
+      ungetc(c, file);
+      break;  // and overwrite c in buf with \0
+    }
+    crflag = (c == '\r');
+  }
+
+  buf[i] = '\0';
+  return i;
+}
+
+/*
+ * function readline()
+ * Provides a hook for scripts to read a line from stdin.
+ */
+static bool ReadLine(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  static constexpr size_t BUFSIZE = 256;
+  FILE* from = stdin;
+  size_t buflength = 0;
+  size_t bufsize = BUFSIZE;
+  char* buf = (char*)JS_malloc(cx, bufsize);
+  if (!buf) {
+    return false;
+  }
+
+  bool sawNewline = false;
+  size_t gotlength;
+  while ((gotlength = js_fgets(buf + buflength, bufsize - buflength, from)) >
+         0) {
+    buflength += gotlength;
+
+    /* Are we done? */
+    if (buf[buflength - 1] == '\n') {
+      buf[buflength - 1] = '\0';
+      sawNewline = true;
+      break;
+    } else if (buflength < bufsize - 1) {
+      break;
+    }
+
+    /* Else, grow our buffer for another pass. */
+    char* tmp;
+    bufsize *= 2;
+    if (bufsize > buflength) {
+      tmp = static_cast<char*>(JS_realloc(cx, buf, bufsize / 2, bufsize));
+    } else {
+      JS_ReportOutOfMemory(cx);
+      tmp = nullptr;
+    }
+
+    if (!tmp) {
+      JS_free(cx, buf);
+      return false;
+    }
+
+    buf = tmp;
+  }
+
+  /* Treat the empty string specially. */
+  if (buflength == 0) {
+    args.rval().set(feof(from) ? NullValue() : JS_GetEmptyStringValue(cx));
+    JS_free(cx, buf);
+    return true;
+  }
+
+  /* Shrink the buffer to the real size. */
+  char* tmp = static_cast<char*>(JS_realloc(cx, buf, bufsize, buflength));
+  if (!tmp) {
+    JS_free(cx, buf);
+    return false;
+  }
+
+  buf = tmp;
+
+  /*
+   * Turn buf into a JSString. Note that buflength includes the trailing null
+   * character.
+   */
+  JSString* str =
+      JS_NewStringCopyN(cx, buf, sawNewline ? buflength - 1 : buflength);
+  JS_free(cx, buf);
+  if (!str) {
+    return false;
+  }
+
+  args.rval().setString(str);
+  return true;
+}
+
+/*
+ * function readlineBuf()
+ * Provides a hook for scripts to emulate readline() using a string object.
+ */
+static bool ReadLineBuf(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+  ShellContext* sc = GetShellContext(cx);
+
+  if (!args.length()) {
+    if (!sc->readLineBuf) {
+      JS_ReportErrorASCII(cx,
+                          "No source buffer set. You must initially "
+                          "call readlineBuf with an argument.");
+      return false;
+    }
+
+    char* currentBuf = sc->readLineBuf.get() + sc->readLineBufPos;
+    size_t buflen = strlen(currentBuf);
+
+    if (!buflen) {
+      args.rval().setNull();
+      return true;
+    }
+
+    size_t len = 0;
+    while (len < buflen) {
+      if (currentBuf[len] == '\n') {
+        break;
+      }
+      len++;
+    }
+
+    JSString* str = JS_NewStringCopyUTF8N(cx, JS::UTF8Chars(currentBuf, len));
+    if (!str) {
+      return false;
+    }
+
+    if (currentBuf[len] == '\0') {
+      sc->readLineBufPos += len;
+    } else {
+      sc->readLineBufPos += len + 1;
+    }
+
+    args.rval().setString(str);
+    return true;
+  }
+
+  if (args.length() == 1) {
+    sc->readLineBuf = nullptr;
+    sc->readLineBufPos = 0;
+
+    RootedString str(cx, JS::ToString(cx, args[0]));
+    if (!str) {
+      return false;
+    }
+    sc->readLineBuf = JS_EncodeStringToUTF8(cx, str);
+    if (!sc->readLineBuf) {
+      return false;
+    }
+
+    args.rval().setUndefined();
+    return true;
+  }
+
+  JS_ReportErrorASCII(cx, "Must specify at most one argument");
+  return false;
+}
+
+static bool PutStr(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  if (args.length() != 0) {
+    if (!gOutFile->isOpen()) {
+      JS_ReportErrorASCII(cx, "output file is closed");
+      return false;
+    }
+
+    RootedString str(cx, JS::ToString(cx, args[0]));
+    if (!str) {
+      return false;
+    }
+    UniqueChars bytes = JS_EncodeStringToUTF8(cx, str);
+    if (!bytes) {
+      return false;
+    }
+    fputs(bytes.get(), gOutFile->fp);
+    fflush(gOutFile->fp);
+  }
+
+  args.rval().setUndefined();
+  return true;
+}
+
+static bool Now(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+  double now = PRMJ_Now() / double(PRMJ_USEC_PER_MSEC);
+  args.rval().setDouble(now);
+  return true;
+}
+
+static bool CpuNow(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+  double now = double(std::clock()) / double(CLOCKS_PER_SEC);
+  args.rval().setDouble(now);
+  return true;
+}
+
+static bool PrintInternal(JSContext* cx, const CallArgs& args, RCFile* file) {
+  if (!file->isOpen()) {
+    JS_ReportErrorASCII(cx, "output file is closed");
+    return false;
+  }
+
+  for (unsigned i = 0; i < args.length(); i++) {
+    RootedString str(cx, JS::ToString(cx, args[i]));
+    if (!str) {
+      return false;
+    }
+    UniqueChars bytes = JS_EncodeStringToUTF8(cx, str);
+    if (!bytes) {
+      return false;
+    }
+    fprintf(file->fp, "%s%s", i ? " " : "", bytes.get());
+  }
+
+  fputc('\n', file->fp);
+  fflush(file->fp);
+
+  args.rval().setUndefined();
+  return true;
+}
+
+static bool Print(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+#ifdef FUZZING_INTERFACES
+  if (fuzzHaveModule && !fuzzDoDebug) {
+    // When fuzzing and not debugging, suppress any print() output,
+    // as it slows down fuzzing and makes libFuzzer's output hard
+    // to read.
+    args.rval().setUndefined();
+    return true;
+  }
+#endif  // FUZZING_INTERFACES
+  return PrintInternal(cx, args, gOutFile);
+}
+
+static bool PrintErr(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+  return PrintInternal(cx, args, gErrFile);
+}
+
+static bool Help(JSContext* cx, unsigned argc, Value* vp);
+
+static bool Quit(JSContext* cx, unsigned argc, Value* vp) {
+  ShellContext* sc = GetShellContext(cx);
+
+  // Print a message to stderr in differential testing to help jsfunfuzz
+  // find uncatchable-exception bugs.
+  if (js::SupportDifferentialTesting()) {
+    fprintf(stderr, "quit called\n");
+  }
+
+  CallArgs args = CallArgsFromVp(argc, vp);
+  int32_t code;
+  if (!ToInt32(cx, args.get(0), &code)) {
+    return false;
+  }
+
+  // The fuzzers check the shell's exit code and assume a value >= 128 means
+  // the process crashed (for instance, SIGSEGV will result in code 139). On
+  // POSIX platforms, the exit code is 8-bit and negative values can also
+  // result in an exit code >= 128. We restrict the value to range [0, 127] to
+  // avoid false positives.
+  if (code < 0 || code >= 128) {
+    JS_ReportErrorASCII(cx, "quit exit code should be in range 0-127");
+    return false;
+  }
+
+  js::StopDrainingJobQueue(cx);
+  sc->exitCode = code;
+  sc->quitting = true;
+  return false;
+}
+
+static bool StartTimingMutator(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+  if (args.length() > 0) {
+    JS_ReportErrorNumberASCII(cx, my_GetErrorMessage, nullptr,
+                              JSSMSG_TOO_MANY_ARGS, "startTimingMutator");
+    return false;
+  }
+
+  if (!cx->runtime()->gc.stats().startTimingMutator()) {
+    JS_ReportErrorASCII(
+        cx, "StartTimingMutator should only be called from outside of GC");
+    return false;
+  }
+
+  args.rval().setUndefined();
+  return true;
+}
+
+static bool StopTimingMutator(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+  if (args.length() > 0) {
+    JS_ReportErrorNumberASCII(cx, my_GetErrorMessage, nullptr,
+                              JSSMSG_TOO_MANY_ARGS, "stopTimingMutator");
+    return false;
+  }
+
+  double mutator_ms, gc_ms;
+  if (!cx->runtime()->gc.stats().stopTimingMutator(mutator_ms, gc_ms)) {
+    JS_ReportErrorASCII(cx,
+                        "stopTimingMutator called when not timing the mutator");
+    return false;
+  }
+  double total_ms = mutator_ms + gc_ms;
+  if (total_ms > 0 && gOutFile->isOpen()) {
+    fprintf(gOutFile->fp, "Mutator: %.3fms (%.1f%%), GC: %.3fms (%.1f%%)\n",
+            mutator_ms, mutator_ms / total_ms * 100.0, gc_ms,
+            gc_ms / total_ms * 100.0);
+  }
+
+  args.rval().setUndefined();
+  return true;
+}
+
+static const char* ToSource(JSContext* cx, HandleValue vp, UniqueChars* bytes) {
+  RootedString str(cx, JS_ValueToSource(cx, vp));
+  if (str) {
+    *bytes = JS_EncodeStringToUTF8(cx, str);
+    if (*bytes) {
+      return bytes->get();
+    }
+  }
+  JS_ClearPendingException(cx);
+  return "<<error converting value to string>>";
+}
+
+static bool AssertEq(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+  if (!(args.length() == 2 || (args.length() == 3 && args[2].isString()))) {
+    JS_ReportErrorNumberASCII(cx, my_GetErrorMessage, nullptr,
+                              (args.length() < 2)    ? JSSMSG_NOT_ENOUGH_ARGS
+                              : (args.length() == 3) ? JSSMSG_INVALID_ARGS
+                                                     : JSSMSG_TOO_MANY_ARGS,
+                              "assertEq");
+    return false;
+  }
+
+  bool same;
+  if (!JS::SameValue(cx, args[0], args[1], &same)) {
+    return false;
+  }
+  if (!same) {
+    UniqueChars bytes0, bytes1;
+    const char* actual = ToSource(cx, args[0], &bytes0);
+    const char* expected = ToSource(cx, args[1], &bytes1);
+    if (args.length() == 2) {
+      JS_ReportErrorNumberUTF8(cx, my_GetErrorMessage, nullptr,
+                               JSSMSG_ASSERT_EQ_FAILED, actual, expected);
+    } else {
+      RootedString message(cx, args[2].toString());
+      UniqueChars bytes2 = QuoteString(cx, message);
+      if (!bytes2) {
+        return false;
+      }
+      JS_ReportErrorNumberUTF8(cx, my_GetErrorMessage, nullptr,
+                               JSSMSG_ASSERT_EQ_FAILED_MSG, actual, expected,
+                               bytes2.get());
+    }
+    return false;
+  }
+  args.rval().setUndefined();
+  return true;
+}
+
+static JSScript* GetTopScript(JSContext* cx) {
+  NonBuiltinScriptFrameIter iter(cx);
+  return iter.done() ? nullptr : iter.script();
+}
+
+static bool GetScriptAndPCArgs(JSContext* cx, CallArgs& args,
+                               MutableHandleScript scriptp, int32_t* ip) {
+  RootedScript script(cx, GetTopScript(cx));
+  *ip = 0;
+  if (!args.get(0).isUndefined()) {
+    HandleValue v = args[0];
+    unsigned intarg = 0;
+    if (v.isObject() && JS::GetClass(&v.toObject())->isJSFunction()) {
+      script = TestingFunctionArgumentToScript(cx, v);
+      if (!script) {
+        return false;
+      }
+      intarg++;
+    }
+    if (!args.get(intarg).isUndefined()) {
+      if (!JS::ToInt32(cx, args[intarg], ip)) {
+        return false;
+      }
+      if ((uint32_t)*ip >= script->length()) {
+        JS_ReportErrorASCII(cx, "Invalid PC");
+        return false;
+      }
+    }
+  }
+
+  scriptp.set(script);
+
+  return true;
+}
+
+static bool LineToPC(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  if (args.length() == 0) {
+    JS_ReportErrorNumberASCII(cx, my_GetErrorMessage, nullptr,
+                              JSSMSG_LINE2PC_USAGE);
+    return false;
+  }
+
+  RootedScript script(cx, GetTopScript(cx));
+  int32_t lineArg = 0;
+  if (args[0].isObject() && args[0].toObject().is<JSFunction>()) {
+    script = TestingFunctionArgumentToScript(cx, args[0]);
+    if (!script) {
+      return false;
+    }
+    lineArg++;
+  }
+
+  uint32_t lineno;
+  if (!ToUint32(cx, args.get(lineArg), &lineno)) {
+    return false;
+  }
+
+  jsbytecode* pc = LineNumberToPC(script, lineno);
+  if (!pc) {
+    return false;
+  }
+  args.rval().setInt32(script->pcToOffset(pc));
+  return true;
+}
+
+static bool PCToLine(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+  RootedScript script(cx);
+  int32_t i;
+  unsigned lineno;
+
+  if (!GetScriptAndPCArgs(cx, args, &script, &i)) {
+    return false;
+  }
+  lineno = PCToLineNumber(script, script->offsetToPC(i));
+  if (!lineno) {
+    return false;
+  }
+  args.rval().setInt32(lineno);
+  return true;
+}
+
+#if defined(DEBUG) || defined(JS_JITSPEW)
+
+static bool Notes(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+  Sprinter sprinter(cx);
+  if (!sprinter.init()) {
+    return false;
+  }
+
+  for (unsigned i = 0; i < args.length(); i++) {
+    RootedScript script(cx, TestingFunctionArgumentToScript(cx, args[i]));
+    if (!script) {
+      return false;
+    }
+
+    if (!JSScript::dumpSrcNotes(cx, script, &sprinter)) {
+      return false;
+    }
+  }
+
+  JSString* str = JS_NewStringCopyZ(cx, sprinter.string());
+  if (!str) {
+    return false;
+  }
+  args.rval().setString(str);
+  return true;
+}
+
+namespace {
+
+struct DisassembleOptionParser {
+  unsigned argc;
+  Value* argv;
+  JSScript::DumpOptions options;
+
+  DisassembleOptionParser(unsigned argc, Value* argv)
+      : argc(argc), argv(argv) {}
+
+  bool parse(JSContext* cx) {
+    options.recursive = false;
+
+    /* Read options off early arguments */
+    while (argc > 0 && argv[0].isString()) {
+      JSString* str = argv[0].toString();
+      JSLinearString* linearStr = JS_EnsureLinearString(cx, str);
+      if (!linearStr) {
+        return false;
+      }
+      if (JS_LinearStringEqualsLiteral(linearStr, "-r")) {
+        options.recursive = true;
+      } else {
+        break;
+      }
+      argv++;
+      argc--;
+    }
+    return true;
+  }
+};
+
+} /* anonymous namespace */
+
+static bool DisassembleToSprinter(JSContext* cx, unsigned argc, Value* vp,
+                                  Sprinter* sprinter) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+  DisassembleOptionParser p(args.length(), args.array());
+  if (!p.parse(cx)) {
+    return false;
+  }
+
+  if (p.argc == 0) {
+    /* Without arguments, disassemble the current script. */
+    RootedScript script(cx, GetTopScript(cx));
+    if (script) {
+      JSAutoRealm ar(cx, script);
+      if (!JSScript::dump(cx, script, p.options, sprinter)) {
+        return false;
+      }
+    }
+  } else {
+    for (unsigned i = 0; i < p.argc; i++) {
+      RootedFunction fun(cx);
+      RootedScript script(cx);
+      RootedValue value(cx, p.argv[i]);
+      if (value.isObject() && value.toObject().is<ShellModuleObjectWrapper>()) {
+        script = value.toObject()
+                     .as<ShellModuleObjectWrapper>()
+                     .get()
+                     ->maybeScript();
+      } else {
+        script = TestingFunctionArgumentToScript(cx, value, fun.address());
+      }
+      if (!script) {
+        return false;
+      }
+
+      if (!JSScript::dump(cx, script, p.options, sprinter)) {
+        return false;
+      }
+    }
+  }
+
+  return !sprinter->hadOutOfMemory();
+}
+
+static bool DisassembleToString(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+  Sprinter sprinter(cx);
+  if (!sprinter.init()) {
+    return false;
+  }
+  if (!DisassembleToSprinter(cx, args.length(), vp, &sprinter)) {
+    return false;
+  }
+
+  JS::ConstUTF8CharsZ utf8chars(sprinter.string(), strlen(sprinter.string()));
+  JSString* str = JS_NewStringCopyUTF8Z(cx, utf8chars);
+  if (!str) {
+    return false;
+  }
+  args.rval().setString(str);
+  return true;
+}
+
+static bool Disassemble(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  if (!gOutFile->isOpen()) {
+    JS_ReportErrorASCII(cx, "output file is closed");
+    return false;
+  }
+
+  Sprinter sprinter(cx);
+  if (!sprinter.init()) {
+    return false;
+  }
+  if (!DisassembleToSprinter(cx, args.length(), vp, &sprinter)) {
+    return false;
+  }
+
+  fprintf(gOutFile->fp, "%s\n", sprinter.string());
+  args.rval().setUndefined();
+  return true;
+}
+
+static bool DisassFile(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  if (!gOutFile->isOpen()) {
+    JS_ReportErrorASCII(cx, "output file is closed");
+    return false;
+  }
+
+  /* Support extra options at the start, just like Disassemble. */
+  DisassembleOptionParser p(args.length(), args.array());
+  if (!p.parse(cx)) {
+    return false;
+  }
+
+  if (!p.argc) {
+    args.rval().setUndefined();
+    return true;
+  }
+
+  // We should change DisassembleOptionParser to store CallArgs.
+  JSString* str = JS::ToString(cx, HandleValue::fromMarkedLocation(&p.argv[0]));
+  if (!str) {
+    return false;
+  }
+  UniqueChars filename = JS_EncodeStringToLatin1(cx, str);
+  if (!filename) {
+    return false;
+  }
+  RootedScript script(cx);
+
+  {
+    CompileOptions options(cx);
+    options.setIntroductionType("js shell disFile")
+        .setFileAndLine(filename.get(), 1)
+        .setIsRunOnce(true)
+        .setNoScriptRval(true)
+        .setEagerDelazificationStrategy(defaultDelazificationMode);
+
+    script = JS::CompileUtf8Path(cx, options, filename.get());
+    if (!script) {
+      return false;
+    }
+  }
+
+  Sprinter sprinter(cx);
+  if (!sprinter.init()) {
+    return false;
+  }
+  if (JSScript::dump(cx, script, p.options, &sprinter)) {
+    return false;
+  }
+
+  fprintf(gOutFile->fp, "%s\n", sprinter.string());
+
+  args.rval().setUndefined();
+  return true;
+}
+
+static bool DisassWithSrc(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  if (!gOutFile->isOpen()) {
+    JS_ReportErrorASCII(cx, "output file is closed");
+    return false;
+  }
+
+  const size_t lineBufLen = 512;
+  unsigned len, line1, line2, bupline;
+  char linebuf[lineBufLen];
+  static const char sep[] = ";-------------------------";
+
+  RootedScript script(cx);
+  for (unsigned i = 0; i < args.length(); i++) {
+    script = TestingFunctionArgumentToScript(cx, args[i]);
+    if (!script) {
+      return false;
+    }
+
+    if (!script->filename()) {
+      JS_ReportErrorNumberASCII(cx, my_GetErrorMessage, nullptr,
+                                JSSMSG_FILE_SCRIPTS_ONLY);
+      return false;
+    }
+
+    FILE* file = fopen(script->filename(), "rb");
+    if (!file) {
+      /* FIXME: script->filename() should become UTF-8 (bug 987069). */
+      ReportCantOpenErrorUnknownEncoding(cx, script->filename());
+      return false;
+    }
+    auto closeFile = MakeScopeExit([file] { fclose(file); });
+
+    jsbytecode* pc = script->code();
+    jsbytecode* end = script->codeEnd();
+
+    Sprinter sprinter(cx);
+    if (!sprinter.init()) {
+      return false;
+    }
+
+    /* burn the leading lines */
+    line2 = PCToLineNumber(script, pc);
+    for (line1 = 0; line1 < line2 - 1; line1++) {
+      char* tmp = fgets(linebuf, lineBufLen, file);
+      if (!tmp) {
+        /* FIXME: This should use UTF-8 (bug 987069). */
+        JS_ReportErrorLatin1(cx, "failed to read %s fully", script->filename());
+        return false;
+      }
+    }
+
+    bupline = 0;
+    while (pc < end) {
+      line2 = PCToLineNumber(script, pc);
+
+      if (line2 < line1) {
+        if (bupline != line2) {
+          bupline = line2;
+          if (!sprinter.jsprintf("%s %3u: BACKUP\n", sep, line2)) {
+            return false;
+          }
+        }
+      } else {
+        if (bupline && line1 == line2) {
+          if (!sprinter.jsprintf("%s %3u: RESTORE\n", sep, line2)) {
+            return false;
+          }
+        }
+        bupline = 0;
+        while (line1 < line2) {
+          if (!fgets(linebuf, lineBufLen, file)) {
+            /*
+             * FIXME: script->filename() should become UTF-8
+             *        (bug 987069).
+             */
+            JS_ReportErrorNumberLatin1(cx, my_GetErrorMessage, nullptr,
+                                       JSSMSG_UNEXPECTED_EOF,
+                                       script->filename());
+            return false;
+          }
+          line1++;
+          if (!sprinter.jsprintf("%s %3u: %s", sep, line1, linebuf)) {
+            return false;
+          }
+        }
+      }
+
+      len =
+          Disassemble1(cx, script, pc, script->pcToOffset(pc), true, &sprinter);
+      if (!len) {
+        return false;
+      }
+
+      pc += len;
+    }
+
+    fprintf(gOutFile->fp, "%s\n", sprinter.string());
+  }
+
+  args.rval().setUndefined();
+  return true;
+}
+
+#endif /* defined(DEBUG) || defined(JS_JITSPEW) */
+
+#ifdef JS_CACHEIR_SPEW
+static bool CacheIRHealthReport(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  js::jit::CacheIRHealth cih;
+  RootedScript script(cx);
+
+  // In the case that we are calling this function from the shell and
+  // the environment variable is not set, AutoSpewChannel automatically
+  // sets and unsets the proper channel for the duration of spewing
+  // a health report.
+  AutoSpewChannel channel(cx, SpewChannel::CacheIRHealthReport, script);
+  if (!argc) {
+    // Calling CacheIRHealthReport without any arguments will create health
+    // reports for all scripts in the zone.
+    for (auto base = cx->zone()->cellIter<BaseScript>(); !base.done();
+         base.next()) {
+      if (!base->hasJitScript() || base->selfHosted()) {
+        continue;
+      }
+
+      script = base->asJSScript();
+      cih.healthReportForScript(cx, script, js::jit::SpewContext::Shell);
+    }
+  } else {
+    RootedValue value(cx, args.get(0));
+
+    if (value.isObject() && value.toObject().is<ShellModuleObjectWrapper>()) {
+      script =
+          value.toObject().as<ShellModuleObjectWrapper>().get()->maybeScript();
+    } else {
+      script = TestingFunctionArgumentToScript(cx, args.get(0));
+    }
+
+    if (!script) {
+      return false;
+    }
+
+    cih.healthReportForScript(cx, script, js::jit::SpewContext::Shell);
+  }
+
+  args.rval().setUndefined();
+  return true;
+}
+#endif /* JS_CACHEIR_SPEW */
+
+/* Pretend we can always preserve wrappers for dummy DOM objects. */
+static bool DummyPreserveWrapperCallback(JSContext* cx, HandleObject obj) {
+  return true;
+}
+
+static bool DummyHasReleasedWrapperCallback(HandleObject obj) { return true; }
+
+#ifdef FUZZING_JS_FUZZILLI
+static bool fuzzilli_hash(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+  args.rval().setUndefined();
+
+  if (argc != 1) {
+    return true;
+  }
+  uint32_t hash;
+  JS::Handle<JS::Value> v = args.get(0);
+  if (v.isInt32()) {
+    int32_t i = v.toInt32();
+    hash = FuzzilliHashDouble((double)i);
+  } else if (v.isDouble()) {
+    double d = v.toDouble();
+    d = JS::CanonicalizeNaN(d);
+    hash = FuzzilliHashDouble(d);
+  } else if (v.isNull()) {
+    hash = FuzzilliHashDouble(1.0);
+  } else if (v.isUndefined()) {
+    hash = FuzzilliHashDouble(2.0);
+  } else if (v.isBoolean()) {
+    hash = FuzzilliHashDouble(3.0 + v.toBoolean());
+  } else if (v.isBigInt()) {
+    JS::BigInt* bigInt = v.toBigInt();
+    hash = FuzzilliHashBigInt(bigInt);
+  } else if (v.isObject()) {
+    JSObject& obj = v.toObject();
+    FuzzilliHashObject(cx, &obj);
+    return true;
+  } else {
+    hash = 0;
+  }
+
+  cx->executionHashInputs += 1;
+  cx->executionHash = mozilla::RotateLeft(cx->executionHash + hash, 1);
+  return true;
+}
+
+// We have to assume that the fuzzer will be able to call this function e.g. by
+// enumerating the properties of the global object and eval'ing them. As such
+// this function is implemented in a way that requires passing some magic value
+// as first argument (with the idea being that the fuzzer won't be able to
+// generate this value) which then also acts as a selector for the operation
+// to perform.
+static bool Fuzzilli(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  RootedString arg(cx, JS::ToString(cx, args.get(0)));
+  if (!arg) {
+    return false;
+  }
+  Rooted<JSLinearString*> operation(cx, StringToLinearString(cx, arg));
+  if (!operation) {
+    return false;
+  }
+
+  if (StringEqualsAscii(operation, "FUZZILLI_CRASH")) {
+    int type;
+    if (!ToInt32(cx, args.get(1), &type)) {
+      return false;
+    }
+
+    // With this, we can test the various ways the JS shell can crash and make
+    // sure that Fuzzilli is able to detect all of these failures properly.
+    switch (type) {
+      case 0:
+        *((int*)0x41414141) = 0x1337;
+        break;
+      case 1:
+        MOZ_RELEASE_ASSERT(false);
+        break;
+      case 2:
+        MOZ_ASSERT(false);
+        break;
+      case 3:
+        __asm__("int3");
+        break;
+      default:
+        exit(1);
+    }
+  } else if (StringEqualsAscii(operation, "FUZZILLI_PRINT")) {
+    static FILE* fzliout = fdopen(REPRL_DWFD, "w");
+    if (!fzliout) {
+      fprintf(
+          stderr,
+          "Fuzzer output channel not available, printing to stdout instead\n");
+      fzliout = stdout;
+    }
+
+    RootedString str(cx, JS::ToString(cx, args.get(1)));
+    if (!str) {
+      return false;
+    }
+    UniqueChars bytes = JS_EncodeStringToUTF8(cx, str);
+    if (!bytes) {
+      return false;
+    }
+    fprintf(fzliout, "%s\n", bytes.get());
+    fflush(fzliout);
+  } else if (StringEqualsAscii(operation, "FUZZILLI_RANDOM")) {
+    // This is an entropy source which can be called during fuzzing.
+    // Its currently used to tests whether Fuzzilli detects non-deterministic
+    // behavior.
+    args.rval().setInt32(static_cast<uint32_t>(mozilla::RandomUint64OrDie()));
+    return true;
+  }
+
+  args.rval().setUndefined();
+  return true;
+}
+
+static bool FuzzilliReprlGetAndRun(JSContext* cx) {
+  size_t scriptSize = 0;
+
+  unsigned action;
+  MOZ_RELEASE_ASSERT(read(REPRL_CRFD, &action, 4) == 4);
+  if (action == 'cexe') {
+    MOZ_RELEASE_ASSERT(read(REPRL_CRFD, &scriptSize, 8) == 8);
+  } else {
+    fprintf(stderr, "Unknown action: %u\n", action);
+    _exit(-1);
+  }
+
+  CompileOptions options(cx);
+  options.setIntroductionType("reprl")
+      .setFileAndLine("reprl", 1)
+      .setIsRunOnce(true)
+      .setNoScriptRval(true)
+      .setEagerDelazificationStrategy(defaultDelazificationMode);
+
+  char* scriptSrc = static_cast<char*>(js_malloc(scriptSize));
+
+  char* ptr = scriptSrc;
+  size_t remaining = scriptSize;
+  while (remaining > 0) {
+    ssize_t rv = read(REPRL_DRFD, ptr, remaining);
+    if (rv <= 0) {
+      fprintf(stderr, "Failed to load script\n");
+      _exit(-1);
+    }
+    remaining -= rv;
+    ptr += rv;
+  }
+
+  JS::SourceText<Utf8Unit> srcBuf;
+  if (!srcBuf.init(cx, scriptSrc, scriptSize,
+                   JS::SourceOwnership::TakeOwnership)) {
+    return false;
+  }
+
+  RootedScript script(cx, JS::Compile(cx, options, srcBuf));
+  if (!script) {
+    return false;
+  }
+
+  if (!JS_ExecuteScript(cx, script)) {
+    return false;
+  }
+
+  return true;
+}
+
+#endif /* FUZZING_JS_FUZZILLI */
+
+static bool FuzzilliUseReprlMode(OptionParser* op) {
+#ifdef FUZZING_JS_FUZZILLI
+  // Check if we should use REPRL mode
+  bool reprl_mode = op->getBoolOption("reprl");
+  if (reprl_mode) {
+    // Check in with parent
+    char helo[] = "HELO";
+    if (write(REPRL_CWFD, helo, 4) != 4 || read(REPRL_CRFD, helo, 4) != 4) {
+      reprl_mode = false;
+    }
+
+    if (memcmp(helo, "HELO", 4) != 0) {
+      fprintf(stderr, "Invalid response from parent\n");
+      _exit(-1);
+    }
+  }
+  return reprl_mode;
+#else
+  return false;
+#endif /* FUZZING_JS_FUZZILLI */
+}
+
+static bool Crash(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+  if (args.length() == 0) {
+    MOZ_CRASH("forced crash");
+  }
+  RootedString message(cx, JS::ToString(cx, args[0]));
+  if (!message) {
+    return false;
+  }
+  UniqueChars utf8chars = JS_EncodeStringToUTF8(cx, message);
+  if (!utf8chars) {
+    return false;
+  }
+  if (args.get(1).isObject()) {
+    RootedValue v(cx);
+    RootedObject opts(cx, &args[1].toObject());
+    if (!JS_GetProperty(cx, opts, "suppress_minidump", &v)) {
+      return false;
+    }
+    if (v.isBoolean() && v.toBoolean()) {
+      js::NoteIntentionalCrash();
+    }
+  }
+#ifndef DEBUG
+  MOZ_ReportCrash(utf8chars.get(), __FILE__, __LINE__);
+#endif
+  MOZ_CRASH_UNSAFE(utf8chars.get());
+}
+
+static bool GetSLX(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+  RootedScript script(cx);
+
+  script = TestingFunctionArgumentToScript(cx, args.get(0));
+  if (!script) {
+    return false;
+  }
+  args.rval().setInt32(GetScriptLineExtent(script));
+  return true;
+}
+
+static bool ThrowError(JSContext* cx, unsigned argc, Value* vp) {
+  JS_ReportErrorASCII(cx, "This is an error");
+  return false;
+}
+
+static bool CopyErrorReportToObject(JSContext* cx, JSErrorReport* report,
+                                    HandleObject obj) {
+  RootedString nameStr(cx);
+  if (report->exnType == JSEXN_WARN) {
+    nameStr = JS_NewStringCopyZ(cx, "Warning");
+    if (!nameStr) {
+      return false;
+    }
+  } else {
+    nameStr = GetErrorTypeName(cx, report->exnType);
+    // GetErrorTypeName doesn't set an exception, but
+    // can fail for InternalError or non-error objects.
+    if (!nameStr) {
+      nameStr = cx->runtime()->emptyString;
+    }
+  }
+  RootedValue nameVal(cx, StringValue(nameStr));
+  if (!DefineDataProperty(cx, obj, cx->names().name, nameVal)) {
+    return false;
+  }
+
+  RootedString messageStr(cx, report->newMessageString(cx));
+  if (!messageStr) {
+    return false;
+  }
+  RootedValue messageVal(cx, StringValue(messageStr));
+  if (!DefineDataProperty(cx, obj, cx->names().message, messageVal)) {
+    return false;
+  }
+
+  RootedValue linenoVal(cx, Int32Value(report->lineno));
+  if (!DefineDataProperty(cx, obj, cx->names().lineNumber, linenoVal)) {
+    return false;
+  }
+
+  RootedValue columnVal(cx, Int32Value(report->column));
+  if (!DefineDataProperty(cx, obj, cx->names().columnNumber, columnVal)) {
+    return false;
+  }
+
+  RootedObject notesArray(cx, CreateErrorNotesArray(cx, report));
+  if (!notesArray) {
+    return false;
+  }
+
+  RootedValue notesArrayVal(cx, ObjectValue(*notesArray));
+  return DefineDataProperty(cx, obj, cx->names().notes, notesArrayVal);
+}
+
+static bool CreateErrorReport(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  // We don't have a stack here, so just initialize with null.
+  JS::ExceptionStack exnStack(cx, args.get(0), nullptr);
+  JS::ErrorReportBuilder report(cx);
+  if (!report.init(cx, exnStack, JS::ErrorReportBuilder::WithSideEffects)) {
+    return false;
+  }
+
+  MOZ_ASSERT(!report.report()->isWarning());
+
+  RootedObject obj(cx, JS_NewPlainObject(cx));
+  if (!obj) {
+    return false;
+  }
+
+  RootedString toString(cx, NewStringCopyUTF8Z(cx, report.toStringResult()));
+  if (!toString) {
+    return false;
+  }
+
+  if (!JS_DefineProperty(cx, obj, "toStringResult", toString,
+                         JSPROP_ENUMERATE)) {
+    return false;
+  }
+
+  if (!CopyErrorReportToObject(cx, report.report(), obj)) {
+    return false;
+  }
+
+  args.rval().setObject(*obj);
+  return true;
+}
+
+#define LAZY_STANDARD_CLASSES
+
+/* A class for easily testing the inner/outer object callbacks. */
+typedef struct ComplexObject {
+  bool isInner;
+  bool frozen;
+  JSObject* inner;
+  JSObject* outer;
+} ComplexObject;
+
+static bool sandbox_enumerate(JSContext* cx, JS::HandleObject obj,
+                              JS::MutableHandleIdVector properties,
+                              bool enumerableOnly) {
+  RootedValue v(cx);
+
+  if (!JS_GetProperty(cx, obj, "lazy", &v)) {
+    return false;
+  }
+
+  if (!ToBoolean(v)) {
+    return true;
+  }
+
+  return JS_NewEnumerateStandardClasses(cx, obj, properties, enumerableOnly);
+}
+
+static bool sandbox_resolve(JSContext* cx, HandleObject obj, HandleId id,
+                            bool* resolvedp) {
+  RootedValue v(cx);
+  if (!JS_GetProperty(cx, obj, "lazy", &v)) {
+    return false;
+  }
+
+  if (ToBoolean(v)) {
+    return JS_ResolveStandardClass(cx, obj, id, resolvedp);
+  }
+  return true;
+}
+
+static const JSClassOps sandbox_classOps = {
+    nullptr,                   // addProperty
+    nullptr,                   // delProperty
+    nullptr,                   // enumerate
+    sandbox_enumerate,         // newEnumerate
+    sandbox_resolve,           // resolve
+    nullptr,                   // mayResolve
+    nullptr,                   // finalize
+    nullptr,                   // call
+    nullptr,                   // construct
+    JS_GlobalObjectTraceHook,  // trace
+};
+
+static const JSClass sandbox_class = {"sandbox", JSCLASS_GLOBAL_FLAGS,
+                                      &sandbox_classOps};
+
+static void SetStandardRealmOptions(JS::RealmOptions& options) {
+  options.creationOptions()
+      .setSharedMemoryAndAtomicsEnabled(enableSharedMemory)
+      .setCoopAndCoepEnabled(false)
+      .setWeakRefsEnabled(enableWeakRefs
+                              ? JS::WeakRefSpecifier::EnabledWithCleanupSome
+                              : JS::WeakRefSpecifier::Disabled)
+      .setToSourceEnabled(enableToSource)
+      .setPropertyErrorMessageFixEnabled(enablePropertyErrorMessageFix)
+      .setIteratorHelpersEnabled(enableIteratorHelpers)
+      .setShadowRealmsEnabled(enableShadowRealms)
+#ifdef NIGHTLY_BUILD
+      .setArrayGroupingEnabled(enableArrayGrouping)
+      .setArrayFromAsyncEnabled(enableArrayFromAsync)
+#endif
+#ifdef ENABLE_CHANGE_ARRAY_BY_COPY
+      .setChangeArrayByCopyEnabled(enableChangeArrayByCopy)
+#endif
+#ifdef ENABLE_NEW_SET_METHODS
+      .setNewSetMethodsEnabled(enableNewSetMethods)
+#endif
+      ;
+}
+
+[[nodiscard]] static bool CheckRealmOptions(JSContext* cx,
+                                            JS::RealmOptions& options,
+                                            JSPrincipals* principals) {
+  JS::RealmCreationOptions& creationOptions = options.creationOptions();
+  if (creationOptions.compartmentSpecifier() !=
+      JS::CompartmentSpecifier::ExistingCompartment) {
+    return true;
+  }
+
+  JS::Compartment* comp = creationOptions.compartment();
+
+  // All realms in a compartment must be either system or non-system.
+  bool isSystem =
+      principals && principals == cx->runtime()->trustedPrincipals();
+  if (isSystem != IsSystemCompartment(comp)) {
+    JS_ReportErrorASCII(cx,
+                        "Cannot create system and non-system realms in the "
+                        "same compartment");
+    return false;
+  }
+
+  // Debugger visibility is per-compartment, not per-realm, so make sure the
+  // requested visibility matches the existing compartment's.
+  if (creationOptions.invisibleToDebugger() != comp->invisibleToDebugger()) {
+    JS_ReportErrorASCII(cx,
+                        "All the realms in a compartment must have "
+                        "the same debugger visibility");
+    return false;
+  }
+
+  return true;
+}
+
+static JSObject* NewSandbox(JSContext* cx, bool lazy) {
+  JS::RealmOptions options;
+  SetStandardRealmOptions(options);
+
+  if (defaultToSameCompartment) {
+    options.creationOptions().setExistingCompartment(cx->global());
+  } else {
+    options.creationOptions().setNewCompartmentAndZone();
+  }
+
+  JSPrincipals* principals = nullptr;
+  if (!CheckRealmOptions(cx, options, principals)) {
+    return nullptr;
+  }
+
+  RootedObject obj(cx,
+                   JS_NewGlobalObject(cx, &sandbox_class, principals,
+                                      JS::DontFireOnNewGlobalHook, options));
+  if (!obj) {
+    return nullptr;
+  }
+
+  {
+    JSAutoRealm ar(cx, obj);
+    if (!lazy && !JS::InitRealmStandardClasses(cx)) {
+      return nullptr;
+    }
+
+    RootedValue value(cx, BooleanValue(lazy));
+    if (!JS_DefineProperty(cx, obj, "lazy", value,
+                           JSPROP_PERMANENT | JSPROP_READONLY)) {
+      return nullptr;
+    }
+
+    JS_FireOnNewGlobalObject(cx, obj);
+  }
+
+  if (!cx->compartment()->wrap(cx, &obj)) {
+    return nullptr;
+  }
+  return obj;
+}
+
+static bool EvalInContext(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+  if (!args.requireAtLeast(cx, "evalcx", 1)) {
+    return false;
+  }
+
+  RootedString str(cx, ToString(cx, args[0]));
+  if (!str) {
+    return false;
+  }
+
+  RootedObject sobj(cx);
+  if (args.hasDefined(1)) {
+    sobj = ToObject(cx, args[1]);
+    if (!sobj) {
+      return false;
+    }
+  }
+
+  AutoStableStringChars strChars(cx);
+  if (!strChars.initTwoByte(cx, str)) {
+    return false;
+  }
+
+  mozilla::Range<const char16_t> chars = strChars.twoByteRange();
+  size_t srclen = chars.length();
+  const char16_t* src = chars.begin().get();
+
+  bool lazy = false;
+  if (srclen == 4) {
+    if (src[0] == 'l' && src[1] == 'a' && src[2] == 'z' && src[3] == 'y') {
+      lazy = true;
+      srclen = 0;
+    }
+  }
+
+  if (!sobj) {
+    sobj = NewSandbox(cx, lazy);
+    if (!sobj) {
+      return false;
+    }
+  }
+
+  if (srclen == 0) {
+    args.rval().setObject(*sobj);
+    return true;
+  }
+
+  JS::AutoFilename filename;
+  unsigned lineno;
+
+  DescribeScriptedCaller(cx, &filename, &lineno);
+  {
+    sobj = UncheckedUnwrap(sobj, true);
+
+    JSAutoRealm ar(cx, sobj);
+
+    sobj = ToWindowIfWindowProxy(sobj);
+
+    if (!JS_IsGlobalObject(sobj)) {
+      JS_ReportErrorASCII(cx, "Invalid scope argument to evalcx");
+      return false;
+    }
+
+    JS::CompileOptions opts(cx);
+    opts.setFileAndLine(filename.get(), lineno)
+        .setEagerDelazificationStrategy(defaultDelazificationMode);
+
+    JS::SourceText<char16_t> srcBuf;
+    if (!srcBuf.init(cx, src, srclen, JS::SourceOwnership::Borrowed) ||
+        !JS::Evaluate(cx, opts, srcBuf, args.rval())) {
+      return false;
+    }
+  }
+
+  if (!cx->compartment()->wrap(cx, args.rval())) {
+    return false;
+  }
+
+  return true;
+}
+
+static bool EnsureGeckoProfilingStackInstalled(JSContext* cx,
+                                               ShellContext* sc) {
+  if (cx->geckoProfiler().infraInstalled()) {
+    MOZ_ASSERT(sc->geckoProfilingStack);
+    return true;
+  }
+
+  MOZ_ASSERT(!sc->geckoProfilingStack);
+  sc->geckoProfilingStack = MakeUnique<ProfilingStack>();
+  if (!sc->geckoProfilingStack) {
+    JS_ReportOutOfMemory(cx);
+    return false;
+  }
+
+  SetContextProfilingStack(cx, sc->geckoProfilingStack.get());
+  return true;
+}
+
+struct WorkerInput {
+  JSRuntime* parentRuntime;
+  UniqueTwoByteChars chars;
+  size_t length;
+
+  WorkerInput(JSRuntime* parentRuntime, UniqueTwoByteChars chars, size_t length)
+      : parentRuntime(parentRuntime), chars(std::move(chars)), length(length) {}
+};
+
+static void DestroyShellCompartmentPrivate(JS::GCContext* gcx,
+                                           JS::Compartment* compartment) {
+  auto priv = static_cast<ShellCompartmentPrivate*>(
+      JS_GetCompartmentPrivate(compartment));
+  js_delete(priv);
+}
+
+static void SetWorkerContextOptions(JSContext* cx);
+static bool ShellBuildId(JS::BuildIdCharVector* buildId);
+
+static constexpr size_t gWorkerStackSize = 2 * 128 * sizeof(size_t) * 1024;
+
+static void WorkerMain(UniquePtr<WorkerInput> input) {
+  MOZ_ASSERT(input->parentRuntime);
+
+  JSContext* cx = JS_NewContext(8L * 1024L * 1024L, input->parentRuntime);
+  if (!cx) {
+    return;
+  }
+
+  ShellContext* sc = js_new<ShellContext>(cx);
+  if (!sc) {
+    return;
+  }
+
+  auto guard = mozilla::MakeScopeExit([&] {
+    CancelOffThreadJobsForContext(cx);
+    sc->markObservers.reset();
+    JS_SetContextPrivate(cx, nullptr);
+    js_delete(sc);
+    JS_DestroyContext(cx);
+  });
+
+  sc->isWorker = true;
+
+  JS_SetContextPrivate(cx, sc);
+  JS_SetGrayGCRootsTracer(cx, TraceGrayRoots, nullptr);
+  SetWorkerContextOptions(cx);
+
+  JS_SetFutexCanWait(cx);
+  JS::SetWarningReporter(cx, WarningReporter);
+  js::SetPreserveWrapperCallbacks(cx, DummyPreserveWrapperCallback,
+                                  DummyHasReleasedWrapperCallback);
+  JS_InitDestroyPrincipalsCallback(cx, ShellPrincipals::destroy);
+  JS_SetDestroyCompartmentCallback(cx, DestroyShellCompartmentPrivate);
+
+  js::SetWindowProxyClass(cx, &ShellWindowProxyClass);
+
+  js::UseInternalJobQueues(cx);
+
+  JS::SetHostCleanupFinalizationRegistryCallback(
+      cx, ShellCleanupFinalizationRegistryCallback, sc);
+
+  if (!JS::InitSelfHostedCode(cx)) {
+    return;
+  }
+
+  EnvironmentPreparer environmentPreparer(cx);
+
+  do {
+    JS::RealmOptions realmOptions;
+    SetStandardRealmOptions(realmOptions);
+
+    RootedObject global(cx, NewGlobalObject(cx, realmOptions, nullptr,
+                                            ShellGlobalKind::WindowProxy,
+                                            /* immutablePrototype = */ true));
+    if (!global) {
+      break;
+    }
+
+    JSAutoRealm ar(cx, global);
+
+    JS::ConstUTF8CharsZ path(processWideModuleLoadPath.get(),
+                             strlen(processWideModuleLoadPath.get()));
+    RootedString moduleLoadPath(cx, JS_NewStringCopyUTF8Z(cx, path));
+    if (!moduleLoadPath) {
+      return;
+    }
+    sc->moduleLoader = js::MakeUnique<ModuleLoader>();
+    if (!sc->moduleLoader || !sc->moduleLoader->init(cx, moduleLoadPath)) {
+      return;
+    }
+
+    JS::CompileOptions options(cx);
+    options.setFileAndLine("<string>", 1)
+        .setIsRunOnce(true)
+        .setEagerDelazificationStrategy(defaultDelazificationMode);
+
+    AutoReportException are(cx);
+    JS::SourceText<char16_t> srcBuf;
+    if (!srcBuf.init(cx, input->chars.get(), input->length,
+                     JS::SourceOwnership::Borrowed)) {
+      break;
+    }
+
+    RootedScript script(cx, JS::Compile(cx, options, srcBuf));
+    if (!script) {
+      break;
+    }
+    RootedValue result(cx);
+    JS_ExecuteScript(cx, script, &result);
+  } while (0);
+
+  KillWatchdog(cx);
+  JS_SetGrayGCRootsTracer(cx, nullptr, nullptr);
+}
+
+// Workers can spawn other workers, so we need a lock to access workerThreads.
+static Mutex* workerThreadsLock = nullptr;
+static Vector<UniquePtr<js::Thread>, 0, SystemAllocPolicy> workerThreads;
+
+class MOZ_RAII AutoLockWorkerThreads : public LockGuard<Mutex> {
+  using Base = LockGuard<Mutex>;
+
+ public:
+  AutoLockWorkerThreads() : Base(*workerThreadsLock) {
+    MOZ_ASSERT(workerThreadsLock);
+  }
+};
+
+static bool EvalInWorker(JSContext* cx, unsigned argc, Value* vp) {
+  if (!CanUseExtraThreads()) {
+    JS_ReportErrorASCII(cx, "Can't create threads with --no-threads");
+    return false;
+  }
+
+  CallArgs args = CallArgsFromVp(argc, vp);
+  if (!args.get(0).isString()) {
+    JS_ReportErrorASCII(cx, "Invalid arguments");
+    return false;
+  }
+
+#if defined(DEBUG) || defined(JS_OOM_BREAKPOINT)
+  if (cx->runningOOMTest) {
+    JS_ReportErrorASCII(
+        cx, "Can't create threads while running simulated OOM test");
+    return false;
+  }
+#endif
+
+  if (!args[0].toString()->ensureLinear(cx)) {
+    return false;
+  }
+
+  if (!workerThreadsLock) {
+    workerThreadsLock = js_new<Mutex>(mutexid::ShellWorkerThreads);
+    if (!workerThreadsLock) {
+      ReportOutOfMemory(cx);
+      return false;
+    }
+  }
+
+  JSLinearString* str = &args[0].toString()->asLinear();
+
+  UniqueTwoByteChars chars(js_pod_malloc<char16_t>(str->length()));
+  if (!chars) {
+    ReportOutOfMemory(cx);
+    return false;
+  }
+
+  CopyChars(chars.get(), *str);
+
+  auto input = js::MakeUnique<WorkerInput>(JS_GetParentRuntime(cx),
+                                           std::move(chars), str->length());
+  if (!input) {
+    ReportOutOfMemory(cx);
+    return false;
+  }
+
+  UniquePtr<Thread> thread;
+  {
+    AutoEnterOOMUnsafeRegion oomUnsafe;
+    thread = js::MakeUnique<Thread>(
+        Thread::Options().setStackSize(gWorkerStackSize + 512 * 1024));
+    if (!thread || !thread->init(WorkerMain, std::move(input))) {
+      oomUnsafe.crash("EvalInWorker");
+    }
+  }
+
+  AutoLockWorkerThreads alwt;
+  if (!workerThreads.append(std::move(thread))) {
+    ReportOutOfMemory(cx);
+    thread->join();
+    return false;
+  }
+
+  args.rval().setUndefined();
+  return true;
+}
+
+static bool ShapeOf(JSContext* cx, unsigned argc, JS::Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+  if (!args.get(0).isObject()) {
+    JS_ReportErrorASCII(cx, "shapeOf: object expected");
+    return false;
+  }
+  JSObject* obj = &args[0].toObject();
+  args.rval().set(JS_NumberValue(double(uintptr_t(obj->shape()) >> 3)));
+  return true;
+}
+
+static bool Sleep_fn(JSContext* cx, unsigned argc, Value* vp) {
+  ShellContext* sc = GetShellContext(cx);
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  TimeDuration duration = TimeDuration::FromSeconds(0.0);
+  if (args.length() > 0) {
+    double t_secs;
+    if (!ToNumber(cx, args[0], &t_secs)) {
+      return false;
+    }
+    if (mozilla::IsNaN(t_secs)) {
+      JS_ReportErrorASCII(cx, "sleep interval is not a number");
+      return false;
+    }
+
+    duration = TimeDuration::FromSeconds(std::max(0.0, t_secs));
+    const TimeDuration MAX_TIMEOUT_INTERVAL =
+        TimeDuration::FromSeconds(MAX_TIMEOUT_SECONDS);
+    if (duration > MAX_TIMEOUT_INTERVAL) {
+      JS_ReportErrorASCII(cx, "Excessive sleep interval");
+      return false;
+    }
+  }
+  {
+    LockGuard<Mutex> guard(sc->watchdogLock);
+    TimeStamp toWakeup = TimeStamp::Now() + duration;
+    for (;;) {
+      sc->sleepWakeup.wait_for(guard, duration);
+      if (sc->serviceInterrupt) {
+        break;
+      }
+      auto now = TimeStamp::Now();
+      if (now >= toWakeup) {
+        break;
+      }
+      duration = toWakeup - now;
+    }
+  }
+  args.rval().setUndefined();
+  return !sc->serviceInterrupt;
+}
+
+static void KillWatchdog(JSContext* cx) {
+  ShellContext* sc = GetShellContext(cx);
+  Maybe<Thread> thread;
+
+  {
+    LockGuard<Mutex> guard(sc->watchdogLock);
+    std::swap(sc->watchdogThread, thread);
+    if (thread) {
+      // The watchdog thread becoming Nothing is its signal to exit.
+      sc->watchdogWakeup.notify_one();
+    }
+  }
+  if (thread) {
+    thread->join();
+  }
+
+  MOZ_ASSERT(!sc->watchdogThread);
+}
+
+static void WatchdogMain(JSContext* cx) {
+  ThisThread::SetName("JS Watchdog");
+
+  ShellContext* sc = GetShellContext(cx);
+
+  {
+    LockGuard<Mutex> guard(sc->watchdogLock);
+    while (sc->watchdogThread) {
+      auto now = TimeStamp::Now();
+      if (sc->watchdogTimeout && now >= sc->watchdogTimeout.value()) {
+        /*
+         * The timeout has just expired. Request an interrupt callback
+         * outside the lock.
+         */
+        sc->watchdogTimeout = Nothing();
+        {
+          UnlockGuard<Mutex> unlock(guard);
+          CancelExecution(cx);
+        }
+
+        /* Wake up any threads doing sleep. */
+        sc->sleepWakeup.notify_all();
+      } else {
+        if (sc->watchdogTimeout) {
+          /*
+           * Time hasn't expired yet. Simulate an interrupt callback
+           * which doesn't abort execution.
+           */
+          JS_RequestInterruptCallback(cx);
+        }
+
+        TimeDuration sleepDuration = sc->watchdogTimeout
+                                         ? TimeDuration::FromSeconds(0.1)
+                                         : TimeDuration::Forever();
+        sc->watchdogWakeup.wait_for(guard, sleepDuration);
+      }
+    }
+  }
+}
+
+static bool ScheduleWatchdog(JSContext* cx, double t) {
+  ShellContext* sc = GetShellContext(cx);
+
+  if (t <= 0) {
+    LockGuard<Mutex> guard(sc->watchdogLock);
+    sc->watchdogTimeout = Nothing();
+    return true;
+  }
+
+#ifdef __wasi__
+  return false;
+#endif
+
+  auto interval = TimeDuration::FromSeconds(t);
+  auto timeout = TimeStamp::Now() + interval;
+  LockGuard<Mutex> guard(sc->watchdogLock);
+  if (!sc->watchdogThread) {
+    MOZ_ASSERT(!sc->watchdogTimeout);
+    sc->watchdogThread.emplace();
+    AutoEnterOOMUnsafeRegion oomUnsafe;
+    if (!sc->watchdogThread->init(WatchdogMain, cx)) {
+      oomUnsafe.crash("watchdogThread.init");
+    }
+  } else if (!sc->watchdogTimeout || timeout < sc->watchdogTimeout.value()) {
+    sc->watchdogWakeup.notify_one();
+  }
+  sc->watchdogTimeout = Some(timeout);
+  return true;
+}
+
+static void KillWorkerThreads(JSContext* cx) {
+  MOZ_ASSERT_IF(!CanUseExtraThreads(), workerThreads.empty());
+
+  if (!workerThreadsLock) {
+    MOZ_ASSERT(workerThreads.empty());
+    return;
+  }
+
+  while (true) {
+    // We need to leave the AutoLockWorkerThreads scope before we call
+    // js::Thread::join, to avoid deadlocks when AutoLockWorkerThreads is
+    // used by the worker thread.
+    UniquePtr<Thread> thread;
+    {
+      AutoLockWorkerThreads alwt;
+      if (workerThreads.empty()) {
+        break;
+      }
+      thread = std::move(workerThreads.back());
+      workerThreads.popBack();
+    }
+    thread->join();
+  }
+
+  workerThreads.clearAndFree();
+
+  js_delete(workerThreadsLock);
+  workerThreadsLock = nullptr;
+}
+
+static void CancelExecution(JSContext* cx) {
+  ShellContext* sc = GetShellContext(cx);
+  sc->serviceInterrupt = true;
+  JS_RequestInterruptCallback(cx);
+}
+
+static bool SetTimeoutValue(JSContext* cx, double t) {
+  if (mozilla::IsNaN(t)) {
+    JS_ReportErrorASCII(cx, "timeout is not a number");
+    return false;
+  }
+  const TimeDuration MAX_TIMEOUT_INTERVAL =
+      TimeDuration::FromSeconds(MAX_TIMEOUT_SECONDS);
+  if (TimeDuration::FromSeconds(t) > MAX_TIMEOUT_INTERVAL) {
+    JS_ReportErrorASCII(cx, "Excessive timeout value");
+    return false;
+  }
+  GetShellContext(cx)->timeoutInterval = t;
+  if (!ScheduleWatchdog(cx, t)) {
+    JS_ReportErrorASCII(cx, "Failed to create the watchdog");
+    return false;
+  }
+  return true;
+}
+
+static bool Timeout(JSContext* cx, unsigned argc, Value* vp) {
+  ShellContext* sc = GetShellContext(cx);
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  if (args.length() == 0) {
+    args.rval().setNumber(sc->timeoutInterval);
+    return true;
+  }
+
+  if (args.length() > 2) {
+    JS_ReportErrorASCII(cx, "Wrong number of arguments");
+    return false;
+  }
+
+  double t;
+  if (!ToNumber(cx, args[0], &t)) {
+    return false;
+  }
+
+  if (args.length() > 1) {
+    RootedValue value(cx, args[1]);
+    if (!value.isObject() || !value.toObject().is<JSFunction>()) {
+      JS_ReportErrorASCII(cx, "Second argument must be a timeout function");
+      return false;
+    }
+    sc->interruptFunc = value;
+    sc->haveInterruptFunc = true;
+  }
+
+  args.rval().setUndefined();
+  return SetTimeoutValue(cx, t);
+}
+
+static bool InterruptIf(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  if (args.length() != 1) {
+    JS_ReportErrorASCII(cx, "Wrong number of arguments");
+    return false;
+  }
+
+  if (ToBoolean(args[0])) {
+    GetShellContext(cx)->serviceInterrupt = true;
+    JS_RequestInterruptCallback(cx);
+  }
+
+  args.rval().setUndefined();
+  return true;
+}
+
+static bool InvokeInterruptCallbackWrapper(JSContext* cx, unsigned argc,
+                                           Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+  if (args.length() != 1) {
+    JS_ReportErrorASCII(cx, "Wrong number of arguments");
+    return false;
+  }
+
+  GetShellContext(cx)->serviceInterrupt = true;
+  JS_RequestInterruptCallback(cx);
+  bool interruptRv = CheckForInterrupt(cx);
+
+  // The interrupt handler could have set a pending exception. Since we call
+  // back into JS, don't have it see the pending exception. If we have an
+  // uncatchable exception that's not propagating a debug mode forced
+  // return, return.
+  if (!interruptRv && !cx->isExceptionPending() &&
+      !cx->isPropagatingForcedReturn()) {
+    return false;
+  }
+
+  JS::AutoSaveExceptionState savedExc(cx);
+
+  FixedInvokeArgs<1> iargs(cx);
+
+  iargs[0].setBoolean(interruptRv);
+
+  RootedValue rv(cx);
+  if (!js::Call(cx, args[0], UndefinedHandleValue, iargs, &rv)) {
+    return false;
+  }
+
+  args.rval().setUndefined();
+  return interruptRv;
+}
+
+static bool SetInterruptCallback(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  if (args.length() != 1) {
+    JS_ReportErrorASCII(cx, "Wrong number of arguments");
+    return false;
+  }
+
+  RootedValue value(cx, args[0]);
+  if (!value.isObject() || !value.toObject().is<JSFunction>()) {
+    JS_ReportErrorASCII(cx, "Argument must be a function");
+    return false;
+  }
+  GetShellContext(cx)->interruptFunc = value;
+  GetShellContext(cx)->haveInterruptFunc = true;
+
+  args.rval().setUndefined();
+  return true;
+}
+
+#ifdef DEBUG
+// var s0 = "A".repeat(10*1024);
+// interruptRegexp(/a(bc|bd)/, s0);
+// first arg is regexp
+// second arg is string
+static bool InterruptRegexp(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+  ShellContext* sc = GetShellContext(cx);
+  RootedObject callee(cx, &args.callee());
+
+  if (args.length() != 2) {
+    ReportUsageErrorASCII(cx, callee, "Wrong number of arguments.");
+    return false;
+  }
+  if (!(args[0].isObject() && args[0].toObject().is<RegExpObject>())) {
+    ReportUsageErrorASCII(cx, callee,
+                          "First argument must be a regular expression.");
+    return false;
+  }
+  if (!args[1].isString()) {
+    ReportUsageErrorASCII(cx, callee, "Second argument must be a String.");
+    return false;
+  }
+  // Set interrupt flags
+  sc->serviceInterrupt = true;
+  js::irregexp::IsolateSetShouldSimulateInterrupt(cx->isolate);
+
+  RootedObject regexp(cx, &args[0].toObject());
+  RootedString string(cx, args[1].toString());
+  int32_t lastIndex = 0;
+
+  return js::RegExpMatcherRaw(cx, regexp, string, lastIndex, nullptr,
+                              args.rval());
+}
+#endif
+
+static bool SetJitCompilerOption(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+  RootedObject callee(cx, &args.callee());
+
+  if (args.length() != 2) {
+    ReportUsageErrorASCII(cx, callee, "Wrong number of arguments.");
+    return false;
+  }
+
+  if (!args[0].isString()) {
+    ReportUsageErrorASCII(cx, callee, "First argument must be a String.");
+    return false;
+  }
+
+  if (!args[1].isInt32()) {
+    ReportUsageErrorASCII(cx, callee, "Second argument must be an Int32.");
+    return false;
+  }
+
+  // Disallow setting JIT options when there are worker threads, to avoid
+  // races.
+  if (workerThreadsLock) {
+    ReportUsageErrorASCII(
+        cx, callee, "Can't set JIT options when there are worker threads.");
+    return false;
+  }
+
+  JSLinearString* strArg = JS_EnsureLinearString(cx, args[0].toString());
+  if (!strArg) {
+    return false;
+  }
+
+#define JIT_COMPILER_MATCH(key, string)                        \
+  else if (JS_LinearStringEqualsLiteral(strArg, string)) opt = \
+      JSJITCOMPILER_##key;
+
+  JSJitCompilerOption opt = JSJITCOMPILER_NOT_AN_OPTION;
+  if (false) {
+  }
+  JIT_COMPILER_OPTIONS(JIT_COMPILER_MATCH);
+#undef JIT_COMPILER_MATCH
+
+  if (opt == JSJITCOMPILER_NOT_AN_OPTION) {
+    ReportUsageErrorASCII(
+        cx, callee,
+        "First argument does not name a valid option (see jsapi.h).");
+    return false;
+  }
+
+  int32_t number = args[1].toInt32();
+  if (number < 0) {
+    number = -1;
+  }
+
+  // Disallow enabling or disabling the Baseline Interpreter at runtime.
+  // Enabling is a problem because the Baseline Interpreter code is only
+  // present if the interpreter was enabled when the JitRuntime was created.
+  // To support disabling we would have to discard all JitScripts. Furthermore,
+  // we really want JitOptions to be immutable after startup so it's better to
+  // use shell flags.
+  if (opt == JSJITCOMPILER_BASELINE_INTERPRETER_ENABLE &&
+      bool(number) != jit::IsBaselineInterpreterEnabled()) {
+    JS_ReportErrorASCII(cx,
+                        "Enabling or disabling the Baseline Interpreter at "
+                        "runtime is not supported.");
+    return false;
+  }
+
+  // Throw if disabling the JITs and there's JIT code on the stack, to avoid
+  // assertion failures.
+  if ((opt == JSJITCOMPILER_BASELINE_ENABLE ||
+       opt == JSJITCOMPILER_ION_ENABLE) &&
+      number == 0) {
+    js::jit::JitActivationIterator iter(cx);
+    if (!iter.done()) {
+      JS_ReportErrorASCII(cx,
+                          "Can't turn off JITs with JIT code on the stack.");
+      return false;
+    }
+  }
+
+  // Throw if trying to disable all the Wasm compilers.  The logic here is that
+  // if we're trying to disable a compiler that is currently enabled and that is
+  // the last compiler enabled then we must throw.
+  //
+  // Note that this check does not prevent an error from being thrown later.
+  // Actual compiler availability is dynamic and depends on other conditions,
+  // such as other options set and whether a debugger is present.
+  if ((opt == JSJITCOMPILER_WASM_JIT_BASELINE ||
+       opt == JSJITCOMPILER_WASM_JIT_OPTIMIZING) &&
+      number == 0) {
+    uint32_t baseline, optimizing;
+    MOZ_ALWAYS_TRUE(JS_GetGlobalJitCompilerOption(
+        cx, JSJITCOMPILER_WASM_JIT_BASELINE, &baseline));
+    MOZ_ALWAYS_TRUE(JS_GetGlobalJitCompilerOption(
+        cx, JSJITCOMPILER_WASM_JIT_OPTIMIZING, &optimizing));
+    if (baseline + optimizing == 1) {
+      if ((opt == JSJITCOMPILER_WASM_JIT_BASELINE && baseline) ||
+          (opt == JSJITCOMPILER_WASM_JIT_OPTIMIZING && optimizing)) {
+        JS_ReportErrorASCII(
+            cx,
+            "Disabling all the Wasm compilers at runtime is not supported.");
+        return false;
+      }
+    }
+  }
+
+  // JIT compiler options are process-wide, so we have to stop off-thread
+  // compilations for all runtimes to avoid races.
+  WaitForAllHelperThreads();
+
+  // Only release JIT code for the current runtime because there's no good
+  // way to discard code for other runtimes.
+  ReleaseAllJITCode(cx->gcContext());
+
+  JS_SetGlobalJitCompilerOption(cx, opt, uint32_t(number));
+
+  args.rval().setUndefined();
+  return true;
+}
+
+static bool EnableLastWarning(JSContext* cx, unsigned argc, Value* vp) {
+  ShellContext* sc = GetShellContext(cx);
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  sc->lastWarningEnabled = true;
+  sc->lastWarning.setNull();
+
+  args.rval().setUndefined();
+  return true;
+}
+
+static bool DisableLastWarning(JSContext* cx, unsigned argc, Value* vp) {
+  ShellContext* sc = GetShellContext(cx);
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  sc->lastWarningEnabled = false;
+  sc->lastWarning.setNull();
+
+  args.rval().setUndefined();
+  return true;
+}
+
+static bool GetLastWarning(JSContext* cx, unsigned argc, Value* vp) {
+  ShellContext* sc = GetShellContext(cx);
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  if (!sc->lastWarningEnabled) {
+    JS_ReportErrorASCII(cx, "Call enableLastWarning first.");
+    return false;
+  }
+
+  if (!JS_WrapValue(cx, &sc->lastWarning)) {
+    return false;
+  }
+
+  args.rval().set(sc->lastWarning);
+  return true;
+}
+
+static bool ClearLastWarning(JSContext* cx, unsigned argc, Value* vp) {
+  ShellContext* sc = GetShellContext(cx);
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  if (!sc->lastWarningEnabled) {
+    JS_ReportErrorASCII(cx, "Call enableLastWarning first.");
+    return false;
+  }
+
+  sc->lastWarning.setNull();
+
+  args.rval().setUndefined();
+  return true;
+}
+
+#if defined(DEBUG) || defined(JS_JITSPEW)
+static bool StackDump(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  if (!gOutFile->isOpen()) {
+    JS_ReportErrorASCII(cx, "output file is closed");
+    return false;
+  }
+
+  bool showArgs = ToBoolean(args.get(0));
+  bool showLocals = ToBoolean(args.get(1));
+  bool showThisProps = ToBoolean(args.get(2));
+
+  JS::UniqueChars buf =
+      JS::FormatStackDump(cx, showArgs, showLocals, showThisProps);
+  if (!buf) {
+    fputs("Failed to format JavaScript stack for dump\n", gOutFile->fp);
+    JS_ClearPendingException(cx);
+  } else {
+    fputs(buf.get(), gOutFile->fp);
+  }
+
+  args.rval().setUndefined();
+  return true;
+}
+#endif
+
+static bool StackPointerInfo(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  // Copy the truncated stack pointer to the result.  This value is not used
+  // as a pointer but as a way to measure frame-size from JS.
+  args.rval().setInt32(int32_t(reinterpret_cast<size_t>(&args) & 0xfffffff));
+  return true;
+}
+
+static bool Elapsed(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+  if (args.length() == 0) {
+    double d = PRMJ_Now() - GetShellContext(cx)->startTime;
+    args.rval().setDouble(d);
+    return true;
+  }
+  JS_ReportErrorASCII(cx, "Wrong number of arguments");
+  return false;
+}
+
+static ShellCompartmentPrivate* EnsureShellCompartmentPrivate(JSContext* cx) {
+  Compartment* comp = cx->compartment();
+  auto priv =
+      static_cast<ShellCompartmentPrivate*>(JS_GetCompartmentPrivate(comp));
+  if (!priv) {
+    priv = cx->new_<ShellCompartmentPrivate>();
+    JS_SetCompartmentPrivate(cx->compartment(), priv);
+  }
+  return priv;
+}
+
+static bool ParseModule(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+  if (!args.requireAtLeast(cx, "parseModule", 1)) {
+    return false;
+  }
+
+  if (!args[0].isString()) {
+    const char* typeName = InformalValueTypeName(args[0]);
+    JS_ReportErrorASCII(cx, "expected string to compile, got %s", typeName);
+    return false;
+  }
+
+  JSString* scriptContents = args[0].toString();
+
+  UniqueChars filename;
+  CompileOptions options(cx);
+  if (args.length() > 1) {
+    if (!args[1].isString()) {
+      const char* typeName = InformalValueTypeName(args[1]);
+      JS_ReportErrorASCII(cx, "expected filename string, got %s", typeName);
+      return false;
+    }
+
+    RootedString str(cx, args[1].toString());
+    filename = JS_EncodeStringToLatin1(cx, str);
+    if (!filename) {
+      return false;
+    }
+
+    options.setFileAndLine(filename.get(), 1);
+  } else {
+    options.setFileAndLine("<string>", 1);
+  }
+  options.setModule();
+
+  AutoStableStringChars linearChars(cx);
+  if (!linearChars.initTwoByte(cx, scriptContents)) {
+    return false;
+  }
+
+  JS::SourceText<char16_t> srcBuf;
+  if (!srcBuf.initMaybeBorrowed(cx, linearChars)) {
+    return false;
+  }
+
+  AutoReportFrontendContext fc(cx);
+  RootedObject module(
+      cx, frontend::CompileModule(cx, &fc, cx->stackLimitForCurrentPrincipal(),
+                                  options, srcBuf));
+  if (!module) {
+    return false;
+  }
+
+  Rooted<ShellModuleObjectWrapper*> wrapper(
+      cx, ShellModuleObjectWrapper::create(cx, module.as<ModuleObject>()));
+  if (!wrapper) {
+    return false;
+  }
+  args.rval().setObject(*wrapper);
+  return true;
+}
+
+// A JSObject that holds XDRBuffer.
+class XDRBufferObject : public NativeObject {
+  static const size_t VECTOR_SLOT = 0;
+  static const unsigned RESERVED_SLOTS = 1;
+
+ public:
+  static const JSClassOps classOps_;
+  static const JSClass class_;
+
+  [[nodiscard]] inline static XDRBufferObject* create(
+      JSContext* cx, JS::TranscodeBuffer&& buf);
+
+  JS::TranscodeBuffer* data() const {
+    Value value = getReservedSlot(VECTOR_SLOT);
+    auto buf = static_cast<JS::TranscodeBuffer*>(value.toPrivate());
+    MOZ_ASSERT(buf);
+    return buf;
+  }
+
+  bool hasData() const {
+    // Data may not be present if we hit OOM in initialization.
+    return !getReservedSlot(VECTOR_SLOT).isUndefined();
+  }
+
+  static void finalize(JS::GCContext* gcx, JSObject* obj);
+};
+
+/*static */ const JSClassOps XDRBufferObject::classOps_ = {
+    nullptr,                    // addProperty
+    nullptr,                    // delProperty
+    nullptr,                    // enumerate
+    nullptr,                    // newEnumerate
+    nullptr,                    // resolve
+    nullptr,                    // mayResolve
+    XDRBufferObject::finalize,  // finalize
+    nullptr,                    // call
+    nullptr,                    // construct
+    nullptr,                    // trace
+};
+
+/*static */ const JSClass XDRBufferObject::class_ = {
+    "XDRBufferObject",
+    JSCLASS_HAS_RESERVED_SLOTS(XDRBufferObject::RESERVED_SLOTS) |
+        JSCLASS_BACKGROUND_FINALIZE,
+    &XDRBufferObject::classOps_};
+
+XDRBufferObject* XDRBufferObject::create(JSContext* cx,
+                                         JS::TranscodeBuffer&& buf) {
+  XDRBufferObject* bufObj =
+      NewObjectWithGivenProto<XDRBufferObject>(cx, nullptr);
+  if (!bufObj) {
+    return nullptr;
+  }
+
+  auto heapBuf = cx->make_unique<JS::TranscodeBuffer>(std::move(buf));
+  if (!heapBuf) {
+    return nullptr;
+  }
+
+  size_t len = heapBuf->length();
+  InitReservedSlot(bufObj, VECTOR_SLOT, heapBuf.release(), len,
+                   MemoryUse::XDRBufferElements);
+
+  return bufObj;
+}
+
+void XDRBufferObject::finalize(JS::GCContext* gcx, JSObject* obj) {
+  XDRBufferObject* buf = &obj->as<XDRBufferObject>();
+  if (buf->hasData()) {
+    gcx->delete_(buf, buf->data(), buf->data()->length(),
+                 MemoryUse::XDRBufferElements);
+  }
+}
+
+static bool InstantiateModuleStencil(JSContext* cx, uint32_t argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  if (!args.requireAtLeast(cx, "instantiateModuleStencil", 1)) {
+    return false;
+  }
+
+  /* Prepare the input byte array. */
+  if (!args[0].isObject() || !args[0].toObject().is<js::StencilObject>()) {
+    JS_ReportErrorASCII(cx,
+                        "instantiateModuleStencil: Stencil object expected");
+    return false;
+  }
+  Rooted<js::StencilObject*> stencilObj(
+      cx, &args[0].toObject().as<js::StencilObject>());
+
+  if (!stencilObj->stencil()->isModule()) {
+    JS_ReportErrorASCII(cx,
+                        "instantiateModuleStencil: Module stencil expected");
+    return false;
+  }
+
+  CompileOptions options(cx);
+  UniqueChars fileNameBytes;
+  if (args.length() == 2) {
+    if (!args[1].isObject()) {
+      JS_ReportErrorASCII(
+          cx, "instantiateModuleStencil: The 2nd argument must be an object");
+      return false;
+    }
+
+    RootedObject opts(cx, &args[1].toObject());
+    if (!js::ParseCompileOptions(cx, options, opts, &fileNameBytes)) {
+      return false;
+    }
+  }
+
+  /* Prepare the CompilationStencil for decoding. */
+  AutoReportFrontendContext fc(cx);
+  Rooted<frontend::CompilationInput> input(cx,
+                                           frontend::CompilationInput(options));
+  if (!input.get().initForModule(cx, &fc)) {
+    return false;
+  }
+
+  /* Instantiate the stencil. */
+  Rooted<frontend::CompilationGCOutput> output(cx);
+  if (!frontend::CompilationStencil::instantiateStencils(
+          cx, input.get(), *stencilObj->stencil(), output.get())) {
+    return false;
+  }
+
+  Rooted<ModuleObject*> modObject(cx, output.get().module);
+  Rooted<ShellModuleObjectWrapper*> wrapper(
+      cx, ShellModuleObjectWrapper::create(cx, modObject));
+  if (!wrapper) {
+    return false;
+  }
+  args.rval().setObject(*wrapper);
+  return true;
+}
+
+static bool InstantiateModuleStencilXDR(JSContext* cx, uint32_t argc,
+                                        Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  if (!args.requireAtLeast(cx, "instantiateModuleStencilXDR", 1)) {
+    return false;
+  }
+
+  /* Prepare the input byte array. */
+  if (!args[0].isObject() || !args[0].toObject().is<StencilXDRBufferObject>()) {
+    JS_ReportErrorASCII(
+        cx, "instantiateModuleStencilXDR: stencil XDR object expected");
+    return false;
+  }
+  Rooted<StencilXDRBufferObject*> xdrObj(
+      cx, &args[0].toObject().as<StencilXDRBufferObject>());
+  MOZ_ASSERT(xdrObj->hasBuffer());
+
+  CompileOptions options(cx);
+  UniqueChars fileNameBytes;
+  if (args.length() == 2) {
+    if (!args[1].isObject()) {
+      JS_ReportErrorASCII(
+          cx,
+          "instantiateModuleStencilXDR: The 2nd argument must be an object");
+      return false;
+    }
+
+    RootedObject opts(cx, &args[1].toObject());
+    if (!js::ParseCompileOptions(cx, options, opts, &fileNameBytes)) {
+      return false;
+    }
+  }
+
+  /* Prepare the CompilationStencil for decoding. */
+  AutoReportFrontendContext fc(cx);
+  Rooted<frontend::CompilationInput> input(cx,
+                                           frontend::CompilationInput(options));
+  if (!input.get().initForModule(cx, &fc)) {
+    return false;
+  }
+  frontend::CompilationStencil stencil(nullptr);
+
+  /* Deserialize the stencil from XDR. */
+  JS::TranscodeRange xdrRange(xdrObj->buffer(), xdrObj->bufferLength());
+  bool succeeded = false;
+  if (!stencil.deserializeStencils(cx, &fc, input.get(), xdrRange,
+                                   &succeeded)) {
+    return false;
+  }
+  if (!succeeded) {
+    fc.clearAutoReport();
+    JS_ReportErrorASCII(cx, "Decoding failure");
+    return false;
+  }
+
+  if (!stencil.isModule()) {
+    fc.clearAutoReport();
+    JS_ReportErrorASCII(cx,
+                        "instantiateModuleStencilXDR: Module stencil expected");
+    return false;
+  }
+
+  /* Instantiate the stencil. */
+  Rooted<frontend::CompilationGCOutput> output(cx);
+  if (!frontend::CompilationStencil::instantiateStencils(
+          cx, input.get(), stencil, output.get())) {
+    return false;
+  }
+
+  Rooted<ModuleObject*> modObject(cx, output.get().module);
+  Rooted<ShellModuleObjectWrapper*> wrapper(
+      cx, ShellModuleObjectWrapper::create(cx, modObject));
+  if (!wrapper) {
+    return false;
+  }
+  args.rval().setObject(*wrapper);
+  return true;
+}
+
+static bool RegisterModule(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+  if (!args.requireAtLeast(cx, "registerModule", 2)) {
+    return false;
+  }
+
+  if (!args[0].isString()) {
+    const char* typeName = InformalValueTypeName(args[0]);
+    JS_ReportErrorASCII(cx, "expected string, got %s", typeName);
+    return false;
+  }
+
+  if (!args[1].isObject() ||
+      !args[1].toObject().is<ShellModuleObjectWrapper>()) {
+    const char* typeName = InformalValueTypeName(args[1]);
+    JS_ReportErrorASCII(cx, "expected module, got %s", typeName);
+    return false;
+  }
+
+  ShellContext* sc = GetShellContext(cx);
+  Rooted<ModuleObject*> module(
+      cx, args[1].toObject().as<ShellModuleObjectWrapper>().get());
+
+  Rooted<JSAtom*> specifier(cx, AtomizeString(cx, args[0].toString()));
+  if (!specifier) {
+    return false;
+  }
+
+  RootedObject moduleRequest(
+      cx, ModuleRequestObject::create(cx, specifier, nullptr));
+  if (!moduleRequest) {
+    return false;
+  }
+
+  if (!sc->moduleLoader->registerTestModule(cx, moduleRequest, module)) {
+    return false;
+  }
+
+  Rooted<ShellModuleObjectWrapper*> wrapper(
+      cx, ShellModuleObjectWrapper::create(cx, module));
+  if (!wrapper) {
+    return false;
+  }
+  args.rval().setObject(*wrapper);
+  return true;
+}
+
+static bool ClearModules(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+  ShellContext* sc = GetShellContext(cx);
+  sc->moduleLoader->clearModules(cx);
+  args.rval().setUndefined();
+  return true;
+}
+
+static bool ModuleLink(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  if (args.length() != 1 || !args[0].isObject()) {
+    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr, JSMSG_INVALID_ARGS,
+                              "moduleLink");
+    return false;
+  }
+
+  RootedObject object(cx, UncheckedUnwrap(&args[0].toObject()));
+  if (!object->is<ShellModuleObjectWrapper>()) {
+    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr, JSMSG_INVALID_ARGS,
+                              "moduleLink");
+    return false;
+  }
+
+  AutoRealm ar(cx, object);
+
+  Rooted<ModuleObject*> module(cx,
+                               object->as<ShellModuleObjectWrapper>().get());
+  if (!js::ModuleLink(cx, module)) {
+    return false;
+  }
+
+  args.rval().setUndefined();
+  return true;
+}
+
+static bool ModuleEvaluate(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  if (args.length() != 1 || !args[0].isObject()) {
+    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr, JSMSG_INVALID_ARGS,
+                              "moduleEvaluate");
+    return false;
+  }
+
+  RootedObject object(cx, UncheckedUnwrap(&args[0].toObject()));
+  if (!object->is<ShellModuleObjectWrapper>()) {
+    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr, JSMSG_INVALID_ARGS,
+                              "moduleEvaluate");
+    return false;
+  }
+
+  {
+    AutoRealm ar(cx, object);
+
+    Rooted<ModuleObject*> module(cx,
+                                 object->as<ShellModuleObjectWrapper>().get());
+    if (!js::ModuleEvaluate(cx, module, args.rval())) {
+      return false;
+    }
+  }
+
+  return JS_WrapValue(cx, args.rval());
+}
+
+static ModuleEnvironmentObject* GetModuleInitialEnvironment(
+    JSContext* cx, Handle<ModuleObject*> module) {
+  // Use the initial environment so that tests can check bindings exists
+  // before they have been instantiated.
+  Rooted<ModuleEnvironmentObject*> env(cx, &module->initialEnvironment());
+  MOZ_ASSERT(env);
+  return env;
+}
+
+static bool GetModuleEnvironmentNames(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+  if (args.length() != 1) {
+    JS_ReportErrorASCII(cx, "Wrong number of arguments");
+    return false;
+  }
+
+  if (!args[0].isObject() ||
+      !args[0].toObject().is<ShellModuleObjectWrapper>()) {
+    JS_ReportErrorASCII(cx,
+                        "First argument should be a ShellModuleObjectWrapper");
+    return false;
+  }
+
+  Rooted<ModuleObject*> module(
+      cx, args[0].toObject().as<ShellModuleObjectWrapper>().get());
+  if (module->hadEvaluationError()) {
+    JS_ReportErrorASCII(cx, "Module environment unavailable");
+    return false;
+  }
+
+  Rooted<ModuleEnvironmentObject*> env(cx,
+                                       GetModuleInitialEnvironment(cx, module));
+  Rooted<IdVector> ids(cx, IdVector(cx));
+  if (!JS_Enumerate(cx, env, &ids)) {
+    return false;
+  }
+
+  // The "*namespace*" binding is a detail of current implementation so hide
+  // it to give stable results in tests.
+  ids.eraseIfEqual(NameToId(cx->names().starNamespaceStar));
+
+  uint32_t length = ids.length();
+  Rooted<ArrayObject*> array(cx, NewDenseFullyAllocatedArray(cx, length));
+  if (!array) {
+    return false;
+  }
+
+  array->setDenseInitializedLength(length);
+  for (uint32_t i = 0; i < length; i++) {
+    array->initDenseElement(i, StringValue(ids[i].toString()));
+  }
+
+  args.rval().setObject(*array);
+  return true;
+}
+
+static bool GetModuleEnvironmentValue(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+  if (args.length() != 2) {
+    JS_ReportErrorASCII(cx, "Wrong number of arguments");
+    return false;
+  }
+
+  if (!args[0].isObject() ||
+      !args[0].toObject().is<ShellModuleObjectWrapper>()) {
+    JS_ReportErrorASCII(cx,
+                        "First argument should be a ShellModuleObjectWrapper");
+    return false;
+  }
+
+  if (!args[1].isString()) {
+    JS_ReportErrorASCII(cx, "Second argument should be a string");
+    return false;
+  }
+
+  Rooted<ModuleObject*> module(
+      cx, args[0].toObject().as<ShellModuleObjectWrapper>().get());
+  if (module->hadEvaluationError()) {
+    JS_ReportErrorASCII(cx, "Module environment unavailable");
+    return false;
+  }
+
+  Rooted<ModuleEnvironmentObject*> env(cx,
+                                       GetModuleInitialEnvironment(cx, module));
+  RootedString name(cx, args[1].toString());
+  RootedId id(cx);
+  if (!JS_StringToId(cx, name, &id)) {
+    return false;
+  }
+
+  if (!GetProperty(cx, env, env, id, args.rval())) {
+    return false;
+  }
+
+  if (args.rval().isMagic(JS_UNINITIALIZED_LEXICAL)) {
+    ReportRuntimeLexicalError(cx, JSMSG_UNINITIALIZED_LEXICAL, id);
+    return false;
+  }
+
+  return true;
+}
+
+enum class DumpType {
+  ParseNode,
+  Stencil,
+};
+
+template <typename Unit>
+static bool DumpAST(JSContext* cx, const JS::ReadOnlyCompileOptions& options,
+                    const Unit* units, size_t length,
+                    js::frontend::CompilationState& compilationState,
+                    js::frontend::ParseGoal goal) {
+  using namespace js::frontend;
+
+  AutoReportFrontendContext fc(cx);
+  Parser<FullParseHandler, Unit> parser(
+      cx, &fc, cx->stackLimitForCurrentPrincipal(), options, units, length,
+      /* foldConstants = */ false, compilationState,
+      /* syntaxParser = */ nullptr);
+  if (!parser.checkOptions()) {
+    return false;
+  }
+
+  // Emplace the top-level stencil.
+  MOZ_ASSERT(compilationState.scriptData.length() ==
+             CompilationStencil::TopLevelIndex);
+  if (!compilationState.appendScriptStencilAndData(&fc)) {
+    return false;
+  }
+
+  js::frontend::ParseNode* pn;
+  if (goal == frontend::ParseGoal::Script) {
+    pn = parser.parse();
+  } else {
+    ModuleBuilder builder(cx, &fc, &parser);
+
+    SourceExtent extent = SourceExtent::makeGlobalExtent(length);
+    ModuleSharedContext modulesc(cx, &fc, options, builder, extent);
+    pn = parser.moduleBody(&modulesc);
+  }
+
+  if (!pn) {
+    return false;
+  }
+
+#if defined(DEBUG)
+  js::Fprinter out(stderr);
+  DumpParseTree(&parser, pn, out);
+#endif
+
+  return true;
+}
+
+template <typename Unit>
+[[nodiscard]] static bool DumpStencil(JSContext* cx,
+                                      const JS::ReadOnlyCompileOptions& options,
+                                      const Unit* units, size_t length,
+                                      js::frontend::ParseGoal goal) {
+  Rooted<frontend::CompilationInput> input(cx,
+                                           frontend::CompilationInput(options));
+
+  JS::SourceText<Unit> srcBuf;
+  if (!srcBuf.init(cx, units, length, JS::SourceOwnership::Borrowed)) {
+    return false;
+  }
+
+  AutoReportFrontendContext fc(cx);
+  js::frontend::NoScopeBindingCache scopeCache;
+  UniquePtr<frontend::ExtensibleCompilationStencil> stencil;
+  if (goal == frontend::ParseGoal::Script) {
+    stencil = frontend::CompileGlobalScriptToExtensibleStencil(
+        cx, &fc, cx->stackLimitForCurrentPrincipal(), input.get(), &scopeCache,
+        srcBuf, ScopeKind::Global);
+  } else {
+    stencil = frontend::ParseModuleToExtensibleStencil(
+        cx, &fc, cx->stackLimitForCurrentPrincipal(), input.get(), &scopeCache,
+        srcBuf);
+  }
+
+  if (!stencil) {
+    return false;
+  }
+
+#if defined(DEBUG) || defined(JS_JITSPEW)
+  stencil->dump();
+#endif
+
+  return true;
+}
+
+static bool FrontendTest(JSContext* cx, unsigned argc, Value* vp,
+                         const char* funcName, DumpType dumpType) {
+  using namespace js::frontend;
+
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  if (!args.requireAtLeast(cx, funcName, 1)) {
+    return false;
+  }
+  if (!args[0].isString()) {
+    const char* typeName = InformalValueTypeName(args[0]);
+    JS_ReportErrorASCII(cx, "expected string to parse, got %s", typeName);
+    return false;
+  }
+
+  frontend::ParseGoal goal = frontend::ParseGoal::Script;
+#ifdef JS_ENABLE_SMOOSH
+  bool smoosh = false;
+#endif
+
+  CompileOptions options(cx);
+  options.setIntroductionType("js shell parse")
+      .setFileAndLine("<string>", 1)
+      .setIsRunOnce(true)
+      .setNoScriptRval(true);
+
+  if (args.length() >= 2) {
+    if (!args[1].isObject()) {
+      JS_ReportErrorASCII(cx, "The 2nd argument must be an object");
+      return false;
+    }
+
+    RootedObject objOptions(cx, &args[1].toObject());
+
+    RootedValue optionModule(cx);
+    if (!JS_GetProperty(cx, objOptions, "module", &optionModule)) {
+      return false;
+    }
+
+    if (optionModule.isBoolean()) {
+      if (optionModule.toBoolean()) {
+        goal = frontend::ParseGoal::Module;
+      }
+    } else if (!optionModule.isUndefined()) {
+      const char* typeName = InformalValueTypeName(optionModule);
+      JS_ReportErrorASCII(cx, "option `module` should be a boolean, got %s",
+                          typeName);
+      return false;
+    }
+    if (!js::ParseCompileOptions(cx, options, objOptions, nullptr)) {
+      return false;
+    }
+
+#ifdef JS_ENABLE_SMOOSH
+    bool found = false;
+    if (!JS_HasProperty(cx, objOptions, "rustFrontend", &found)) {
+      return false;
+    }
+    if (found) {
+      JS_ReportErrorASCII(cx, "'rustFrontend' option is renamed to 'smoosh'");
+      return false;
+    }
+
+    RootedValue optionSmoosh(cx);
+    if (!JS_GetProperty(cx, objOptions, "smoosh", &optionSmoosh)) {
+      return false;
+    }
+
+    if (optionSmoosh.isBoolean()) {
+      smoosh = optionSmoosh.toBoolean();
+    } else if (!optionSmoosh.isUndefined()) {
+      const char* typeName = InformalValueTypeName(optionSmoosh);
+      JS_ReportErrorASCII(cx, "option `smoosh` should be a boolean, got %s",
+                          typeName);
+      return false;
+    }
+#endif  // JS_ENABLE_SMOOSH
+  }
+
+  JSString* scriptContents = args[0].toString();
+  Rooted<JSLinearString*> linearString(cx, scriptContents->ensureLinear(cx));
+  if (!linearString) {
+    return false;
+  }
+
+  bool isAscii = false;
+  if (linearString->hasLatin1Chars()) {
+    JS::AutoCheckCannotGC nogc;
+    isAscii = JS::StringIsASCII(mozilla::Span(
+        reinterpret_cast<const char*>(linearString->latin1Chars(nogc)),
+        linearString->length()));
+  }
+
+  AutoStableStringChars stableChars(cx);
+  if (isAscii) {
+    if (!stableChars.init(cx, scriptContents)) {
+      return false;
+    }
+    MOZ_ASSERT(stableChars.isLatin1());
+  } else {
+    if (!stableChars.initTwoByte(cx, scriptContents)) {
+      return false;
+    }
+  }
+
+  size_t length = scriptContents->length();
+#ifdef JS_ENABLE_SMOOSH
+  if (dumpType == DumpType::ParseNode) {
+    if (smoosh) {
+      if (isAscii) {
+        const Latin1Char* chars = stableChars.latin1Range().begin().get();
+
+        if (goal == frontend::ParseGoal::Script) {
+          if (!SmooshParseScript(cx, chars, length)) {
+            return false;
+          }
+        } else {
+          if (!SmooshParseModule(cx, chars, length)) {
+            return false;
+          }
+        }
+        args.rval().setUndefined();
+        return true;
+      }
+      JS_ReportErrorASCII(cx,
+                          "SmooshMonkey does not support non-ASCII chars yet");
+      return false;
+    }
+  }
+#endif  // JS_ENABLE_SMOOSH
+
+  if (goal == frontend::ParseGoal::Module) {
+    // See frontend::CompileModule.
+    options.setForceStrictMode();
+    options.allowHTMLComments = false;
+  }
+
+  if (dumpType == DumpType::Stencil) {
+#ifdef JS_ENABLE_SMOOSH
+    if (smoosh) {
+      if (isAscii) {
+        if (goal == frontend::ParseGoal::Script) {
+          const Latin1Char* latin1 = stableChars.latin1Range().begin().get();
+          auto utf8 = reinterpret_cast<const mozilla::Utf8Unit*>(latin1);
+          JS::SourceText<Utf8Unit> srcBuf;
+          if (!srcBuf.init(cx, utf8, length, JS::SourceOwnership::Borrowed)) {
+            return false;
+          }
+
+          AutoReportFrontendContext fc(cx);
+          Rooted<frontend::CompilationInput> input(
+              cx, frontend::CompilationInput(options));
+          UniquePtr<frontend::ExtensibleCompilationStencil> stencil;
+          if (!Smoosh::tryCompileGlobalScriptToExtensibleStencil(
+                  cx, &fc, cx->stackLimitForCurrentPrincipal(), input.get(),
+                  srcBuf, stencil)) {
+            return false;
+          }
+          if (!stencil) {
+            fc.clearAutoReport();
+            JS_ReportErrorASCII(cx, "SmooshMonkey failed to parse");
+            return false;
+          }
+
+#  ifdef DEBUG
+          {
+            frontend::BorrowingCompilationStencil borrowingStencil(*stencil);
+            borrowingStencil.dump();
+          }
+#  endif
+        } else {
+          JS_ReportErrorASCII(cx,
+                              "SmooshMonkey does not support module stencil");
+          return false;
+        }
+        args.rval().setUndefined();
+        return true;
+      }
+      JS_ReportErrorASCII(cx,
+                          "SmooshMonkey does not support non-ASCII chars yet");
+      return false;
+    }
+#endif  // JS_ENABLE_SMOOSH
+
+    if (isAscii) {
+      const Latin1Char* latin1 = stableChars.latin1Range().begin().get();
+      auto utf8 = reinterpret_cast<const mozilla::Utf8Unit*>(latin1);
+      if (!DumpStencil<mozilla::Utf8Unit>(cx, options, utf8, length, goal)) {
+        return false;
+      }
+    } else {
+      MOZ_ASSERT(stableChars.isTwoByte());
+      const char16_t* chars = stableChars.twoByteRange().begin().get();
+      if (!DumpStencil<char16_t>(cx, options, chars, length, goal)) {
+        return false;
+      }
+    }
+
+    args.rval().setUndefined();
+    return true;
+  }
+
+  AutoReportFrontendContext fc(cx);
+  Rooted<frontend::CompilationInput> input(cx,
+                                           frontend::CompilationInput(options));
+  if (goal == frontend::ParseGoal::Script) {
+    if (!input.get().initForGlobal(cx, &fc)) {
+      return false;
+    }
+  } else {
+    if (!input.get().initForModule(cx, &fc)) {
+      return false;
+    }
+  }
+
+  LifoAllocScope allocScope(&cx->tempLifoAlloc());
+  frontend::NoScopeBindingCache scopeCache;
+  frontend::CompilationState compilationState(cx, &fc, allocScope, input.get());
+  if (!compilationState.init(cx, &fc, &scopeCache)) {
+    return false;
+  }
+
+  if (isAscii) {
+    const Latin1Char* latin1 = stableChars.latin1Range().begin().get();
+    auto utf8 = reinterpret_cast<const mozilla::Utf8Unit*>(latin1);
+    if (!DumpAST<mozilla::Utf8Unit>(cx, options, utf8, length, compilationState,
+                                    goal)) {
+      return false;
+    }
+  } else {
+    MOZ_ASSERT(stableChars.isTwoByte());
+    const char16_t* chars = stableChars.twoByteRange().begin().get();
+    if (!DumpAST<char16_t>(cx, options, chars, length, compilationState,
+                           goal)) {
+      return false;
+    }
+  }
+  args.rval().setUndefined();
+  return true;
+}
+
+static bool DumpStencil(JSContext* cx, unsigned argc, Value* vp) {
+  return FrontendTest(cx, argc, vp, "dumpStencil", DumpType::Stencil);
+}
+
+static bool Parse(JSContext* cx, unsigned argc, Value* vp) {
+  // Parse returns local scope information with variables ordered
+  // differently, depending on the underlying JIT implementation.
+  if (js::SupportDifferentialTesting()) {
+    JS_ReportErrorASCII(cx,
+                        "Function not available in differential testing mode.");
+    return false;
+  }
+
+  return FrontendTest(cx, argc, vp, "parse", DumpType::ParseNode);
+}
+
+static bool SyntaxParse(JSContext* cx, unsigned argc, Value* vp) {
+  using namespace js::frontend;
+
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  if (!args.requireAtLeast(cx, "syntaxParse", 1)) {
+    return false;
+  }
+  if (!args[0].isString()) {
+    const char* typeName = InformalValueTypeName(args[0]);
+    JS_ReportErrorASCII(cx, "expected string to parse, got %s", typeName);
+    return false;
+  }
+
+  JSString* scriptContents = args[0].toString();
+
+  CompileOptions options(cx);
+  options.setIntroductionType("js shell syntaxParse")
+      .setFileAndLine("<string>", 1);
+
+  AutoStableStringChars stableChars(cx);
+  if (!stableChars.initTwoByte(cx, scriptContents)) {
+    return false;
+  }
+
+  const char16_t* chars = stableChars.twoByteRange().begin().get();
+  size_t length = scriptContents->length();
+
+  AutoReportFrontendContext fc(cx);
+  Rooted<frontend::CompilationInput> input(cx,
+                                           frontend::CompilationInput(options));
+  if (!input.get().initForGlobal(cx, &fc)) {
+    return false;
+  }
+
+  LifoAllocScope allocScope(&cx->tempLifoAlloc());
+  frontend::NoScopeBindingCache scopeCache;
+  frontend::CompilationState compilationState(cx, &fc, allocScope, input.get());
+  if (!compilationState.init(cx, &fc, &scopeCache)) {
+    return false;
+  }
+
+  Parser<frontend::SyntaxParseHandler, char16_t> parser(
+      cx, &fc, cx->stackLimitForCurrentPrincipal(), options, chars, length,
+      /* foldConstants = */ false, compilationState,
+      /* syntaxParser = */ nullptr);
+  if (!parser.checkOptions()) {
+    return false;
+  }
+
+  bool succeeded = parser.parse();
+  if (fc.hadErrors()) {
+    return false;
+  }
+
+  if (!succeeded && !parser.hadAbortedSyntaxParse()) {
+    // If no exception is posted, either there was an OOM or a language
+    // feature unhandled by the syntax parser was encountered.
+    MOZ_ASSERT(fc.hadOutOfMemory());
+    return false;
+  }
+
+  args.rval().setBoolean(succeeded);
+  return true;
+}
+
+static void OffThreadCompileScriptCallback(JS::OffThreadToken* token,
+                                           void* callbackData) {
+  auto job = static_cast<OffThreadJob*>(callbackData);
+  job->markDone(token);
+}
+
+static bool OffThreadCompileToStencil(JSContext* cx, unsigned argc, Value* vp) {
+  if (!CanUseExtraThreads()) {
+    JS_ReportErrorASCII(
+        cx, "Can't use offThreadCompileToStencil with --no-threads");
+    return false;
+  }
+
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  if (!args.requireAtLeast(cx, "offThreadCompileToStencil", 1)) {
+    return false;
+  }
+  if (!args[0].isString()) {
+    const char* typeName = InformalValueTypeName(args[0]);
+    JS_ReportErrorASCII(cx, "expected string to parse, got %s", typeName);
+    return false;
+  }
+
+  UniqueChars fileNameBytes;
+  CompileOptions options(cx);
+  options.setIntroductionType("js shell offThreadCompileToStencil")
+      .setFileAndLine("<string>", 1);
+
+  if (args.length() >= 2) {
+    if (!args[1].isObject()) {
+      JS_ReportErrorASCII(
+          cx, "offThreadCompileToStencil: The 2nd argument must be an object");
+      return false;
+    }
+
+    // Offthread compilation requires that the debug metadata be set when the
+    // script is collected from offthread, rather than when compiled.
+    RootedObject opts(cx, &args[1].toObject());
+    if (!js::ParseCompileOptions(cx, options, opts, &fileNameBytes)) {
+      return false;
+    }
+  }
+
+  // This option setting must override whatever the caller requested.
+  options.setIsRunOnce(true);
+
+  // We assume the caller wants caching if at all possible, ignoring
+  // heuristics that make sense for a real browser.
+  options.forceAsync = true;
+
+  JSString* scriptContents = args[0].toString();
+  AutoStableStringChars stableChars(cx);
+  if (!stableChars.initTwoByte(cx, scriptContents)) {
+    return false;
+  }
+
+  size_t length = scriptContents->length();
+  const char16_t* chars = stableChars.twoByteChars();
+
+  // Make sure we own the string's chars, so that they are not freed before
+  // the compilation is finished.
+  UniqueTwoByteChars ownedChars;
+  if (stableChars.maybeGiveOwnershipToCaller()) {
+    ownedChars.reset(const_cast<char16_t*>(chars));
+  } else {
+    ownedChars.reset(cx->pod_malloc<char16_t>(length));
+    if (!ownedChars) {
+      return false;
+    }
+
+    mozilla::PodCopy(ownedChars.get(), chars, length);
+  }
+
+  if (!JS::CanCompileOffThread(cx, options, length)) {
+    JS_ReportErrorASCII(cx, "cannot compile code on worker thread");
+    return false;
+  }
+
+  OffThreadJob* job =
+      NewOffThreadJob(cx, options, OffThreadJob::Source(std::move(ownedChars)));
+  if (!job) {
+    return false;
+  }
+
+  JS::SourceText<char16_t> srcBuf;
+  if (!srcBuf.init(cx, job->sourceChars(), length,
+                   JS::SourceOwnership::Borrowed) ||
+      !JS::CompileToStencilOffThread(cx, options, srcBuf,
+                                     OffThreadCompileScriptCallback, job)) {
+    job->cancel();
+    DeleteOffThreadJob(cx, job);
+    return false;
+  }
+
+  args.rval().setInt32(job->id);
+  return true;
+}
+
+static bool FinishOffThreadStencil(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  OffThreadJob* job = LookupOffThreadJobForArgs(cx, args, 0);
+  if (!job) {
+    return false;
+  }
+
+  JS::OffThreadToken* token = job->waitUntilDone(cx);
+  MOZ_ASSERT(token);
+
+  RefPtr<JS::Stencil> stencil = JS::FinishOffThreadStencil(cx, token);
+  DeleteOffThreadJob(cx, job);
+  if (!stencil) {
+    return false;
+  }
+  RootedObject stencilObj(cx,
+                          js::StencilObject::create(cx, std::move(stencil)));
+  if (!stencilObj) {
+    return false;
+  }
+
+  args.rval().setObject(*stencilObj);
+  return true;
+}
+
+static bool OffThreadCompileModuleToStencil(JSContext* cx, unsigned argc,
+                                            Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  if (args.length() != 1 || !args[0].isString()) {
+    JS_ReportErrorNumberASCII(cx, my_GetErrorMessage, nullptr,
+                              JSSMSG_INVALID_ARGS,
+                              "offThreadCompileModuleToStencil");
+    return false;
+  }
+
+  UniqueChars fileNameBytes;
+  CompileOptions options(cx);
+  options.setIntroductionType("js shell offThreadCompileModuleToStencil")
+      .setFileAndLine("<string>", 1);
+  options.setIsRunOnce(true).setSourceIsLazy(false);
+  options.forceAsync = true;
+
+  JSString* scriptContents = args[0].toString();
+  AutoStableStringChars stableChars(cx);
+  if (!stableChars.initTwoByte(cx, scriptContents)) {
+    return false;
+  }
+
+  size_t length = scriptContents->length();
+  const char16_t* chars = stableChars.twoByteChars();
+
+  // Make sure we own the string's chars, so that they are not freed before
+  // the compilation is finished.
+  UniqueTwoByteChars ownedChars;
+  if (stableChars.maybeGiveOwnershipToCaller()) {
+    ownedChars.reset(const_cast<char16_t*>(chars));
+  } else {
+    ownedChars.reset(cx->pod_malloc<char16_t>(length));
+    if (!ownedChars) {
+      return false;
+    }
+
+    mozilla::PodCopy(ownedChars.get(), chars, length);
+  }
+
+  if (!JS::CanCompileOffThread(cx, options, length)) {
+    JS_ReportErrorASCII(cx, "cannot compile code on worker thread");
+    return false;
+  }
+
+  OffThreadJob* job =
+      NewOffThreadJob(cx, options, OffThreadJob::Source(std::move(ownedChars)));
+  if (!job) {
+    return false;
+  }
+
+  JS::SourceText<char16_t> srcBuf;
+  if (!srcBuf.init(cx, job->sourceChars(), length,
+                   JS::SourceOwnership::Borrowed) ||
+      !JS::CompileModuleToStencilOffThread(
+          cx, options, srcBuf, OffThreadCompileScriptCallback, job)) {
+    job->cancel();
+    DeleteOffThreadJob(cx, job);
+    return false;
+  }
+
+  args.rval().setInt32(job->id);
+  return true;
+}
+
+static bool OffThreadDecodeStencil(JSContext* cx, unsigned argc, Value* vp) {
+  if (!CanUseExtraThreads()) {
+    JS_ReportErrorASCII(cx,
+                        "Can't use offThreadDecodeStencil with --no-threads");
+    return false;
+  }
+
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  if (!args.requireAtLeast(cx, "offThreadDecodeStencil", 1)) {
+    return false;
+  }
+  if (!args[0].isObject() || !CacheEntry_isCacheEntry(&args[0].toObject())) {
+    const char* typeName = InformalValueTypeName(args[0]);
+    JS_ReportErrorASCII(cx, "expected cache entry, got %s", typeName);
+    return false;
+  }
+  RootedObject cacheEntry(cx, &args[0].toObject());
+
+  UniqueChars fileNameBytes;
+  CompileOptions options(cx);
+  options.setIntroductionType("js shell offThreadDecodeStencil")
+      .setFileAndLine("<string>", 1);
+
+  if (args.length() >= 2) {
+    if (!args[1].isObject()) {
+      JS_ReportErrorASCII(
+          cx, "offThreadDecodeStencil: The 2nd argument must be an object");
+      return false;
+    }
+
+    RootedObject opts(cx, &args[1].toObject());
+    if (!js::ParseCompileOptions(cx, options, opts, &fileNameBytes)) {
+      return false;
+    }
+  }
+
+  // This option setting must override whatever the caller requested, and
+  // this should match `Evaluate` that encodes the script.
+  options.setIsRunOnce(false);
+
+  // We assume the caller wants caching if at all possible, ignoring
+  // heuristics that make sense for a real browser.
+  options.forceAsync = true;
+
+  JS::TranscodeBuffer loadBuffer;
+  size_t loadLength = 0;
+  uint8_t* loadData = nullptr;
+  loadData = CacheEntry_getBytecode(cx, cacheEntry, &loadLength);
+  if (!loadData) {
+    return false;
+  }
+  if (!loadBuffer.append(loadData, loadLength)) {
+    JS_ReportOutOfMemory(cx);
+    return false;
+  }
+
+  JS::DecodeOptions decodeOptions(options);
+  if (!JS::CanDecodeOffThread(cx, decodeOptions, loadLength)) {
+    JS_ReportErrorASCII(cx, "cannot compile code on worker thread");
+    return false;
+  }
+
+  OffThreadJob* job =
+      NewOffThreadJob(cx, options, OffThreadJob::Source(std::move(loadBuffer)));
+  if (!job) {
+    return false;
+  }
+
+  if (!JS::DecodeStencilOffThread(cx, decodeOptions, job->xdrBuffer(), 0,
+                                  OffThreadCompileScriptCallback, job)) {
+    job->cancel();
+    DeleteOffThreadJob(cx, job);
+    return false;
+  }
+
+  args.rval().setInt32(job->id);
+  return true;
+}
+
+class AutoCStringVector {
+  Vector<char*> argv_;
+
+ public:
+  explicit AutoCStringVector(JSContext* cx) : argv_(cx) {}
+  ~AutoCStringVector() {
+    for (size_t i = 0; i < argv_.length(); i++) {
+      js_free(argv_[i]);
+    }
+  }
+  bool append(UniqueChars&& arg) {
+    if (!argv_.append(arg.get())) {
+      return false;
+    }
+
+    // Now owned by this vector.
+    (void)arg.release();
+    return true;
+  }
+  char* const* get() const { return argv_.begin(); }
+  size_t length() const { return argv_.length(); }
+  char* operator[](size_t i) const { return argv_[i]; }
+  void replace(size_t i, UniqueChars arg) {
+    js_free(argv_[i]);
+    argv_[i] = arg.release();
+  }
+};
+
+#if defined(XP_WIN)
+static bool EscapeForShell(JSContext* cx, AutoCStringVector& argv) {
+  // Windows will break arguments in argv by various spaces, so we wrap each
+  // argument in quotes and escape quotes within. Even with quotes, \ will be
+  // treated like an escape character, so inflate each \ to \\.
+
+  for (size_t i = 0; i < argv.length(); i++) {
+    if (!argv[i]) {
+      continue;
+    }
+
+    size_t newLen = 3;  // quotes before and after and null-terminator
+    for (char* p = argv[i]; *p; p++) {
+      newLen++;
+      if (*p == '\"' || *p == '\\') {
+        newLen++;
+      }
+    }
+
+    auto escaped = cx->make_pod_array<char>(newLen);
+    if (!escaped) {
+      return false;
+    }
+
+    char* src = argv[i];
+    char* dst = escaped.get();
+    *dst++ = '\"';
+    while (*src) {
+      if (*src == '\"' || *src == '\\') {
+        *dst++ = '\\';
+      }
+      *dst++ = *src++;
+    }
+    *dst++ = '\"';
+    *dst++ = '\0';
+    MOZ_ASSERT(escaped.get() + newLen == dst);
+
+    argv.replace(i, std::move(escaped));
+  }
+  return true;
+}
+#endif
+
+#ifndef __wasi__
+static bool ReadAll(int fd, wasm::Bytes* bytes) {
+  size_t lastLength = bytes->length();
+  while (true) {
+    static const int ChunkSize = 64 * 1024;
+    if (!bytes->growBy(ChunkSize)) {
+      return false;
+    }
+
+    intptr_t readCount;
+    while (true) {
+      readCount = read(fd, bytes->begin() + lastLength, ChunkSize);
+      if (readCount >= 0) {
+        break;
+      }
+      if (errno != EINTR) {
+        return false;
+      }
+    }
+
+    if (readCount < ChunkSize) {
+      bytes->shrinkTo(lastLength + readCount);
+      if (readCount == 0) {
+        return true;
+      }
+    }
+
+    lastLength = bytes->length();
+  }
+}
+
+static bool WriteAll(int fd, const uint8_t* bytes, size_t length) {
+  while (length > 0) {
+    int written = write(fd, bytes, length);
+    if (written < 0) {
+      if (errno == EINTR) {
+        continue;
+      }
+      return false;
+    }
+    MOZ_ASSERT(unsigned(written) <= length);
+    length -= written;
+    bytes += written;
+  }
+
+  return true;
+}
+
+class AutoPipe {
+  int fds_[2];
+
+ public:
+  AutoPipe() {
+    fds_[0] = -1;
+    fds_[1] = -1;
+  }
+
+  ~AutoPipe() {
+    if (fds_[0] != -1) {
+      close(fds_[0]);
+    }
+    if (fds_[1] != -1) {
+      close(fds_[1]);
+    }
+  }
+
+  bool init() {
+#  ifdef XP_WIN
+    return !_pipe(fds_, 4096, O_BINARY);
+#  else
+    return !pipe(fds_);
+#  endif
+  }
+
+  int reader() const {
+    MOZ_ASSERT(fds_[0] != -1);
+    return fds_[0];
+  }
+
+  int writer() const {
+    MOZ_ASSERT(fds_[1] != -1);
+    return fds_[1];
+  }
+
+  void closeReader() {
+    MOZ_ASSERT(fds_[0] != -1);
+    close(fds_[0]);
+    fds_[0] = -1;
+  }
+
+  void closeWriter() {
+    MOZ_ASSERT(fds_[1] != -1);
+    close(fds_[1]);
+    fds_[1] = -1;
+  }
+};
+#endif  // __wasi__
+
+int shell::sArgc;
+char** shell::sArgv;
+
+#ifndef __wasi__
+static const char sWasmCompileAndSerializeFlag[] =
+    "--wasm-compile-and-serialize";
+static Vector<const char*, 5, js::SystemAllocPolicy> sCompilerProcessFlags;
+
+static bool CompileAndSerializeInSeparateProcess(JSContext* cx,
+                                                 const uint8_t* bytecode,
+                                                 size_t bytecodeLength,
+                                                 wasm::Bytes* serialized) {
+  AutoPipe stdIn, stdOut;
+  if (!stdIn.init() || !stdOut.init()) {
+    return false;
+  }
+
+  AutoCStringVector argv(cx);
+
+  UniqueChars argv0 = DuplicateString(cx, sArgv[0]);
+  if (!argv0 || !argv.append(std::move(argv0))) {
+    return false;
+  }
+
+  // Put compiler flags first since they must precede the non-option
+  // file-descriptor args (passed on Windows, below).
+  for (unsigned i = 0; i < sCompilerProcessFlags.length(); i++) {
+    UniqueChars flags = DuplicateString(cx, sCompilerProcessFlags[i]);
+    if (!flags || !argv.append(std::move(flags))) {
+      return false;
+    }
+  }
+
+  UniqueChars arg;
+
+  arg = DuplicateString(sWasmCompileAndSerializeFlag);
+  if (!arg || !argv.append(std::move(arg))) {
+    return false;
+  }
+
+#  ifdef XP_WIN
+  // The spawned process will have all the stdIn/stdOut file handles open, but
+  // without the power of fork, we need some other way to communicate the
+  // integer fd values so we encode them in argv and WasmCompileAndSerialize()
+  // has a matching #ifdef XP_WIN to parse them out. Communicate both ends of
+  // both pipes so the child process can closed the unused ends.
+
+  arg = JS_smprintf("%d", stdIn.reader());
+  if (!arg || !argv.append(std::move(arg))) {
+    return false;
+  }
+
+  arg = JS_smprintf("%d", stdIn.writer());
+  if (!arg || !argv.append(std::move(arg))) {
+    return false;
+  }
+
+  arg = JS_smprintf("%d", stdOut.reader());
+  if (!arg || !argv.append(std::move(arg))) {
+    return false;
+  }
+
+  arg = JS_smprintf("%d", stdOut.writer());
+  if (!arg || !argv.append(std::move(arg))) {
+    return false;
+  }
+#  endif
+
+  // Required by both _spawnv and exec.
+  if (!argv.append(nullptr)) {
+    return false;
+  }
+
+#  ifdef XP_WIN
+  if (!EscapeForShell(cx, argv)) {
+    return false;
+  }
+
+  int childPid = _spawnv(P_NOWAIT, sArgv[0], argv.get());
+  if (childPid == -1) {
+    return false;
+  }
+#  else
+  pid_t childPid = fork();
+  switch (childPid) {
+    case -1:
+      return false;
+    case 0:
+      // In the child process. Redirect stdin/stdout to the respective ends of
+      // the pipes. Closing stdIn.writer() is necessary for stdin to hit EOF.
+      // This case statement must not return before exec() takes over. Rather,
+      // exit(-1) is used to return failure to the parent process.
+      if (dup2(stdIn.reader(), STDIN_FILENO) == -1) {
+        exit(-1);
+      }
+      if (dup2(stdOut.writer(), STDOUT_FILENO) == -1) {
+        exit(-1);
+      }
+      close(stdIn.reader());
+      close(stdIn.writer());
+      close(stdOut.reader());
+      close(stdOut.writer());
+      execv(sArgv[0], argv.get());
+      exit(-1);
+  }
+#  endif
+
+  // In the parent process. Closing stdOut.writer() is necessary for
+  // stdOut.reader() below to hit EOF.
+  stdIn.closeReader();
+  stdOut.closeWriter();
+
+  if (!WriteAll(stdIn.writer(), bytecode, bytecodeLength)) {
+    return false;
+  }
+
+  stdIn.closeWriter();
+
+  if (!ReadAll(stdOut.reader(), serialized)) {
+    return false;
+  }
+
+  stdOut.closeReader();
+
+  int status;
+#  ifdef XP_WIN
+  if (_cwait(&status, childPid, WAIT_CHILD) == -1) {
+    return false;
+  }
+#  else
+  while (true) {
+    if (waitpid(childPid, &status, 0) >= 0) {
+      break;
+    }
+    if (errno != EINTR) {
+      return false;
+    }
+  }
+#  endif
+
+  return status == 0;
+}
+
+static bool WasmCompileAndSerialize(JSContext* cx) {
+  MOZ_ASSERT(wasm::CodeCachingAvailable(cx));
+
+#  ifdef XP_WIN
+  // See CompileAndSerializeInSeparateProcess for why we've had to smuggle
+  // these fd values through argv. Closing the writing ends is necessary for
+  // the reading ends to hit EOF.
+  int flagIndex = 0;
+  for (; flagIndex < sArgc; flagIndex++) {
+    if (!strcmp(sArgv[flagIndex], sWasmCompileAndSerializeFlag)) {
+      break;
+    }
+  }
+  MOZ_RELEASE_ASSERT(flagIndex < sArgc);
+
+  int fdsIndex = flagIndex + 1;
+  MOZ_RELEASE_ASSERT(fdsIndex + 4 == sArgc);
+
+  int stdInReader = atoi(sArgv[fdsIndex + 0]);
+  int stdInWriter = atoi(sArgv[fdsIndex + 1]);
+  int stdOutReader = atoi(sArgv[fdsIndex + 2]);
+  int stdOutWriter = atoi(sArgv[fdsIndex + 3]);
+
+  int stdIn = stdInReader;
+  close(stdInWriter);
+  close(stdOutReader);
+  int stdOut = stdOutWriter;
+#  else
+  int stdIn = STDIN_FILENO;
+  int stdOut = STDOUT_FILENO;
+#  endif
+
+  wasm::MutableBytes bytecode = js_new<wasm::ShareableBytes>();
+  if (!ReadAll(stdIn, &bytecode->bytes)) {
+    return false;
+  }
+
+  wasm::Bytes serialized;
+  if (!wasm::CompileAndSerialize(cx, *bytecode, &serialized)) {
+    return false;
+  }
+
+  if (!WriteAll(stdOut, serialized.begin(), serialized.length())) {
+    return false;
+  }
+
+  return true;
+}
+
+static bool WasmCompileInSeparateProcess(JSContext* cx, unsigned argc,
+                                         Value* vp) {
+  if (!wasm::CodeCachingAvailable(cx)) {
+    JS_ReportErrorASCII(cx, "WebAssembly caching not supported");
+    return false;
+  }
+
+  CallArgs args = CallArgsFromVp(argc, vp);
+  if (!args.requireAtLeast(cx, "wasmCompileInSeparateProcess", 1)) {
+    return false;
+  }
+
+  SharedMem<uint8_t*> bytecode;
+  size_t numBytes;
+  if (!args[0].isObject() ||
+      !IsBufferSource(&args[0].toObject(), &bytecode, &numBytes)) {
+    RootedObject callee(cx, &args.callee());
+    ReportUsageErrorASCII(cx, callee, "Argument must be a buffer source");
+    return false;
+  }
+
+  wasm::Bytes serialized;
+  if (!CompileAndSerializeInSeparateProcess(cx, bytecode.unwrap(), numBytes,
+                                            &serialized)) {
+    if (!cx->isExceptionPending()) {
+      JS_ReportErrorASCII(cx, "creating and executing child process");
+    }
+    return false;
+  }
+
+  RootedObject module(cx);
+  if (!wasm::DeserializeModule(cx, serialized, &module)) {
+    return false;
+  }
+
+  args.rval().setObject(*module);
+  return true;
+}
+#endif  // __wasi__
+
+static bool DecompileFunction(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+  if (args.length() < 1 || !args[0].isObject() ||
+      !args[0].toObject().is<JSFunction>()) {
+    args.rval().setUndefined();
+    return true;
+  }
+  RootedFunction fun(cx, &args[0].toObject().as<JSFunction>());
+  JSString* result = JS_DecompileFunction(cx, fun);
+  if (!result) {
+    return false;
+  }
+  args.rval().setString(result);
+  return true;
+}
+
+static bool DecompileThisScript(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  NonBuiltinScriptFrameIter iter(cx);
+  if (iter.done()) {
+    args.rval().setString(cx->runtime()->emptyString);
+    return true;
+  }
+
+  {
+    JSAutoRealm ar(cx, iter.script());
+
+    RootedScript script(cx, iter.script());
+    JSString* result = JS_DecompileScript(cx, script);
+    if (!result) {
+      return false;
+    }
+
+    args.rval().setString(result);
+  }
+
+  return JS_WrapValue(cx, args.rval());
+}
+
+static bool ValueToSource(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  JSString* str = ValueToSource(cx, args.get(0));
+  if (!str) {
+    return false;
+  }
+
+  args.rval().setString(str);
+  return true;
+}
+
+static bool ThisFilename(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  JS::AutoFilename filename;
+  if (!DescribeScriptedCaller(cx, &filename) || !filename.get()) {
+    args.rval().setString(cx->runtime()->emptyString);
+    return true;
+  }
+
+  JSString* str = JS_NewStringCopyZ(cx, filename.get());
+  if (!str) {
+    return false;
+  }
+
+  args.rval().setString(str);
+  return true;
+}
+
+static bool WrapWithProto(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+  Value obj = args.get(0);
+  Value proto = args.get(1);
+  if (!obj.isObject() || !proto.isObjectOrNull()) {
+    JS_ReportErrorNumberASCII(cx, my_GetErrorMessage, nullptr,
+                              JSSMSG_INVALID_ARGS, "wrapWithProto");
+    return false;
+  }
+
+  // Disallow constructing (deeply) nested wrapper chains, to avoid running
+  // out of stack space in isCallable/isConstructor. See bug 1126105.
+  if (IsWrapper(&obj.toObject())) {
+    JS_ReportErrorASCII(cx, "wrapWithProto cannot wrap a wrapper");
+    return false;
+  }
+
+  WrapperOptions options(cx);
+  options.setProto(proto.toObjectOrNull());
+  JSObject* wrapped = Wrapper::New(cx, &obj.toObject(),
+                                   &Wrapper::singletonWithPrototype, options);
+  if (!wrapped) {
+    return false;
+  }
+
+  args.rval().setObject(*wrapped);
+  return true;
+}
+
+static bool NewGlobal(JSContext* cx, unsigned argc, Value* vp) {
+  JS::RealmOptions options;
+  JS::RealmCreationOptions& creationOptions = options.creationOptions();
+  JS::RealmBehaviors& behaviors = options.behaviors();
+  ShellGlobalKind kind = ShellGlobalKind::WindowProxy;
+  bool immutablePrototype = true;
+
+  SetStandardRealmOptions(options);
+
+  // Default to creating the global in the current compartment unless
+  // --more-compartments is used.
+  if (defaultToSameCompartment) {
+    creationOptions.setExistingCompartment(cx->global());
+  } else {
+    creationOptions.setNewCompartmentAndZone();
+  }
+
+  JS::AutoHoldPrincipals principals(cx);
+
+  CallArgs args = CallArgsFromVp(argc, vp);
+  if (args.length() == 1 && args[0].isObject()) {
+    RootedObject opts(cx, &args[0].toObject());
+    RootedValue v(cx);
+
+    if (!JS_GetProperty(cx, opts, "invisibleToDebugger", &v)) {
+      return false;
+    }
+    if (v.isBoolean()) {
+      creationOptions.setInvisibleToDebugger(v.toBoolean());
+    }
+
+    if (!JS_GetProperty(cx, opts, "sameZoneAs", &v)) {
+      return false;
+    }
+    if (v.isObject()) {
+      creationOptions.setNewCompartmentInExistingZone(
+          UncheckedUnwrap(&v.toObject()));
+    }
+
+    if (!JS_GetProperty(cx, opts, "sameCompartmentAs", &v)) {
+      return false;
+    }
+    if (v.isObject()) {
+      creationOptions.setExistingCompartment(UncheckedUnwrap(&v.toObject()));
+    }
+
+    if (!JS_GetProperty(cx, opts, "newCompartment", &v)) {
+      return false;
+    }
+    if (v.isBoolean() && v.toBoolean()) {
+      creationOptions.setNewCompartmentAndZone();
+    }
+
+    if (!JS_GetProperty(cx, opts, "discardSource", &v)) {
+      return false;
+    }
+    if (v.isBoolean()) {
+      behaviors.setDiscardSource(v.toBoolean());
+    }
+
+    if (!JS_GetProperty(cx, opts, "useWindowProxy", &v)) {
+      return false;
+    }
+    if (v.isBoolean()) {
+      kind = v.toBoolean() ? ShellGlobalKind::WindowProxy
+                           : ShellGlobalKind::GlobalObject;
+    }
+
+    if (!JS_GetProperty(cx, opts, "immutablePrototype", &v)) {
+      return false;
+    }
+    if (v.isBoolean()) {
+      immutablePrototype = v.toBoolean();
+    }
+
+    if (!JS_GetProperty(cx, opts, "systemPrincipal", &v)) {
+      return false;
+    }
+    if (v.isBoolean()) {
+      principals.reset(&ShellPrincipals::fullyTrusted);
+    }
+
+    if (!JS_GetProperty(cx, opts, "principal", &v)) {
+      return false;
+    }
+    if (!v.isUndefined()) {
+      uint32_t bits;
+      if (!ToUint32(cx, v, &bits)) {
+        return false;
+      }
+      JSPrincipals* newPrincipals = cx->new_<ShellPrincipals>(bits);
+      if (!newPrincipals) {
+        return false;
+      }
+      principals.reset(newPrincipals);
+    }
+
+    if (!JS_GetProperty(cx, opts, "enableCoopAndCoep", &v)) {
+      return false;
+    }
+    if (v.isBoolean()) {
+      creationOptions.setCoopAndCoepEnabled(v.toBoolean());
+    }
+
+    if (!JS_GetProperty(cx, opts, "freezeBuiltins", &v)) {
+      return false;
+    }
+    if (v.isBoolean()) {
+      creationOptions.setFreezeBuiltins(v.toBoolean());
+    }
+
+    // On the web, the SharedArrayBuffer constructor is not installed as a
+    // global property in pages that aren't isolated in a separate process (and
+    // thus can't allow the structured cloning of shared memory).  Specify false
+    // for this option to reproduce this behavior.
+    if (!JS_GetProperty(cx, opts, "defineSharedArrayBufferConstructor", &v)) {
+      return false;
+    }
+    if (v.isBoolean()) {
+      creationOptions.setDefineSharedArrayBufferConstructor(v.toBoolean());
+    }
+  }
+
+  if (!CheckRealmOptions(cx, options, principals.get())) {
+    return false;
+  }
+
+  RootedObject global(cx, NewGlobalObject(cx, options, principals.get(), kind,
+                                          immutablePrototype));
+  if (!global) {
+    return false;
+  }
+
+  RootedObject wrapped(cx, ToWindowProxyIfWindow(global));
+  if (!JS_WrapObject(cx, &wrapped)) {
+    return false;
+  }
+
+  args.rval().setObject(*wrapped);
+  return true;
+}
+
+static bool NukeAllCCWs(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  if (args.length() != 0) {
+    JS_ReportErrorNumberASCII(cx, my_GetErrorMessage, nullptr,
+                              JSSMSG_INVALID_ARGS, "nukeAllCCWs");
+    return false;
+  }
+
+  NukeCrossCompartmentWrappers(cx, AllCompartments(), cx->realm(),
+                               NukeWindowReferences, NukeAllReferences);
+  args.rval().setUndefined();
+  return true;
+}
+
+static bool RecomputeWrappers(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  if (args.length() > 2) {
+    JS_ReportErrorNumberASCII(cx, my_GetErrorMessage, nullptr,
+                              JSSMSG_INVALID_ARGS, "recomputeWrappers");
+    return false;
+  }
+
+  JS::Compartment* sourceComp = nullptr;
+  if (args.get(0).isObject()) {
+    sourceComp = JS::GetCompartment(UncheckedUnwrap(&args[0].toObject()));
+  }
+
+  JS::Compartment* targetComp = nullptr;
+  if (args.get(1).isObject()) {
+    targetComp = JS::GetCompartment(UncheckedUnwrap(&args[1].toObject()));
+  }
+
+  struct SingleOrAllCompartments final : public CompartmentFilter {
+    JS::Compartment* comp;
+    explicit SingleOrAllCompartments(JS::Compartment* c) : comp(c) {}
+    virtual bool match(JS::Compartment* c) const override {
+      return !comp || comp == c;
+    }
+  };
+
+  if (!js::RecomputeWrappers(cx, SingleOrAllCompartments(sourceComp),
+                             SingleOrAllCompartments(targetComp))) {
+    return false;
+  }
+
+  args.rval().setUndefined();
+  return true;
+}
+
+static bool DumpObjectWrappers(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  bool printedHeader = false;
+  for (ZonesIter zone(cx->runtime(), WithAtoms); !zone.done(); zone.next()) {
+    bool printedZoneInfo = false;
+    for (CompartmentsInZoneIter comp(zone); !comp.done(); comp.next()) {
+      bool printedCompartmentInfo = false;
+      for (Compartment::ObjectWrapperEnum e(comp); !e.empty(); e.popFront()) {
+        JSObject* wrapper = e.front().value().unbarrieredGet();
+        JSObject* wrapped = e.front().key();
+        if (!printedHeader) {
+          fprintf(stderr, "Cross-compartment object wrappers:\n");
+          printedHeader = true;
+        }
+        if (!printedZoneInfo) {
+          fprintf(stderr, "  Zone %p:\n", zone.get());
+          printedZoneInfo = true;
+        }
+        if (!printedCompartmentInfo) {
+          fprintf(stderr, "    Compartment %p:\n", comp.get());
+          printedCompartmentInfo = true;
+        }
+        fprintf(stderr,
+                "      Object wrapper %p -> %p in zone %p compartment %p\n",
+                wrapper, wrapped, wrapped->zone(), wrapped->compartment());
+      }
+    }
+  }
+
+  if (!printedHeader) {
+    fprintf(stderr, "No cross-compartment object wrappers.\n");
+  }
+
+  args.rval().setUndefined();
+  return true;
+}
+
+static bool GetMaxArgs(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+  args.rval().setInt32(ARGS_LENGTH_MAX);
+  return true;
+}
+
+static bool IsHTMLDDA_Call(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  // These are the required conditions under which this object may be called
+  // by test262 tests, and the required behavior under those conditions.
+  if (args.length() == 0 ||
+      (args[0].isString() && args[0].toString()->length() == 0)) {
+    args.rval().setNull();
+    return true;
+  }
+
+  JS_ReportErrorASCII(
+      cx, "IsHTMLDDA object is being called in an impermissible manner");
+  return false;
+}
+
+static bool CreateIsHTMLDDA(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  static const JSClassOps classOps = {
+      nullptr,         // addProperty
+      nullptr,         // delProperty
+      nullptr,         // enumerate
+      nullptr,         // newEnumerate
+      nullptr,         // resolve
+      nullptr,         // mayResolve
+      nullptr,         // finalize
+      IsHTMLDDA_Call,  // call
+      nullptr,         // construct
+      nullptr,         // trace
+  };
+
+  static const JSClass cls = {
+      "IsHTMLDDA",
+      JSCLASS_EMULATES_UNDEFINED,
+      &classOps,
+  };
+
+  JSObject* obj = JS_NewObject(cx, &cls);
+  if (!obj) {
+    return false;
+  }
+  args.rval().setObject(*obj);
+  return true;
+}
+
+static bool GetSelfHostedValue(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  if (args.length() != 1 || !args[0].isString()) {
+    JS_ReportErrorNumberASCII(cx, my_GetErrorMessage, nullptr,
+                              JSSMSG_INVALID_ARGS, "getSelfHostedValue");
+    return false;
+  }
+  Rooted<JSAtom*> srcAtom(cx, ToAtom<CanGC>(cx, args[0]));
+  if (!srcAtom) {
+    return false;
+  }
+  Rooted<PropertyName*> srcName(cx, srcAtom->asPropertyName());
+  return GlobalObject::getIntrinsicValue(cx, cx->global(), srcName,
+                                         args.rval());
+}
+
+class ShellSourceHook : public SourceHook {
+  // The function we should call to lazily retrieve source code.
+  PersistentRootedFunction fun;
+
+ public:
+  ShellSourceHook(JSContext* cx, JSFunction& fun) : fun(cx, &fun) {}
+
+  bool load(JSContext* cx, const char* filename, char16_t** twoByteSource,
+            char** utf8Source, size_t* length) override {
+    MOZ_ASSERT((twoByteSource != nullptr) != (utf8Source != nullptr),
+               "must be called requesting only one of UTF-8 or UTF-16 source");
+
+    RootedString str(cx, JS_NewStringCopyZ(cx, filename));
+    if (!str) {
+      return false;
+    }
+    RootedValue filenameValue(cx, StringValue(str));
+
+    RootedValue result(cx);
+    if (!Call(cx, UndefinedHandleValue, fun, HandleValueArray(filenameValue),
+              &result)) {
+      return false;
+    }
+
+    str = JS::ToString(cx, result);
+    if (!str) {
+      return false;
+    }
+
+    Rooted<JSLinearString*> linear(cx, str->ensureLinear(cx));
+    if (!linear) {
+      return false;
+    }
+
+    if (twoByteSource) {
+      *length = JS_GetStringLength(linear);
+
+      *twoByteSource = cx->pod_malloc<char16_t>(*length);
+      if (!*twoByteSource) {
+        return false;
+      }
+
+      CopyChars(*twoByteSource, *linear);
+    } else {
+      MOZ_ASSERT(utf8Source != nullptr);
+
+      *length = JS::GetDeflatedUTF8StringLength(linear);
+
+      *utf8Source = cx->pod_malloc<char>(*length);
+      if (!*utf8Source) {
+        return false;
+      }
+
+      mozilla::DebugOnly<size_t> dstLen = JS::DeflateStringToUTF8Buffer(
+          linear, mozilla::Span(*utf8Source, *length));
+      MOZ_ASSERT(dstLen == *length);
+    }
+
+    return true;
+  }
+};
+
+static bool WithSourceHook(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+  RootedObject callee(cx, &args.callee());
+
+  if (args.length() != 2) {
+    ReportUsageErrorASCII(cx, callee, "Wrong number of arguments.");
+    return false;
+  }
+
+  if (!args[0].isObject() || !args[0].toObject().is<JSFunction>() ||
+      !args[1].isObject() || !args[1].toObject().is<JSFunction>()) {
+    ReportUsageErrorASCII(cx, callee,
+                          "First and second arguments must be functions.");
+    return false;
+  }
+
+  mozilla::UniquePtr<ShellSourceHook> hook =
+      mozilla::MakeUnique<ShellSourceHook>(cx,
+                                           args[0].toObject().as<JSFunction>());
+  if (!hook) {
+    return false;
+  }
+
+  mozilla::UniquePtr<SourceHook> savedHook = js::ForgetSourceHook(cx);
+  js::SetSourceHook(cx, std::move(hook));
+
+  RootedObject fun(cx, &args[1].toObject());
+  bool result = Call(cx, UndefinedHandleValue, fun,
+                     JS::HandleValueArray::empty(), args.rval());
+  js::SetSourceHook(cx, std::move(savedHook));
+  return result;
+}
+
+static void PrintProfilerEvents_Callback(const char* msg, const char* details) {
+  fprintf(stderr, "PROFILER EVENT: %s %s\n", msg, details);
+}
+
+static bool PrintProfilerEvents(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+  if (cx->runtime()->geckoProfiler().enabled()) {
+    js::RegisterContextProfilingEventMarker(cx, &PrintProfilerEvents_Callback);
+  }
+  args.rval().setUndefined();
+  return true;
+}
+
+#ifdef SINGLESTEP_PROFILING
+static void SingleStepCallback(void* arg, jit::Simulator* sim, void* pc) {
+  JSContext* cx = reinterpret_cast<JSContext*>(arg);
+
+  // If profiling is not enabled, don't do anything.
+  if (!cx->runtime()->geckoProfiler().enabled()) {
+    return;
+  }
+
+  JS::ProfilingFrameIterator::RegisterState state;
+  state.pc = pc;
+#  if defined(JS_SIMULATOR_ARM)
+  state.sp = (void*)sim->get_register(jit::Simulator::sp);
+  state.lr = (void*)sim->get_register(jit::Simulator::lr);
+  state.fp = (void*)sim->get_register(jit::Simulator::fp);
+#  elif defined(JS_SIMULATOR_MIPS64) || defined(JS_SIMULATOR_MIPS32)
+  state.sp = (void*)sim->getRegister(jit::Simulator::sp);
+  state.lr = (void*)sim->getRegister(jit::Simulator::ra);
+  state.fp = (void*)sim->getRegister(jit::Simulator::fp);
+#  elif defined(JS_SIMULATOR_LOONG64)
+  state.sp = (void*)sim->getRegister(jit::Simulator::sp);
+  state.lr = (void*)sim->getRegister(jit::Simulator::ra);
+  state.fp = (void*)sim->getRegister(jit::Simulator::fp);
+#  else
+#    error "NYI: Single-step profiling support"
+#  endif
+
+  mozilla::DebugOnly<void*> lastStackAddress = nullptr;
+  StackChars stack;
+  uint32_t frameNo = 0;
+  AutoEnterOOMUnsafeRegion oomUnsafe;
+  for (JS::ProfilingFrameIterator i(cx, state); !i.done(); ++i) {
+    MOZ_ASSERT(i.stackAddress() != nullptr);
+    MOZ_ASSERT(lastStackAddress <= i.stackAddress());
+    lastStackAddress = i.stackAddress();
+    JS::ProfilingFrameIterator::Frame frames[16];
+    uint32_t nframes = i.extractStack(frames, 0, 16);
+    for (uint32_t i = 0; i < nframes; i++) {
+      // Assert endStackAddress never exceeds sp (bug 1782188).
+      MOZ_ASSERT(frames[i].endStackAddress >= state.sp);
+      if (frameNo > 0) {
+        if (!stack.append(",", 1)) {
+          oomUnsafe.crash("stack.append");
+        }
+      }
+      if (!stack.append(frames[i].label, strlen(frames[i].label))) {
+        oomUnsafe.crash("stack.append");
+      }
+      frameNo++;
+    }
+  }
+
+  ShellContext* sc = GetShellContext(cx);
+
+  // Only append the stack if it differs from the last stack.
+  if (sc->stacks.empty() || sc->stacks.back().length() != stack.length() ||
+      !ArrayEqual(sc->stacks.back().begin(), stack.begin(), stack.length())) {
+    if (!sc->stacks.append(std::move(stack))) {
+      oomUnsafe.crash("stacks.append");
+    }
+  }
+}
+#endif
+
+static bool EnableSingleStepProfiling(JSContext* cx, unsigned argc, Value* vp) {
+#ifdef SINGLESTEP_PROFILING
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  jit::Simulator* sim = cx->simulator();
+  sim->enable_single_stepping(SingleStepCallback, cx);
+
+  args.rval().setUndefined();
+  return true;
+#else
+  JS_ReportErrorASCII(cx, "single-step profiling not enabled on this platform");
+  return false;
+#endif
+}
+
+static bool DisableSingleStepProfiling(JSContext* cx, unsigned argc,
+                                       Value* vp) {
+#ifdef SINGLESTEP_PROFILING
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  jit::Simulator* sim = cx->simulator();
+  sim->disable_single_stepping();
+
+  ShellContext* sc = GetShellContext(cx);
+
+  RootedValueVector elems(cx);
+  for (size_t i = 0; i < sc->stacks.length(); i++) {
+    JSString* stack =
+        JS_NewUCStringCopyN(cx, sc->stacks[i].begin(), sc->stacks[i].length());
+    if (!stack) {
+      return false;
+    }
+    if (!elems.append(StringValue(stack))) {
+      return false;
+    }
+  }
+
+  JSObject* array = JS::NewArrayObject(cx, elems);
+  if (!array) {
+    return false;
+  }
+
+  sc->stacks.clear();
+  args.rval().setObject(*array);
+  return true;
+#else
+  JS_ReportErrorASCII(cx, "single-step profiling not enabled on this platform");
+  return false;
+#endif
+}
+
+static bool IsLatin1(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+  bool isLatin1 =
+      args.get(0).isString() && args[0].toString()->hasLatin1Chars();
+  args.rval().setBoolean(isLatin1);
+  return true;
+}
+
+static bool EnableGeckoProfiling(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  if (!EnsureGeckoProfilingStackInstalled(cx, GetShellContext(cx))) {
+    return false;
+  }
+
+  cx->runtime()->geckoProfiler().enableSlowAssertions(false);
+  cx->runtime()->geckoProfiler().enable(true);
+
+  args.rval().setUndefined();
+  return true;
+}
+
+static bool EnableGeckoProfilingWithSlowAssertions(JSContext* cx, unsigned argc,
+                                                   Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+  args.rval().setUndefined();
+
+  if (cx->runtime()->geckoProfiler().enabled()) {
+    // If profiling already enabled with slow assertions disabled,
+    // this is a no-op.
+    if (cx->runtime()->geckoProfiler().slowAssertionsEnabled()) {
+      return true;
+    }
+
+    // Slow assertions are off.  Disable profiling before re-enabling
+    // with slow assertions on.
+    cx->runtime()->geckoProfiler().enable(false);
+  }
+
+  if (!EnsureGeckoProfilingStackInstalled(cx, GetShellContext(cx))) {
+    return false;
+  }
+
+  cx->runtime()->geckoProfiler().enableSlowAssertions(true);
+  cx->runtime()->geckoProfiler().enable(true);
+
+  return true;
+}
+
+static bool DisableGeckoProfiling(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+  args.rval().setUndefined();
+
+  if (!cx->runtime()->geckoProfiler().enabled()) {
+    return true;
+  }
+
+  cx->runtime()->geckoProfiler().enable(false);
+  return true;
+}
+
+// Global mailbox that is used to communicate a shareable object value from one
+// worker to another.
+//
+// These object types are shareable:
+//
+//   - SharedArrayBuffer
+//   - WasmMemoryObject (when constructed with shared:true)
+//   - WasmModuleObject
+//
+// For the SharedArrayBuffer and WasmMemoryObject we transmit the underlying
+// SharedArrayRawBuffer ("SARB"). For the WasmModuleObject we transmit the
+// underlying JS::WasmModule.  The transmitted types are refcounted.  When they
+// are in the mailbox their reference counts are at least 1, accounting for the
+// reference from the mailbox.
+//
+// The lock guards the mailbox variable and prevents a race where two workers
+// try to set the mailbox at the same time to replace an object that is only
+// referenced from the mailbox: the workers will both decrement the reference
+// count on the old object, and one of those decrements will be on a garbage
+// object.  We could implement this with atomics and a CAS loop but it's not
+// worth the bother.
+//
+// Note that if a thread reads the mailbox repeatedly it will get distinct
+// objects on each read.  The alternatives are to cache created objects locally,
+// but this retains storage we don't need to retain, or to somehow clear the
+// mailbox locally, but this creates a coordination headache.  Buyer beware.
+
+enum class MailboxTag {
+  Empty,
+  SharedArrayBuffer,
+  WasmMemory,
+  WasmModule,
+  Number,
+};
+
+struct SharedObjectMailbox {
+  union Value {
+    struct {
+      SharedArrayRawBuffer* buffer;
+      size_t length;
+      bool isHugeMemory;  // For a WasmMemory tag, otherwise false
+    } sarb;
+    JS::WasmModule* module;
+    double number;
+
+    Value() : number(0.0) {}
+  };
+
+  MailboxTag tag = MailboxTag::Empty;
+  Value val;
+};
+
+typedef ExclusiveData<SharedObjectMailbox> SOMailbox;
+
+// Never null after successful initialization.
+static SOMailbox* sharedObjectMailbox;
+
+static bool InitSharedObjectMailbox() {
+  sharedObjectMailbox = js_new<SOMailbox>(mutexid::ShellObjectMailbox);
+  return sharedObjectMailbox != nullptr;
+}
+
+static void DestructSharedObjectMailbox() {
+  // All workers need to have terminated at this point.
+
+  {
+    auto mbx = sharedObjectMailbox->lock();
+    switch (mbx->tag) {
+      case MailboxTag::Empty:
+      case MailboxTag::Number:
+        break;
+      case MailboxTag::SharedArrayBuffer:
+      case MailboxTag::WasmMemory:
+        mbx->val.sarb.buffer->dropReference();
+        break;
+      case MailboxTag::WasmModule:
+        mbx->val.module->Release();
+        break;
+      default:
+        MOZ_CRASH();
+    }
+  }
+
+  js_delete(sharedObjectMailbox);
+  sharedObjectMailbox = nullptr;
+}
+
+static bool GetSharedObject(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+  RootedObject newObj(cx);
+
+  {
+    auto mbx = sharedObjectMailbox->lock();
+    switch (mbx->tag) {
+      case MailboxTag::Empty: {
+        break;
+      }
+      case MailboxTag::Number: {
+        args.rval().setNumber(mbx->val.number);
+        return true;
+      }
+      case MailboxTag::SharedArrayBuffer:
+      case MailboxTag::WasmMemory: {
+        // Flag was set in the sender; ensure it is set in the receiver.
+        MOZ_ASSERT(
+            cx->realm()->creationOptions().getSharedMemoryAndAtomicsEnabled());
+
+        // The protocol for creating a SAB requires the refcount to be
+        // incremented prior to the SAB creation.
+
+        SharedArrayRawBuffer* buf = mbx->val.sarb.buffer;
+        size_t length = mbx->val.sarb.length;
+        if (!buf->addReference()) {
+          JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                                    JSMSG_SC_SAB_REFCNT_OFLO);
+          return false;
+        }
+
+        // If the allocation fails we must decrement the refcount before
+        // returning.
+
+        Rooted<ArrayBufferObjectMaybeShared*> maybesab(
+            cx, SharedArrayBufferObject::New(cx, buf, length));
+        if (!maybesab) {
+          buf->dropReference();
+          return false;
+        }
+
+        // At this point the SAB was created successfully and it owns the
+        // refcount-increase on the buffer that we performed above.  So even
+        // if we fail to allocate along any path below we must not decrement
+        // the refcount; the garbage collector must be allowed to handle
+        // that via finalization of the orphaned SAB object.
+
+        if (mbx->tag == MailboxTag::SharedArrayBuffer) {
+          newObj = maybesab;
+        } else {
+          if (!GlobalObject::ensureConstructor(cx, cx->global(),
+                                               JSProto_WebAssembly)) {
+            return false;
+          }
+          RootedObject proto(cx,
+                             &cx->global()->getPrototype(JSProto_WasmMemory));
+          newObj = WasmMemoryObject::create(cx, maybesab,
+                                            mbx->val.sarb.isHugeMemory, proto);
+          MOZ_ASSERT_IF(newObj, newObj->as<WasmMemoryObject>().isShared());
+          if (!newObj) {
+            return false;
+          }
+        }
+
+        break;
+      }
+      case MailboxTag::WasmModule: {
+        // Flag was set in the sender; ensure it is set in the receiver.
+        MOZ_ASSERT(
+            cx->realm()->creationOptions().getSharedMemoryAndAtomicsEnabled());
+
+        if (!GlobalObject::ensureConstructor(cx, cx->global(),
+                                             JSProto_WebAssembly)) {
+          return false;
+        }
+
+        // WasmModuleObject::create() increments the refcount on the module
+        // and signals an error and returns null if that fails.
+        newObj = mbx->val.module->createObject(cx);
+        if (!newObj) {
+          return false;
+        }
+        break;
+      }
+      default: {
+        MOZ_CRASH();
+      }
+    }
+  }
+
+  args.rval().setObjectOrNull(newObj);
+  return true;
+}
+
+static bool SetSharedObject(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  MailboxTag tag = MailboxTag::Empty;
+  SharedObjectMailbox::Value value;
+
+  // Increase refcounts when we obtain the value to avoid operating on dead
+  // storage during self-assignment.
+
+  if (args.get(0).isObject()) {
+    RootedObject obj(cx, &args[0].toObject());
+    if (obj->is<SharedArrayBufferObject>()) {
+      Rooted<SharedArrayBufferObject*> sab(cx,
+                                           &obj->as<SharedArrayBufferObject>());
+      tag = MailboxTag::SharedArrayBuffer;
+      value.sarb.buffer = sab->rawBufferObject();
+      value.sarb.length = sab->byteLength();
+      value.sarb.isHugeMemory = false;
+      if (!value.sarb.buffer->addReference()) {
+        JS_ReportErrorASCII(cx,
+                            "Reference count overflow on SharedArrayBuffer");
+        return false;
+      }
+    } else if (obj->is<WasmMemoryObject>()) {
+      // Here we must transmit sab.byteLength() as the length; the SARB has its
+      // own notion of the length which may be greater, and that's fine.
+      if (obj->as<WasmMemoryObject>().isShared()) {
+        Rooted<SharedArrayBufferObject*> sab(
+            cx, &obj->as<WasmMemoryObject>()
+                     .buffer()
+                     .as<SharedArrayBufferObject>());
+        tag = MailboxTag::WasmMemory;
+        value.sarb.buffer = sab->rawBufferObject();
+        value.sarb.length = sab->byteLength();
+        value.sarb.isHugeMemory = obj->as<WasmMemoryObject>().isHuge();
+        if (!value.sarb.buffer->addReference()) {
+          JS_ReportErrorASCII(cx,
+                              "Reference count overflow on SharedArrayBuffer");
+          return false;
+        }
+      } else {
+        JS_ReportErrorASCII(cx, "Invalid argument to SetSharedObject");
+        return false;
+      }
+    } else if (JS::IsWasmModuleObject(obj)) {
+      tag = MailboxTag::WasmModule;
+      value.module = JS::GetWasmModule(obj).forget().take();
+    } else {
+      JS_ReportErrorASCII(cx, "Invalid argument to SetSharedObject");
+      return false;
+    }
+  } else if (args.get(0).isNumber()) {
+    tag = MailboxTag::Number;
+    value.number = args.get(0).toNumber();
+    // Nothing
+  } else if (args.get(0).isNullOrUndefined()) {
+    // Nothing
+  } else {
+    JS_ReportErrorASCII(cx, "Invalid argument to SetSharedObject");
+    return false;
+  }
+
+  {
+    auto mbx = sharedObjectMailbox->lock();
+
+    switch (mbx->tag) {
+      case MailboxTag::Empty:
+      case MailboxTag::Number:
+        break;
+      case MailboxTag::SharedArrayBuffer:
+      case MailboxTag::WasmMemory:
+        mbx->val.sarb.buffer->dropReference();
+        break;
+      case MailboxTag::WasmModule:
+        mbx->val.module->Release();
+        break;
+      default:
+        MOZ_CRASH();
+    }
+
+    mbx->tag = tag;
+    mbx->val = value;
+  }
+
+  args.rval().setUndefined();
+  return true;
+}
+
+typedef Vector<uint8_t, 0, SystemAllocPolicy> Uint8Vector;
+
+class StreamCacheEntry : public AtomicRefCounted<StreamCacheEntry>,
+                         public JS::OptimizedEncodingListener {
+  typedef AtomicRefCounted<StreamCacheEntry> AtomicBase;
+
+  Uint8Vector bytes_;
+  ExclusiveData<Uint8Vector> optimized_;
+
+ public:
+  explicit StreamCacheEntry(Uint8Vector&& original)
+      : bytes_(std::move(original)),
+        optimized_(mutexid::ShellStreamCacheEntryState) {}
+
+  // Implement JS::OptimizedEncodingListener:
+
+  MozExternalRefCountType MOZ_XPCOM_ABI AddRef() override {
+    AtomicBase::AddRef();
+    return 1;  // unused
+  }
+  MozExternalRefCountType MOZ_XPCOM_ABI Release() override {
+    AtomicBase::Release();
+    return 0;  // unused
+  }
+
+  const Uint8Vector& bytes() const { return bytes_; }
+
+  void storeOptimizedEncoding(const uint8_t* srcBytes,
+                              size_t srcLength) override {
+    MOZ_ASSERT(srcLength > 0);
+
+    // Tolerate races since a single StreamCacheEntry object can be used as
+    // the source of multiple streaming compilations.
+    auto dstBytes = optimized_.lock();
+    if (dstBytes->length() > 0) {
+      return;
+    }
+
+    if (!dstBytes->resize(srcLength)) {
+      return;
+    }
+    memcpy(dstBytes->begin(), srcBytes, srcLength);
+  }
+
+  bool hasOptimizedEncoding() const { return !optimized_.lock()->empty(); }
+  const Uint8Vector& optimizedEncoding() const {
+    return optimized_.lock().get();
+  }
+};
+
+typedef RefPtr<StreamCacheEntry> StreamCacheEntryPtr;
+
+class StreamCacheEntryObject : public NativeObject {
+  static const unsigned CACHE_ENTRY_SLOT = 0;
+  static const JSClassOps classOps_;
+  static const JSPropertySpec properties_;
+
+  static void finalize(JS::GCContext* gcx, JSObject* obj) {
+    obj->as<StreamCacheEntryObject>().cache().Release();
+  }
+
+  static bool cachedGetter(JSContext* cx, unsigned argc, Value* vp) {
+    CallArgs args = CallArgsFromVp(argc, vp);
+    if (!args.thisv().isObject() ||
+        !args.thisv().toObject().is<StreamCacheEntryObject>()) {
+      return false;
+    }
+
+    StreamCacheEntryObject& obj =
+        args.thisv().toObject().as<StreamCacheEntryObject>();
+    args.rval().setBoolean(obj.cache().hasOptimizedEncoding());
+    return true;
+  }
+  static bool getBuffer(JSContext* cx, unsigned argc, Value* vp) {
+    CallArgs args = CallArgsFromVp(argc, vp);
+    if (!args.thisv().isObject() ||
+        !args.thisv().toObject().is<StreamCacheEntryObject>()) {
+      return false;
+    }
+
+    auto& bytes =
+        args.thisv().toObject().as<StreamCacheEntryObject>().cache().bytes();
+    RootedArrayBufferObject buffer(
+        cx, ArrayBufferObject::createZeroed(cx, bytes.length()));
+    if (!buffer) {
+      return false;
+    }
+
+    memcpy(buffer->dataPointer(), bytes.begin(), bytes.length());
+
+    args.rval().setObject(*buffer);
+    return true;
+  }
+
+ public:
+  static const unsigned RESERVED_SLOTS = 1;
+  static const JSClass class_;
+  static const JSPropertySpec properties[];
+
+  static bool construct(JSContext* cx, unsigned argc, Value* vp) {
+    CallArgs args = CallArgsFromVp(argc, vp);
+    if (!args.requireAtLeast(cx, "streamCacheEntry", 1)) {
+      return false;
+    }
+
+    SharedMem<uint8_t*> ptr;
+    size_t numBytes;
+    if (!args[0].isObject() ||
+        !IsBufferSource(&args[0].toObject(), &ptr, &numBytes)) {
+      RootedObject callee(cx, &args.callee());
+      ReportUsageErrorASCII(cx, callee, "Argument must be an ArrayBuffer");
+      return false;
+    }
+
+    Uint8Vector bytes;
+    if (!bytes.resize(numBytes)) {
+      return false;
+    }
+
+    memcpy(bytes.begin(), ptr.unwrap(), numBytes);
+
+    RefPtr<StreamCacheEntry> cache =
+        cx->new_<StreamCacheEntry>(std::move(bytes));
+    if (!cache) {
+      return false;
+    }
+
+    Rooted<NativeObject*> obj(
+        cx, NewObjectWithGivenProto<StreamCacheEntryObject>(cx, nullptr));
+    if (!obj) {
+      return false;
+    }
+    obj->initReservedSlot(CACHE_ENTRY_SLOT,
+                          PrivateValue(cache.forget().take()));
+
+    if (!JS_DefineProperty(cx, obj, "cached", cachedGetter, nullptr, 0)) {
+      return false;
+    }
+    if (!JS_DefineFunction(cx, obj, "getBuffer", getBuffer, 0, 0)) {
+      return false;
+    }
+
+    args.rval().setObject(*obj);
+    return true;
+  }
+
+  StreamCacheEntry& cache() const {
+    return *(StreamCacheEntry*)getReservedSlot(CACHE_ENTRY_SLOT).toPrivate();
+  }
+};
+
+const JSClassOps StreamCacheEntryObject::classOps_ = {
+    nullptr,                           // addProperty
+    nullptr,                           // delProperty
+    nullptr,                           // enumerate
+    nullptr,                           // newEnumerate
+    nullptr,                           // resolve
+    nullptr,                           // mayResolve
+    StreamCacheEntryObject::finalize,  // finalize
+    nullptr,                           // call
+    nullptr,                           // construct
+    nullptr,                           // trace
+};
+
+const JSClass StreamCacheEntryObject::class_ = {
+    "StreamCacheEntryObject",
+    JSCLASS_HAS_RESERVED_SLOTS(StreamCacheEntryObject::RESERVED_SLOTS) |
+        JSCLASS_BACKGROUND_FINALIZE,
+    &StreamCacheEntryObject::classOps_};
+
+struct BufferStreamJob {
+  Variant<Uint8Vector, StreamCacheEntryPtr> source;
+  Thread thread;
+  JS::StreamConsumer* consumer;
+
+  BufferStreamJob(Uint8Vector&& source, JS::StreamConsumer* consumer)
+      : source(AsVariant<Uint8Vector>(std::move(source))), consumer(consumer) {}
+  BufferStreamJob(StreamCacheEntry& source, JS::StreamConsumer* consumer)
+      : source(AsVariant<StreamCacheEntryPtr>(&source)), consumer(consumer) {}
+};
+
+struct BufferStreamState {
+  Vector<UniquePtr<BufferStreamJob>, 0, SystemAllocPolicy> jobs;
+  size_t delayMillis;
+  size_t chunkSize;
+  bool shutdown;
+
+  BufferStreamState() : delayMillis(1), chunkSize(10), shutdown(false) {}
+
+  ~BufferStreamState() { MOZ_ASSERT(jobs.empty()); }
+};
+
+static ExclusiveWaitableData<BufferStreamState>* bufferStreamState;
+
+static void BufferStreamMain(BufferStreamJob* job) {
+  const uint8_t* bytes;
+  size_t byteLength;
+  JS::OptimizedEncodingListener* listener;
+  if (job->source.is<StreamCacheEntryPtr>()) {
+    StreamCacheEntry& cache = *job->source.as<StreamCacheEntryPtr>();
+    if (cache.hasOptimizedEncoding()) {
+      const Uint8Vector& optimized = cache.optimizedEncoding();
+      job->consumer->consumeOptimizedEncoding(optimized.begin(),
+                                              optimized.length());
+      goto done;
+    }
+
+    bytes = cache.bytes().begin();
+    byteLength = cache.bytes().length();
+    listener = &cache;
+  } else {
+    bytes = job->source.as<Uint8Vector>().begin();
+    byteLength = job->source.as<Uint8Vector>().length();
+    listener = nullptr;
+  }
+
+  size_t byteOffset;
+  byteOffset = 0;
+  while (true) {
+    if (byteOffset == byteLength) {
+      job->consumer->streamEnd(listener);
+      break;
+    }
+
+    bool shutdown;
+    size_t delayMillis;
+    size_t chunkSize;
+    {
+      auto state = bufferStreamState->lock();
+      shutdown = state->shutdown;
+      delayMillis = state->delayMillis;
+      chunkSize = state->chunkSize;
+    }
+
+    if (shutdown) {
+      job->consumer->streamError(JSMSG_STREAM_CONSUME_ERROR);
+      break;
+    }
+
+    ThisThread::SleepMilliseconds(delayMillis);
+
+    chunkSize = std::min(chunkSize, byteLength - byteOffset);
+
+    if (!job->consumer->consumeChunk(bytes + byteOffset, chunkSize)) {
+      break;
+    }
+
+    byteOffset += chunkSize;
+  }
+
+done:
+  auto state = bufferStreamState->lock();
+  size_t jobIndex = 0;
+  while (state->jobs[jobIndex].get() != job) {
+    jobIndex++;
+  }
+  job->thread.detach();  // quiet assert in ~Thread() called by erase().
+  state->jobs.erase(state->jobs.begin() + jobIndex);
+  if (state->jobs.empty()) {
+    state.notify_all(/* jobs empty */);
+  }
+}
+
+static bool EnsureLatin1CharsLinearString(JSContext* cx, HandleValue value,
+                                          UniqueChars* result) {
+  if (!value.isString()) {
+    result->reset(nullptr);
+    return true;
+  }
+  RootedString str(cx, value.toString());
+  if (!str->isLinear() || !str->hasLatin1Chars()) {
+    JS_ReportErrorASCII(cx,
+                        "only latin1 chars and linear strings are expected");
+    return false;
+  }
+
+  // Use JS_EncodeStringToLatin1 to null-terminate.
+  *result = JS_EncodeStringToLatin1(cx, str);
+  return !!*result;
+}
+
+static bool ConsumeBufferSource(JSContext* cx, JS::HandleObject obj,
+                                JS::MimeType, JS::StreamConsumer* consumer) {
+  {
+    RootedValue url(cx);
+    if (!JS_GetProperty(cx, obj, "url", &url)) {
+      return false;
+    }
+    UniqueChars urlChars;
+    if (!EnsureLatin1CharsLinearString(cx, url, &urlChars)) {
+      return false;
+    }
+
+    RootedValue mapUrl(cx);
+    if (!JS_GetProperty(cx, obj, "sourceMappingURL", &mapUrl)) {
+      return false;
+    }
+    UniqueChars mapUrlChars;
+    if (!EnsureLatin1CharsLinearString(cx, mapUrl, &mapUrlChars)) {
+      return false;
+    }
+
+    consumer->noteResponseURLs(urlChars.get(), mapUrlChars.get());
+  }
+
+  UniquePtr<BufferStreamJob> job;
+
+  SharedMem<uint8_t*> dataPointer;
+  size_t byteLength;
+  if (IsBufferSource(obj, &dataPointer, &byteLength)) {
+    Uint8Vector bytes;
+    if (!bytes.resize(byteLength)) {
+      JS_ReportOutOfMemory(cx);
+      return false;
+    }
+
+    memcpy(bytes.begin(), dataPointer.unwrap(), byteLength);
+    job = cx->make_unique<BufferStreamJob>(std::move(bytes), consumer);
+  } else if (obj->is<StreamCacheEntryObject>()) {
+    job = cx->make_unique<BufferStreamJob>(
+        obj->as<StreamCacheEntryObject>().cache(), consumer);
+  } else {
+    JS_ReportErrorASCII(
+        cx,
+        "shell streaming consumes a buffer source (buffer or view) "
+        "or StreamCacheEntryObject");
+    return false;
+  }
+  if (!job) {
+    return false;
+  }
+
+  BufferStreamJob* jobPtr = job.get();
+
+  {
+    auto state = bufferStreamState->lock();
+    MOZ_ASSERT(!state->shutdown);
+    if (!state->jobs.append(std::move(job))) {
+      JS_ReportOutOfMemory(cx);
+      return false;
+    }
+  }
+
+  {
+    AutoEnterOOMUnsafeRegion oomUnsafe;
+    if (!jobPtr->thread.init(BufferStreamMain, jobPtr)) {
+      oomUnsafe.crash("ConsumeBufferSource");
+    }
+  }
+
+  return true;
+}
+
+static void ReportStreamError(JSContext* cx, size_t errorNumber) {
+  JS_ReportErrorNumberUTF8(cx, GetErrorMessage, nullptr, errorNumber);
+}
+
+static bool SetBufferStreamParams(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+  if (!args.requireAtLeast(cx, "setBufferStreamParams", 2)) {
+    return false;
+  }
+
+  double delayMillis;
+  if (!ToNumber(cx, args[0], &delayMillis)) {
+    return false;
+  }
+
+  double chunkSize;
+  if (!ToNumber(cx, args[1], &chunkSize)) {
+    return false;
+  }
+
+  {
+    auto state = bufferStreamState->lock();
+    state->delayMillis = delayMillis;
+    state->chunkSize = chunkSize;
+  }
+
+  args.rval().setUndefined();
+  return true;
+}
+
+static void ShutdownBufferStreams() {
+  auto state = bufferStreamState->lock();
+  state->shutdown = true;
+  while (!state->jobs.empty()) {
+    state.wait(/* jobs empty */);
+  }
+  state->jobs.clearAndFree();
+}
+
+static bool DumpScopeChain(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+  RootedObject callee(cx, &args.callee());
+
+  if (js::SupportDifferentialTesting()) {
+    ReportUsageErrorASCII(
+        cx, callee, "Function not available in differential testing mode.");
+    return false;
+  }
+
+  if (args.length() != 1) {
+    ReportUsageErrorASCII(cx, callee, "Wrong number of arguments");
+    return false;
+  }
+
+  if (!args[0].isObject() ||
+      !(args[0].toObject().is<JSFunction>() ||
+        args[0].toObject().is<ShellModuleObjectWrapper>())) {
+    ReportUsageErrorASCII(
+        cx, callee, "Argument must be an interpreted function or a module");
+    return false;
+  }
+
+  RootedObject obj(cx, &args[0].toObject());
+  RootedScript script(cx);
+
+  if (obj->is<JSFunction>()) {
+    RootedFunction fun(cx, &obj->as<JSFunction>());
+    if (!fun->isInterpreted()) {
+      ReportUsageErrorASCII(cx, callee,
+                            "Argument must be an interpreted function");
+      return false;
+    }
+    script = JSFunction::getOrCreateScript(cx, fun);
+    if (!script) {
+      return false;
+    }
+  } else {
+    script = obj->as<ShellModuleObjectWrapper>().get()->maybeScript();
+    if (!script) {
+      JS_ReportErrorASCII(cx, "module does not have an associated script");
+      return false;
+    }
+  }
+
+  script->bodyScope()->dump();
+
+  args.rval().setUndefined();
+  return true;
+}
+
+// For testing gray marking, grayRoot() will heap-allocate an address
+// where we can store a JSObject*, and create a new object if one doesn't
+// already exist.
+//
+// Note that EnsureGrayRoot() will blacken the returned object, so it will not
+// actually end up marked gray until the following GC clears the black bit
+// (assuming nothing is holding onto it.)
+//
+// The idea is that you can set up a whole graph of objects to be marked gray,
+// hanging off of the object returned from grayRoot(). Then you GC to clear the
+// black bits and set the gray bits.
+//
+// To test grayness, register the objects of interest with addMarkObservers(),
+// which takes an Array of objects (which will be marked black at the time
+// they're passed in). Their mark bits may be retrieved at any time with
+// getMarks(), in the form of an array of strings with each index corresponding
+// to the original objects passed to addMarkObservers().
+
+static bool EnsureGrayRoot(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  auto priv = EnsureShellCompartmentPrivate(cx);
+  if (!priv) {
+    return false;
+  }
+
+  if (!priv->grayRoot) {
+    if (!(priv->grayRoot = NewTenuredDenseEmptyArray(cx))) {
+      return false;
+    }
+  }
+
+  // Barrier to enforce the invariant that JS does not touch gray objects.
+  JSObject* obj = priv->grayRoot;
+  JS::ExposeObjectToActiveJS(obj);
+
+  args.rval().setObject(*obj);
+  return true;
+}
+
+static MarkBitObservers* EnsureMarkBitObservers(JSContext* cx) {
+  ShellContext* sc = GetShellContext(cx);
+  if (!sc->markObservers) {
+    auto* observers =
+        cx->new_<MarkBitObservers>(cx->runtime(), NonshrinkingGCObjectVector());
+    if (!observers) {
+      return nullptr;
+    }
+    sc->markObservers.reset(observers);
+  }
+  return sc->markObservers.get();
+}
+
+static bool ClearMarkObservers(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  auto markObservers = EnsureMarkBitObservers(cx);
+  if (!markObservers) {
+    return false;
+  }
+
+  markObservers->get().clear();
+
+  args.rval().setUndefined();
+  return true;
+}
+
+static bool AddMarkObservers(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  auto markObservers = EnsureMarkBitObservers(cx);
+  if (!markObservers) {
+    return false;
+  }
+
+  if (!args.get(0).isObject()) {
+    JS_ReportErrorASCII(cx, "argument must be an Array of objects");
+    return false;
+  }
+
+  RootedObject observersArg(cx, &args[0].toObject());
+  uint64_t length;
+  if (!GetLengthProperty(cx, observersArg, &length)) {
+    return false;
+  }
+
+  if (length > UINT32_MAX) {
+    JS_ReportErrorASCII(cx, "Invalid length for observers array");
+    return false;
+  }
+
+  RootedValue value(cx);
+  RootedObject object(cx);
+  for (uint32_t i = 0; i < length; i++) {
+    if (!JS_GetElement(cx, observersArg, i, &value)) {
+      return false;
+    }
+
+    if (!value.isObject()) {
+      JS_ReportErrorASCII(cx, "argument must be an Array of objects");
+      return false;
+    }
+
+    object = &value.toObject();
+    if (gc::IsInsideNursery(object)) {
+      // WeakCaches are not swept during a minor GC. To prevent
+      // nursery-allocated contents from having the mark bits be deceptively
+      // black until the second GC, they would need to be marked weakly (cf
+      // NurseryAwareHashMap). It is simpler to evict the nursery to prevent
+      // nursery objects from being observed.
+      cx->runtime()->gc.evictNursery();
+    }
+
+    if (!markObservers->get().append(object)) {
+      return false;
+    }
+  }
+
+  args.rval().setInt32(length);
+  return true;
+}
+
+static bool GetMarks(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  auto& observers = GetShellContext(cx)->markObservers;
+  if (!observers) {
+    args.rval().setUndefined();
+    return true;
+  }
+
+  size_t length = observers->get().length();
+  Rooted<ArrayObject*> ret(cx, js::NewDenseEmptyArray(cx));
+  if (!ret) {
+    return false;
+  }
+
+  for (uint32_t i = 0; i < length; i++) {
+    const char* color;
+    JSObject* obj = observers->get()[i];
+    if (!obj) {
+      color = "dead";
+    } else if (obj->zone()->isGCPreparing()) {
+      color = "unmarked";
+    } else {
+      gc::TenuredCell* cell = &obj->asTenured();
+      if (cell->isMarkedGray()) {
+        color = "gray";
+      } else if (cell->isMarkedBlack()) {
+        color = "black";
+      } else {
+        color = "unmarked";
+      }
+    }
+    JSString* s = JS_NewStringCopyZ(cx, color);
+    if (!s) {
+      return false;
+    }
+    if (!NewbornArrayPush(cx, ret, StringValue(s))) {
+      return false;
+    }
+  }
+
+  args.rval().setObject(*ret);
+  return true;
+}
+
+namespace js {
+namespace shell {
+
+class ShellAutoEntryMonitor : JS::dbg::AutoEntryMonitor {
+  Vector<UniqueChars, 1, js::SystemAllocPolicy> log;
+  bool oom;
+  bool enteredWithoutExit;
+
+ public:
+  explicit ShellAutoEntryMonitor(JSContext* cx)
+      : AutoEntryMonitor(cx), oom(false), enteredWithoutExit(false) {}
+
+  ~ShellAutoEntryMonitor() { MOZ_ASSERT(!enteredWithoutExit); }
+
+  void Entry(JSContext* cx, JSFunction* function, JS::HandleValue asyncStack,
+             const char* asyncCause) override {
+    MOZ_ASSERT(!enteredWithoutExit);
+    enteredWithoutExit = true;
+
+    RootedString displayId(cx, JS_GetFunctionDisplayId(function));
+    if (displayId) {
+      UniqueChars displayIdStr = JS_EncodeStringToUTF8(cx, displayId);
+      if (!displayIdStr) {
+        // We report OOM in buildResult.
+        cx->recoverFromOutOfMemory();
+        oom = true;
+        return;
+      }
+      oom = !log.append(std::move(displayIdStr));
+      return;
+    }
+
+    oom = !log.append(DuplicateString("anonymous"));
+  }
+
+  void Entry(JSContext* cx, JSScript* script, JS::HandleValue asyncStack,
+             const char* asyncCause) override {
+    MOZ_ASSERT(!enteredWithoutExit);
+    enteredWithoutExit = true;
+
+    UniqueChars label(JS_smprintf("eval:%s", JS_GetScriptFilename(script)));
+    oom = !label || !log.append(std::move(label));
+  }
+
+  void Exit(JSContext* cx) override {
+    MOZ_ASSERT(enteredWithoutExit);
+    enteredWithoutExit = false;
+  }
+
+  bool buildResult(JSContext* cx, MutableHandleValue resultValue) {
+    if (oom) {
+      JS_ReportOutOfMemory(cx);
+      return false;
+    }
+
+    RootedObject result(cx, JS::NewArrayObject(cx, log.length()));
+    if (!result) {
+      return false;
+    }
+
+    for (size_t i = 0; i < log.length(); i++) {
+      char* name = log[i].get();
+      RootedString string(cx, Atomize(cx, name, strlen(name)));
+      if (!string) {
+        return false;
+      }
+      RootedValue value(cx, StringValue(string));
+      if (!JS_SetElement(cx, result, i, value)) {
+        return false;
+      }
+    }
+
+    resultValue.setObject(*result.get());
+    return true;
+  }
+};
+
+}  // namespace shell
+}  // namespace js
+
+static bool EntryPoints(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  if (args.length() != 1) {
+    JS_ReportErrorASCII(cx, "Wrong number of arguments");
+    return false;
+  }
+
+  RootedObject opts(cx, ToObject(cx, args[0]));
+  if (!opts) {
+    return false;
+  }
+
+  // { function: f } --- Call f.
+  {
+    RootedValue fun(cx), dummy(cx);
+
+    if (!JS_GetProperty(cx, opts, "function", &fun)) {
+      return false;
+    }
+    if (!fun.isUndefined()) {
+      js::shell::ShellAutoEntryMonitor sarep(cx);
+      if (!Call(cx, UndefinedHandleValue, fun, JS::HandleValueArray::empty(),
+                &dummy)) {
+        return false;
+      }
+      return sarep.buildResult(cx, args.rval());
+    }
+  }
+
+  // { object: o, property: p, value: v } --- Fetch o[p], or if
+  // v is present, assign o[p] = v.
+  {
+    RootedValue objectv(cx), propv(cx), valuev(cx);
+
+    if (!JS_GetProperty(cx, opts, "object", &objectv) ||
+        !JS_GetProperty(cx, opts, "property", &propv))
+      return false;
+    if (!objectv.isUndefined() && !propv.isUndefined()) {
+      RootedObject object(cx, ToObject(cx, objectv));
+      if (!object) {
+        return false;
+      }
+
+      RootedString string(cx, ToString(cx, propv));
+      if (!string) {
+        return false;
+      }
+      RootedId id(cx);
+      if (!JS_StringToId(cx, string, &id)) {
+        return false;
+      }
+
+      if (!JS_GetProperty(cx, opts, "value", &valuev)) {
+        return false;
+      }
+
+      js::shell::ShellAutoEntryMonitor sarep(cx);
+
+      if (!valuev.isUndefined()) {
+        if (!JS_SetPropertyById(cx, object, id, valuev)) {
+          return false;
+        }
+      } else {
+        if (!JS_GetPropertyById(cx, object, id, &valuev)) {
+          return false;
+        }
+      }
+
+      return sarep.buildResult(cx, args.rval());
+    }
+  }
+
+  // { ToString: v } --- Apply JS::ToString to v.
+  {
+    RootedValue v(cx);
+
+    if (!JS_GetProperty(cx, opts, "ToString", &v)) {
+      return false;
+    }
+    if (!v.isUndefined()) {
+      js::shell::ShellAutoEntryMonitor sarep(cx);
+      if (!JS::ToString(cx, v)) {
+        return false;
+      }
+      return sarep.buildResult(cx, args.rval());
+    }
+  }
+
+  // { ToNumber: v } --- Apply JS::ToNumber to v.
+  {
+    RootedValue v(cx);
+    double dummy;
+
+    if (!JS_GetProperty(cx, opts, "ToNumber", &v)) {
+      return false;
+    }
+    if (!v.isUndefined()) {
+      js::shell::ShellAutoEntryMonitor sarep(cx);
+      if (!JS::ToNumber(cx, v, &dummy)) {
+        return false;
+      }
+      return sarep.buildResult(cx, args.rval());
+    }
+  }
+
+  // { eval: code } --- Apply ToString and then Evaluate to code.
+  {
+    RootedValue code(cx), dummy(cx);
+
+    if (!JS_GetProperty(cx, opts, "eval", &code)) {
+      return false;
+    }
+    if (!code.isUndefined()) {
+      RootedString codeString(cx, ToString(cx, code));
+      if (!codeString) {
+        return false;
+      }
+
+      AutoStableStringChars linearChars(cx);
+      if (!linearChars.initTwoByte(cx, codeString)) {
+        return false;
+      }
+      JS::SourceText<char16_t> srcBuf;
+      if (!srcBuf.initMaybeBorrowed(cx, linearChars)) {
+        return false;
+      }
+
+      CompileOptions options(cx);
+      options.setIntroductionType("entryPoint eval")
+          .setFileAndLine("entryPoint eval", 1);
+
+      js::shell::ShellAutoEntryMonitor sarep(cx);
+      if (!JS::Evaluate(cx, options, srcBuf, &dummy)) {
+        return false;
+      }
+      return sarep.buildResult(cx, args.rval());
+    }
+  }
+
+  JS_ReportErrorASCII(cx, "bad 'params' object");
+  return false;
+}
+
+#ifndef __wasi__
+static bool WasmTextToBinary(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+  RootedObject callee(cx, &args.callee());
+
+  if (!args.requireAtLeast(cx, "wasmTextToBinary", 1)) {
+    return false;
+  }
+
+  if (!args[0].isString()) {
+    ReportUsageErrorASCII(cx, callee, "First argument must be a String");
+    return false;
+  }
+
+  size_t textLen = args[0].toString()->length();
+
+  AutoStableStringChars twoByteChars(cx);
+  if (!twoByteChars.initTwoByte(cx, args[0].toString())) {
+    return false;
+  }
+
+  wasm::Bytes bytes;
+  UniqueChars error;
+  if (!wasm::TextToBinary(twoByteChars.twoByteChars(), textLen, &bytes,
+                          &error)) {
+    JS_ReportErrorNumberUTF8(cx, GetErrorMessage, nullptr, JSMSG_WASM_TEXT_FAIL,
+                             error.get() ? error.get() : "out of memory");
+    return false;
+  }
+
+  RootedObject binary(cx, JS_NewUint8Array(cx, bytes.length()));
+  if (!binary) {
+    return false;
+  }
+
+  memcpy(binary->as<TypedArrayObject>().dataPointerUnshared(), bytes.begin(),
+         bytes.length());
+
+  args.rval().setObject(*binary);
+  return true;
+}
+
+static bool WasmCodeOffsets(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+  RootedObject callee(cx, &args.callee());
+
+  if (!args.requireAtLeast(cx, "wasmCodeOffsets", 1)) {
+    return false;
+  }
+
+  if (!args.get(0).isObject()) {
+    JS_ReportErrorASCII(cx, "argument is not an object");
+    return false;
+  }
+
+  SharedMem<uint8_t*> bytes;
+  size_t byteLength;
+
+  JSObject* bufferObject = &args[0].toObject();
+  JSObject* unwrappedBufferObject = CheckedUnwrapStatic(bufferObject);
+  if (!unwrappedBufferObject ||
+      !IsBufferSource(unwrappedBufferObject, &bytes, &byteLength)) {
+    JS_ReportErrorNumberUTF8(cx, GetErrorMessage, nullptr,
+                             JSMSG_WASM_BAD_BUF_ARG);
+    return false;
+  }
+
+  wasm::Uint32Vector offsets;
+  wasm::CodeOffsets(bytes.unwrap(), byteLength, &offsets);
+
+  RootedObject jsOffsets(cx, JS::NewArrayObject(cx, offsets.length()));
+  if (!jsOffsets) {
+    return false;
+  }
+  for (size_t i = 0; i < offsets.length(); i++) {
+    uint32_t offset = offsets[i];
+    RootedValue offsetVal(cx, NumberValue(offset));
+    if (!JS_SetElement(cx, jsOffsets, i, offsetVal)) {
+      return false;
+    }
+  }
+  args.rval().setObject(*jsOffsets);
+  return true;
+}
+
+#  ifndef __AFL_HAVE_MANUAL_CONTROL
+#    define __AFL_LOOP(x) true
+#  endif
+
+static bool WasmLoop(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+  RootedObject callee(cx, &args.callee());
+
+  if (args.length() < 1 || args.length() > 2) {
+    ReportUsageErrorASCII(cx, callee, "Wrong number of arguments");
+    return false;
+  }
+
+  if (!args[0].isString()) {
+    ReportUsageErrorASCII(cx, callee, "First argument must be a String");
+    return false;
+  }
+
+  RootedObject importObj(cx);
+  if (!args.get(1).isUndefined()) {
+    if (!args.get(1).isObject()) {
+      ReportUsageErrorASCII(cx, callee,
+                            "Second argument, if present, must be an Object");
+      return false;
+    }
+    importObj = &args[1].toObject();
+  }
+
+  RootedString givenPath(cx, args[0].toString());
+  RootedString filename(cx, ResolvePath(cx, givenPath, RootRelative));
+  if (!filename) {
+    return false;
+  }
+
+  while (__AFL_LOOP(1000)) {
+    Rooted<JSObject*> ret(cx, FileAsTypedArray(cx, filename));
+    if (!ret) {
+      return false;
+    }
+
+    Rooted<TypedArrayObject*> typedArray(cx, &ret->as<TypedArrayObject>());
+    Rooted<WasmInstanceObject*> instanceObj(cx);
+    if (!wasm::Eval(cx, typedArray, importObj, &instanceObj)) {
+      // Clear any pending exceptions, we don't care about them
+      cx->clearPendingException();
+    }
+  }
+
+#  ifdef __AFL_HAVE_MANUAL_CONTROL  // to silence unreachable code warning
+  return true;
+#  endif
+}
+#endif  // __wasi__
+
+static constexpr uint32_t DOM_OBJECT_SLOT = 0;
+static constexpr uint32_t DOM_OBJECT_SLOT2 = 1;
+
+static const JSClass* GetDomClass();
+
+static JSObject* GetDOMPrototype(JSContext* cx, JSObject* global);
+
+static const JSClass TransplantableDOMObjectClass = {
+    "TransplantableDOMObject",
+    JSCLASS_IS_DOMJSCLASS | JSCLASS_HAS_RESERVED_SLOTS(1)};
+
+static const JSClass TransplantableDOMProxyObjectClass =
+    PROXY_CLASS_DEF("TransplantableDOMProxyObject",
+                    JSCLASS_IS_DOMJSCLASS | JSCLASS_HAS_RESERVED_SLOTS(1));
+
+class TransplantableDOMProxyHandler final : public ForwardingProxyHandler {
+ public:
+  static const TransplantableDOMProxyHandler singleton;
+  static const char family;
+
+  constexpr TransplantableDOMProxyHandler() : ForwardingProxyHandler(&family) {}
+
+  // These two proxy traps are called in |js::DeadProxyTargetValue|, which in
+  // turn is called when nuking proxies. Because this proxy can temporarily be
+  // without an object in its private slot, see |EnsureExpandoObject|, the
+  // default implementation inherited from ForwardingProxyHandler can't be used,
+  // since it tries to derive the callable/constructible value from the target.
+  bool isCallable(JSObject* obj) const override { return false; }
+  bool isConstructor(JSObject* obj) const override { return false; }
+
+  // Simplified implementation of |DOMProxyHandler::GetAndClearExpandoObject|.
+  static JSObject* GetAndClearExpandoObject(JSObject* obj) {
+    const Value& v = GetProxyPrivate(obj);
+    if (v.isUndefined()) {
+      return nullptr;
+    }
+
+    JSObject* expandoObject = &v.toObject();
+    SetProxyPrivate(obj, UndefinedValue());
+    return expandoObject;
+  }
+
+  // Simplified implementation of |DOMProxyHandler::EnsureExpandoObject|.
+  static JSObject* EnsureExpandoObject(JSContext* cx, JS::HandleObject obj) {
+    const Value& v = GetProxyPrivate(obj);
+    if (v.isObject()) {
+      return &v.toObject();
+    }
+    MOZ_ASSERT(v.isUndefined());
+
+    JSObject* expando = JS_NewObjectWithGivenProto(cx, nullptr, nullptr);
+    if (!expando) {
+      return nullptr;
+    }
+    SetProxyPrivate(obj, ObjectValue(*expando));
+    return expando;
+  }
+};
+
+const TransplantableDOMProxyHandler TransplantableDOMProxyHandler::singleton;
+const char TransplantableDOMProxyHandler::family = 0;
+
+enum TransplantObjectSlots {
+  TransplantSourceObject = 0,
+};
+
+static bool TransplantObject(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+  RootedFunction callee(cx, &args.callee().as<JSFunction>());
+
+  if (args.length() != 1 || !args[0].isObject()) {
+    JS_ReportErrorASCII(cx, "transplant() must be called with an object");
+    return false;
+  }
+
+  // |newGlobal| needs to be a GlobalObject.
+  RootedObject newGlobal(
+      cx, js::CheckedUnwrapDynamic(&args[0].toObject(), cx,
+                                   /* stopAtWindowProxy = */ false));
+  if (!newGlobal) {
+    ReportAccessDenied(cx);
+    return false;
+  }
+  if (!JS_IsGlobalObject(newGlobal)) {
+    JS_ReportErrorNumberASCII(
+        cx, GetErrorMessage, nullptr, JSMSG_UNEXPECTED_TYPE,
+        "\"global\" passed to transplant()", "not a global object");
+    return false;
+  }
+
+  const Value& reserved =
+      GetFunctionNativeReserved(callee, TransplantSourceObject);
+  RootedObject source(cx, CheckedUnwrapStatic(&reserved.toObject()));
+  if (!source) {
+    ReportAccessDenied(cx);
+    return false;
+  }
+  MOZ_ASSERT(source->getClass()->isDOMClass());
+
+  // The following steps aim to replicate the behavior of UpdateReflectorGlobal
+  // in dom/bindings/BindingUtils.cpp. In detail:
+  // 1. Check the recursion depth using checkConservative.
+  // 2. Enter the target compartment.
+  // 3. Clone the source object using JS_CloneObject.
+  // 4. Check if new wrappers can be created if source and target are in
+  //    different compartments.
+  // 5. Copy all properties from source to a temporary holder object.
+  // 6. Actually transplant the object.
+  // 7. And finally copy the properties back to the source object.
+  //
+  // As an extension to the algorithm in UpdateReflectorGlobal, we also allow
+  // to transplant an object into the same compartment as the source object to
+  // cover all operations supported by JS_TransplantObject.
+
+  AutoCheckRecursionLimit recursion(cx);
+  if (!recursion.checkConservative(cx)) {
+    return false;
+  }
+
+  bool isProxy = IsProxy(source);
+  RootedObject expandoObject(cx);
+  if (isProxy) {
+    expandoObject =
+        TransplantableDOMProxyHandler::GetAndClearExpandoObject(source);
+  }
+
+  JSAutoRealm ar(cx, newGlobal);
+
+  RootedObject proto(cx);
+  if (JS::GetClass(source) == GetDomClass()) {
+    proto = GetDOMPrototype(cx, newGlobal);
+  } else {
+    proto = JS::GetRealmObjectPrototype(cx);
+  }
+  if (!proto) {
+    return false;
+  }
+
+  RootedObject target(cx, JS_CloneObject(cx, source, proto));
+  if (!target) {
+    return false;
+  }
+
+  if (JS::GetCompartment(source) != JS::GetCompartment(target) &&
+      !AllowNewWrapper(JS::GetCompartment(source), target)) {
+    JS_ReportErrorASCII(cx, "Cannot transplant into nuked compartment");
+    return false;
+  }
+
+  RootedObject copyFrom(cx, isProxy ? expandoObject : source);
+  RootedObject propertyHolder(cx,
+                              JS_NewObjectWithGivenProto(cx, nullptr, nullptr));
+  if (!propertyHolder) {
+    return false;
+  }
+
+  if (!JS_CopyOwnPropertiesAndPrivateFields(cx, propertyHolder, copyFrom)) {
+    return false;
+  }
+
+  JS::SetReservedSlot(target, DOM_OBJECT_SLOT,
+                      JS::GetReservedSlot(source, DOM_OBJECT_SLOT));
+  JS::SetReservedSlot(source, DOM_OBJECT_SLOT, JS::PrivateValue(nullptr));
+  if (JS::GetClass(source) == GetDomClass()) {
+    JS::SetReservedSlot(target, DOM_OBJECT_SLOT2,
+                        JS::GetReservedSlot(source, DOM_OBJECT_SLOT2));
+    JS::SetReservedSlot(source, DOM_OBJECT_SLOT2, UndefinedValue());
+  }
+
+  source = JS_TransplantObject(cx, source, target);
+  if (!source) {
+    return false;
+  }
+
+  RootedObject copyTo(cx);
+  if (isProxy) {
+    copyTo = TransplantableDOMProxyHandler::EnsureExpandoObject(cx, source);
+    if (!copyTo) {
+      return false;
+    }
+  } else {
+    copyTo = source;
+  }
+  if (!JS_CopyOwnPropertiesAndPrivateFields(cx, copyTo, propertyHolder)) {
+    return false;
+  }
+
+  args.rval().setUndefined();
+  return true;
+}
+
+static bool TransplantableObject(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+  RootedObject callee(cx, &args.callee());
+
+  if (args.length() > 1) {
+    ReportUsageErrorASCII(cx, callee, "Wrong number of arguments");
+    return false;
+  }
+
+  bool createProxy = false;
+  RootedObject source(cx);
+  if (args.length() == 1 && !args[0].isUndefined()) {
+    if (!args[0].isObject()) {
+      ReportUsageErrorASCII(cx, callee, "Argument must be an object");
+      return false;
+    }
+
+    RootedObject options(cx, &args[0].toObject());
+    RootedValue value(cx);
+
+    if (!JS_GetProperty(cx, options, "proxy", &value)) {
+      return false;
+    }
+    createProxy = JS::ToBoolean(value);
+
+    if (!JS_GetProperty(cx, options, "object", &value)) {
+      return false;
+    }
+    if (!value.isUndefined()) {
+      if (!value.isObject()) {
+        ReportUsageErrorASCII(cx, callee, "'object' option must be an object");
+        return false;
+      }
+
+      source = &value.toObject();
+      if (JS::GetClass(source) != GetDomClass()) {
+        ReportUsageErrorASCII(cx, callee, "Object not a FakeDOMObject");
+        return false;
+      }
+
+      // |source| must be a tenured object to be transplantable.
+      if (gc::IsInsideNursery(source)) {
+        JS_GC(cx);
+
+        MOZ_ASSERT(!gc::IsInsideNursery(source),
+                   "Live objects should be tenured after one GC, because "
+                   "the nursery has only a single generation");
+      }
+    }
+  }
+
+  if (!source) {
+    if (!createProxy) {
+      source = NewBuiltinClassInstance(cx, &TransplantableDOMObjectClass,
+                                       TenuredObject);
+      if (!source) {
+        return false;
+      }
+
+      JS::SetReservedSlot(source, DOM_OBJECT_SLOT, JS::PrivateValue(nullptr));
+    } else {
+      JSObject* expando = JS_NewPlainObject(cx);
+      if (!expando) {
+        return false;
+      }
+      RootedValue expandoVal(cx, ObjectValue(*expando));
+
+      ProxyOptions options;
+      options.setClass(&TransplantableDOMProxyObjectClass);
+      options.setLazyProto(true);
+
+      source = NewProxyObject(cx, &TransplantableDOMProxyHandler::singleton,
+                              expandoVal, nullptr, options);
+      if (!source) {
+        return false;
+      }
+
+      SetProxyReservedSlot(source, DOM_OBJECT_SLOT, JS::PrivateValue(nullptr));
+    }
+  }
+
+  jsid emptyId = NameToId(cx->names().empty);
+  RootedObject transplant(
+      cx, NewFunctionByIdWithReserved(cx, TransplantObject, 0, 0, emptyId));
+  if (!transplant) {
+    return false;
+  }
+
+  SetFunctionNativeReserved(transplant, TransplantSourceObject,
+                            ObjectValue(*source));
+
+  RootedObject result(cx, JS_NewPlainObject(cx));
+  if (!result) {
+    return false;
+  }
+
+  RootedValue sourceVal(cx, ObjectValue(*source));
+  RootedValue transplantVal(cx, ObjectValue(*transplant));
+  if (!JS_DefineProperty(cx, result, "object", sourceVal, 0) ||
+      !JS_DefineProperty(cx, result, "transplant", transplantVal, 0)) {
+    return false;
+  }
+
+  args.rval().setObject(*result);
+  return true;
+}
+
+#ifdef DEBUG
+static bool DebugGetQueuedJobs(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  JSObject* jobs = js::GetJobsInInternalJobQueue(cx);
+  if (!jobs) {
+    return false;
+  }
+
+  args.rval().setObject(*jobs);
+  return true;
+}
+#endif
+
+#ifdef FUZZING_INTERFACES
+extern "C" {
+size_t gluesmith(uint8_t* data, size_t size, uint8_t* out, size_t maxsize);
+}
+
+static bool GetWasmSmithModule(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+  RootedObject callee(cx, &args.callee());
+
+  if (args.length() != 1) {
+    ReportUsageErrorASCII(cx, callee, "Wrong number of arguments");
+    return false;
+  }
+
+  if (!args[0].isObject() || !args[0].toObject().is<ArrayBufferObject>()) {
+    ReportUsageErrorASCII(cx, callee, "Argument must be ArrayBuffer.");
+    return false;
+  }
+
+  ArrayBufferObject* arrayBuffer = &args[0].toObject().as<ArrayBufferObject>();
+  size_t length = arrayBuffer->byteLength();
+  uint8_t* data = arrayBuffer->dataPointer();
+
+  const size_t maxModuleSize = 4096;
+  uint8_t tmp[maxModuleSize];
+
+  size_t outSize = gluesmith(data, length, tmp, maxModuleSize);
+  if (!outSize) {
+    JS_ReportErrorASCII(cx, "Generated module is too large.");
+    return false;
+  }
+
+  JS::Rooted<JSObject*> outArr(cx, JS_NewUint8ClampedArray(cx, outSize));
+  if (!outArr) {
+    return false;
+  }
+
+  {
+    JS::AutoCheckCannotGC nogc;
+    bool isShared;
+    uint8_t* data = JS_GetUint8ClampedArrayData(outArr, &isShared, nogc);
+    MOZ_RELEASE_ASSERT(!isShared);
+    memcpy(data, tmp, outSize);
+  }
+
+  args.rval().setObject(*outArr);
+  return true;
+}
+
+#endif
+
+// clang-format off
+static const JSFunctionSpecWithHelp shell_functions[] = {
+    JS_FN_HELP("options", Options, 0, 0,
+"options([option ...])",
+"  Get or toggle JavaScript options."),
+
+    JS_FN_HELP("load", Load, 1, 0,
+"load(['foo.js' ...])",
+"  Load files named by string arguments. Filename is relative to the\n"
+"      current working directory."),
+
+    JS_FN_HELP("loadRelativeToScript", LoadScriptRelativeToScript, 1, 0,
+"loadRelativeToScript(['foo.js' ...])",
+"  Load files named by string arguments. Filename is relative to the\n"
+"      calling script."),
+
+    JS_FN_HELP("evaluate", Evaluate, 2, 0,
+"evaluate(code[, options])",
+"  Evaluate code as though it were the contents of a file.\n"
+"  options is an optional object that may have these properties:\n"
+"      isRunOnce: use the isRunOnce compiler option (default: false)\n"
+"      noScriptRval: use the no-script-rval compiler option (default: false)\n"
+"      fileName: filename for error messages and debug info\n"
+"      skipFileNameValidation: skip the filename-validation callback\n"
+"      lineNumber: starting line number for error messages and debug info\n"
+"      columnNumber: starting column number for error messages and debug info\n"
+"      global: global in which to execute the code\n"
+"      newContext: if true, create and use a new cx (default: false)\n"
+"      catchTermination: if true, catch termination (failure without\n"
+"         an exception value, as for slow scripts or out-of-memory)\n"
+"         and return 'terminated'\n"
+"      element: if present with value |v|, convert |v| to an object |o| and\n"
+"         mark the source as being attached to the DOM element |o|. If the\n"
+"         property is omitted or |v| is null, don't attribute the source to\n"
+"         any DOM element.\n"
+"      elementAttributeName: if present and not undefined, the name of\n"
+"         property of 'element' that holds this code. This is what\n"
+"         Debugger.Source.prototype.elementAttributeName returns.\n"
+"      sourceMapURL: if present with value |v|, convert |v| to a string, and\n"
+"         provide that as the code's source map URL. If omitted, attach no\n"
+"         source map URL to the code (although the code may provide one itself,\n"
+"         via a //#sourceMappingURL comment).\n"
+"      sourceIsLazy: if present and true, indicates that, after compilation, \n"
+"          script source should not be cached by the JS engine and should be \n"
+"          lazily loaded from the embedding as-needed.\n"
+"      forceFullParse: if present and true, disable syntax-parse.\n"
+"      loadBytecode: if true, and if the source is a CacheEntryObject,\n"
+"         the bytecode would be loaded and decoded from the cache entry instead\n"
+"         of being parsed, then it would be executed as usual.\n"
+"      saveIncrementalBytecode: if true, and if the source is a\n"
+"         CacheEntryObject, the bytecode would be incrementally encoded and\n"
+"         saved into the cache entry.\n"
+"      execute: if false, do not execute the script, but do parse and/or\n"
+"               transcode.\n"
+"      assertEqBytecode: if true, and if both loadBytecode and either\n"
+"         saveIncrementalBytecode is true, then the loaded\n"
+"         bytecode and the encoded bytecode are compared.\n"
+"         and an assertion is raised if they differ.\n"
+"      envChainObject: object to put on the scope chain, with its fields added\n"
+"         as var bindings, akin to how elements are added to the environment in\n"
+"         event handlers in Gecko.\n"
+),
+
+    JS_FN_HELP("run", Run, 1, 0,
+"run('foo.js')",
+"  Run the file named by the first argument, returning the number of\n"
+"  of milliseconds spent compiling and executing it."),
+
+    JS_FN_HELP("readline", ReadLine, 0, 0,
+"readline()",
+"  Read a single line from stdin."),
+
+    JS_FN_HELP("readlineBuf", ReadLineBuf, 1, 0,
+"readlineBuf([ buf ])",
+"  Emulate readline() on the specified string. The first call with a string\n"
+"  argument sets the source buffer. Subsequent calls without an argument\n"
+"  then read from this buffer line by line.\n"),
+
+    JS_FN_HELP("print", Print, 0, 0,
+"print([exp ...])",
+"  Evaluate and print expressions to stdout."),
+
+    JS_FN_HELP("printErr", PrintErr, 0, 0,
+"printErr([exp ...])",
+"  Evaluate and print expressions to stderr."),
+
+    JS_FN_HELP("putstr", PutStr, 0, 0,
+"putstr([exp])",
+"  Evaluate and print expression without newline."),
+
+    JS_FN_HELP("dateNow", Now, 0, 0,
+"dateNow()",
+"  Return the current time with sub-ms precision."),
+
+    JS_FN_HELP("help", Help, 0, 0,
+"help([function or interface object or /pattern/])",
+"  Display usage and help messages."),
+
+    JS_FN_HELP("quit", Quit, 0, 0,
+"quit()",
+"  Quit the shell."),
+
+    JS_FN_HELP("assertEq", AssertEq, 2, 0,
+"assertEq(actual, expected[, msg])",
+"  Throw if the first two arguments are not the same (both +0 or both -0,\n"
+"  both NaN, or non-zero and ===)."),
+
+    JS_FN_HELP("startTimingMutator", StartTimingMutator, 0, 0,
+"startTimingMutator()",
+"  Start accounting time to mutator vs GC."),
+
+    JS_FN_HELP("stopTimingMutator", StopTimingMutator, 0, 0,
+"stopTimingMutator()",
+"  Stop accounting time to mutator vs GC and dump the results."),
+
+    JS_FN_HELP("throwError", ThrowError, 0, 0,
+"throwError()",
+"  Throw an error from JS_ReportError."),
+
+    JS_FN_HELP("createErrorReport", CreateErrorReport, 1, 0,
+"createErrorReport(value)",
+"  Create an JS::ErrorReportBuilder object from the given value and serialize\n"
+"  to an object."),
+
+#if defined(DEBUG) || defined(JS_JITSPEW)
+    JS_FN_HELP("disassemble", DisassembleToString, 1, 0,
+"disassemble([fun/code])",
+"  Return the disassembly for the given function or code.\n"
+"  All disassembly functions take these options as leading string arguments:\n"
+"    \"-r\" (disassemble recursively)\n"
+"    \"-l\" (show line numbers)\n"
+"    \"-S\" (omit source notes)"),
+
+    JS_FN_HELP("dis", Disassemble, 1, 0,
+"dis([fun/code])",
+"  Disassemble functions into bytecodes."),
+
+    JS_FN_HELP("disfile", DisassFile, 1, 0,
+"disfile('foo.js')",
+"  Disassemble script file into bytecodes.\n"),
+
+    JS_FN_HELP("dissrc", DisassWithSrc, 1, 0,
+"dissrc([fun/code])",
+"  Disassemble functions with source lines."),
+
+    JS_FN_HELP("notes", Notes, 1, 0,
+"notes([fun])",
+"  Show source notes for functions."),
+
+    JS_FN_HELP("stackDump", StackDump, 3, 0,
+"stackDump(showArgs, showLocals, showThisProps)",
+"  Tries to print a lot of information about the current stack. \n"
+"  Similar to the DumpJSStack() function in the browser."),
+
+#endif
+
+    JS_FN_HELP("getslx", GetSLX, 1, 0,
+"getslx(obj)",
+"  Get script line extent."),
+
+    JS_FN_HELP("evalcx", EvalInContext, 1, 0,
+"evalcx(s[, o])",
+"  Evaluate s in optional sandbox object o.\n"
+"  if (s == '' && !o) return new o with eager standard classes\n"
+"  if (s == 'lazy' && !o) return new o with lazy standard classes"),
+
+    JS_FN_HELP("evalInWorker", EvalInWorker, 1, 0,
+"evalInWorker(str)",
+"  Evaluate 'str' in a separate thread with its own runtime.\n"),
+
+    JS_FN_HELP("getSharedObject", GetSharedObject, 0, 0,
+"getSharedObject()",
+"  Retrieve the shared object from the cross-worker mailbox.\n"
+"  The object retrieved may not be identical to the object that was\n"
+"  installed, but it references the same shared memory.\n"
+"  getSharedObject performs an ordering memory barrier.\n"),
+
+    JS_FN_HELP("setSharedObject", SetSharedObject, 0, 0,
+"setSharedObject(obj)",
+"  Install the shared object in the cross-worker mailbox.  The object\n"
+"  may be null.  setSharedObject performs an ordering memory barrier.\n"),
+
+    JS_FN_HELP("getSharedArrayBuffer", GetSharedObject, 0, 0,
+"getSharedArrayBuffer()",
+"  Obsolete alias for getSharedObject().\n"),
+
+    JS_FN_HELP("setSharedArrayBuffer", SetSharedObject, 0, 0,
+"setSharedArrayBuffer(obj)",
+"  Obsolete alias for setSharedObject(obj).\n"),
+
+    JS_FN_HELP("shapeOf", ShapeOf, 1, 0,
+"shapeOf(obj)",
+"  Get the shape of obj (an implementation detail)."),
+
+#ifdef DEBUG
+    JS_FN_HELP("arrayInfo", ArrayInfo, 1, 0,
+"arrayInfo(a1, a2, ...)",
+"  Report statistics about arrays."),
+#endif
+
+    JS_FN_HELP("sleep", Sleep_fn, 1, 0,
+"sleep(dt)",
+"  Sleep for dt seconds."),
+
+    JS_FN_HELP("parseModule", ParseModule, 1, 0,
+"parseModule(code)",
+"  Parses source text as a module and returns a ModuleObject wrapper object."),
+
+    JS_FN_HELP("instantiateModuleStencil", InstantiateModuleStencil, 1, 0,
+"instantiateModuleStencil(stencil, [options])",
+"  Instantiates the given stencil as module, and return the module object."),
+
+    JS_FN_HELP("instantiateModuleStencilXDR", InstantiateModuleStencilXDR, 1, 0,
+"instantiateModuleStencilXDR(stencil, [options])",
+"  Reads the given stencil XDR object, instantiates the stencil as module, and"
+"  return the module object."),
+
+    JS_FN_HELP("registerModule", RegisterModule, 2, 0,
+"registerModule(specifier, module)",
+"  Register a module with the module loader, so that subsequent import from\n"
+"  |specifier| will resolve to |module|.  Returns |module|."),
+
+    JS_FN_HELP("clearModules", ClearModules, 0, 0,
+"clearModules()",
+"  Clear knowledge of all loaded modules."),
+
+    JS_FN_HELP("moduleLink", ModuleLink, 1, 0,
+"moduleLink(moduleOjbect)",
+"  Link a module graph, performing the spec's Link method."),
+
+    JS_FN_HELP("moduleEvaluate", ModuleEvaluate, 1, 0,
+"moduleEvaluate(moduleOjbect)",
+"  Evaluate a module graph, performing the spec's Evaluate method."),
+
+    JS_FN_HELP("getModuleEnvironmentNames", GetModuleEnvironmentNames, 1, 0,
+"getModuleEnvironmentNames(module)",
+"  Get the list of a module environment's bound names for a specified module.\n"),
+
+    JS_FN_HELP("getModuleEnvironmentValue", GetModuleEnvironmentValue, 2, 0,
+"getModuleEnvironmentValue(module, name)",
+"  Get the value of a bound name in a module environment.\n"),
+
+    JS_FN_HELP("dumpStencil", DumpStencil, 1, 0,
+"dumpStencil(code, [options])",
+"  Parses a string and returns string that represents stencil.\n"
+"  If present, |options| may have properties saying how the code should be\n"
+"  compiled:\n"
+"      module: if present and true, compile the source as module.\n"
+"      smoosh: if present and true, use SmooshMonkey.\n"
+"  CompileOptions-related properties of evaluate function's option can also\n"
+"  be used."),
+
+    JS_FN_HELP("parse", Parse, 1, 0,
+"parse(code, [options])",
+"  Parses a string, potentially throwing. If present, |options| may\n"
+"  have properties saying how the code should be compiled:\n"
+"      module: if present and true, compile the source as module.\n"
+"      smoosh: if present and true, use SmooshMonkey.\n"
+"  CompileOptions-related properties of evaluate function's option can also\n"
+"  be used. except forceFullParse. This function always use full parse."),
+
+    JS_FN_HELP("syntaxParse", SyntaxParse, 1, 0,
+"syntaxParse(code)",
+"  Check the syntax of a string, returning success value"),
+
+    JS_FN_HELP("offThreadCompileModuleToStencil", OffThreadCompileModuleToStencil, 1, 0,
+"offThreadCompileModuleToStencil(code)",
+"  Compile |code| on a helper thread, returning a job ID. To wait for the\n"
+"  compilation to finish and and get the module stencil object call\n"
+"  |finishOffThreadStencil| passing the job ID."),
+
+    JS_FN_HELP("offThreadDecodeStencil", OffThreadDecodeStencil, 1, 0,
+"offThreadDecodeStencil(cacheEntry[, options])",
+"  Decode |code| on a helper thread, returning a job ID. To wait for the\n"
+"  decoding to finish and run the code, call |finishOffThreadStencil| passing\n"
+"  the job ID. If present, |options| may have properties saying how the code\n"
+"  should be compiled (see also offThreadCompileToStencil)."),
+
+    JS_FN_HELP("offThreadCompileToStencil", OffThreadCompileToStencil, 1, 0,
+"offThreadCompileToStencil(code[, options])",
+"  Compile |code| on a helper thread, returning a job ID. To wait for the\n"
+"  compilation to finish and get the stencil object, call\n"
+"  |finishOffThreadStencil| passing the job ID.  If present, \n"
+"  |options| may have properties saying how the code should be compiled:\n"
+"      noScriptRval: use the no-script-rval compiler option (default: false)\n"
+"      fileName: filename for error messages and debug info\n"
+"      lineNumber: starting line number for error messages and debug info\n"
+"      columnNumber: starting column number for error messages and debug info\n"
+"      element: if present with value |v|, convert |v| to an object |o| and\n"
+"         mark the source as being attached to the DOM element |o|. If the\n"
+"         property is omitted or |v| is null, don't attribute the source to\n"
+"         any DOM element.\n"
+"      elementAttributeName: if present and not undefined, the name of\n"
+"         property of 'element' that holds this code. This is what\n"
+"         Debugger.Source.prototype.elementAttributeName returns."),
+
+    JS_FN_HELP("finishOffThreadStencil", FinishOffThreadStencil, 0, 0,
+"finishOffThreadStencil([jobID])",
+"  Wait for an off-thread compilation or decode job to complete. The job ID\n"
+"  can be ommitted if there is only one job pending. If an error occurred,\n"
+"  throw the appropriate exception; otherwise, return the stencil object,"
+"  that can be passed to |evalStencil|."),
+
+    JS_FN_HELP("timeout", Timeout, 1, 0,
+"timeout([seconds], [func])",
+"  Get/Set the limit in seconds for the execution time for the current context.\n"
+"  When the timeout expires the current interrupt callback is invoked.\n"
+"  The timeout is used just once.  If the callback returns a falsy value, the\n"
+"  script is aborted.  A negative value for seconds (this is the default) cancels\n"
+"  any pending timeout.\n"
+"  If a second argument is provided, it is installed as the interrupt handler,\n"
+"  exactly as if by |setInterruptCallback|.\n"),
+
+    JS_FN_HELP("interruptIf", InterruptIf, 1, 0,
+"interruptIf(cond)",
+"  Requests interrupt callback if cond is true. If a callback function is set via\n"
+"  |timeout| or |setInterruptCallback|, it will be called. No-op otherwise."),
+
+    JS_FN_HELP("invokeInterruptCallback", InvokeInterruptCallbackWrapper, 0, 0,
+"invokeInterruptCallback(fun)",
+"  Forcefully set the interrupt flag and invoke the interrupt handler. If a\n"
+"  callback function is set via |timeout| or |setInterruptCallback|, it will\n"
+"  be called. Before returning, fun is called with the return value of the\n"
+"  interrupt handler."),
+
+    JS_FN_HELP("setInterruptCallback", SetInterruptCallback, 1, 0,
+"setInterruptCallback(func)",
+"  Sets func as the interrupt callback function.\n"
+"  Calling this function will replace any callback set by |timeout|.\n"
+"  If the callback returns a falsy value, the script is aborted.\n"),
+
+    JS_FN_HELP("setJitCompilerOption", SetJitCompilerOption, 2, 0,
+"setJitCompilerOption(<option>, <number>)",
+"  Set a compiler option indexed in JSCompileOption enum to a number.\n"),
+#ifdef DEBUG
+    JS_FN_HELP("interruptRegexp", InterruptRegexp, 2, 0,
+"interruptRegexp(<regexp>, <string>)",
+"  Interrrupt the execution of regular expression.\n"),
+#endif
+    JS_FN_HELP("enableLastWarning", EnableLastWarning, 0, 0,
+"enableLastWarning()",
+"  Enable storing the last warning."),
+
+    JS_FN_HELP("disableLastWarning", DisableLastWarning, 0, 0,
+"disableLastWarning()",
+"  Disable storing the last warning."),
+
+    JS_FN_HELP("getLastWarning", GetLastWarning, 0, 0,
+"getLastWarning()",
+"  Returns an object that represents the last warning."),
+
+    JS_FN_HELP("clearLastWarning", ClearLastWarning, 0, 0,
+"clearLastWarning()",
+"  Clear the last warning."),
+
+    JS_FN_HELP("elapsed", Elapsed, 0, 0,
+"elapsed()",
+"  Execution time elapsed for the current thread."),
+
+    JS_FN_HELP("decompileFunction", DecompileFunction, 1, 0,
+"decompileFunction(func)",
+"  Decompile a function."),
+
+    JS_FN_HELP("decompileThis", DecompileThisScript, 0, 0,
+"decompileThis()",
+"  Decompile the currently executing script."),
+
+    JS_FN_HELP("valueToSource", ValueToSource, 1, 0,
+"valueToSource(value)",
+"  Format a value for inspection."),
+
+    JS_FN_HELP("thisFilename", ThisFilename, 0, 0,
+"thisFilename()",
+"  Return the filename of the current script"),
+
+    JS_FN_HELP("newGlobal", NewGlobal, 1, 0,
+"newGlobal([options])",
+"  Return a new global object/realm. The new global is created in the\n"
+"  'newGlobal' function object's compartment and zone, unless the\n"
+"  '--more-compartments' command-line flag was given, in which case new\n"
+"  globals get a fresh compartment and zone. If options is given, it may\n"
+"  have any of the following properties:\n"
+"      sameCompartmentAs: If an object, the global will be in the same\n"
+"         compartment and zone as the given object.\n"
+"      sameZoneAs: The global will be in a new compartment in the same zone\n"
+"         as the given object.\n"
+"      newCompartment: If true, the global will always be created in a new\n"
+"         compartment and zone.\n"
+"      invisibleToDebugger: If true, the global will be invisible to the\n"
+"         debugger (default false)\n"
+"      discardSource: If true, discard source after compiling a script\n"
+"         (default false).\n"
+"      useWindowProxy: the global will be created with a WindowProxy attached. In this\n"
+"          case, the WindowProxy will be returned.\n"
+"      freezeBuiltins: certain builtin constructors will be frozen when created and\n"
+"          their prototypes will be sealed. These constructors will be defined on the\n"
+"          global as non-configurable and non-writable.\n"
+"      immutablePrototype: whether the global's prototype is immutable.\n"
+"      principal: if present, its value converted to a number must be an\n"
+"         integer that fits in 32 bits; use that as the new realm's\n"
+"         principal. Shell principals are toys, meant only for testing; one\n"
+"         shell principal subsumes another if its set bits are a superset of\n"
+"         the other's. Thus, a principal of 0 subsumes nothing, while a\n"
+"         principals of ~0 subsumes all other principals. The absence of a\n"
+"         principal is treated as if its bits were 0xffff, for subsumption\n"
+"         purposes. If this property is omitted, supply no principal.\n"
+"      systemPrincipal: If true, use the shell's trusted principals for the\n"
+"         new realm. This creates a realm that's marked as a 'system' realm."),
+
+    JS_FN_HELP("nukeAllCCWs", NukeAllCCWs, 0, 0,
+"nukeAllCCWs()",
+"  Like nukeCCW, but for all CrossCompartmentWrappers targeting the current realm."),
+
+    JS_FN_HELP("recomputeWrappers", RecomputeWrappers, 2, 0,
+"recomputeWrappers([src, [target]])",
+"  Recompute all cross-compartment wrappers. src and target are both optional\n"
+"  and can be used to filter source or target compartments: the unwrapped\n"
+"  object's compartment is used as CompartmentFilter.\n"),
+
+    JS_FN_HELP("dumpObjectWrappers", DumpObjectWrappers, 2, 0,
+"dumpObjectWrappers()",
+"  Print information about cross-compartment object wrappers.\n"),
+
+    JS_FN_HELP("wrapWithProto", WrapWithProto, 2, 0,
+"wrapWithProto(obj)",
+"  Wrap an object into a noop wrapper with prototype semantics."),
+
+    JS_FN_HELP("createExternalArrayBuffer", CreateExternalArrayBuffer, 1, 0,
+"createExternalArrayBuffer(size)",
+"  Create an array buffer that has external data of size."),
+
+    JS_FN_HELP("createMappedArrayBuffer", CreateMappedArrayBuffer, 1, 0,
+"createMappedArrayBuffer(filename, [offset, [size]])",
+"  Create an array buffer that mmaps the given file."),
+
+    JS_FN_HELP("addPromiseReactions", AddPromiseReactions, 3, 0,
+"addPromiseReactions(promise, onResolve, onReject)",
+"  Calls the JS::AddPromiseReactions JSAPI function with the given arguments."),
+
+    JS_FN_HELP("ignoreUnhandledRejections", IgnoreUnhandledRejections, 0, 0,
+"ignoreUnhandledRejections()",
+"  By default, js shell tracks unhandled promise rejections and reports\n"
+"  them at the end of the exectuion.  If a testcase isn't interested\n"
+"  in those rejections, call this to stop tracking and reporting."),
+
+    JS_FN_HELP("getMaxArgs", GetMaxArgs, 0, 0,
+"getMaxArgs()",
+"  Return the maximum number of supported args for a call."),
+
+    JS_FN_HELP("createIsHTMLDDA", CreateIsHTMLDDA, 0, 0,
+"createIsHTMLDDA()",
+"  Return an object |obj| that \"looks like\" the |document.all| object in\n"
+"  browsers in certain ways: |typeof obj === \"undefined\"|, |obj == null|\n"
+"  and |obj == undefined| (vice versa for !=), |ToBoolean(obj) === false|,\n"
+"  and when called with no arguments or the single argument \"\" returns\n"
+"  null.  (Calling |obj| any other way crashes or throws an exception.)\n"
+"  This function implements the exact requirements of the $262.IsHTMLDDA\n"
+"  property in test262."),
+
+    JS_FN_HELP("cacheEntry", CacheEntry, 1, 0,
+"cacheEntry(code)",
+"  Return a new opaque object which emulates a cache entry of a script.  This\n"
+"  object encapsulates the code and its cached content. The cache entry is filled\n"
+"  and read by the \"evaluate\" function by using it in place of the source, and\n"
+"  by setting \"saveIncrementalBytecode\" and \"loadBytecode\" options."),
+
+    JS_FN_HELP("streamCacheEntry", StreamCacheEntryObject::construct, 1, 0,
+"streamCacheEntry(buffer)",
+"  Create a shell-only object that holds wasm bytecode and can be streaming-\n"
+"  compiled and cached by WebAssembly.{compile,instantiate}Streaming(). On a\n"
+"  second compilation of the same cache entry, the cached code will be used."),
+
+    JS_FN_HELP("printProfilerEvents", PrintProfilerEvents, 0, 0,
+"printProfilerEvents()",
+"  Register a callback with the profiler that prints javascript profiler events\n"
+"  to stderr.  Callback is only registered if profiling is enabled."),
+
+    JS_FN_HELP("enableSingleStepProfiling", EnableSingleStepProfiling, 0, 0,
+"enableSingleStepProfiling()",
+"  This function will fail on platforms that don't support single-step profiling\n"
+"  (currently ARM and MIPS64 support it). When enabled, at every instruction a\n"
+"  backtrace will be recorded and stored in an array. Adjacent duplicate backtraces\n"
+"  are discarded."),
+
+    JS_FN_HELP("disableSingleStepProfiling", DisableSingleStepProfiling, 0, 0,
+"disableSingleStepProfiling()",
+"  Return the array of backtraces recorded by enableSingleStepProfiling."),
+
+    JS_FN_HELP("enableGeckoProfiling", EnableGeckoProfiling, 0, 0,
+"enableGeckoProfiling()",
+"  Enables Gecko Profiler instrumentation and corresponding assertions, with slow\n"
+"  assertions disabled.\n"),
+
+    JS_FN_HELP("enableGeckoProfilingWithSlowAssertions", EnableGeckoProfilingWithSlowAssertions, 0, 0,
+"enableGeckoProfilingWithSlowAssertions()",
+"  Enables Gecko Profiler instrumentation and corresponding assertions, with slow\n"
+"  assertions enabled.\n"),
+
+    JS_FN_HELP("disableGeckoProfiling", DisableGeckoProfiling, 0, 0,
+"disableGeckoProfiling()",
+"  Disables Gecko Profiler instrumentation"),
+
+    JS_FN_HELP("isLatin1", IsLatin1, 1, 0,
+"isLatin1(s)",
+"  Return true iff the string's characters are stored as Latin1."),
+
+    JS_FN_HELP("stackPointerInfo", StackPointerInfo, 0, 0,
+"stackPointerInfo()",
+"  Return an int32 value which corresponds to the offset of the latest stack\n"
+"  pointer, such that one can take the differences of 2 to estimate a frame-size."),
+
+    JS_FN_HELP("entryPoints", EntryPoints, 1, 0,
+"entryPoints(params)",
+"Carry out some JSAPI operation as directed by |params|, and return an array of\n"
+"objects describing which JavaScript entry points were invoked as a result.\n"
+"|params| is an object whose properties indicate what operation to perform. Here\n"
+"are the recognized groups of properties:\n"
+"\n"
+"{ function }: Call the object |params.function| with no arguments.\n"
+"\n"
+"{ object, property }: Fetch the property named |params.property| of\n"
+"|params.object|.\n"
+"\n"
+"{ ToString }: Apply JS::ToString to |params.toString|.\n"
+"\n"
+"{ ToNumber }: Apply JS::ToNumber to |params.toNumber|.\n"
+"\n"
+"{ eval }: Apply JS::Evaluate to |params.eval|.\n"
+"\n"
+"The return value is an array of strings, with one element for each\n"
+"JavaScript invocation that occurred as a result of the given\n"
+"operation. Each element is the name of the function invoked, or the\n"
+"string 'eval:FILENAME' if the code was invoked by 'eval' or something\n"
+"similar.\n"),
+
+    JS_FN_HELP("enqueueJob", EnqueueJob, 1, 0,
+"enqueueJob(fn)",
+"  Enqueue 'fn' on the shell's job queue."),
+
+    JS_FN_HELP("globalOfFirstJobInQueue", GlobalOfFirstJobInQueue, 0, 0,
+"globalOfFirstJobInQueue()",
+"  Returns the global of the first item in the job queue. Throws an exception\n"
+"  if the queue is empty.\n"),
+
+    JS_FN_HELP("drainJobQueue", DrainJobQueue, 0, 0,
+"drainJobQueue()",
+"Take jobs from the shell's job queue in FIFO order and run them until the\n"
+"queue is empty.\n"),
+
+    JS_FN_HELP("setPromiseRejectionTrackerCallback", SetPromiseRejectionTrackerCallback, 1, 0,
+"setPromiseRejectionTrackerCallback()",
+"Sets the callback to be invoked whenever a Promise rejection is unhandled\n"
+"or a previously-unhandled rejection becomes handled."),
+
+    JS_FN_HELP("dumpScopeChain", DumpScopeChain, 1, 0,
+"dumpScopeChain(obj)",
+"  Prints the scope chain of an interpreted function or a module."),
+
+    JS_FN_HELP("grayRoot", EnsureGrayRoot, 0, 0,
+"grayRoot()",
+"  Create a gray root Array, if needed, for the current compartment, and\n"
+"  return it."),
+
+    JS_FN_HELP("addMarkObservers", AddMarkObservers, 1, 0,
+"addMarkObservers(array_of_objects)",
+"  Register an array of objects whose mark bits will be tested by calls to\n"
+"  getMarks. The objects will be in calling compartment. Objects from\n"
+"  multiple compartments may be monitored by calling this function in\n"
+"  different compartments."),
+
+    JS_FN_HELP("clearMarkObservers", ClearMarkObservers, 1, 0,
+"clearMarkObservers()",
+"  Clear out the list of objects whose mark bits will be tested.\n"),
+
+    JS_FN_HELP("getMarks", GetMarks, 0, 0,
+"getMarks()",
+"  Return an array of strings representing the current state of the mark\n"
+"  bits ('gray' or 'black', or 'dead' if the object has been collected)\n"
+"  for the objects registered via addMarkObservers. Note that some of the\n"
+"  objects tested may be from different compartments than the one in which\n"
+"  this function runs."),
+
+    JS_FN_HELP("bindToAsyncStack", BindToAsyncStack, 2, 0,
+"bindToAsyncStack(fn, { stack, cause, explicit })",
+"  Returns a new function that calls 'fn' with no arguments, passing\n"
+"  'undefined' as the 'this' value, and supplies an async stack for the\n"
+"  call as described by the second argument, an object with the following\n"
+"  properties (which are not optional, unless specified otherwise):\n"
+"\n"
+"  stack:    A SavedFrame object, like that returned by 'saveStack'. Stacks\n"
+"            captured during calls to the returned function capture this as\n"
+"            their async stack parent, accessible via a SavedFrame's\n"
+"            'asyncParent' property.\n"
+"\n"
+"  cause:    A string, supplied as the async cause on the top frame of\n"
+"            captured async stacks.\n"
+"\n"
+"  explicit: A boolean value, indicating whether the given 'stack' should\n"
+"            always supplant the returned function's true callers (true),\n"
+"            or only when there are no other JavaScript frames on the stack\n"
+"            below it (false). If omitted, this is treated as 'true'."),
+
+#ifdef JS_HAS_INTL_API
+    JS_FN_HELP("addIntlExtras", AddIntlExtras, 1, 0,
+"addIntlExtras(obj)",
+"Adds various not-yet-standardized Intl functions as properties on the\n"
+"provided object (this should generally be Intl itself).  The added\n"
+"functions and their behavior are experimental: don't depend upon them\n"
+"unless you're willing to update your code if these experimental APIs change\n"
+"underneath you."),
+#endif // JS_HAS_INTL_API
+
+#ifndef __wasi__
+    JS_FN_HELP("wasmCompileInSeparateProcess", WasmCompileInSeparateProcess, 1, 0,
+"wasmCompileInSeparateProcess(buffer)",
+"  Compile the given buffer in a separate process, serialize the resulting\n"
+"  wasm::Module into bytes, and deserialize those bytes in the current\n"
+"  process, returning the resulting WebAssembly.Module."),
+
+    JS_FN_HELP("wasmTextToBinary", WasmTextToBinary, 1, 0,
+"wasmTextToBinary(str)",
+"  Translates the given text wasm module into its binary encoding."),
+
+    JS_FN_HELP("wasmCodeOffsets", WasmCodeOffsets, 1, 0,
+"wasmCodeOffsets(binary)",
+"  Decodes the given wasm binary to find the offsets of every instruction in the"
+"  code section."),
+#endif // __wasi__
+
+    JS_FN_HELP("transplantableObject", TransplantableObject, 0, 0,
+"transplantableObject([options])",
+"  Returns the pair {object, transplant}. |object| is an object which can be\n"
+"  transplanted into a new object when the |transplant| function, which must\n"
+"  be invoked with a global object, is called.\n"
+"  |object| is swapped with a cross-compartment wrapper if the global object\n"
+"  is in a different compartment.\n"
+"\n"
+"  If options is given, it may have any of the following properties:\n"
+"    proxy: Create a DOM Proxy object instead of a plain DOM object.\n"
+"    object: Don't create a new DOM object, but instead use the supplied\n"
+"            FakeDOMObject."),
+
+    JS_FN_HELP("cpuNow", CpuNow, /* nargs= */ 0, /* flags = */ 0,
+"cpuNow()",
+" Returns the approximate processor time used by the process since an arbitrary epoch, in seconds.\n"
+" Only the difference between two calls to `cpuNow()` is meaningful."),
+
+#ifdef FUZZING_JS_FUZZILLI
+    JS_FN_HELP("fuzzilli", Fuzzilli, 0, 0,
+"fuzzilli(operation, arg)",
+"  Exposes functionality used by the Fuzzilli JavaScript fuzzer."),
+#endif
+
+#ifdef FUZZING_INTERFACES
+    JS_FN_HELP("getWasmSmithModule", GetWasmSmithModule, 1, 0,
+"getWasmSmithModule(arrayBuffer)",
+"  Call wasm-smith to generate a random wasm module from the provided data."),
+#endif
+
+    JS_FS_HELP_END
+};
+// clang-format on
+
+// clang-format off
+#ifdef FUZZING_JS_FUZZILLI
+static const JSFunctionSpec shell_function_fuzzilli_hash[] = {
+    JS_INLINABLE_FN("fuzzilli_hash", fuzzilli_hash, 1, 0, FuzzilliHash),
+    JS_FS_END
+};
+#endif
+// clang-format on
+
+// clang-format off
+static const JSFunctionSpecWithHelp diff_testing_unsafe_functions[] = {
+
+    JS_FS_HELP_END
+};
+// clang-format on
+
+// clang-format off
+static const JSFunctionSpecWithHelp fuzzing_unsafe_functions[] = {
+    JS_FN_HELP("getSelfHostedValue", GetSelfHostedValue, 1, 0,
+"getSelfHostedValue()",
+"  Get a self-hosted value by its name. Note that these values don't get \n"
+"  cached, so repeatedly getting the same value creates multiple distinct clones."),
+
+    JS_FN_HELP("line2pc", LineToPC, 0, 0,
+"line2pc([fun,] line)",
+"  Map line number to PC."),
+
+    JS_FN_HELP("pc2line", PCToLine, 0, 0,
+"pc2line(fun[, pc])",
+"  Map PC to line number."),
+
+    JS_INLINABLE_FN_HELP("assertFloat32", testingFunc_assertFloat32, 2, 0, TestAssertFloat32,
+"assertFloat32(value, isFloat32)",
+"  In IonMonkey only, asserts that value has (resp. hasn't) the MIRType::Float32 if isFloat32 is true (resp. false)."),
+
+    JS_INLINABLE_FN_HELP("assertRecoveredOnBailout", testingFunc_assertRecoveredOnBailout, 2, 0,
+TestAssertRecoveredOnBailout,
+"assertRecoveredOnBailout(var)",
+"  In IonMonkey only, asserts that variable has RecoveredOnBailout flag."),
+
+    JS_FN_HELP("withSourceHook", WithSourceHook, 1, 0,
+"withSourceHook(hook, fun)",
+"  Set this JS runtime's lazy source retrieval hook (that is, the hook\n"
+"  used to find sources compiled with |CompileOptions::LAZY_SOURCE|) to\n"
+"  |hook|; call |fun| with no arguments; and then restore the runtime's\n"
+"  original hook. Return or throw whatever |fun| did. |hook| gets\n"
+"  passed the requested code's URL, and should return a string.\n"
+"\n"
+"  Notes:\n"
+"\n"
+"  1) SpiderMonkey may assert if the returned code isn't close enough\n"
+"  to the script's real code, so this function is not fuzzer-safe.\n"
+"\n"
+"  2) The runtime can have only one source retrieval hook active at a\n"
+"  time. If |fun| is not careful, |hook| could be asked to retrieve the\n"
+"  source code for compilations that occurred long before it was set,\n"
+"  and that it knows nothing about. The reverse applies as well: the\n"
+"  original hook, that we reinstate after the call to |fun| completes,\n"
+"  might be asked for the source code of compilations that |fun|\n"
+"  performed, and which, presumably, only |hook| knows how to find.\n"),
+
+    JS_FN_HELP("crash", Crash, 0, 0,
+"crash([message, [{disable_minidump:true}]])",
+"  Crashes the process with a MOZ_CRASH, optionally providing a message.\n"
+"  An options object may be passed as the second argument. If the key\n"
+"  'suppress_minidump' is set to true, then a minidump will not be\n"
+"  generated by the crash (which only has an effect if the breakpad\n"
+"  dumping library is loaded.)"),
+
+#ifndef __wasi__
+    JS_FN_HELP("wasmLoop", WasmLoop, 2, 0,
+"wasmLoop(filename, imports)",
+"  Performs an AFL-style persistent loop reading data from the given file and passing it\n"
+"  to the 'wasmEval' function together with the specified imports object."),
+#endif // __wasi__
+
+    JS_FN_HELP("setBufferStreamParams", SetBufferStreamParams, 2, 0,
+"setBufferStreamParams(delayMillis, chunkByteSize)",
+"  Set the delay time (between calls to StreamConsumer::consumeChunk) and chunk\n"
+"  size (in bytes)."),
+
+#ifdef JS_CACHEIR_SPEW
+  JS_FN_HELP("cacheIRHealthReport", CacheIRHealthReport, 0, 0,
+"cacheIRHealthReport()",
+"  Show health rating of CacheIR stubs."),
+#endif
+
+#ifdef DEBUG
+  JS_FN_HELP("debugGetQueuedJobs", DebugGetQueuedJobs, 0, 0,
+"debugGetQueuedJobs()",
+"  Returns an array of queued jobs."),
+#endif
+
+    JS_FS_HELP_END
+};
+// clang-format on
+
+// clang-format off
+static const JSFunctionSpecWithHelp performance_functions[] = {
+    JS_FN_HELP("now", Now, 0, 0,
+"now()",
+"  Return the current time with sub-ms precision.\n"
+"  This function is an alias of the dateNow() function."),
+    JS_FS_HELP_END
+};
+// clang-format on
+
+// clang-format off
+static const JSFunctionSpecWithHelp console_functions[] = {
+    JS_FN_HELP("log", Print, 0, 0,
+"log([exp ...])",
+"  Evaluate and print expressions to stdout.\n"
+"  This function is an alias of the print() function."),
+    JS_FS_HELP_END
+};
+// clang-format on
+
+bool DefineConsole(JSContext* cx, HandleObject global) {
+  RootedObject obj(cx, JS_NewPlainObject(cx));
+  return obj && JS_DefineFunctionsWithHelp(cx, obj, console_functions) &&
+         JS_DefineProperty(cx, global, "console", obj, 0);
+}
+
+#ifdef MOZ_PROFILING
+#  define PROFILING_FUNCTION_COUNT 5
+#  ifdef MOZ_CALLGRIND
+#    define CALLGRIND_FUNCTION_COUNT 3
+#  else
+#    define CALLGRIND_FUNCTION_COUNT 0
+#  endif
+#  ifdef MOZ_VTUNE
+#    define VTUNE_FUNCTION_COUNT 4
+#  else
+#    define VTUNE_FUNCTION_COUNT 0
+#  endif
+#  define EXTERNAL_FUNCTION_COUNT \
+    (PROFILING_FUNCTION_COUNT + CALLGRIND_FUNCTION_COUNT + VTUNE_FUNCTION_COUNT)
+#else
+#  define EXTERNAL_FUNCTION_COUNT 0
+#endif
+
+#undef PROFILING_FUNCTION_COUNT
+#undef CALLGRIND_FUNCTION_COUNT
+#undef VTUNE_FUNCTION_COUNT
+#undef EXTERNAL_FUNCTION_COUNT
+
+static bool PrintHelpString(JSContext* cx, HandleValue v) {
+  RootedString str(cx, v.toString());
+  MOZ_ASSERT(gOutFile->isOpen());
+
+  UniqueChars bytes = JS_EncodeStringToUTF8(cx, str);
+  if (!bytes) {
+    return false;
+  }
+
+  fprintf(gOutFile->fp, "%s\n", bytes.get());
+  return true;
+}
+
+static bool PrintHelp(JSContext* cx, HandleObject obj) {
+  RootedValue usage(cx);
+  if (!JS_GetProperty(cx, obj, "usage", &usage)) {
+    return false;
+  }
+  RootedValue help(cx);
+  if (!JS_GetProperty(cx, obj, "help", &help)) {
+    return false;
+  }
+
+  if (!usage.isString() || !help.isString()) {
+    return true;
+  }
+
+  return PrintHelpString(cx, usage) && PrintHelpString(cx, help);
+}
+
+static bool PrintEnumeratedHelp(JSContext* cx, HandleObject obj,
+                                HandleObject pattern, bool brief) {
+  RootedIdVector idv(cx);
+  if (!GetPropertyKeys(cx, obj, JSITER_OWNONLY | JSITER_HIDDEN, &idv)) {
+    return false;
+  }
+
+  Rooted<RegExpObject*> regex(cx);
+  if (pattern) {
+    regex = &UncheckedUnwrap(pattern)->as<RegExpObject>();
+  }
+
+  for (size_t i = 0; i < idv.length(); i++) {
+    RootedValue v(cx);
+    RootedId id(cx, idv[i]);
+    if (!JS_GetPropertyById(cx, obj, id, &v)) {
+      return false;
+    }
+    if (!v.isObject()) {
+      continue;
+    }
+
+    RootedObject funcObj(cx, &v.toObject());
+    if (regex) {
+      // Only pay attention to objects with a 'help' property, which will
+      // either be documented functions or interface objects.
+      if (!JS_GetProperty(cx, funcObj, "help", &v)) {
+        return false;
+      }
+      if (!v.isString()) {
+        continue;
+      }
+
+      // For functions, match against the name. For interface objects,
+      // match against the usage string.
+      if (!JS_GetProperty(cx, funcObj, "name", &v)) {
+        return false;
+      }
+      if (!v.isString()) {
+        if (!JS_GetProperty(cx, funcObj, "usage", &v)) {
+          return false;
+        }
+        if (!v.isString()) {
+          continue;
+        }
+      }
+
+      size_t ignored = 0;
+      if (!JSString::ensureLinear(cx, v.toString())) {
+        return false;
+      }
+      Rooted<JSLinearString*> input(cx, &v.toString()->asLinear());
+      if (!ExecuteRegExpLegacy(cx, nullptr, regex, input, &ignored, true, &v)) {
+        return false;
+      }
+      if (v.isNull()) {
+        continue;
+      }
+    }
+
+    if (!PrintHelp(cx, funcObj)) {
+      return false;
+    }
+  }
+
+  return true;
+}
+
+static bool Help(JSContext* cx, unsigned argc, Value* vp) {
+  if (!gOutFile->isOpen()) {
+    JS_ReportErrorASCII(cx, "output file is closed");
+    return false;
+  }
+
+  CallArgs args = CallArgsFromVp(argc, vp);
+  args.rval().setUndefined();
+  RootedObject global(cx, JS::CurrentGlobalOrNull(cx));
+
+  // help() - display the version and dump out help for all functions on the
+  // global.
+  if (args.length() == 0) {
+    fprintf(gOutFile->fp, "%s\n", JS_GetImplementationVersion());
+
+    if (!PrintEnumeratedHelp(cx, global, nullptr, false)) {
+      return false;
+    }
+    return true;
+  }
+
+  RootedValue v(cx);
+
+  if (args[0].isPrimitive()) {
+    // help("foo")
+    JS_ReportErrorASCII(cx, "primitive arg");
+    return false;
+  }
+
+  RootedObject obj(cx, &args[0].toObject());
+  if (!obj) {
+    return true;
+  }
+  bool isRegexp;
+  if (!JS::ObjectIsRegExp(cx, obj, &isRegexp)) {
+    return false;
+  }
+
+  if (isRegexp) {
+    // help(/pattern/)
+    return PrintEnumeratedHelp(cx, global, obj, false);
+  }
+
+  // help(function)
+  // help(namespace_obj)
+  return PrintHelp(cx, obj);
+}
+
+static const JSErrorFormatString jsShell_ErrorFormatString[JSShellErr_Limit] = {
+#define MSG_DEF(name, count, exception, format) \
+  {#name, format, count, JSEXN_ERR},
+#include "jsshell.msg"
+#undef MSG_DEF
+};
+
+const JSErrorFormatString* js::shell::my_GetErrorMessage(
+    void* userRef, const unsigned errorNumber) {
+  if (errorNumber == 0 || errorNumber >= JSShellErr_Limit) {
+    return nullptr;
+  }
+
+  return &jsShell_ErrorFormatString[errorNumber];
+}
+
+static bool CreateLastWarningObject(JSContext* cx, JSErrorReport* report) {
+  RootedObject warningObj(cx, JS_NewObject(cx, nullptr));
+  if (!warningObj) {
+    return false;
+  }
+
+  if (!CopyErrorReportToObject(cx, report, warningObj)) {
+    return false;
+  }
+
+  GetShellContext(cx)->lastWarning.setObject(*warningObj);
+  return true;
+}
+
+static FILE* ErrorFilePointer() {
+  if (gErrFile->isOpen()) {
+    return gErrFile->fp;
+  }
+
+  fprintf(stderr, "error file is closed; falling back to stderr\n");
+  return stderr;
+}
+
+bool shell::PrintStackTrace(JSContext* cx, HandleObject stackObj) {
+  if (!stackObj || !stackObj->is<SavedFrame>()) {
+    return true;
+  }
+
+  JSPrincipals* principals = stackObj->nonCCWRealm()->principals();
+  RootedString stackStr(cx);
+  if (!BuildStackString(cx, principals, stackObj, &stackStr, 2)) {
+    return false;
+  }
+
+  UniqueChars stack = JS_EncodeStringToUTF8(cx, stackStr);
+  if (!stack) {
+    return false;
+  }
+
+  FILE* fp = ErrorFilePointer();
+  fputs("Stack:\n", fp);
+  fputs(stack.get(), fp);
+
+  return true;
+}
+
+js::shell::AutoReportException::~AutoReportException() {
+  if (!JS_IsExceptionPending(cx)) {
+    return;
+  }
+
+  auto printError = [](JSContext* cx, auto& report, const auto& exnStack,
+                       const char* prefix = nullptr) {
+    if (!report.init(cx, exnStack, JS::ErrorReportBuilder::WithSideEffects)) {
+      fprintf(stderr, "out of memory initializing JS::ErrorReportBuilder\n");
+      fflush(stderr);
+      JS_ClearPendingException(cx);
+      return false;
+    }
+
+    MOZ_ASSERT(!report.report()->isWarning());
+
+    FILE* fp = ErrorFilePointer();
+    if (prefix) {
+      fputs(prefix, fp);
+    }
+    JS::PrintError(fp, report, reportWarnings);
+    JS_ClearPendingException(cx);
+
+    // If possible, use the original error stack as the source of truth, because
+    // finally block handlers may have overwritten the exception stack.
+    RootedObject stack(cx, exnStack.stack());
+    if (exnStack.exception().isObject()) {
+      RootedObject exception(cx, &exnStack.exception().toObject());
+      if (JSObject* exceptionStack = JS::ExceptionStackOrNull(exception)) {
+        stack.set(exceptionStack);
+      }
+    }
+
+    if (!PrintStackTrace(cx, stack)) {
+      fputs("(Unable to print stack trace)\n", fp);
+      JS_ClearPendingException(cx);
+    }
+
+    return true;
+  };
+
+  // Get exception object and stack before printing and clearing exception.
+  JS::ExceptionStack exnStack(cx);
+  if (!JS::StealPendingExceptionStack(cx, &exnStack)) {
+    fprintf(stderr, "out of memory while stealing exception\n");
+    fflush(stderr);
+    JS_ClearPendingException(cx);
+    return;
+  }
+
+  ShellContext* sc = GetShellContext(cx);
+  JS::ErrorReportBuilder report(cx);
+  if (!printError(cx, report, exnStack)) {
+    // Return if we couldn't initialize the error report.
+    return;
+  }
+
+  // Print the error's cause, if available.
+  if (exnStack.exception().isObject()) {
+    JSObject* exception = &exnStack.exception().toObject();
+    if (exception->is<ErrorObject>()) {
+      auto* error = &exception->as<ErrorObject>();
+      if (auto maybeCause = error->getCause()) {
+        RootedValue cause(cx, maybeCause.value());
+
+        RootedObject causeStack(cx);
+        if (cause.isObject()) {
+          RootedObject causeObj(cx, &cause.toObject());
+          causeStack = JS::ExceptionStackOrNull(causeObj);
+        }
+
+        JS::ExceptionStack exnStack(cx, cause, causeStack);
+        JS::ErrorReportBuilder report(cx);
+        printError(cx, report, exnStack, "Caused by: ");
+      }
+    }
+  }
+
+#if defined(DEBUG) || defined(JS_OOM_BREAKPOINT)
+  // Don't quit the shell if an unhandled exception is reported during OOM
+  // testing.
+  if (cx->runningOOMTest) {
+    return;
+  }
+#endif
+
+  if (report.report()->errorNumber == JSMSG_OUT_OF_MEMORY) {
+    sc->exitCode = EXITCODE_OUT_OF_MEMORY;
+  } else {
+    sc->exitCode = EXITCODE_RUNTIME_ERROR;
+  }
+}
+
+void js::shell::WarningReporter(JSContext* cx, JSErrorReport* report) {
+  ShellContext* sc = GetShellContext(cx);
+  FILE* fp = ErrorFilePointer();
+
+  MOZ_ASSERT(report->isWarning());
+
+  if (sc->lastWarningEnabled) {
+    JS::AutoSaveExceptionState savedExc(cx);
+    if (!CreateLastWarningObject(cx, report)) {
+      fputs("Unhandled error happened while creating last warning object.\n",
+            fp);
+      fflush(fp);
+    }
+    savedExc.restore();
+  }
+
+  // Print the warning.
+  JS::PrintError(fp, report, reportWarnings);
+}
+
+static bool global_enumerate(JSContext* cx, JS::HandleObject obj,
+                             JS::MutableHandleIdVector properties,
+                             bool enumerableOnly) {
+#ifdef LAZY_STANDARD_CLASSES
+  return JS_NewEnumerateStandardClasses(cx, obj, properties, enumerableOnly);
+#else
+  return true;
+#endif
+}
+
+static bool global_resolve(JSContext* cx, HandleObject obj, HandleId id,
+                           bool* resolvedp) {
+#ifdef LAZY_STANDARD_CLASSES
+  if (!JS_ResolveStandardClass(cx, obj, id, resolvedp)) {
+    return false;
+  }
+#endif
+  return true;
+}
+
+static bool global_mayResolve(const JSAtomState& names, jsid id,
+                              JSObject* maybeObj) {
+  return JS_MayResolveStandardClass(names, id, maybeObj);
+}
+
+static const JSClassOps global_classOps = {
+    nullptr,                   // addProperty
+    nullptr,                   // delProperty
+    nullptr,                   // enumerate
+    global_enumerate,          // newEnumerate
+    global_resolve,            // resolve
+    global_mayResolve,         // mayResolve
+    nullptr,                   // finalize
+    nullptr,                   // call
+    nullptr,                   // construct
+    JS_GlobalObjectTraceHook,  // trace
+};
+
+static constexpr uint32_t DOM_PROTOTYPE_SLOT = JSCLASS_GLOBAL_SLOT_COUNT;
+static constexpr uint32_t DOM_GLOBAL_SLOTS = 1;
+
+static const JSClass global_class = {
+    "global",
+    JSCLASS_GLOBAL_FLAGS | JSCLASS_GLOBAL_FLAGS_WITH_SLOTS(DOM_GLOBAL_SLOTS),
+    &global_classOps};
+
+/*
+ * Define a FakeDOMObject constructor. It returns an object with a getter,
+ * setter and method with attached JitInfo. This object can be used to test
+ * IonMonkey DOM optimizations in the shell.
+ */
+
+/* Fow now just use to a constant we can check. */
+static const void* DOM_PRIVATE_VALUE = (void*)0x1234;
+
+static bool dom_genericGetter(JSContext* cx, unsigned argc, JS::Value* vp);
+
+static bool dom_genericSetter(JSContext* cx, unsigned argc, JS::Value* vp);
+
+static bool dom_genericMethod(JSContext* cx, unsigned argc, JS::Value* vp);
+
+static bool dom_get_x(JSContext* cx, HandleObject obj, void* self,
+                      JSJitGetterCallArgs args) {
+  MOZ_ASSERT(JS::GetClass(obj) == GetDomClass());
+  MOZ_ASSERT(self == DOM_PRIVATE_VALUE);
+  args.rval().set(JS_NumberValue(double(3.14)));
+  return true;
+}
+
+static bool dom_set_x(JSContext* cx, HandleObject obj, void* self,
+                      JSJitSetterCallArgs args) {
+  MOZ_ASSERT(JS::GetClass(obj) == GetDomClass());
+  MOZ_ASSERT(self == DOM_PRIVATE_VALUE);
+  return true;
+}
+
+static bool dom_get_slot(JSContext* cx, HandleObject obj, void* self,
+                         JSJitGetterCallArgs args) {
+  MOZ_ASSERT(JS::GetClass(obj) == GetDomClass());
+  MOZ_ASSERT(self == DOM_PRIVATE_VALUE);
+
+  Value v = JS::GetReservedSlot(obj, DOM_OBJECT_SLOT2);
+  MOZ_ASSERT(v.toInt32() == 42);
+  args.rval().set(v);
+  return true;
+}
+
+static bool dom_get_global(JSContext* cx, HandleObject obj, void* self,
+                           JSJitGetterCallArgs args) {
+  MOZ_ASSERT(JS::GetClass(obj) == GetDomClass());
+  MOZ_ASSERT(self == DOM_PRIVATE_VALUE);
+
+  // Return the current global (instead of obj->global()) to test cx->realm
+  // switching in the JIT.
+  args.rval().setObject(*ToWindowProxyIfWindow(cx->global()));
+
+  return true;
+}
+
+static bool dom_set_global(JSContext* cx, HandleObject obj, void* self,
+                           JSJitSetterCallArgs args) {
+  MOZ_ASSERT(JS::GetClass(obj) == GetDomClass());
+  MOZ_ASSERT(self == DOM_PRIVATE_VALUE);
+
+  // Throw an exception if our argument is not the current global. This lets
+  // us test cx->realm switching.
+  if (!args[0].isObject() ||
+      ToWindowIfWindowProxy(&args[0].toObject()) != cx->global()) {
+    JS_ReportErrorASCII(cx, "Setter not called with matching global argument");
+    return false;
+  }
+
+  return true;
+}
+
+static bool dom_doFoo(JSContext* cx, HandleObject obj, void* self,
+                      const JSJitMethodCallArgs& args) {
+  MOZ_ASSERT(JS::GetClass(obj) == GetDomClass());
+  MOZ_ASSERT(self == DOM_PRIVATE_VALUE);
+  MOZ_ASSERT(cx->realm() == args.callee().as<JSFunction>().realm());
+
+  /* Just return args.length(). */
+  args.rval().setInt32(args.length());
+  return true;
+}
+
+static const JSJitInfo dom_x_getterinfo = {
+    {(JSJitGetterOp)dom_get_x},
+    {0}, /* protoID */
+    {0}, /* depth */
+    JSJitInfo::Getter,
+    JSJitInfo::AliasNone, /* aliasSet */
+    JSVAL_TYPE_UNKNOWN,   /* returnType */
+    true,                 /* isInfallible. False in setters. */
+    true,                 /* isMovable */
+    true,                 /* isEliminatable */
+    false,                /* isAlwaysInSlot */
+    false,                /* isLazilyCachedInSlot */
+    false,                /* isTypedMethod */
+    0                     /* slotIndex */
+};
+
+static const JSJitInfo dom_x_setterinfo = {
+    {(JSJitGetterOp)dom_set_x},
+    {0}, /* protoID */
+    {0}, /* depth */
+    JSJitInfo::Setter,
+    JSJitInfo::AliasEverything, /* aliasSet */
+    JSVAL_TYPE_UNKNOWN,         /* returnType */
+    false,                      /* isInfallible. False in setters. */
+    false,                      /* isMovable. */
+    false,                      /* isEliminatable. */
+    false,                      /* isAlwaysInSlot */
+    false,                      /* isLazilyCachedInSlot */
+    false,                      /* isTypedMethod */
+    0                           /* slotIndex */
+};
+
+static const JSJitInfo dom_slot_getterinfo = {
+    {(JSJitGetterOp)dom_get_slot},
+    {0}, /* protoID */
+    {0}, /* depth */
+    JSJitInfo::Getter,
+    JSJitInfo::AliasNone, /* aliasSet */
+    JSVAL_TYPE_INT32,     /* returnType */
+    false,                /* isInfallible. False in setters. */
+    true,                 /* isMovable */
+    true,                 /* isEliminatable */
+    true,                 /* isAlwaysInSlot */
+    false,                /* isLazilyCachedInSlot */
+    false,                /* isTypedMethod */
+    DOM_OBJECT_SLOT2      /* slotIndex */
+};
+
+// Note: this getter uses AliasEverything and is marked as fallible and
+// non-movable (1) to prevent Ion from getting too clever optimizing it and
+// (2) it's nice to have a few different kinds of getters in the shell.
+static const JSJitInfo dom_global_getterinfo = {
+    {(JSJitGetterOp)dom_get_global},
+    {0}, /* protoID */
+    {0}, /* depth */
+    JSJitInfo::Getter,
+    JSJitInfo::AliasEverything, /* aliasSet */
+    JSVAL_TYPE_OBJECT,          /* returnType */
+    false,                      /* isInfallible. False in setters. */
+    false,                      /* isMovable */
+    false,                      /* isEliminatable */
+    false,                      /* isAlwaysInSlot */
+    false,                      /* isLazilyCachedInSlot */
+    false,                      /* isTypedMethod */
+    0                           /* slotIndex */
+};
+
+static const JSJitInfo dom_global_setterinfo = {
+    {(JSJitGetterOp)dom_set_global},
+    {0}, /* protoID */
+    {0}, /* depth */
+    JSJitInfo::Setter,
+    JSJitInfo::AliasEverything, /* aliasSet */
+    JSVAL_TYPE_UNKNOWN,         /* returnType */
+    false,                      /* isInfallible. False in setters. */
+    false,                      /* isMovable. */
+    false,                      /* isEliminatable. */
+    false,                      /* isAlwaysInSlot */
+    false,                      /* isLazilyCachedInSlot */
+    false,                      /* isTypedMethod */
+    0                           /* slotIndex */
+};
+
+static const JSJitInfo doFoo_methodinfo = {
+    {(JSJitGetterOp)dom_doFoo},
+    {0}, /* protoID */
+    {0}, /* depth */
+    JSJitInfo::Method,
+    JSJitInfo::AliasEverything, /* aliasSet */
+    JSVAL_TYPE_UNKNOWN,         /* returnType */
+    false,                      /* isInfallible. False in setters. */
+    false,                      /* isMovable */
+    false,                      /* isEliminatable */
+    false,                      /* isAlwaysInSlot */
+    false,                      /* isLazilyCachedInSlot */
+    false,                      /* isTypedMethod */
+    0                           /* slotIndex */
+};
+
+static const JSPropertySpec dom_props[] = {
+    JSPropertySpec::nativeAccessors("x", JSPROP_ENUMERATE, dom_genericGetter,
+                                    &dom_x_getterinfo, dom_genericSetter,
+                                    &dom_x_setterinfo),
+    JSPropertySpec::nativeAccessors("slot", JSPROP_ENUMERATE, dom_genericGetter,
+                                    &dom_slot_getterinfo),
+    JSPropertySpec::nativeAccessors("global", JSPROP_ENUMERATE,
+                                    dom_genericGetter, &dom_global_getterinfo,
+                                    dom_genericSetter, &dom_global_setterinfo),
+    JS_PS_END};
+
+static const JSFunctionSpec dom_methods[] = {
+    JS_FNINFO("doFoo", dom_genericMethod, &doFoo_methodinfo, 3,
+              JSPROP_ENUMERATE),
+    JS_FS_END};
+
+static const JSClass dom_class = {
+    "FakeDOMObject", JSCLASS_IS_DOMJSCLASS | JSCLASS_HAS_RESERVED_SLOTS(2)};
+
+static const JSClass* GetDomClass() { return &dom_class; }
+
+static bool dom_genericGetter(JSContext* cx, unsigned argc, JS::Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  if (!args.thisv().isObject()) {
+    args.rval().setUndefined();
+    return true;
+  }
+
+  RootedObject obj(cx, &args.thisv().toObject());
+  if (JS::GetClass(obj) != &dom_class) {
+    args.rval().set(UndefinedValue());
+    return true;
+  }
+
+  JS::Value val = JS::GetReservedSlot(obj, DOM_OBJECT_SLOT);
+
+  const JSJitInfo* info = FUNCTION_VALUE_TO_JITINFO(args.calleev());
+  MOZ_ASSERT(info->type() == JSJitInfo::Getter);
+  JSJitGetterOp getter = info->getter;
+  return getter(cx, obj, val.toPrivate(), JSJitGetterCallArgs(args));
+}
+
+static bool dom_genericSetter(JSContext* cx, unsigned argc, JS::Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  if (args.length() < 1 || !args.thisv().isObject()) {
+    args.rval().setUndefined();
+    return true;
+  }
+
+  RootedObject obj(cx, &args.thisv().toObject());
+  if (JS::GetClass(obj) != &dom_class) {
+    args.rval().set(UndefinedValue());
+    return true;
+  }
+
+  JS::Value val = JS::GetReservedSlot(obj, DOM_OBJECT_SLOT);
+
+  const JSJitInfo* info = FUNCTION_VALUE_TO_JITINFO(args.calleev());
+  MOZ_ASSERT(info->type() == JSJitInfo::Setter);
+  JSJitSetterOp setter = info->setter;
+  if (!setter(cx, obj, val.toPrivate(), JSJitSetterCallArgs(args))) {
+    return false;
+  }
+  args.rval().set(UndefinedValue());
+  return true;
+}
+
+static bool dom_genericMethod(JSContext* cx, unsigned argc, JS::Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  if (!args.thisv().isObject()) {
+    args.rval().setUndefined();
+    return true;
+  }
+
+  RootedObject obj(cx, &args.thisv().toObject());
+  if (JS::GetClass(obj) != &dom_class) {
+    args.rval().set(UndefinedValue());
+    return true;
+  }
+
+  JS::Value val = JS::GetReservedSlot(obj, DOM_OBJECT_SLOT);
+
+  const JSJitInfo* info = FUNCTION_VALUE_TO_JITINFO(args.calleev());
+  MOZ_ASSERT(info->type() == JSJitInfo::Method);
+  JSJitMethodOp method = info->method;
+  return method(cx, obj, val.toPrivate(), JSJitMethodCallArgs(args));
+}
+
+static void InitDOMObject(HandleObject obj) {
+  JS::SetReservedSlot(obj, DOM_OBJECT_SLOT,
+                      PrivateValue(const_cast<void*>(DOM_PRIVATE_VALUE)));
+  JS::SetReservedSlot(obj, DOM_OBJECT_SLOT2, Int32Value(42));
+}
+
+static JSObject* GetDOMPrototype(JSContext* cx, JSObject* global) {
+  MOZ_ASSERT(JS_IsGlobalObject(global));
+  if (JS::GetClass(global) != &global_class) {
+    JS_ReportErrorASCII(cx, "Can't get FakeDOMObject prototype in sandbox");
+    return nullptr;
+  }
+
+  const JS::Value& slot = JS::GetReservedSlot(global, DOM_PROTOTYPE_SLOT);
+  MOZ_ASSERT(slot.isObject());
+  return &slot.toObject();
+}
+
+static bool dom_constructor(JSContext* cx, unsigned argc, JS::Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  RootedObject callee(cx, &args.callee());
+  RootedValue protov(cx);
+  if (!GetProperty(cx, callee, callee, cx->names().prototype, &protov)) {
+    return false;
+  }
+
+  if (!protov.isObject()) {
+    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr, JSMSG_BAD_PROTOTYPE,
+                              "FakeDOMObject");
+    return false;
+  }
+
+  RootedObject proto(cx, &protov.toObject());
+  RootedObject domObj(cx, JS_NewObjectWithGivenProto(cx, &dom_class, proto));
+  if (!domObj) {
+    return false;
+  }
+
+  InitDOMObject(domObj);
+
+  args.rval().setObject(*domObj);
+  return true;
+}
+
+static bool InstanceClassHasProtoAtDepth(const JSClass* clasp, uint32_t protoID,
+                                         uint32_t depth) {
+  // Only the (fake) DOM object supports any JIT optimizations.
+  return clasp == GetDomClass();
+}
+
+static bool ShellBuildId(JS::BuildIdCharVector* buildId) {
+  // The browser embeds the date into the buildid and the buildid is embedded
+  // in the binary, so every 'make' necessarily builds a new firefox binary.
+  // Fortunately, the actual firefox executable is tiny -- all the code is in
+  // libxul.so and other shared modules -- so this isn't a big deal. Not so
+  // for the statically-linked JS shell. To avoid recompiling js.cpp and
+  // re-linking 'js' on every 'make', we use a constant buildid and rely on
+  // the shell user to manually clear any caches between cache-breaking updates.
+  const char buildid[] = "JS-shell";
+  return buildId->append(buildid, sizeof(buildid));
+}
+
+static bool TimesAccessed(JSContext* cx, unsigned argc, Value* vp) {
+  static int32_t accessed = 0;
+  CallArgs args = CallArgsFromVp(argc, vp);
+  args.rval().setInt32(++accessed);
+  return true;
+}
+
+static const JSPropertySpec TestingProperties[] = {
+    JS_PSG("timesAccessed", TimesAccessed, 0), JS_PS_END};
+
+static JSObject* NewGlobalObject(JSContext* cx, JS::RealmOptions& options,
+                                 JSPrincipals* principals, ShellGlobalKind kind,
+                                 bool immutablePrototype) {
+  RootedObject glob(cx,
+                    JS_NewGlobalObject(cx, &global_class, principals,
+                                       JS::DontFireOnNewGlobalHook, options));
+  if (!glob) {
+    return nullptr;
+  }
+
+  {
+    JSAutoRealm ar(cx, glob);
+
+    if (kind == ShellGlobalKind::WindowProxy) {
+      RootedObject proxy(cx, NewShellWindowProxy(cx, glob));
+      if (!proxy) {
+        return nullptr;
+      }
+      js::SetWindowProxy(cx, glob, proxy);
+    }
+
+#ifndef LAZY_STANDARD_CLASSES
+    if (!JS::InitRealmStandardClasses(cx)) {
+      return nullptr;
+    }
+#endif
+
+    if (immutablePrototype) {
+      bool succeeded;
+      if (!JS_SetImmutablePrototype(cx, glob, &succeeded)) {
+        return nullptr;
+      }
+      MOZ_ASSERT(succeeded,
+                 "a fresh, unexposed global object is always capable of "
+                 "having its [[Prototype]] be immutable");
+    }
+
+#ifdef JS_HAS_CTYPES
+    if (!fuzzingSafe && !JS::InitCTypesClass(cx, glob)) {
+      return nullptr;
+    }
+#endif
+    if (!JS_InitReflectParse(cx, glob)) {
+      return nullptr;
+    }
+    if (!JS_DefineDebuggerObject(cx, glob)) {
+      return nullptr;
+    }
+    if (!JS_DefineFunctionsWithHelp(cx, glob, shell_functions) ||
+        !JS_DefineProfilingFunctions(cx, glob)) {
+      return nullptr;
+    }
+#ifdef FUZZING_JS_FUZZILLI
+    if (!JS_DefineFunctions(cx, glob, shell_function_fuzzilli_hash)) {
+      return nullptr;
+    }
+#endif
+    if (!js::DefineTestingFunctions(cx, glob, fuzzingSafe,
+                                    disableOOMFunctions)) {
+      return nullptr;
+    }
+    if (!JS_DefineProperties(cx, glob, TestingProperties)) {
+      return nullptr;
+    }
+
+    if (!fuzzingSafe) {
+      if (!JS_DefineFunctionsWithHelp(cx, glob, fuzzing_unsafe_functions)) {
+        return nullptr;
+      }
+      if (!DefineConsole(cx, glob)) {
+        return nullptr;
+      }
+    }
+
+    if (!DefineOS(cx, glob, fuzzingSafe, &gOutFile, &gErrFile)) {
+      return nullptr;
+    }
+
+    if (!js::SupportDifferentialTesting()) {
+      if (!JS_DefineFunctionsWithHelp(cx, glob,
+                                      diff_testing_unsafe_functions)) {
+        return nullptr;
+      }
+
+      RootedObject performanceObj(cx, JS_NewObject(cx, nullptr));
+      if (!performanceObj) {
+        return nullptr;
+      }
+      if (!JS_DefineFunctionsWithHelp(cx, performanceObj,
+                                      performance_functions)) {
+        return nullptr;
+      }
+      RootedObject mozMemoryObj(cx, JS_NewObject(cx, nullptr));
+      if (!mozMemoryObj) {
+        return nullptr;
+      }
+      RootedObject gcObj(cx, gc::NewMemoryInfoObject(cx));
+      if (!gcObj) {
+        return nullptr;
+      }
+      if (!JS_DefineProperty(cx, glob, "performance", performanceObj,
+                             JSPROP_ENUMERATE)) {
+        return nullptr;
+      }
+      if (!JS_DefineProperty(cx, performanceObj, "mozMemory", mozMemoryObj,
+                             JSPROP_ENUMERATE)) {
+        return nullptr;
+      }
+      if (!JS_DefineProperty(cx, mozMemoryObj, "gc", gcObj, JSPROP_ENUMERATE)) {
+        return nullptr;
+      }
+    }
+
+    /* Initialize FakeDOMObject. */
+    static const js::DOMCallbacks DOMcallbacks = {InstanceClassHasProtoAtDepth};
+    SetDOMCallbacks(cx, &DOMcallbacks);
+
+    RootedObject domProto(
+        cx, JS_InitClass(cx, glob, &dom_class, nullptr, "FakeDOMObject",
+                         dom_constructor, 0, dom_props, dom_methods, nullptr,
+                         nullptr));
+    if (!domProto) {
+      return nullptr;
+    }
+
+    // FakeDOMObject.prototype is the only DOM object which needs to retrieved
+    // in the shell; store it directly instead of creating a separate layer
+    // (ProtoAndIfaceCache) as done in the browser.
+    JS::SetReservedSlot(glob, DOM_PROTOTYPE_SLOT, ObjectValue(*domProto));
+
+    /* Initialize FakeDOMObject.prototype */
+    InitDOMObject(domProto);
+
+    if (!DefineToStringTag(cx, glob, cx->names().global)) {
+      return nullptr;
+    }
+
+    JS_FireOnNewGlobalObject(cx, glob);
+  }
+
+  return glob;
+}
+
+static bool BindScriptArgs(JSContext* cx, OptionParser* op) {
+  AutoReportException are(cx);
+
+  MultiStringRange msr = op->getMultiStringArg("scriptArgs");
+  RootedObject scriptArgs(cx);
+  scriptArgs = JS::NewArrayObject(cx, 0);
+  if (!scriptArgs) {
+    return false;
+  }
+
+  if (!JS_DefineProperty(cx, cx->global(), "scriptArgs", scriptArgs, 0)) {
+    return false;
+  }
+
+  for (size_t i = 0; !msr.empty(); msr.popFront(), ++i) {
+    const char* scriptArg = msr.front();
+    JS::RootedString str(cx, JS_NewStringCopyZ(cx, scriptArg));
+    if (!str || !JS_DefineElement(cx, scriptArgs, i, str, JSPROP_ENUMERATE)) {
+      return false;
+    }
+  }
+
+  const char* scriptPath = op->getStringArg("script");
+  RootedValue scriptPathValue(cx);
+  if (scriptPath) {
+    RootedString scriptPathString(cx, JS_NewStringCopyZ(cx, scriptPath));
+    if (!scriptPathString) {
+      return false;
+    }
+    scriptPathValue = StringValue(scriptPathString);
+  } else {
+    scriptPathValue = UndefinedValue();
+  }
+
+  if (!JS_DefineProperty(cx, cx->global(), "scriptPath", scriptPathValue, 0)) {
+    return false;
+  }
+
+  return true;
+}
+
+static bool OptionFailure(const char* option, const char* str) {
+  fprintf(stderr, "Unrecognized option for %s: %s\n", option, str);
+  return false;
+}
+
+template <typename... Ts>
+auto minVal(Ts... args);
+template <typename T>
+auto minVal(T a) {
+  return a;
+}
+
+template <typename T, typename... Ts>
+auto minVal(T a, Ts... args) {
+  return std::min(a, minVal(args...));
+}
+
+[[nodiscard]] static bool ProcessArgs(JSContext* cx, OptionParser* op) {
+  ShellContext* sc = GetShellContext(cx);
+
+#ifdef JS_ENABLE_SMOOSH
+  if (op->getBoolOption("smoosh")) {
+    JS::ContextOptionsRef(cx).setTrySmoosh(true);
+    js::frontend::InitSmoosh();
+  }
+
+  if (const char* filename = op->getStringOption("not-implemented-watchfile")) {
+    FILE* out = fopen(filename, "a");
+    MOZ_RELEASE_ASSERT(out);
+    setbuf(out, nullptr);  // Make unbuffered
+    cx->runtime()->parserWatcherFile.init(out);
+    JS::ContextOptionsRef(cx).setTrackNotImplemented(true);
+  }
+#endif
+
+  if (const char* mode = op->getStringOption("delazification-mode")) {
+    if (strcmp(mode, "on-demand") == 0) {
+      defaultDelazificationMode = JS::DelazificationOption::OnDemandOnly;
+    } else if (strcmp(mode, "concurrent-df") == 0) {
+      defaultDelazificationMode =
+          JS::DelazificationOption::ConcurrentDepthFirst;
+    } else if (strcmp(mode, "eager") == 0) {
+      defaultDelazificationMode =
+          JS::DelazificationOption::ParseEverythingEagerly;
+    } else if (strcmp(mode, "concurrent-df+on-demand") == 0 ||
+               strcmp(mode, "on-demand+concurrent-df") == 0) {
+      defaultDelazificationMode =
+          JS::DelazificationOption::CheckConcurrentWithOnDemand;
+    } else {
+      return OptionFailure("delazification-mode", mode);
+    }
+  }
+
+  /* |scriptArgs| gets bound on the global before any code is run. */
+  if (!BindScriptArgs(cx, op)) {
+    return false;
+  }
+
+  RootedString moduleLoadPath(cx);
+  if (const char* option = op->getStringOption("module-load-path")) {
+    RootedString jspath(cx, JS_NewStringCopyZ(cx, option));
+    if (!jspath) {
+      return false;
+    }
+
+    moduleLoadPath = js::shell::ResolvePath(cx, jspath, RootRelative);
+  } else {
+    UniqueChars cwd = js::shell::GetCWD();
+    moduleLoadPath = JS_NewStringCopyZ(cx, cwd.get());
+  }
+
+  if (!moduleLoadPath) {
+    return false;
+  }
+
+  processWideModuleLoadPath = JS_EncodeStringToUTF8(cx, moduleLoadPath);
+  if (!processWideModuleLoadPath) {
+    MOZ_ASSERT(cx->isExceptionPending());
+    return false;
+  }
+
+  sc->moduleLoader = js::MakeUnique<ModuleLoader>();
+  if (!sc->moduleLoader || !sc->moduleLoader->init(cx, moduleLoadPath)) {
+    return false;
+  }
+
+  MultiStringRange filePaths = op->getMultiStringOption('f');
+  MultiStringRange utf16FilePaths = op->getMultiStringOption('u');
+  MultiStringRange preludePaths = op->getMultiStringOption('p');
+  MultiStringRange codeChunks = op->getMultiStringOption('e');
+  MultiStringRange modulePaths = op->getMultiStringOption('m');
+
+#ifdef FUZZING_JS_FUZZILLI
+  // Check for REPRL file source
+  if (op->getBoolOption("reprl")) {
+    return FuzzilliReprlGetAndRun(cx);
+  }
+#endif /* FUZZING_JS_FUZZILLI */
+
+  if (filePaths.empty() && utf16FilePaths.empty() && codeChunks.empty() &&
+      modulePaths.empty() && !op->getStringArg("script")) {
+    // Always use the interactive shell when -i is used. Without -i we let
+    // Process figure it out based on isatty.
+    bool forceTTY = op->getBoolOption('i');
+    return Process(cx, nullptr, forceTTY, FileScript);
+  }
+
+  while (!preludePaths.empty() || !filePaths.empty() ||
+         !utf16FilePaths.empty() || !codeChunks.empty() ||
+         !modulePaths.empty()) {
+    size_t ppArgno = preludePaths.empty() ? SIZE_MAX : preludePaths.argno();
+    size_t fpArgno = filePaths.empty() ? SIZE_MAX : filePaths.argno();
+    size_t ufpArgno =
+        utf16FilePaths.empty() ? SIZE_MAX : utf16FilePaths.argno();
+    size_t ccArgno = codeChunks.empty() ? SIZE_MAX : codeChunks.argno();
+    size_t mpArgno = modulePaths.empty() ? SIZE_MAX : modulePaths.argno();
+    size_t minArgno = minVal(ppArgno, fpArgno, ufpArgno, ccArgno, mpArgno);
+
+    if (ppArgno == minArgno) {
+      char* path = preludePaths.front();
+      if (!Process(cx, path, false, PreludeScript)) {
+        return false;
+      }
+
+      preludePaths.popFront();
+      continue;
+    }
+
+    if (fpArgno == minArgno) {
+      char* path = filePaths.front();
+      if (!Process(cx, path, false, FileScript)) {
+        return false;
+      }
+
+      filePaths.popFront();
+      continue;
+    }
+
+    if (ufpArgno == minArgno) {
+      char* path = utf16FilePaths.front();
+      if (!Process(cx, path, false, FileScriptUtf16)) {
+        return false;
+      }
+
+      utf16FilePaths.popFront();
+      continue;
+    }
+
+    if (ccArgno == minArgno) {
+      const char* code = codeChunks.front();
+
+      // Command line scripts are always parsed with full-parse to evaluate
+      // conditions which might filter code coverage conditions.
+      JS::CompileOptions opts(cx);
+      opts.setFileAndLine("-e", 1).setForceFullParse();
+
+      JS::SourceText<Utf8Unit> srcBuf;
+      if (!srcBuf.init(cx, code, strlen(code), JS::SourceOwnership::Borrowed)) {
+        return false;
+      }
+
+      RootedValue rval(cx);
+      if (!JS::Evaluate(cx, opts, srcBuf, &rval)) {
+        return false;
+      }
+
+      codeChunks.popFront();
+      if (sc->quitting) {
+        break;
+      }
+
+      continue;
+    }
+
+    MOZ_ASSERT(mpArgno == minArgno);
+
+    char* path = modulePaths.front();
+    if (!Process(cx, path, false, FileModule)) {
+      return false;
+    }
+
+    modulePaths.popFront();
+  }
+
+  if (sc->quitting) {
+    return false;
+  }
+
+  /* The |script| argument is processed after all options. */
+  if (const char* path = op->getStringArg("script")) {
+    if (!Process(cx, path, false, FileScript)) {
+      return false;
+    }
+  }
+
+  if (op->getBoolOption('i')) {
+    if (!Process(cx, nullptr, true, FileScript)) {
+      return false;
+    }
+  }
+
+  return true;
+}
+
+static bool SetContextOptions(JSContext* cx, const OptionParser& op) {
+  enableAsmJS = !op.getBoolOption("no-asmjs");
+
+  enableWasm = true;
+  enableWasmBaseline = true;
+  enableWasmOptimizing = true;
+
+  if (const char* str = op.getStringOption("wasm-compiler")) {
+    if (strcmp(str, "none") == 0) {
+      enableWasm = false;
+    } else if (strcmp(str, "baseline") == 0) {
+      MOZ_ASSERT(enableWasmBaseline);
+      enableWasmOptimizing = false;
+    } else if (strcmp(str, "optimizing") == 0 ||
+               strcmp(str, "optimized") == 0) {
+      enableWasmBaseline = false;
+      MOZ_ASSERT(enableWasmOptimizing);
+    } else if (strcmp(str, "baseline+optimizing") == 0 ||
+               strcmp(str, "baseline+optimized") == 0) {
+      MOZ_ASSERT(enableWasmBaseline);
+      MOZ_ASSERT(enableWasmOptimizing);
+    } else if (strcmp(str, "ion") == 0) {
+      enableWasmBaseline = false;
+      enableWasmOptimizing = true;
+    } else if (strcmp(str, "baseline+ion") == 0) {
+      MOZ_ASSERT(enableWasmBaseline);
+      enableWasmOptimizing = true;
+    } else {
+      return OptionFailure("wasm-compiler", str);
+    }
+  }
+
+#define WASM_DEFAULT_FEATURE(NAME, LOWER_NAME, COMPILE_PRED, COMPILER_PRED, \
+                             FLAG_PRED, SHELL, ...)                         \
+  enableWasm##NAME = !op.getBoolOption("no-wasm-" SHELL);
+#define WASM_EXPERIMENTAL_FEATURE(NAME, LOWER_NAME, COMPILE_PRED,       \
+                                  COMPILER_PRED, FLAG_PRED, SHELL, ...) \
+  enableWasm##NAME = op.getBoolOption("wasm-" SHELL);
+  JS_FOR_WASM_FEATURES(WASM_DEFAULT_FEATURE, WASM_DEFAULT_FEATURE,
+                       WASM_EXPERIMENTAL_FEATURE);
+#undef WASM_DEFAULT_FEATURE
+#undef WASM_EXPERIMENTAL_FEATURE
+
+  enableWasmVerbose = op.getBoolOption("wasm-verbose");
+  enableTestWasmAwaitTier2 = op.getBoolOption("test-wasm-await-tier2");
+  enableSourcePragmas = !op.getBoolOption("no-source-pragmas");
+  enableAsyncStacks = !op.getBoolOption("no-async-stacks");
+  enableAsyncStackCaptureDebuggeeOnly =
+      op.getBoolOption("async-stacks-capture-debuggee-only");
+  enableWeakRefs = !op.getBoolOption("disable-weak-refs");
+  enableToSource = !op.getBoolOption("disable-tosource");
+  enablePropertyErrorMessageFix =
+      !op.getBoolOption("disable-property-error-message-fix");
+  enableIteratorHelpers = op.getBoolOption("enable-iterator-helpers");
+  enableShadowRealms = op.getBoolOption("enable-shadow-realms");
+#ifdef NIGHTLY_BUILD
+  enableArrayGrouping = op.getBoolOption("enable-array-grouping");
+  enableArrayFromAsync = op.getBoolOption("enable-array-from-async");
+#endif
+#ifdef ENABLE_CHANGE_ARRAY_BY_COPY
+  enableChangeArrayByCopy = op.getBoolOption("enable-change-array-by-copy");
+#endif
+#ifdef ENABLE_NEW_SET_METHODS
+  enableNewSetMethods = op.getBoolOption("enable-new-set-methods");
+#endif
+  enableImportAssertions = op.getBoolOption("enable-import-assertions");
+  useFdlibmForSinCosTan = op.getBoolOption("use-fdlibm-for-sin-cos-tan");
+
+  JS::ContextOptionsRef(cx)
+      .setAsmJS(enableAsmJS)
+      .setWasm(enableWasm)
+      .setWasmForTrustedPrinciples(enableWasm)
+      .setWasmBaseline(enableWasmBaseline)
+      .setWasmIon(enableWasmOptimizing)
+
+#define WASM_FEATURE(NAME, ...) .setWasm##NAME(enableWasm##NAME)
+          JS_FOR_WASM_FEATURES(WASM_FEATURE, WASM_FEATURE, WASM_FEATURE)
+#undef WASM_FEATURE
+
+      .setWasmVerbose(enableWasmVerbose)
+      .setTestWasmAwaitTier2(enableTestWasmAwaitTier2)
+      .setSourcePragmas(enableSourcePragmas)
+      .setAsyncStack(enableAsyncStacks)
+      .setAsyncStackCaptureDebuggeeOnly(enableAsyncStackCaptureDebuggeeOnly)
+      .setImportAssertions(enableImportAssertions);
+
+  JS::SetUseFdlibmForSinCosTan(useFdlibmForSinCosTan);
+
+  // Check --fast-warmup first because it sets default warm-up thresholds. These
+  // thresholds can then be overridden below by --ion-eager and other flags.
+  if (op.getBoolOption("fast-warmup")) {
+    jit::JitOptions.setFastWarmUp();
+  }
+
+  if (op.getBoolOption("no-ion-for-main-context")) {
+    JS::ContextOptionsRef(cx).setDisableIon();
+  }
+
+  if (const char* str = op.getStringOption("cache-ir-stubs")) {
+    if (strcmp(str, "on") == 0) {
+      jit::JitOptions.disableCacheIR = false;
+    } else if (strcmp(str, "off") == 0) {
+      jit::JitOptions.disableCacheIR = true;
+    } else {
+      return OptionFailure("cache-ir-stubs", str);
+    }
+  }
+
+  if (const char* str = op.getStringOption("spectre-mitigations")) {
+    if (strcmp(str, "on") == 0) {
+      jit::JitOptions.spectreIndexMasking = true;
+      jit::JitOptions.spectreObjectMitigations = true;
+      jit::JitOptions.spectreStringMitigations = true;
+      jit::JitOptions.spectreValueMasking = true;
+      jit::JitOptions.spectreJitToCxxCalls = true;
+    } else if (strcmp(str, "off") == 0) {
+      jit::JitOptions.spectreIndexMasking = false;
+      jit::JitOptions.spectreObjectMitigations = false;
+      jit::JitOptions.spectreStringMitigations = false;
+      jit::JitOptions.spectreValueMasking = false;
+      jit::JitOptions.spectreJitToCxxCalls = false;
+    } else {
+      return OptionFailure("spectre-mitigations", str);
+    }
+  }
+
+  if (const char* str = op.getStringOption("ion-scalar-replacement")) {
+    if (strcmp(str, "on") == 0) {
+      jit::JitOptions.disableScalarReplacement = false;
+    } else if (strcmp(str, "off") == 0) {
+      jit::JitOptions.disableScalarReplacement = true;
+    } else {
+      return OptionFailure("ion-scalar-replacement", str);
+    }
+  }
+
+  if (op.getStringOption("ion-shared-stubs")) {
+    // Dead option, preserved for now for potential fuzzer interaction.
+  }
+
+  if (const char* str = op.getStringOption("ion-gvn")) {
+    if (strcmp(str, "off") == 0) {
+      jit::JitOptions.disableGvn = true;
+    } else if (strcmp(str, "on") != 0 && strcmp(str, "optimistic") != 0 &&
+               strcmp(str, "pessimistic") != 0) {
+      // We accept "pessimistic" and "optimistic" as synonyms for "on"
+      // for backwards compatibility.
+      return OptionFailure("ion-gvn", str);
+    }
+  }
+
+  if (const char* str = op.getStringOption("ion-licm")) {
+    if (strcmp(str, "on") == 0) {
+      jit::JitOptions.disableLicm = false;
+    } else if (strcmp(str, "off") == 0) {
+      jit::JitOptions.disableLicm = true;
+    } else {
+      return OptionFailure("ion-licm", str);
+    }
+  }
+
+  if (const char* str = op.getStringOption("ion-edgecase-analysis")) {
+    if (strcmp(str, "on") == 0) {
+      jit::JitOptions.disableEdgeCaseAnalysis = false;
+    } else if (strcmp(str, "off") == 0) {
+      jit::JitOptions.disableEdgeCaseAnalysis = true;
+    } else {
+      return OptionFailure("ion-edgecase-analysis", str);
+    }
+  }
+
+  if (const char* str = op.getStringOption("ion-pruning")) {
+    if (strcmp(str, "on") == 0) {
+      jit::JitOptions.disablePruning = false;
+    } else if (strcmp(str, "off") == 0) {
+      jit::JitOptions.disablePruning = true;
+    } else {
+      return OptionFailure("ion-pruning", str);
+    }
+  }
+
+  if (const char* str = op.getStringOption("ion-range-analysis")) {
+    if (strcmp(str, "on") == 0) {
+      jit::JitOptions.disableRangeAnalysis = false;
+    } else if (strcmp(str, "off") == 0) {
+      jit::JitOptions.disableRangeAnalysis = true;
+    } else {
+      return OptionFailure("ion-range-analysis", str);
+    }
+  }
+
+  if (const char* str = op.getStringOption("ion-sink")) {
+    if (strcmp(str, "on") == 0) {
+      jit::JitOptions.disableSink = false;
+    } else if (strcmp(str, "off") == 0) {
+      jit::JitOptions.disableSink = true;
+    } else {
+      return OptionFailure("ion-sink", str);
+    }
+  }
+
+  if (const char* str = op.getStringOption("ion-optimize-shapeguards")) {
+    if (strcmp(str, "on") == 0) {
+      jit::JitOptions.disableRedundantShapeGuards = false;
+    } else if (strcmp(str, "off") == 0) {
+      jit::JitOptions.disableRedundantShapeGuards = true;
+    } else {
+      return OptionFailure("ion-optimize-shapeguards", str);
+    }
+  }
+
+  if (const char* str = op.getStringOption("ion-instruction-reordering")) {
+    if (strcmp(str, "on") == 0) {
+      jit::JitOptions.disableInstructionReordering = false;
+    } else if (strcmp(str, "off") == 0) {
+      jit::JitOptions.disableInstructionReordering = true;
+    } else {
+      return OptionFailure("ion-instruction-reordering", str);
+    }
+  }
+
+  if (op.getBoolOption("ion-check-range-analysis")) {
+    jit::JitOptions.checkRangeAnalysis = true;
+  }
+
+  if (op.getBoolOption("ion-extra-checks")) {
+    jit::JitOptions.runExtraChecks = true;
+  }
+
+  if (const char* str = op.getStringOption("ion-inlining")) {
+    if (strcmp(str, "on") == 0) {
+      jit::JitOptions.disableInlining = false;
+    } else if (strcmp(str, "off") == 0) {
+      jit::JitOptions.disableInlining = true;
+    } else {
+      return OptionFailure("ion-inlining", str);
+    }
+  }
+
+  if (const char* str = op.getStringOption("ion-osr")) {
+    if (strcmp(str, "on") == 0) {
+      jit::JitOptions.osr = true;
+    } else if (strcmp(str, "off") == 0) {
+      jit::JitOptions.osr = false;
+    } else {
+      return OptionFailure("ion-osr", str);
+    }
+  }
+
+  if (const char* str = op.getStringOption("ion-limit-script-size")) {
+    if (strcmp(str, "on") == 0) {
+      jit::JitOptions.limitScriptSize = true;
+    } else if (strcmp(str, "off") == 0) {
+      jit::JitOptions.limitScriptSize = false;
+    } else {
+      return OptionFailure("ion-limit-script-size", str);
+    }
+  }
+
+  int32_t warmUpThreshold = op.getIntOption("ion-warmup-threshold");
+  if (warmUpThreshold >= 0) {
+    jit::JitOptions.setNormalIonWarmUpThreshold(warmUpThreshold);
+  }
+
+  warmUpThreshold = op.getIntOption("baseline-warmup-threshold");
+  if (warmUpThreshold >= 0) {
+    jit::JitOptions.baselineJitWarmUpThreshold = warmUpThreshold;
+  }
+
+  warmUpThreshold = op.getIntOption("trial-inlining-warmup-threshold");
+  if (warmUpThreshold >= 0) {
+    jit::JitOptions.trialInliningWarmUpThreshold = warmUpThreshold;
+  }
+
+  warmUpThreshold = op.getIntOption("regexp-warmup-threshold");
+  if (warmUpThreshold >= 0) {
+    jit::JitOptions.regexpWarmUpThreshold = warmUpThreshold;
+  }
+
+  if (op.getBoolOption("baseline-eager")) {
+    jit::JitOptions.setEagerBaselineCompilation();
+  }
+
+  if (op.getBoolOption("blinterp")) {
+    jit::JitOptions.baselineInterpreter = true;
+  }
+
+  if (op.getBoolOption("no-blinterp")) {
+    jit::JitOptions.baselineInterpreter = false;
+  }
+
+  warmUpThreshold = op.getIntOption("blinterp-warmup-threshold");
+  if (warmUpThreshold >= 0) {
+    jit::JitOptions.baselineInterpreterWarmUpThreshold = warmUpThreshold;
+  }
+
+  if (op.getBoolOption("blinterp-eager")) {
+    jit::JitOptions.baselineInterpreterWarmUpThreshold = 0;
+  }
+
+  if (op.getBoolOption("no-baseline")) {
+    jit::JitOptions.baselineJit = false;
+  }
+
+  if (op.getBoolOption("no-ion")) {
+    jit::JitOptions.ion = false;
+  }
+
+  if (op.getBoolOption("no-native-regexp")) {
+    jit::JitOptions.nativeRegExp = false;
+  }
+
+  if (op.getBoolOption("trace-regexp-parser")) {
+    jit::JitOptions.trace_regexp_parser = true;
+  }
+  if (op.getBoolOption("trace-regexp-assembler")) {
+    jit::JitOptions.trace_regexp_assembler = true;
+  }
+  if (op.getBoolOption("trace-regexp-interpreter")) {
+    jit::JitOptions.trace_regexp_bytecodes = true;
+  }
+  if (op.getBoolOption("trace-regexp-peephole")) {
+    jit::JitOptions.trace_regexp_peephole_optimization = true;
+  }
+
+  if (op.getBoolOption("less-debug-code")) {
+    jit::JitOptions.lessDebugCode = true;
+  }
+
+  int32_t inliningEntryThreshold = op.getIntOption("inlining-entry-threshold");
+  if (inliningEntryThreshold > 0) {
+    jit::JitOptions.inliningEntryThreshold = inliningEntryThreshold;
+  }
+
+  int32_t smallFunctionLength = op.getIntOption("small-function-length");
+  if (smallFunctionLength > 0) {
+    jit::JitOptions.smallFunctionMaxBytecodeLength = smallFunctionLength;
+  }
+
+  if (const char* str = op.getStringOption("ion-regalloc")) {
+    jit::JitOptions.forcedRegisterAllocator = jit::LookupRegisterAllocator(str);
+    if (!jit::JitOptions.forcedRegisterAllocator.isSome()) {
+      return OptionFailure("ion-regalloc", str);
+    }
+  }
+
+  if (op.getBoolOption("ion-eager")) {
+    jit::JitOptions.setEagerIonCompilation();
+  }
+
+  offthreadCompilation = true;
+  if (const char* str = op.getStringOption("ion-offthread-compile")) {
+    if (strcmp(str, "off") == 0) {
+      offthreadCompilation = false;
+    } else if (strcmp(str, "on") != 0) {
+      return OptionFailure("ion-offthread-compile", str);
+    }
+  }
+  cx->runtime()->setOffthreadIonCompilationEnabled(offthreadCompilation);
+
+  if (op.getStringOption("ion-parallel-compile")) {
+    fprintf(stderr,
+            "--ion-parallel-compile is deprecated. Please use "
+            "--ion-offthread-compile instead.\n");
+    return false;
+  }
+
+  if (const char* str = op.getStringOption("shared-memory")) {
+    if (strcmp(str, "off") == 0) {
+      enableSharedMemory = false;
+    } else if (strcmp(str, "on") == 0) {
+      enableSharedMemory = true;
+    } else {
+      return OptionFailure("shared-memory", str);
+    }
+  }
+
+  if (op.getBoolOption("disable-bailout-loop-check")) {
+    jit::JitOptions.disableBailoutLoopCheck = true;
+  }
+
+  if (op.getBoolOption("enable-watchtower")) {
+    jit::JitOptions.enableWatchtowerMegamorphic = true;
+  }
+  if (op.getBoolOption("disable-watchtower")) {
+    jit::JitOptions.enableWatchtowerMegamorphic = false;
+  }
+
+#if defined(JS_SIMULATOR_ARM)
+  if (op.getBoolOption("arm-sim-icache-checks")) {
+    jit::SimulatorProcess::ICacheCheckingDisableCount = 0;
+  }
+
+  int32_t stopAt = op.getIntOption("arm-sim-stop-at");
+  if (stopAt >= 0) {
+    jit::Simulator::StopSimAt = stopAt;
+  }
+#elif defined(JS_SIMULATOR_MIPS32) || defined(JS_SIMULATOR_MIPS64)
+  if (op.getBoolOption("mips-sim-icache-checks")) {
+    jit::SimulatorProcess::ICacheCheckingDisableCount = 0;
+  }
+
+  int32_t stopAt = op.getIntOption("mips-sim-stop-at");
+  if (stopAt >= 0) {
+    jit::Simulator::StopSimAt = stopAt;
+  }
+#elif defined(JS_SIMULATOR_LOONG64)
+  if (op.getBoolOption("loong64-sim-icache-checks")) {
+    jit::SimulatorProcess::ICacheCheckingDisableCount = 0;
+  }
+
+  int32_t stopAt = op.getIntOption("loong64-sim-stop-at");
+  if (stopAt >= 0) {
+    jit::Simulator::StopSimAt = stopAt;
+  }
+#endif
+
+  reportWarnings = op.getBoolOption('w');
+  compileOnly = op.getBoolOption('c');
+  printTiming = op.getBoolOption('b');
+  enableDisassemblyDumps = op.getBoolOption('D');
+  cx->runtime()->profilingScripts =
+      enableCodeCoverage || enableDisassemblyDumps;
+
+#ifdef DEBUG
+  dumpEntrainedVariables = op.getBoolOption("dump-entrained-variables");
+#endif
+
+#ifdef JS_GC_ZEAL
+  const char* zealStr = op.getStringOption("gc-zeal");
+  if (zealStr) {
+    if (!cx->runtime()->gc.parseAndSetZeal(zealStr)) {
+      return false;
+    }
+    uint32_t nextScheduled;
+    cx->runtime()->gc.getZealBits(&gZealBits, &gZealFrequency, &nextScheduled);
+  }
+#endif
+
+  return true;
+}
+
+static void SetWorkerContextOptions(JSContext* cx) {
+  // Copy option values from the main thread.
+  JS::ContextOptionsRef(cx)
+      .setAsmJS(enableAsmJS)
+      .setWasm(enableWasm)
+      .setWasmBaseline(enableWasmBaseline)
+      .setWasmIon(enableWasmOptimizing)
+#define WASM_FEATURE(NAME, ...) .setWasm##NAME(enableWasm##NAME)
+          JS_FOR_WASM_FEATURES(WASM_FEATURE, WASM_FEATURE, WASM_FEATURE)
+#undef WASM_FEATURE
+
+      .setWasmVerbose(enableWasmVerbose)
+      .setTestWasmAwaitTier2(enableTestWasmAwaitTier2)
+      .setSourcePragmas(enableSourcePragmas);
+
+  cx->runtime()->setOffthreadIonCompilationEnabled(offthreadCompilation);
+  cx->runtime()->profilingScripts =
+      enableCodeCoverage || enableDisassemblyDumps;
+
+#ifdef JS_GC_ZEAL
+  if (gZealBits && gZealFrequency) {
+    for (size_t i = 0; i < size_t(gc::ZealMode::Count); i++) {
+      if (gZealBits & (1 << i)) {
+        cx->runtime()->gc.setZeal(i, gZealFrequency);
+      }
+    }
+  }
+#endif
+
+  JS_SetNativeStackQuota(cx, gWorkerStackSize);
+}
+
+[[nodiscard]] static bool PrintUnhandledRejection(
+    JSContext* cx, Handle<PromiseObject*> promise) {
+  RootedValue reason(cx, promise->reason());
+  RootedObject site(cx, promise->resolutionSite());
+
+  RootedString str(cx, JS_ValueToSource(cx, reason));
+  if (!str) {
+    return false;
+  }
+
+  UniqueChars utf8chars = JS_EncodeStringToUTF8(cx, str);
+  if (!utf8chars) {
+    return false;
+  }
+
+  FILE* fp = ErrorFilePointer();
+  fprintf(fp, "Unhandled rejection: %s\n", utf8chars.get());
+
+  if (!site) {
+    fputs("(no stack trace available)\n", stderr);
+    return true;
+  }
+
+  JSPrincipals* principals = cx->realm()->principals();
+  RootedString stackStr(cx);
+  if (!BuildStackString(cx, principals, site, &stackStr, 2)) {
+    return false;
+  }
+
+  UniqueChars stack = JS_EncodeStringToUTF8(cx, stackStr);
+  if (!stack) {
+    return false;
+  }
+
+  fputs("Stack:\n", fp);
+  fputs(stack.get(), fp);
+
+  return true;
+}
+
+[[nodiscard]] static bool ReportUnhandledRejections(JSContext* cx) {
+  ShellContext* sc = GetShellContext(cx);
+  if (!sc->trackUnhandledRejections) {
+    return true;
+  }
+
+  if (!sc->unhandledRejectedPromises) {
+    return true;
+  }
+
+  AutoRealm ar(cx, sc->unhandledRejectedPromises);
+
+  if (!SetObject::size(cx, sc->unhandledRejectedPromises)) {
+    return true;
+  }
+
+  sc->exitCode = EXITCODE_RUNTIME_ERROR;
+
+  RootedValue iter(cx);
+  if (!SetObject::iterator(cx, SetObject::IteratorKind::Values,
+                           sc->unhandledRejectedPromises, &iter)) {
+    return false;
+  }
+
+  Rooted<SetIteratorObject*> iterObj(cx,
+                                     &iter.toObject().as<SetIteratorObject>());
+  JSObject* obj = SetIteratorObject::createResult(cx);
+  if (!obj) {
+    return false;
+  }
+
+  Rooted<ArrayObject*> resultObj(cx, &obj->as<ArrayObject>());
+  while (true) {
+    bool done = SetIteratorObject::next(iterObj, resultObj);
+    if (done) {
+      break;
+    }
+
+    RootedObject obj(cx, &resultObj->getDenseElement(0).toObject());
+    Rooted<PromiseObject*> promise(cx, obj->maybeUnwrapIf<PromiseObject>());
+    if (!promise) {
+      FILE* fp = ErrorFilePointer();
+      fputs(
+          "Unhandled rejection: dead proxy found in unhandled "
+          "rejections set\n",
+          fp);
+      continue;
+    }
+
+    AutoRealm ar2(cx, promise);
+
+    if (!PrintUnhandledRejection(cx, promise)) {
+      return false;
+    }
+  }
+
+  sc->unhandledRejectedPromises = nullptr;
+
+  return true;
+}
+
+static int Shell(JSContext* cx, OptionParser* op) {
+#ifdef JS_STRUCTURED_SPEW
+  cx->spewer().enableSpewing();
+#endif
+
+  auto exitShell = MakeScopeExit([&] {
+#ifdef JS_STRUCTURED_SPEW
+    cx->spewer().disableSpewing();
+#endif
+  });
+
+  if (op->getBoolOption("wasm-compile-and-serialize")) {
+#ifdef __wasi__
+    MOZ_CRASH("WASI doesn't support wasm");
+#else
+    if (!WasmCompileAndSerialize(cx)) {
+      // Errors have been printed directly to stderr.
+      MOZ_ASSERT(!cx->isExceptionPending());
+      return -1;
+    }
+#endif
+    return EXIT_SUCCESS;
+  }
+
+#ifdef MOZ_CODE_COVERAGE
+  InstallCoverageSignalHandlers();
+#endif
+
+  Maybe<JS::AutoDisableGenerationalGC> noggc;
+  if (op->getBoolOption("no-ggc")) {
+    noggc.emplace(cx);
+  }
+
+  Maybe<AutoDisableCompactingGC> nocgc;
+  if (op->getBoolOption("no-cgc")) {
+    nocgc.emplace(cx);
+  }
+
+  if (op->getBoolOption("fuzzing-safe")) {
+    fuzzingSafe = true;
+  } else {
+    fuzzingSafe =
+        (getenv("MOZ_FUZZING_SAFE") && getenv("MOZ_FUZZING_SAFE")[0] != '0');
+  }
+
+#ifdef DEBUG
+  if (op->getBoolOption("differential-testing")) {
+    JS::SetSupportDifferentialTesting(true);
+  }
+#endif
+
+  if (op->getBoolOption("disable-oom-functions")) {
+    disableOOMFunctions = true;
+  }
+
+  if (op->getBoolOption("more-compartments")) {
+    defaultToSameCompartment = false;
+  }
+
+  bool reprl_mode = FuzzilliUseReprlMode(op);
+
+  // Begin REPRL Loop
+  int result = EXIT_SUCCESS;
+  do {
+    JS::RealmOptions options;
+    SetStandardRealmOptions(options);
+    RootedObject glob(
+        cx, NewGlobalObject(cx, options, nullptr, ShellGlobalKind::WindowProxy,
+                            /* immutablePrototype = */ true));
+    if (!glob) {
+      return 1;
+    }
+
+    JSAutoRealm ar(cx, glob);
+
+#ifdef FUZZING_INTERFACES
+    if (fuzzHaveModule) {
+      return FuzzJSRuntimeStart(cx, &sArgc, &sArgv);
+    }
+#endif
+
+    ShellContext* sc = GetShellContext(cx);
+    sc->exitCode = 0;
+    result = EXIT_SUCCESS;
+    {
+      AutoReportException are(cx);
+      if (!ProcessArgs(cx, op) && !sc->quitting) {
+        result = EXITCODE_RUNTIME_ERROR;
+      }
+    }
+
+    /*
+     * The job queue must be drained even on error to finish outstanding async
+     * tasks before the main thread JSRuntime is torn down. Drain after
+     * uncaught exceptions have been reported since draining runs callbacks.
+     */
+    RunShellJobs(cx);
+
+    // Only if there's no other error, report unhandled rejections.
+    if (!result && !sc->exitCode) {
+      AutoReportException are(cx);
+      if (!ReportUnhandledRejections(cx)) {
+        FILE* fp = ErrorFilePointer();
+        fputs("Error while printing unhandled rejection\n", fp);
+      }
+    }
+
+    if (sc->exitCode) {
+      result = sc->exitCode;
+    }
+
+#ifdef FUZZING_JS_FUZZILLI
+    if (reprl_mode) {
+      fflush(stdout);
+      fflush(stderr);
+      // Send return code to parent and reset edge counters.
+      struct {
+        int status;
+        uint32_t execHash;
+        uint32_t execHashInputs;
+      } s;
+      s.status = (result & 0xff) << 8;
+      s.execHash = cx->executionHash;
+      s.execHashInputs = cx->executionHashInputs;
+      MOZ_RELEASE_ASSERT(write(REPRL_CWFD, &s, 12) == 12);
+      __sanitizer_cov_reset_edgeguards();
+      cx->executionHash = 1;
+      cx->executionHashInputs = 0;
+    }
+#endif
+
+    if (enableDisassemblyDumps) {
+      AutoReportException are(cx);
+      if (!js::DumpRealmPCCounts(cx)) {
+        result = EXITCODE_OUT_OF_MEMORY;
+      }
+    }
+
+    // End REPRL loop
+  } while (reprl_mode);
+
+  return result;
+}
+
+// Used to allocate memory when jemalloc isn't yet initialized.
+JS_DECLARE_NEW_METHODS(SystemAlloc_New, malloc, static)
+
+static void SetOutputFile(const char* const envVar, RCFile* defaultOut,
+                          RCFile** outFileP) {
+  RCFile* outFile;
+
+  const char* outPath = getenv(envVar);
+  FILE* newfp;
+  if (outPath && *outPath && (newfp = fopen(outPath, "w"))) {
+    outFile = SystemAlloc_New<RCFile>(newfp);
+  } else {
+    outFile = defaultOut;
+  }
+
+  if (!outFile) {
+    MOZ_CRASH("Failed to allocate output file");
+  }
+
+  outFile->acquire();
+  *outFileP = outFile;
+}
+
+static void PreInit() {
+#ifdef XP_WIN
+  const char* crash_option = getenv("XRE_NO_WINDOWS_CRASH_DIALOG");
+  if (crash_option && crash_option[0] == '1') {
+    // Disable the segfault dialog. We want to fail the tests immediately
+    // instead of hanging automation.
+    UINT newMode = SEM_NOGPFAULTERRORBOX | SEM_NOOPENFILEERRORBOX;
+    UINT prevMode = SetErrorMode(newMode);
+    SetErrorMode(prevMode | newMode);
+  }
+#endif
+}
+
+#ifndef JS_WITHOUT_NSPR
+class AutoLibraryLoader {
+  Vector<PRLibrary*, 4, SystemAllocPolicy> libraries;
+
+ public:
+  ~AutoLibraryLoader() {
+    for (auto dll : libraries) {
+      PR_UnloadLibrary(dll);
+    }
+  }
+
+  PRLibrary* load(const char* path) {
+    PRLibSpec libSpec;
+    libSpec.type = PR_LibSpec_Pathname;
+    libSpec.value.pathname = path;
+    PRLibrary* dll = PR_LoadLibraryWithFlags(libSpec, PR_LD_NOW | PR_LD_GLOBAL);
+    if (!dll) {
+      fprintf(stderr, "LoadLibrary '%s' failed with code %d\n", path,
+              PR_GetError());
+      MOZ_CRASH("Failed to load library");
+    }
+
+    MOZ_ALWAYS_TRUE(libraries.append(dll));
+    return dll;
+  }
+};
+#endif
+
+static bool ReadSelfHostedXDRFile(JSContext* cx, FileContents& buf) {
+  FILE* file = fopen(selfHostedXDRPath, "rb");
+  if (!file) {
+    fprintf(stderr, "Can't open self-hosted stencil XDR file.\n");
+    return false;
+  }
+  AutoCloseFile autoClose(file);
+
+  struct stat st;
+  if (fstat(fileno(file), &st) < 0) {
+    fprintf(stderr, "Unable to stat self-hosted stencil XDR file.\n");
+    return false;
+  }
+
+  if (st.st_size >= INT32_MAX) {
+    fprintf(stderr, "self-hosted stencil XDR file too large.\n");
+    return false;
+  }
+  uint32_t filesize = uint32_t(st.st_size);
+
+  if (!buf.growBy(filesize)) {
+    return false;
+  }
+  size_t cc = fread(buf.begin(), 1, filesize, file);
+  if (cc != filesize) {
+    fprintf(stderr, "Short read on self-hosted stencil XDR file.\n");
+    return false;
+  }
+
+  return true;
+}
+
+static bool WriteSelfHostedXDRFile(JSContext* cx, JS::SelfHostedCache buffer) {
+  FILE* file = fopen(selfHostedXDRPath, "wb");
+  if (!file) {
+    JS_ReportErrorUTF8(cx, "Can't open self-hosted stencil XDR file.");
+    return false;
+  }
+  AutoCloseFile autoClose(file);
+
+  size_t cc = fwrite(buffer.Elements(), 1, buffer.LengthBytes(), file);
+  if (cc != buffer.LengthBytes()) {
+    JS_ReportErrorUTF8(cx, "Short write on self-hosted stencil XDR file.");
+    return false;
+  }
+
+  return true;
+}
+
+static bool SetGCParameterFromArg(JSContext* cx, char* arg) {
+  char* c = strchr(arg, '=');
+  if (!c) {
+    fprintf(stderr,
+            "Error: --gc-param argument '%s' must be of the form "
+            "name=decimalValue\n",
+            arg);
+    return false;
+  }
+
+  *c = '\0';
+  const char* name = arg;
+  const char* valueStr = c + 1;
+
+  JSGCParamKey key;
+  bool writable;
+  if (!GetGCParameterInfo(name, &key, &writable)) {
+    fprintf(stderr, "Error: Unknown GC parameter name '%s'\n", name);
+    fprintf(stderr, "Writable GC parameter names are:\n");
+#define PRINT_WRITABLE_PARAM_NAME(name, _, writable) \
+  if (writable) {                                    \
+    fprintf(stderr, "  %s\n", name);                 \
+  }
+    FOR_EACH_GC_PARAM(PRINT_WRITABLE_PARAM_NAME)
+#undef PRINT_WRITABLE_PARAM_NAME
+    return false;
+  }
+
+  if (!writable) {
+    fprintf(stderr, "Error: GC parameter '%s' is not writable\n", name);
+    return false;
+  }
+
+  char* end = nullptr;
+  unsigned long int value = strtoul(valueStr, &end, 10);
+  if (end == valueStr || *end) {
+    fprintf(stderr,
+            "Error: Could not parse '%s' as decimal for GC parameter '%s'\n",
+            valueStr, name);
+    return false;
+  }
+
+  uint32_t paramValue = uint32_t(value);
+  if (value == ULONG_MAX || value != paramValue ||
+      !cx->runtime()->gc.setParameter(cx, key, paramValue)) {
+    fprintf(stderr, "Error: Value %s is out of range for GC parameter '%s'\n",
+            valueStr, name);
+    return false;
+  }
+
+  return true;
+}
+
+int main(int argc, char** argv) {
+  PreInit();
+
+  sArgc = argc;
+  sArgv = argv;
+
+  int result;
+
+  setlocale(LC_ALL, "");
+
+  // Special-case stdout and stderr. We bump their refcounts to prevent them
+  // from getting closed and then having some printf fail somewhere.
+  RCFile rcStdout(stdout);
+  rcStdout.acquire();
+  RCFile rcStderr(stderr);
+  rcStderr.acquire();
+
+  SetOutputFile("JS_STDOUT", &rcStdout, &gOutFile);
+  SetOutputFile("JS_STDERR", &rcStderr, &gErrFile);
+
+  OptionParser op("Usage: {progname} [options] [[script] scriptArgs*]");
+
+  op.setDescription(
+      "The SpiderMonkey shell provides a command line interface to the "
+      "JavaScript engine. Code and file options provided via the command line "
+      "are "
+      "run left to right. If provided, the optional script argument is run "
+      "after "
+      "all options have been processed. Just-In-Time compilation modes may be "
+      "enabled via "
+      "command line options.");
+  op.setDescriptionWidth(72);
+  op.setHelpWidth(80);
+  op.setVersion(JS_GetImplementationVersion());
+
+  if (!op.addMultiStringOption(
+          'f', "file", "PATH",
+          "File path to run, parsing file contents as UTF-8") ||
+      !op.addMultiStringOption(
+          'u', "utf16-file", "PATH",
+          "File path to run, inflating the file's UTF-8 contents to UTF-16 and "
+          "then parsing that") ||
+      !op.addMultiStringOption('m', "module", "PATH", "Module path to run") ||
+      !op.addMultiStringOption('p', "prelude", "PATH", "Prelude path to run") ||
+      !op.addMultiStringOption('e', "execute", "CODE", "Inline code to run") ||
+      !op.addStringOption('\0', "selfhosted-xdr-path", "[filename]",
+                          "Read/Write selfhosted script data from/to the given "
+                          "XDR file") ||
+      !op.addStringOption('\0', "selfhosted-xdr-mode", "(encode,decode,off)",
+                          "Whether to encode/decode data of the file provided"
+                          "with --selfhosted-xdr-path.") ||
+      !op.addBoolOption('i', "shell", "Enter prompt after running code") ||
+      !op.addBoolOption('c', "compileonly",
+                        "Only compile, don't run (syntax checking mode)") ||
+      !op.addBoolOption('w', "warnings", "Emit warnings") ||
+      !op.addBoolOption('W', "nowarnings", "Don't emit warnings") ||
+      !op.addBoolOption('D', "dump-bytecode",
+                        "Dump bytecode with exec count for all scripts") ||
+      !op.addBoolOption('b', "print-timing",
+                        "Print sub-ms runtime for each file that's run") ||
+      !op.addBoolOption('\0', "code-coverage",
+                        "Enable code coverage instrumentation.") ||
+      !op.addBoolOption(
+          '\0', "disable-parser-deferred-alloc",
+          "Disable deferred allocation of GC objects until after parser") ||
+#ifdef DEBUG
+      !op.addBoolOption('O', "print-alloc",
+                        "Print the number of allocations at exit") ||
+#endif
+      !op.addOptionalStringArg("script",
+                               "A script to execute (after all options)") ||
+      !op.addOptionalMultiStringArg(
+          "scriptArgs",
+          "String arguments to bind as |scriptArgs| in the "
+          "shell's global") ||
+      !op.addIntOption(
+          '\0', "cpu-count", "COUNT",
+          "Set the number of CPUs (hardware threads) to COUNT, the "
+          "default is the actual number of CPUs. The total number of "
+          "background helper threads is the CPU count plus some constant.",
+          -1) ||
+      !op.addIntOption('\0', "thread-count", "COUNT", "Alias for --cpu-count.",
+                       -1) ||
+      !op.addBoolOption('\0', "ion", "Enable IonMonkey (default)") ||
+      !op.addBoolOption('\0', "no-ion", "Disable IonMonkey") ||
+      !op.addBoolOption('\0', "no-ion-for-main-context",
+                        "Disable IonMonkey for the main context only") ||
+      !op.addIntOption('\0', "inlining-entry-threshold", "COUNT",
+                       "The minimum stub entry count before trial-inlining a"
+                       " call",
+                       -1) ||
+      !op.addIntOption('\0', "small-function-length", "COUNT",
+                       "The maximum bytecode length of a 'small function' for "
+                       "the purpose of inlining.",
+                       -1) ||
+      !op.addBoolOption('\0', "no-asmjs", "Disable asm.js compilation") ||
+      !op.addStringOption(
+          '\0', "wasm-compiler", "[option]",
+          "Choose to enable a subset of the wasm compilers, valid options are "
+          "'none', 'baseline', 'ion', 'optimizing', "
+          "'baseline+ion', 'baseline+optimizing'.") ||
+      !op.addBoolOption('\0', "wasm-verbose",
+                        "Enable WebAssembly verbose logging") ||
+      !op.addBoolOption('\0', "disable-wasm-huge-memory",
+                        "Disable WebAssembly huge memory") ||
+      !op.addBoolOption('\0', "test-wasm-await-tier2",
+                        "Forcibly activate tiering and block "
+                        "instantiation on completion of tier2") ||
+#define WASM_DEFAULT_FEATURE(NAME, LOWER_NAME, COMPILE_PRED, COMPILER_PRED, \
+                             FLAG_PRED, SHELL, ...)                         \
+  !op.addBoolOption('\0', "no-wasm-" SHELL, "Disable wasm " SHELL "feature.") ||
+#define WASM_TENTATIVE_FEATURE(NAME, LOWER_NAME, COMPILE_PRED, COMPILER_PRED, \
+                               FLAG_PRED, SHELL, ...)                         \
+  !op.addBoolOption('\0', "no-wasm-" SHELL,                                   \
+                    "Disable wasm " SHELL "feature.") ||                      \
+      !op.addBoolOption('\0', "wasm-" SHELL, "No-op.") ||
+#define WASM_EXPERIMENTAL_FEATURE(NAME, LOWER_NAME, COMPILE_PRED,       \
+                                  COMPILER_PRED, FLAG_PRED, SHELL, ...) \
+  !op.addBoolOption('\0', "wasm-" SHELL,                                \
+                    "Enable experimental wasm " SHELL "feature.") ||    \
+      !op.addBoolOption('\0', "no-wasm-" SHELL, "No-op.") ||
+      JS_FOR_WASM_FEATURES(WASM_DEFAULT_FEATURE, WASM_TENTATIVE_FEATURE,
+                           WASM_EXPERIMENTAL_FEATURE)
+#undef WASM_DEFAULT_FEATURE
+#undef WASM_TENTATIVE_FEATURE
+#undef WASM_EXPERIMENTAL_FEATURE
+          !op.addBoolOption('\0', "no-native-regexp",
+                            "Disable native regexp compilation") ||
+      !op.addIntOption(
+          '\0', "regexp-warmup-threshold", "COUNT",
+          "Wait for COUNT invocations before compiling regexps to native code "
+          "(default 10)",
+          -1) ||
+      !op.addBoolOption('\0', "trace-regexp-parser", "Trace regexp parsing") ||
+      !op.addBoolOption('\0', "trace-regexp-assembler",
+                        "Trace regexp assembler") ||
+      !op.addBoolOption('\0', "trace-regexp-interpreter",
+                        "Trace regexp interpreter") ||
+      !op.addBoolOption('\0', "trace-regexp-peephole",
+                        "Trace regexp peephole optimization") ||
+      !op.addBoolOption('\0', "less-debug-code",
+                        "Emit less machine code for "
+                        "checking assertions under DEBUG.") ||
+      !op.addBoolOption('\0', "disable-weak-refs", "Disable weak references") ||
+      !op.addBoolOption('\0', "disable-tosource", "Disable toSource/uneval") ||
+      !op.addBoolOption('\0', "disable-property-error-message-fix",
+                        "Disable fix for the error message when accessing "
+                        "property of null or undefined") ||
+      !op.addBoolOption('\0', "enable-iterator-helpers",
+                        "Enable iterator helpers") ||
+      !op.addBoolOption('\0', "enable-shadow-realms", "Enable ShadowRealms") ||
+      !op.addBoolOption('\0', "enable-array-grouping",
+                        "Enable Array.fromAsync") ||
+      !op.addBoolOption('\0', "enable-array-from-async",
+                        "Enable Array Grouping") ||
+#ifdef ENABLE_CHANGE_ARRAY_BY_COPY
+      !op.addBoolOption('\0', "enable-change-array-by-copy",
+                        "Enable change-array-by-copy methods") ||
+      !op.addBoolOption('\0', "disable-change-array-by-copy",
+                        "Disable change-array-by-copy methods") ||
+#else
+      !op.addBoolOption('\0', "enable-change-array-by-copy", "no-op") ||
+      !op.addBoolOption('\0', "disable-change-array-by-copy", "no-op") ||
+#endif
+#ifdef ENABLE_NEW_SET_METHODS
+      !op.addBoolOption('\0', "enable-new-set-methods",
+                        "Enable New Set methods") ||
+      !op.addBoolOption('\0', "disable-new-set-methods",
+                        "Disable New Set methods") ||
+#else
+      !op.addBoolOption('\0', "enable-new-set-methods", "no-op") ||
+      !op.addBoolOption('\0', "disable-new-set-methods", "no-op") ||
+#endif
+      !op.addBoolOption('\0', "enable-top-level-await",
+                        "Enable top-level await") ||
+      !op.addBoolOption('\0', "enable-class-static-blocks",
+                        "(no-op) Enable class static blocks") ||
+      !op.addBoolOption('\0', "enable-import-assertions",
+                        "Enable import assertions") ||
+      !op.addStringOption('\0', "shared-memory", "on/off",
+                          "SharedArrayBuffer and Atomics "
+#if SHARED_MEMORY_DEFAULT
+                          "(default: on, off to disable)"
+#else
+                          "(default: off, on to enable)"
+#endif
+                          ) ||
+      !op.addStringOption('\0', "spectre-mitigations", "on/off",
+                          "Whether Spectre mitigations are enabled (default: "
+                          "off, on to enable)") ||
+      !op.addStringOption('\0', "cache-ir-stubs", "on/off/call",
+                          "Use CacheIR stubs (default: on, off to disable, "
+                          "call to enable work-in-progress call ICs)") ||
+      !op.addStringOption('\0', "ion-shared-stubs", "on/off",
+                          "Use shared stubs (default: on, off to disable)") ||
+      !op.addStringOption('\0', "ion-scalar-replacement", "on/off",
+                          "Scalar Replacement (default: on, off to disable)") ||
+      !op.addStringOption('\0', "ion-gvn", "[mode]",
+                          "Specify Ion global value numbering:\n"
+                          "  off: disable GVN\n"
+                          "  on:  enable GVN (default)\n") ||
+      !op.addStringOption(
+          '\0', "ion-licm", "on/off",
+          "Loop invariant code motion (default: on, off to disable)") ||
+      !op.addStringOption('\0', "ion-edgecase-analysis", "on/off",
+                          "Find edge cases where Ion can avoid bailouts "
+                          "(default: on, off to disable)") ||
+      !op.addStringOption('\0', "ion-pruning", "on/off",
+                          "Branch pruning (default: on, off to disable)") ||
+      !op.addStringOption('\0', "ion-range-analysis", "on/off",
+                          "Range analysis (default: on, off to disable)") ||
+      !op.addStringOption('\0', "ion-sink", "on/off",
+                          "Sink code motion (default: off, on to enable)") ||
+      !op.addStringOption('\0', "ion-optimization-levels", "on/off",
+                          "No-op for fuzzing") ||
+      !op.addStringOption('\0', "ion-loop-unrolling", "on/off",
+                          "(NOP for fuzzers)") ||
+      !op.addStringOption(
+          '\0', "ion-instruction-reordering", "on/off",
+          "Instruction reordering (default: off, on to enable)") ||
+      !op.addStringOption(
+          '\0', "ion-optimize-shapeguards", "on/off",
+          "Eliminate redundant shape guards (default: on, off to disable)") ||
+      !op.addBoolOption('\0', "ion-check-range-analysis",
+                        "Range analysis checking") ||
+      !op.addBoolOption('\0', "ion-extra-checks",
+                        "Perform extra dynamic validation checks") ||
+      !op.addStringOption(
+          '\0', "ion-inlining", "on/off",
+          "Inline methods where possible (default: on, off to disable)") ||
+      !op.addStringOption(
+          '\0', "ion-osr", "on/off",
+          "On-Stack Replacement (default: on, off to disable)") ||
+      !op.addBoolOption('\0', "disable-bailout-loop-check",
+                        "Turn off bailout loop check") ||
+      !op.addBoolOption('\0', "enable-watchtower",
+                        "Enable Watchtower optimizations") ||
+      !op.addBoolOption('\0', "disable-watchtower",
+                        "Disable Watchtower optimizations") ||
+      !op.addBoolOption('\0', "scalar-replace-arguments",
+                        "Use scalar replacement to optimize ArgumentsObject") ||
+      !op.addStringOption(
+          '\0', "ion-limit-script-size", "on/off",
+          "Don't compile very large scripts (default: on, off to disable)") ||
+      !op.addIntOption('\0', "ion-warmup-threshold", "COUNT",
+                       "Wait for COUNT calls or iterations before compiling "
+                       "at the normal optimization level (default: 1000)",
+                       -1) ||
+      !op.addIntOption('\0', "ion-full-warmup-threshold", "COUNT",
+                       "No-op for fuzzing", -1) ||
+      !op.addStringOption(
+          '\0', "ion-regalloc", "[mode]",
+          "Specify Ion register allocation:\n"
+          "  backtracking: Priority based backtracking register allocation "
+          "(default)\n"
+          "  testbed: Backtracking allocator with experimental features\n"
+          "  stupid: Simple block local register allocation") ||
+      !op.addBoolOption(
+          '\0', "ion-eager",
+          "Always ion-compile methods (implies --baseline-eager)") ||
+      !op.addBoolOption('\0', "fast-warmup",
+                        "Reduce warmup thresholds for each tier.") ||
+      !op.addStringOption('\0', "ion-offthread-compile", "on/off",
+                          "Compile scripts off thread (default: on)") ||
+      !op.addStringOption('\0', "ion-parallel-compile", "on/off",
+                          "--ion-parallel compile is deprecated. Use "
+                          "--ion-offthread-compile.") ||
+      !op.addBoolOption('\0', "baseline",
+                        "Enable baseline compiler (default)") ||
+      !op.addBoolOption('\0', "no-baseline", "Disable baseline compiler") ||
+      !op.addBoolOption('\0', "baseline-eager",
+                        "Always baseline-compile methods") ||
+      !op.addIntOption(
+          '\0', "baseline-warmup-threshold", "COUNT",
+          "Wait for COUNT calls or iterations before baseline-compiling "
+          "(default: 10)",
+          -1) ||
+      !op.addBoolOption('\0', "blinterp",
+                        "Enable Baseline Interpreter (default)") ||
+      !op.addBoolOption('\0', "no-blinterp", "Disable Baseline Interpreter") ||
+      !op.addBoolOption('\0', "blinterp-eager",
+                        "Always Baseline-interpret scripts") ||
+      !op.addIntOption(
+          '\0', "blinterp-warmup-threshold", "COUNT",
+          "Wait for COUNT calls or iterations before Baseline-interpreting "
+          "(default: 10)",
+          -1) ||
+      !op.addIntOption(
+          '\0', "trial-inlining-warmup-threshold", "COUNT",
+          "Wait for COUNT calls or iterations before trial-inlining "
+          "(default: 500)",
+          -1) ||
+      !op.addBoolOption(
+          '\0', "non-writable-jitcode",
+          "(NOP for fuzzers) Allocate JIT code as non-writable memory.") ||
+      !op.addBoolOption(
+          '\0', "no-sse3",
+          "Pretend CPU does not support SSE3 instructions and above "
+          "to test JIT codegen (no-op on platforms other than x86 and x64).") ||
+      !op.addBoolOption(
+          '\0', "no-ssse3",
+          "Pretend CPU does not support SSSE3 [sic] instructions and above "
+          "to test JIT codegen (no-op on platforms other than x86 and x64).") ||
+      !op.addBoolOption(
+          '\0', "no-sse41",
+          "Pretend CPU does not support SSE4.1 instructions "
+          "to test JIT codegen (no-op on platforms other than x86 and x64).") ||
+      !op.addBoolOption('\0', "no-sse4", "Alias for --no-sse41") ||
+      !op.addBoolOption(
+          '\0', "no-sse42",
+          "Pretend CPU does not support SSE4.2 instructions "
+          "to test JIT codegen (no-op on platforms other than x86 and x64).") ||
+#ifdef ENABLE_WASM_AVX
+      !op.addBoolOption('\0', "enable-avx",
+                        "No-op. AVX is enabled by default, if available.") ||
+      !op.addBoolOption(
+          '\0', "no-avx",
+          "Pretend CPU does not support AVX or AVX2 instructions "
+          "to test JIT codegen (no-op on platforms other than x86 and x64).") ||
+#else
+      !op.addBoolOption('\0', "enable-avx",
+                        "AVX is disabled by default. Enable AVX. "
+                        "(no-op on platforms other than x86 and x64).") ||
+      !op.addBoolOption('\0', "no-avx",
+                        "No-op. AVX is currently disabled by default.") ||
+#endif
+      !op.addBoolOption('\0', "more-compartments",
+                        "Make newGlobal default to creating a new "
+                        "compartment.") ||
+      !op.addBoolOption('\0', "fuzzing-safe",
+                        "Don't expose functions that aren't safe for "
+                        "fuzzers to call") ||
+#ifdef DEBUG
+      !op.addBoolOption('\0', "differential-testing",
+                        "Avoid random/undefined behavior that disturbs "
+                        "differential testing (correctness fuzzing)") ||
+#endif
+      !op.addBoolOption('\0', "disable-oom-functions",
+                        "Disable functions that cause "
+                        "artificial OOMs") ||
+      !op.addBoolOption('\0', "no-threads", "Disable helper threads") ||
+      !op.addBoolOption(
+          '\0', "no-jit-backend",
+          "Disable the JIT backend completely for this process") ||
+#ifdef DEBUG
+      !op.addBoolOption('\0', "dump-entrained-variables",
+                        "Print variables which are "
+                        "unnecessarily entrained by inner functions") ||
+#endif
+      !op.addBoolOption('\0', "no-ggc", "Disable Generational GC") ||
+      !op.addBoolOption('\0', "no-cgc", "Disable Compacting GC") ||
+      !op.addBoolOption('\0', "no-incremental-gc", "Disable Incremental GC") ||
+      !op.addBoolOption('\0', "enable-parallel-marking",
+                        "Turn on parallel marking") ||
+      !op.addStringOption('\0', "nursery-strings", "on/off",
+                          "Allocate strings in the nursery") ||
+      !op.addStringOption('\0', "nursery-bigints", "on/off",
+                          "Allocate BigInts in the nursery") ||
+      !op.addIntOption('\0', "available-memory", "SIZE",
+                       "Select GC settings based on available memory (MB)",
+                       0) ||
+      !op.addStringOption('\0', "arm-hwcap", "[features]",
+                          "Specify ARM code generation features, or 'help' to "
+                          "list all features.") ||
+      !op.addIntOption('\0', "arm-asm-nop-fill", "SIZE",
+                       "Insert the given number of NOP instructions at all "
+                       "possible pool locations.",
+                       0) ||
+      !op.addIntOption('\0', "asm-pool-max-offset", "OFFSET",
+                       "The maximum pc relative OFFSET permitted in pool "
+                       "reference instructions.",
+                       1024) ||
+      !op.addBoolOption('\0', "arm-sim-icache-checks",
+                        "Enable icache flush checks in the ARM "
+                        "simulator.") ||
+      !op.addIntOption('\0', "arm-sim-stop-at", "NUMBER",
+                       "Stop the ARM simulator after the given "
+                       "NUMBER of instructions.",
+                       -1) ||
+      !op.addBoolOption('\0', "mips-sim-icache-checks",
+                        "Enable icache flush checks in the MIPS "
+                        "simulator.") ||
+      !op.addIntOption('\0', "mips-sim-stop-at", "NUMBER",
+                       "Stop the MIPS simulator after the given "
+                       "NUMBER of instructions.",
+                       -1) ||
+      !op.addBoolOption('\0', "loong64-sim-icache-checks",
+                        "Enable icache flush checks in the LoongArch64 "
+                        "simulator.") ||
+      !op.addIntOption('\0', "loong64-sim-stop-at", "NUMBER",
+                       "Stop the LoongArch64 simulator after the given "
+                       "NUMBER of instructions.",
+                       -1) ||
+      !op.addIntOption('\0', "nursery-size", "SIZE-MB",
+                       "Set the maximum nursery size in MB",
+                       JS::DefaultNurseryMaxBytes / 1024 / 1024) ||
+#ifdef JS_GC_ZEAL
+      !op.addStringOption('z', "gc-zeal", "LEVEL(;LEVEL)*[,N]",
+                          gc::ZealModeHelpText) ||
+#else
+      !op.addStringOption('z', "gc-zeal", "LEVEL(;LEVEL)*[,N]",
+                          "option ignored in non-gc-zeal builds") ||
+#endif
+      !op.addMultiStringOption('\0', "gc-param", "NAME=VALUE",
+                               "Set a named GC parameter") ||
+      !op.addStringOption('\0', "module-load-path", "DIR",
+                          "Set directory to load modules from") ||
+      !op.addBoolOption('\0', "no-source-pragmas",
+                        "Disable source(Mapping)URL pragma parsing") ||
+      !op.addBoolOption('\0', "no-async-stacks", "Disable async stacks") ||
+      !op.addBoolOption('\0', "async-stacks-capture-debuggee-only",
+                        "Limit async stack capture to only debuggees") ||
+      !op.addMultiStringOption('\0', "dll", "LIBRARY",
+                               "Dynamically load LIBRARY") ||
+      !op.addBoolOption('\0', "suppress-minidump",
+                        "Suppress crash minidumps") ||
+#ifdef JS_ENABLE_SMOOSH
+      !op.addBoolOption('\0', "smoosh", "Use SmooshMonkey") ||
+      !op.addStringOption('\0', "not-implemented-watchfile", "[filename]",
+                          "Track NotImplemented errors in the new frontend") ||
+#else
+      !op.addBoolOption('\0', "smoosh", "No-op") ||
+#endif
+      !op.addStringOption(
+          '\0', "delazification-mode", "[option]",
+          "Select one of the delazification mode for scripts given on the "
+          "command line, valid options are: "
+          "'on-demand', 'concurrent-df', 'eager', 'concurrent-df+on-demand'. "
+          "Choosing 'concurrent-df+on-demand' will run both concurrent-df and "
+          "on-demand delazification mode, and compare compilation outcome. ") ||
+      !op.addBoolOption('\0', "wasm-compile-and-serialize",
+                        "Compile the wasm bytecode from stdin and serialize "
+                        "the results to stdout") ||
+#ifdef FUZZING_JS_FUZZILLI
+      !op.addBoolOption('\0', "reprl", "Enable REPRL mode for fuzzing") ||
+#endif
+      !op.addStringOption('\0', "telemetry-dir", "[directory]",
+                          "Output telemetry results in a directory") ||
+      !op.addBoolOption('\0', "use-fdlibm-for-sin-cos-tan",
+                        "Use fdlibm for Math.sin, Math.cos, and Math.tan")) {
+    return EXIT_FAILURE;
+  }
+
+  op.setArgTerminatesOptions("script", true);
+  op.setArgCapturesRest("scriptArgs");
+
+  switch (op.parseArgs(argc, argv)) {
+    case OptionParser::EarlyExit:
+      return EXIT_SUCCESS;
+    case OptionParser::ParseError:
+      op.printHelp(argv[0]);
+      return EXIT_FAILURE;
+    case OptionParser::Fail:
+      return EXIT_FAILURE;
+    case OptionParser::Okay:
+      break;
+  }
+
+  if (op.getHelpOption()) {
+    return EXIT_SUCCESS;
+  }
+
+  // Note: DisableJitBackend must be called before JS_InitWithFailureDiagnostic.
+  if (op.getBoolOption("no-jit-backend")) {
+    JS::DisableJitBackend();
+  }
+
+#if defined(JS_CODEGEN_ARM)
+  if (const char* str = op.getStringOption("arm-hwcap")) {
+    jit::SetARMHwCapFlagsString(str);
+  }
+
+  int32_t fill = op.getIntOption("arm-asm-nop-fill");
+  if (fill >= 0) {
+    jit::Assembler::NopFill = fill;
+  }
+
+  int32_t poolMaxOffset = op.getIntOption("asm-pool-max-offset");
+  if (poolMaxOffset >= 5 && poolMaxOffset <= 1024) {
+    jit::Assembler::AsmPoolMaxOffset = poolMaxOffset;
+  }
+#endif
+
+  // Fish around in `op` for various important compiler-configuration flags
+  // and make sure they get handed on to any child processes we might create.
+  // See bug 1700900.  Semantically speaking, this is all rather dubious:
+  //
+  // * What set of flags need to be propagated in order to guarantee that the
+  //   child produces code that is "compatible" (in whatever sense) with that
+  //   produced by the parent?  This isn't always easy to determine.
+  //
+  // * There's nothing that ensures that flags given to the child are
+  //   presented in the same order that they exist in the parent's `argv[]`.
+  //   That could be a problem in the case where two flags with contradictory
+  //   meanings are given, and they are presented to the child in the opposite
+  //   order.  For example: --wasm-compiler=optimizing --wasm-compiler=baseline.
+
+#if defined(JS_CODEGEN_X86) || defined(JS_CODEGEN_X64)
+  MOZ_ASSERT(!js::jit::CPUFlagsHaveBeenComputed());
+
+  if (op.getBoolOption("no-sse3")) {
+    js::jit::CPUInfo::SetSSE3Disabled();
+    if (!sCompilerProcessFlags.append("--no-sse3")) {
+      return EXIT_FAILURE;
+    }
+  }
+  if (op.getBoolOption("no-ssse3")) {
+    js::jit::CPUInfo::SetSSSE3Disabled();
+    if (!sCompilerProcessFlags.append("--no-ssse3")) {
+      return EXIT_FAILURE;
+    }
+  }
+  if (op.getBoolOption("no-sse4") || op.getBoolOption("no-sse41")) {
+    js::jit::CPUInfo::SetSSE41Disabled();
+    if (!sCompilerProcessFlags.append("--no-sse41")) {
+      return EXIT_FAILURE;
+    }
+  }
+  if (op.getBoolOption("no-sse42")) {
+    js::jit::CPUInfo::SetSSE42Disabled();
+    if (!sCompilerProcessFlags.append("--no-sse42")) {
+      return EXIT_FAILURE;
+    }
+  }
+  if (op.getBoolOption("no-avx")) {
+    js::jit::CPUInfo::SetAVXDisabled();
+    if (!sCompilerProcessFlags.append("--no-avx")) {
+      return EXIT_FAILURE;
+    }
+  }
+  if (op.getBoolOption("enable-avx")) {
+    js::jit::CPUInfo::SetAVXEnabled();
+    if (!sCompilerProcessFlags.append("--enable-avx")) {
+      return EXIT_FAILURE;
+    }
+  }
+#endif
+
+  // Start the engine.
+  if (const char* message = JS_InitWithFailureDiagnostic()) {
+    fprintf(gErrFile->fp, "JS_Init failed: %s\n", message);
+    return 1;
+  }
+
+  // `selfHostedXDRBuffer` contains XDR buffer of the self-hosted JS.
+  // A part of it is borrowed by ImmutableScriptData of the self-hosted scripts.
+  //
+  // This buffer's should outlive JS_Shutdown.
+  Maybe<FileContents> selfHostedXDRBuffer;
+
+  auto shutdownEngine = MakeScopeExit([] { JS_ShutDown(); });
+
+  // Record aggregated telemetry data on disk. Do this as early as possible such
+  // that the telemetry is recording both before starting the context and after
+  // closing it.
+  if (op.getStringOption("telemetry-dir")) {
+    if (!telemetryLock) {
+      telemetryLock = js_new<Mutex>(mutexid::ShellTelemetry);
+      if (!telemetryLock) {
+        return EXIT_FAILURE;
+      }
+    }
+  }
+  auto writeTelemetryResults = MakeScopeExit([&op] {
+    if (const char* dir = op.getStringOption("telemetry-dir")) {
+      WriteTelemetryDataToDisk(dir);
+      js_free(telemetryLock);
+      telemetryLock = nullptr;
+    }
+  });
+
+  /*
+   * Allow dumping on Linux with the fuzzing flag set, even when running with
+   * the suid/sgid flag set on the shell.
+   */
+#ifdef XP_LINUX
+  if (op.getBoolOption("fuzzing-safe")) {
+    prctl(PR_SET_DUMPABLE, 1);
+  }
+#endif
+
+#ifdef DEBUG
+  /*
+   * Process OOM options as early as possible so that we can observe as many
+   * allocations as possible.
+   */
+  OOM_printAllocationCount = op.getBoolOption('O');
+#endif
+
+  if (op.getBoolOption("no-threads")) {
+    js::DisableExtraThreads();
+  }
+
+  enableCodeCoverage = op.getBoolOption("code-coverage");
+  if (enableCodeCoverage) {
+    js::EnableCodeCoverage();
+  }
+
+  // If LCov is enabled, then the default delazification mode should be changed
+  // to parse everything eagerly, such that we know the location of every
+  // instruction, to report them in the LCov summary, even if there is no uses
+  // of these instructions.
+  //
+  // Note: code coverage can be enabled either using the --code-coverage command
+  // line, or the JS_CODE_COVERAGE_OUTPUT_DIR environment variable, which is
+  // processed by JS_InitWithFailureDiagnostic.
+  if (coverage::IsLCovEnabled()) {
+    defaultDelazificationMode =
+        JS::DelazificationOption::ParseEverythingEagerly;
+  }
+
+  if (const char* xdr = op.getStringOption("selfhosted-xdr-path")) {
+    shell::selfHostedXDRPath = xdr;
+  }
+  if (const char* opt = op.getStringOption("selfhosted-xdr-mode")) {
+    if (strcmp(opt, "encode") == 0) {
+      shell::encodeSelfHostedCode = true;
+    } else if (strcmp(opt, "decode") == 0) {
+      shell::encodeSelfHostedCode = false;
+    } else if (strcmp(opt, "off") == 0) {
+      shell::selfHostedXDRPath = nullptr;
+    } else {
+      MOZ_CRASH(
+          "invalid option value for --selfhosted-xdr-mode, must be "
+          "encode/decode");
+    }
+  }
+
+#ifdef JS_WITHOUT_NSPR
+  if (!op.getMultiStringOption("dll").empty()) {
+    fprintf(stderr, "Error: --dll requires NSPR support!\n");
+    return EXIT_FAILURE;
+  }
+#else
+  AutoLibraryLoader loader;
+  MultiStringRange dllPaths = op.getMultiStringOption("dll");
+  while (!dllPaths.empty()) {
+    char* path = dllPaths.front();
+    loader.load(path);
+    dllPaths.popFront();
+  }
+#endif
+
+  if (op.getBoolOption("suppress-minidump")) {
+    js::NoteIntentionalCrash();
+  }
+
+  if (!InitSharedObjectMailbox()) {
+    return 1;
+  }
+
+  JS::SetProcessBuildIdOp(ShellBuildId);
+
+  // The fake CPU count must be set before initializing the Runtime,
+  // which spins up the thread pool.
+  int32_t cpuCount = op.getIntOption("cpu-count");  // What we're really setting
+  if (cpuCount < 0) {
+    cpuCount = op.getIntOption("thread-count");  // Legacy name
+  }
+  if (cpuCount >= 0 && !SetFakeCPUCount(cpuCount)) {
+    return 1;
+  }
+
+  /* Use the same parameters as the browser in xpcjsruntime.cpp. */
+  JSContext* const cx = JS_NewContext(JS::DefaultHeapMaxBytes);
+  if (!cx) {
+    return 1;
+  }
+
+  // Register telemetry callbacks, if needed.
+  if (telemetryLock) {
+    JS_SetAccumulateTelemetryCallback(cx, AccumulateTelemetryDataCallback);
+  }
+
+  size_t nurseryBytes = op.getIntOption("nursery-size") * 1024L * 1024L;
+  if (nurseryBytes == 0) {
+    fprintf(stderr, "Error: --nursery-size parameter must be non-zero.\n");
+    fprintf(stderr,
+            "The nursery can be disabled by passing the --no-ggc option.\n");
+    return EXIT_FAILURE;
+  }
+  JS_SetGCParameter(cx, JSGC_MAX_NURSERY_BYTES, nurseryBytes);
+
+  auto destroyCx = MakeScopeExit([cx] { JS_DestroyContext(cx); });
+
+  UniquePtr<ShellContext> sc = MakeUnique<ShellContext>(cx);
+  if (!sc) {
+    return 1;
+  }
+  auto destroyShellContext = MakeScopeExit([cx, &sc] {
+    // Must clear out some of sc's pointer containers before JS_DestroyContext.
+    sc->markObservers.reset();
+
+    JS_SetContextPrivate(cx, nullptr);
+    sc.reset();
+  });
+
+  JS_SetContextPrivate(cx, sc.get());
+  JS_SetGrayGCRootsTracer(cx, TraceGrayRoots, nullptr);
+  auto resetGrayGCRootsTracer =
+      MakeScopeExit([cx] { JS_SetGrayGCRootsTracer(cx, nullptr, nullptr); });
+
+  // Waiting is allowed on the shell's main thread, for now.
+  JS_SetFutexCanWait(cx);
+  JS::SetWarningReporter(cx, WarningReporter);
+
+  if (!SetContextOptions(cx, op)) {
+    return 1;
+  }
+
+  JS_SetGCParameter(cx, JSGC_MAX_BYTES, 0xffffffff);
+
+  size_t availMemMB = op.getIntOption("available-memory");
+  if (availMemMB > 0) {
+    JS_SetGCParametersBasedOnAvailableMemory(cx, availMemMB);
+  }
+
+  JS_SetTrustedPrincipals(cx, &ShellPrincipals::fullyTrusted);
+  JS_SetSecurityCallbacks(cx, &ShellPrincipals::securityCallbacks);
+  JS_InitDestroyPrincipalsCallback(cx, ShellPrincipals::destroy);
+  JS_SetDestroyCompartmentCallback(cx, DestroyShellCompartmentPrivate);
+
+  js::SetWindowProxyClass(cx, &ShellWindowProxyClass);
+
+  JS_AddInterruptCallback(cx, ShellInterruptCallback);
+
+  bufferStreamState = js_new<ExclusiveWaitableData<BufferStreamState>>(
+      mutexid::BufferStreamState);
+  if (!bufferStreamState) {
+    return 1;
+  }
+  auto shutdownBufferStreams = MakeScopeExit([] {
+    ShutdownBufferStreams();
+    js_delete(bufferStreamState);
+  });
+  JS::InitConsumeStreamCallback(cx, ConsumeBufferSource, ReportStreamError);
+
+  JS::SetPromiseRejectionTrackerCallback(
+      cx, ForwardingPromiseRejectionTrackerCallback);
+
+  JS::dbg::SetDebuggerMallocSizeOf(cx, moz_malloc_size_of);
+
+  js::UseInternalJobQueues(cx);
+
+  JS::SetHostCleanupFinalizationRegistryCallback(
+      cx, ShellCleanupFinalizationRegistryCallback, sc.get());
+
+  auto shutdownShellThreads = MakeScopeExit([cx] {
+    KillWatchdog(cx);
+    KillWorkerThreads(cx);
+    DestructSharedObjectMailbox();
+    CancelOffThreadJobsForRuntime(cx);
+  });
+
+  if (const char* opt = op.getStringOption("nursery-strings")) {
+    if (strcmp(opt, "on") == 0) {
+      cx->runtime()->gc.nursery().enableStrings();
+    } else if (strcmp(opt, "off") == 0) {
+      cx->runtime()->gc.nursery().disableStrings();
+    } else {
+      MOZ_CRASH("invalid option value for --nursery-strings, must be on/off");
+    }
+  }
+
+  if (const char* opt = op.getStringOption("nursery-bigints")) {
+    if (strcmp(opt, "on") == 0) {
+      cx->runtime()->gc.nursery().enableBigInts();
+    } else if (strcmp(opt, "off") == 0) {
+      cx->runtime()->gc.nursery().disableBigInts();
+    } else {
+      MOZ_CRASH("invalid option value for --nursery-bigints, must be on/off");
+    }
+  }
+
+  // The file content should stay alive as long as Worker thread can be
+  // initialized.
+  JS::SelfHostedCache xdrSpan = nullptr;
+  JS::SelfHostedWriter xdrWriter = nullptr;
+  if (selfHostedXDRPath) {
+    if (encodeSelfHostedCode) {
+      xdrWriter = WriteSelfHostedXDRFile;
+    } else {
+      selfHostedXDRBuffer.emplace(cx);
+      if (ReadSelfHostedXDRFile(cx, *selfHostedXDRBuffer)) {
+        MOZ_ASSERT(selfHostedXDRBuffer->length() > 0);
+        JS::SelfHostedCache span(selfHostedXDRBuffer->begin(),
+                                 selfHostedXDRBuffer->end());
+        xdrSpan = span;
+      } else {
+        fprintf(stderr, "Falling back on parsing source.\n");
+        selfHostedXDRPath = nullptr;
+      }
+    }
+  }
+
+#ifndef __wasi__
+  // This must be set before self-hosted code is initialized, as self-hosted
+  // code reads the property and the property may not be changed later.
+  bool disabledHugeMemory = false;
+  if (op.getBoolOption("disable-wasm-huge-memory")) {
+    disabledHugeMemory = JS::DisableWasmHugeMemory();
+    MOZ_RELEASE_ASSERT(disabledHugeMemory);
+  }
+#endif
+
+  if (!JS::InitSelfHostedCode(cx, xdrSpan, xdrWriter)) {
+    return 1;
+  }
+
+  EnvironmentPreparer environmentPreparer(cx);
+
+  bool incrementalGC = !op.getBoolOption("no-incremental-gc");
+  JS_SetGCParameter(cx, JSGC_INCREMENTAL_GC_ENABLED, incrementalGC);
+
+  if (op.getBoolOption("enable-parallel-marking")) {
+    JS_SetGCParameter(cx, JSGC_PARALLEL_MARKING_ENABLED, true);
+  }
+
+  JS_SetGCParameter(cx, JSGC_SLICE_TIME_BUDGET_MS, 5);
+
+  JS_SetGCParameter(cx, JSGC_PER_ZONE_GC_ENABLED, true);
+
+  for (MultiStringRange args = op.getMultiStringOption("gc-param");
+       !args.empty(); args.popFront()) {
+    if (!SetGCParameterFromArg(cx, args.front())) {
+      return EXIT_FAILURE;
+    }
+  }
+
+  JS::SetProcessLargeAllocationFailureCallback(my_LargeAllocFailCallback);
+
+  js::SetPreserveWrapperCallbacks(cx, DummyPreserveWrapperCallback,
+                                  DummyHasReleasedWrapperCallback);
+
+#ifndef __wasi__
+  // --disable-wasm-huge-memory needs to be propagated.  See bug 1518210.
+  if (disabledHugeMemory &&
+      !sCompilerProcessFlags.append("--disable-wasm-huge-memory")) {
+    return EXIT_FAILURE;
+  }
+
+  // Also the following are to be propagated.
+  const char* to_propagate[] = {
+#  define WASM_DEFAULT_FEATURE(NAME, LOWER_NAME, COMPILE_PRED, COMPILER_PRED, \
+                               FLAG_PRED, SHELL, ...)                         \
+    "--no-wasm-" SHELL,
+#  define WASM_EXPERIMENTAL_FEATURE(NAME, LOWER_NAME, COMPILE_PRED,       \
+                                    COMPILER_PRED, FLAG_PRED, SHELL, ...) \
+    "--wasm-" SHELL,
+      JS_FOR_WASM_FEATURES(WASM_DEFAULT_FEATURE, WASM_DEFAULT_FEATURE,
+                           WASM_EXPERIMENTAL_FEATURE)
+#  undef WASM_DEFAULT_FEATURE
+#  undef WASM_EXPERIMENTAL_FEATURE
+      // Compiler selection options
+      "--test-wasm-await-tier2",
+      NULL};
+  for (const char** p = &to_propagate[0]; *p; p++) {
+    if (op.getBoolOption(&(*p)[2] /* 2 => skip the leading '--' */)) {
+      if (!sCompilerProcessFlags.append(*p)) {
+        return EXIT_FAILURE;
+      }
+    }
+  }
+
+  // Also --wasm-compiler= is to be propagated.  This is tricky because it is
+  // necessary to reconstitute the --wasm-compiler=<whatever> string from its
+  // pieces, without causing a leak.  Hence it is copied into a static buffer.
+  // This is thread-unsafe, but we're in `main()` and on the process' root
+  // thread.  Also, we do this only once -- it wouldn't work properly if we
+  // handled multiple --wasm-compiler= flags in a loop.
+  const char* wasm_compiler = op.getStringOption("wasm-compiler");
+  if (wasm_compiler) {
+    size_t n_needed =
+        2 + strlen("wasm-compiler") + 1 + strlen(wasm_compiler) + 1;
+    const size_t n_avail = 128;
+    static char buf[n_avail];
+    // `n_needed` depends on the compiler name specified.  However, it can't
+    // be arbitrarily long, since previous flag-checking should have limited
+    // it to a set of known possibilities: "baseline", "ion",
+    // "baseline+ion",  Still, assert this for safety.
+    MOZ_RELEASE_ASSERT(n_needed < n_avail);
+    memset(buf, 0, sizeof(buf));
+    SprintfBuf(buf, n_avail, "--%s=%s", "wasm-compiler", wasm_compiler);
+    if (!sCompilerProcessFlags.append(buf)) {
+      return EXIT_FAILURE;
+    }
+  }
+#endif  // __wasi__
+
+  result = Shell(cx, &op);
+
+#ifdef DEBUG
+  if (OOM_printAllocationCount) {
+    printf("OOM max count: %" PRIu64 "\n", js::oom::simulator.counter());
+  }
+#endif
+
+  return result;
+}
diff --git a/js/src/shell/jsoptparse.cpp b/js/src/shell/jsoptparse.cpp
new file mode 100644
index 0000000000..5632598d7d
--- /dev/null
+++ b/js/src/shell/jsoptparse.cpp
@@ -0,0 +1,639 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "shell/jsoptparse.h"
+
+#include <algorithm>
+#include <stdarg.h>
+#include <string_view>
+
+#include "util/Unicode.h"
+
+using namespace js;
+using namespace js::cli;
+using namespace js::cli::detail;
+
+#define OPTION_CONVERT_IMPL(__cls)                                             \
+  bool Option::is##__cls##Option() const { return kind == OptionKind##__cls; } \
+  __cls##Option* Option::as##__cls##Option() {                                 \
+    MOZ_ASSERT(is##__cls##Option());                                           \
+    return static_cast<__cls##Option*>(this);                                  \
+  }                                                                            \
+  const __cls##Option* Option::as##__cls##Option() const {                     \
+    return const_cast<Option*>(this)->as##__cls##Option();                     \
+  }
+
+ValuedOption* Option::asValued() {
+  MOZ_ASSERT(isValued());
+  return static_cast<ValuedOption*>(this);
+}
+
+const ValuedOption* Option::asValued() const {
+  return const_cast<Option*>(this)->asValued();
+}
+
+OPTION_CONVERT_IMPL(Bool)
+OPTION_CONVERT_IMPL(String)
+OPTION_CONVERT_IMPL(Int)
+OPTION_CONVERT_IMPL(MultiString)
+
+void OptionParser::setArgTerminatesOptions(const char* name, bool enabled) {
+  findArgument(name)->setTerminatesOptions(enabled);
+}
+
+void OptionParser::setArgCapturesRest(const char* name) {
+  MOZ_ASSERT(restArgument == -1,
+             "only one argument may be set to capture the rest");
+  restArgument = findArgumentIndex(name);
+  MOZ_ASSERT(restArgument != -1,
+             "unknown argument name passed to setArgCapturesRest");
+}
+
+OptionParser::Result OptionParser::error(const char* fmt, ...) {
+  va_list args;
+  va_start(args, fmt);
+  fprintf(stderr, "Error: ");
+  vfprintf(stderr, fmt, args);
+  va_end(args);
+  fputs("\n\n", stderr);
+  return ParseError;
+}
+
+/* Quick and dirty paragraph printer. */
+static void PrintParagraph(const char* text, unsigned startColno,
+                           const unsigned limitColno, bool padFirstLine) {
+  unsigned colno = startColno;
+  unsigned indent = 0;
+  const char* it = text;
+
+  if (padFirstLine) {
+    printf("%*s", int(startColno), "");
+  }
+
+  /* Skip any leading spaces. */
+  while (*it != '\0' && unicode::IsSpace(*it)) {
+    ++it;
+  }
+
+  while (*it != '\0') {
+    MOZ_ASSERT(!unicode::IsSpace(*it) || *it == '\n');
+
+    /* Delimit the current token. */
+    const char* limit = it;
+    while (!unicode::IsSpace(*limit) && *limit != '\0') {
+      ++limit;
+    }
+
+    /*
+     * If the current token is longer than the available number of columns,
+     * then make a line break before printing the token.
+     */
+    size_t tokLen = limit - it;
+    if (tokLen + colno >= limitColno) {
+      printf("\n%*s%.*s", int(startColno + indent), "", int(tokLen), it);
+      colno = startColno + tokLen;
+    } else {
+      printf("%.*s", int(tokLen), it);
+      colno += tokLen;
+    }
+
+    switch (*limit) {
+      case '\0':
+        return;
+      case ' ':
+        putchar(' ');
+        colno += 1;
+        it = limit;
+        while (*it == ' ') {
+          ++it;
+        }
+        break;
+      case '\n':
+        /* |text| wants to force a newline here. */
+        printf("\n%*s", int(startColno), "");
+        colno = startColno;
+        it = limit + 1;
+        /* Could also have line-leading spaces. */
+        indent = 0;
+        while (*it == ' ') {
+          putchar(' ');
+          ++colno;
+          ++indent;
+          ++it;
+        }
+        break;
+      default:
+        MOZ_CRASH("unhandled token splitting character in text");
+    }
+  }
+}
+
+static const char* OptionFlagsToFormatInfo(char shortflag, bool isValued,
+                                           size_t* length) {
+  static const char* const fmt[4] = {"  -%c --%s ", "  --%s ", "  -%c --%s=%s ",
+                                     "  --%s=%s "};
+
+  /* How mny chars w/o longflag? */
+  size_t lengths[4] = {strlen(fmt[0]) - 3, strlen(fmt[1]) - 3,
+                       strlen(fmt[2]) - 5, strlen(fmt[3]) - 5};
+  int index = isValued ? 2 : 0;
+  if (!shortflag) {
+    index++;
+  }
+
+  *length = lengths[index];
+  return fmt[index];
+}
+
+OptionParser::Result OptionParser::printHelp(const char* progname) {
+  constexpr std::string_view prognameMeta = "{progname}";
+
+  const char* prefixEnd = strstr(usage, prognameMeta.data());
+  if (prefixEnd) {
+    printf("%.*s%s%s\n", int(prefixEnd - usage), usage, progname,
+           prefixEnd + prognameMeta.length());
+  } else {
+    puts(usage);
+  }
+
+  if (descr) {
+    putchar('\n');
+    PrintParagraph(descr, 2, descrWidth, true);
+    putchar('\n');
+  }
+
+  if (version) {
+    printf("\nVersion: %s\n\n", version);
+  }
+
+  if (!arguments.empty()) {
+    printf("Arguments:\n");
+
+    static const char fmt[] = "  %s ";
+    size_t fmtChars = sizeof(fmt) - 2;
+    size_t lhsLen = 0;
+    for (Option* arg : arguments) {
+      lhsLen = std::max(lhsLen, strlen(arg->longflag) + fmtChars);
+    }
+
+    for (Option* arg : arguments) {
+      size_t chars = printf(fmt, arg->longflag);
+      for (; chars < lhsLen; ++chars) {
+        putchar(' ');
+      }
+      PrintParagraph(arg->help, lhsLen, helpWidth, false);
+      putchar('\n');
+    }
+    putchar('\n');
+  }
+
+  if (!options.empty()) {
+    printf("Options:\n");
+
+    /* Calculate sizes for column alignment. */
+    size_t lhsLen = 0;
+    for (Option* opt : options) {
+      size_t longflagLen = strlen(opt->longflag);
+
+      size_t fmtLen;
+      OptionFlagsToFormatInfo(opt->shortflag, opt->isValued(), &fmtLen);
+
+      size_t len = fmtLen + longflagLen;
+      if (opt->isValued()) {
+        len += strlen(opt->asValued()->metavar);
+      }
+      lhsLen = std::max(lhsLen, len);
+    }
+
+    /* Print option help text. */
+    for (Option* opt : options) {
+      size_t fmtLen;
+      const char* fmt =
+          OptionFlagsToFormatInfo(opt->shortflag, opt->isValued(), &fmtLen);
+      size_t chars;
+      if (opt->isValued()) {
+        if (opt->shortflag) {
+          chars = printf(fmt, opt->shortflag, opt->longflag,
+                         opt->asValued()->metavar);
+        } else {
+          chars = printf(fmt, opt->longflag, opt->asValued()->metavar);
+        }
+      } else {
+        if (opt->shortflag) {
+          chars = printf(fmt, opt->shortflag, opt->longflag);
+        } else {
+          chars = printf(fmt, opt->longflag);
+        }
+      }
+      for (; chars < lhsLen; ++chars) {
+        putchar(' ');
+      }
+      PrintParagraph(opt->help, lhsLen, helpWidth, false);
+      putchar('\n');
+    }
+  }
+
+  return EarlyExit;
+}
+
+OptionParser::Result OptionParser::printVersion() {
+  MOZ_ASSERT(version);
+  printf("%s\n", version);
+  return EarlyExit;
+}
+
+OptionParser::Result OptionParser::extractValue(size_t argc, char** argv,
+                                                size_t* i, char** value) {
+  MOZ_ASSERT(*i < argc);
+  char* eq = strchr(argv[*i], '=');
+  if (eq) {
+    *value = eq + 1;
+    if (*value[0] == '\0') {
+      return error("A value is required for option %.*s", (int)(eq - argv[*i]),
+                   argv[*i]);
+    }
+    return Okay;
+  }
+
+  if (argc == *i + 1) {
+    return error("Expected a value for option %s", argv[*i]);
+  }
+
+  *i += 1;
+  *value = argv[*i];
+  return Okay;
+}
+
+OptionParser::Result OptionParser::handleOption(Option* opt, size_t argc,
+                                                char** argv, size_t* i,
+                                                bool* optionsAllowed) {
+  if (opt->getTerminatesOptions()) {
+    *optionsAllowed = false;
+  }
+
+  switch (opt->kind) {
+    case OptionKindBool: {
+      if (opt == &helpOption) {
+        return printHelp(argv[0]);
+      }
+      if (opt == &versionOption) {
+        return printVersion();
+      }
+      opt->asBoolOption()->value = true;
+      return Okay;
+    }
+    /*
+     * Valued options are allowed to specify their values either via
+     * successive arguments or a single --longflag=value argument.
+     */
+    case OptionKindString: {
+      char* value = nullptr;
+      if (Result r = extractValue(argc, argv, i, &value)) {
+        return r;
+      }
+      opt->asStringOption()->value = value;
+      return Okay;
+    }
+    case OptionKindInt: {
+      char* value = nullptr;
+      if (Result r = extractValue(argc, argv, i, &value)) {
+        return r;
+      }
+      opt->asIntOption()->value = atoi(value);
+      return Okay;
+    }
+    case OptionKindMultiString: {
+      char* value = nullptr;
+      if (Result r = extractValue(argc, argv, i, &value)) {
+        return r;
+      }
+      StringArg arg(value, *i);
+      return opt->asMultiStringOption()->strings.append(arg) ? Okay : Fail;
+    }
+    default:
+      MOZ_CRASH("unhandled option kind");
+  }
+}
+
+OptionParser::Result OptionParser::handleArg(size_t argc, char** argv,
+                                             size_t* i, bool* optionsAllowed) {
+  if (nextArgument >= arguments.length()) {
+    return error("Too many arguments provided");
+  }
+
+  Option* arg = arguments[nextArgument];
+
+  if (arg->getTerminatesOptions()) {
+    *optionsAllowed = false;
+  }
+
+  switch (arg->kind) {
+    case OptionKindString:
+      arg->asStringOption()->value = argv[*i];
+      nextArgument += 1;
+      return Okay;
+    case OptionKindMultiString: {
+      // Don't advance the next argument -- there can only be one (final)
+      // variadic argument.
+      StringArg value(argv[*i], *i);
+      return arg->asMultiStringOption()->strings.append(value) ? Okay : Fail;
+    }
+    default:
+      MOZ_CRASH("unhandled argument kind");
+  }
+}
+
+OptionParser::Result OptionParser::parseArgs(int inputArgc, char** argv) {
+  MOZ_ASSERT(inputArgc >= 0);
+  size_t argc = inputArgc;
+  // Permit a "no more options" capability, like |--| offers in many shell
+  // interfaces.
+  bool optionsAllowed = true;
+
+  for (size_t i = 1; i < argc; ++i) {
+    char* arg = argv[i];
+    Result r;
+    /* Note: solo dash option is actually a 'stdin' argument. */
+    if (arg[0] == '-' && arg[1] != '\0' && optionsAllowed) {
+      /* Option. */
+      Option* opt;
+      if (arg[1] == '-') {
+        if (arg[2] == '\0') {
+          /* End of options */
+          optionsAllowed = false;
+          nextArgument = restArgument;
+          continue;
+        } else {
+          /* Long option. */
+          opt = findOption(arg + 2);
+          if (!opt) {
+            return error("Invalid long option: %s", arg);
+          }
+        }
+      } else {
+        /* Short option */
+        if (arg[2] != '\0') {
+          return error("Short option followed by junk: %s", arg);
+        }
+        opt = findOption(arg[1]);
+        if (!opt) {
+          return error("Invalid short option: %s", arg);
+        }
+      }
+
+      r = handleOption(opt, argc, argv, &i, &optionsAllowed);
+    } else {
+      /* Argument. */
+      r = handleArg(argc, argv, &i, &optionsAllowed);
+    }
+
+    if (r != Okay) {
+      return r;
+    }
+  }
+  return Okay;
+}
+
+void OptionParser::setHelpOption(char shortflag, const char* longflag,
+                                 const char* help) {
+  helpOption.setFlagInfo(shortflag, longflag, help);
+}
+
+bool OptionParser::getHelpOption() const { return helpOption.value; }
+
+bool OptionParser::getBoolOption(char shortflag) const {
+  return tryFindOption(shortflag)->asBoolOption()->value;
+}
+
+int OptionParser::getIntOption(char shortflag) const {
+  return tryFindOption(shortflag)->asIntOption()->value;
+}
+
+const char* OptionParser::getStringOption(char shortflag) const {
+  return tryFindOption(shortflag)->asStringOption()->value;
+}
+
+MultiStringRange OptionParser::getMultiStringOption(char shortflag) const {
+  const MultiStringOption* mso =
+      tryFindOption(shortflag)->asMultiStringOption();
+  return MultiStringRange(mso->strings.begin(), mso->strings.end());
+}
+
+bool OptionParser::getBoolOption(const char* longflag) const {
+  return tryFindOption(longflag)->asBoolOption()->value;
+}
+
+int OptionParser::getIntOption(const char* longflag) const {
+  return tryFindOption(longflag)->asIntOption()->value;
+}
+
+const char* OptionParser::getStringOption(const char* longflag) const {
+  return tryFindOption(longflag)->asStringOption()->value;
+}
+
+MultiStringRange OptionParser::getMultiStringOption(
+    const char* longflag) const {
+  const MultiStringOption* mso = tryFindOption(longflag)->asMultiStringOption();
+  return MultiStringRange(mso->strings.begin(), mso->strings.end());
+}
+
+OptionParser::~OptionParser() {
+  for (Option* opt : options) {
+    js_delete<Option>(opt);
+  }
+  for (Option* arg : arguments) {
+    js_delete<Option>(arg);
+  }
+}
+
+Option* OptionParser::findOption(char shortflag) {
+  for (Option* opt : options) {
+    if (opt->shortflag == shortflag) {
+      return opt;
+    }
+  }
+
+  if (versionOption.shortflag == shortflag) {
+    return &versionOption;
+  }
+
+  return helpOption.shortflag == shortflag ? &helpOption : nullptr;
+}
+
+const Option* OptionParser::findOption(char shortflag) const {
+  return const_cast<OptionParser*>(this)->findOption(shortflag);
+}
+
+const Option* OptionParser::tryFindOption(char shortflag) const {
+  const Option* maybeOption = findOption(shortflag);
+  if (!maybeOption) {
+    fprintf(stderr, "Failed to find short option %c\n", shortflag);
+    MOZ_CRASH();
+  }
+  return maybeOption;
+}
+
+Option* OptionParser::findOption(const char* longflag) {
+  for (Option* opt : options) {
+    const char* target = opt->longflag;
+    if (opt->isValued()) {
+      size_t targetLen = strlen(target);
+      /* Permit a trailing equals sign on the longflag argument. */
+      for (size_t i = 0; i < targetLen; ++i) {
+        if (longflag[i] == '\0' || longflag[i] != target[i]) {
+          goto no_match;
+        }
+      }
+      if (longflag[targetLen] == '\0' || longflag[targetLen] == '=') {
+        return opt;
+      }
+    } else {
+      if (strcmp(target, longflag) == 0) {
+        return opt;
+      }
+    }
+  no_match:;
+  }
+
+  if (strcmp(versionOption.longflag, longflag) == 0) {
+    return &versionOption;
+  }
+
+  return strcmp(helpOption.longflag, longflag) ? nullptr : &helpOption;
+}
+
+const Option* OptionParser::findOption(const char* longflag) const {
+  return const_cast<OptionParser*>(this)->findOption(longflag);
+}
+
+const Option* OptionParser::tryFindOption(const char* longflag) const {
+  const Option* maybeOption = findOption(longflag);
+  if (!maybeOption) {
+    fprintf(stderr, "Failed to find long option %s\n", longflag);
+    MOZ_CRASH();
+  }
+  return maybeOption;
+}
+
+/* Argument accessors */
+
+int OptionParser::findArgumentIndex(const char* name) const {
+  for (Option* const* it = arguments.begin(); it != arguments.end(); ++it) {
+    const char* target = (*it)->longflag;
+    if (strcmp(target, name) == 0) {
+      return it - arguments.begin();
+    }
+  }
+  return -1;
+}
+
+Option* OptionParser::findArgument(const char* name) {
+  int index = findArgumentIndex(name);
+  return (index == -1) ? nullptr : arguments[index];
+}
+
+const Option* OptionParser::findArgument(const char* name) const {
+  int index = findArgumentIndex(name);
+  return (index == -1) ? nullptr : arguments[index];
+}
+
+const char* OptionParser::getStringArg(const char* name) const {
+  return findArgument(name)->asStringOption()->value;
+}
+
+MultiStringRange OptionParser::getMultiStringArg(const char* name) const {
+  const MultiStringOption* mso = findArgument(name)->asMultiStringOption();
+  return MultiStringRange(mso->strings.begin(), mso->strings.end());
+}
+
+/* Option builders */
+
+// Use vanilla malloc for allocations. See OptionAllocPolicy.
+JS_DECLARE_NEW_METHODS(opt_new, malloc, static MOZ_ALWAYS_INLINE)
+
+bool OptionParser::addIntOption(char shortflag, const char* longflag,
+                                const char* metavar, const char* help,
+                                int defaultValue) {
+  if (!options.reserve(options.length() + 1)) {
+    return false;
+  }
+  IntOption* io =
+      opt_new<IntOption>(shortflag, longflag, help, metavar, defaultValue);
+  if (!io) {
+    return false;
+  }
+  options.infallibleAppend(io);
+  return true;
+}
+
+bool OptionParser::addBoolOption(char shortflag, const char* longflag,
+                                 const char* help) {
+  if (!options.reserve(options.length() + 1)) {
+    return false;
+  }
+  BoolOption* bo = opt_new<BoolOption>(shortflag, longflag, help);
+  if (!bo) {
+    return false;
+  }
+  options.infallibleAppend(bo);
+  return true;
+}
+
+bool OptionParser::addStringOption(char shortflag, const char* longflag,
+                                   const char* metavar, const char* help) {
+  if (!options.reserve(options.length() + 1)) {
+    return false;
+  }
+  StringOption* so = opt_new<StringOption>(shortflag, longflag, help, metavar);
+  if (!so) {
+    return false;
+  }
+  options.infallibleAppend(so);
+  return true;
+}
+
+bool OptionParser::addMultiStringOption(char shortflag, const char* longflag,
+                                        const char* metavar, const char* help) {
+  if (!options.reserve(options.length() + 1)) {
+    return false;
+  }
+  MultiStringOption* mso =
+      opt_new<MultiStringOption>(shortflag, longflag, help, metavar);
+  if (!mso) {
+    return false;
+  }
+  options.infallibleAppend(mso);
+  return true;
+}
+
+/* Argument builders */
+
+bool OptionParser::addOptionalStringArg(const char* name, const char* help) {
+  if (!arguments.reserve(arguments.length() + 1)) {
+    return false;
+  }
+  StringOption* so = opt_new<StringOption>(1, name, help, (const char*)nullptr);
+  if (!so) {
+    return false;
+  }
+  arguments.infallibleAppend(so);
+  return true;
+}
+
+bool OptionParser::addOptionalMultiStringArg(const char* name,
+                                             const char* help) {
+  MOZ_ASSERT_IF(!arguments.empty(), !arguments.back()->isVariadic());
+  if (!arguments.reserve(arguments.length() + 1)) {
+    return false;
+  }
+  MultiStringOption* mso =
+      opt_new<MultiStringOption>(1, name, help, (const char*)nullptr);
+  if (!mso) {
+    return false;
+  }
+  arguments.infallibleAppend(mso);
+  return true;
+}
diff --git a/js/src/shell/jsoptparse.h b/js/src/shell/jsoptparse.h
new file mode 100644
index 0000000000..17e4878969
--- /dev/null
+++ b/js/src/shell/jsoptparse.h
@@ -0,0 +1,336 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef shell_jsoptparse_h
+#define shell_jsoptparse_h
+
+#include <stdio.h>
+
+#include "js/AllocPolicy.h"
+#include "js/Utility.h"
+#include "js/Vector.h"
+
+namespace js {
+namespace cli {
+
+namespace detail {
+
+// We want to use the shell's option parser before initializing the JS engine.
+// The JS malloc arena isn't available yet at this point, so we use a custom
+// allocation policy that uses the system malloc instead.
+class OptionAllocPolicy {
+ public:
+  template <typename T>
+  T* pod_malloc(size_t numElems) {
+    size_t bytes;
+    if (MOZ_UNLIKELY(!js::CalculateAllocSize<T>(numElems, &bytes))) {
+      return nullptr;
+    }
+    return static_cast<T*>(malloc(bytes));
+  }
+
+  template <typename T>
+  T* pod_realloc(T* p, size_t oldSize, size_t newSize) {
+    size_t bytes;
+    if (MOZ_UNLIKELY(!js::CalculateAllocSize<T>(newSize, &bytes))) {
+      return nullptr;
+    }
+    return static_cast<T*>(realloc(p, bytes));
+  }
+
+  void reportAllocOverflow() const {}
+  bool checkSimulatedOOM() const { return !js::oom::ShouldFailWithOOM(); }
+
+  template <typename T>
+  void free_(T* p, size_t numElems = 0) {
+    free(p);
+  }
+};
+
+struct BoolOption;
+struct MultiStringOption;
+struct ValuedOption;
+struct StringOption;
+struct IntOption;
+
+enum OptionKind {
+  OptionKindBool,
+  OptionKindString,
+  OptionKindInt,
+  OptionKindMultiString,
+  OptionKindInvalid
+};
+
+struct Option {
+  const char* longflag;
+  const char* help;
+  OptionKind kind;
+  char shortflag;
+  bool terminatesOptions;
+
+  Option(OptionKind kind, char shortflag, const char* longflag,
+         const char* help)
+      : longflag(longflag),
+        help(help),
+        kind(kind),
+        shortflag(shortflag),
+        terminatesOptions(false) {}
+
+  virtual ~Option() = 0;
+
+  void setTerminatesOptions(bool enabled) { terminatesOptions = enabled; }
+  bool getTerminatesOptions() const { return terminatesOptions; }
+
+  virtual bool isValued() const { return false; }
+
+  /* Only some valued options are variadic (like MultiStringOptions). */
+  virtual bool isVariadic() const { return false; }
+
+  /*
+   * For arguments, the shortflag field is used to indicate whether the
+   * argument is optional.
+   */
+  bool isOptional() { return shortflag; }
+
+  void setFlagInfo(char shortflag, const char* longflag, const char* help) {
+    this->shortflag = shortflag;
+    this->longflag = longflag;
+    this->help = help;
+  }
+
+  ValuedOption* asValued();
+  const ValuedOption* asValued() const;
+
+#define OPTION_CONVERT_DECL(__cls)    \
+  bool is##__cls##Option() const;     \
+  __cls##Option* as##__cls##Option(); \
+  const __cls##Option* as##__cls##Option() const;
+
+  OPTION_CONVERT_DECL(Bool)
+  OPTION_CONVERT_DECL(String)
+  OPTION_CONVERT_DECL(Int)
+  OPTION_CONVERT_DECL(MultiString)
+};
+
+inline Option::~Option() {}
+
+struct BoolOption : public Option {
+  size_t argno;
+  bool value;
+
+  BoolOption(char shortflag, const char* longflag, const char* help)
+      : Option(OptionKindBool, shortflag, longflag, help), value(false) {}
+
+  virtual ~BoolOption() {}
+};
+
+struct ValuedOption : public Option {
+  const char* metavar;
+
+  ValuedOption(OptionKind kind, char shortflag, const char* longflag,
+               const char* help, const char* metavar)
+      : Option(kind, shortflag, longflag, help), metavar(metavar) {}
+
+  virtual ~ValuedOption() = 0;
+  virtual bool isValued() const override { return true; }
+};
+
+inline ValuedOption::~ValuedOption() {}
+
+struct StringOption : public ValuedOption {
+  const char* value;
+
+  StringOption(char shortflag, const char* longflag, const char* help,
+               const char* metavar)
+      : ValuedOption(OptionKindString, shortflag, longflag, help, metavar),
+        value(nullptr) {}
+
+  virtual ~StringOption() {}
+};
+
+struct IntOption : public ValuedOption {
+  int value;
+
+  IntOption(char shortflag, const char* longflag, const char* help,
+            const char* metavar, int defaultValue)
+      : ValuedOption(OptionKindInt, shortflag, longflag, help, metavar),
+        value(defaultValue) {}
+
+  virtual ~IntOption() {}
+};
+
+struct StringArg {
+  char* value;
+  size_t argno;
+
+  StringArg(char* value, size_t argno) : value(value), argno(argno) {}
+};
+
+struct MultiStringOption : public ValuedOption {
+  Vector<StringArg, 0, detail::OptionAllocPolicy> strings;
+
+  MultiStringOption(char shortflag, const char* longflag, const char* help,
+                    const char* metavar)
+      : ValuedOption(OptionKindMultiString, shortflag, longflag, help,
+                     metavar) {}
+
+  virtual ~MultiStringOption() {}
+
+  virtual bool isVariadic() const override { return true; }
+};
+
+} /* namespace detail */
+
+class MultiStringRange {
+  typedef detail::StringArg StringArg;
+  const StringArg* cur;
+  const StringArg* end;
+
+ public:
+  explicit MultiStringRange(const StringArg* cur, const StringArg* end)
+      : cur(cur), end(end) {
+    MOZ_ASSERT(end - cur >= 0);
+  }
+
+  bool empty() const { return cur == end; }
+  void popFront() {
+    MOZ_ASSERT(!empty());
+    ++cur;
+  }
+  char* front() const {
+    MOZ_ASSERT(!empty());
+    return cur->value;
+  }
+  size_t argno() const {
+    MOZ_ASSERT(!empty());
+    return cur->argno;
+  }
+};
+
+/*
+ * Builder for describing a command line interface and parsing the resulting
+ * specification.
+ *
+ * - A multi-option is an option that can appear multiple times and still
+ *   parse as valid command line arguments.
+ * - An "optional argument" is supported for backwards compatibility with prior
+ *   command line interface usage. Once one optional argument has been added,
+ *   *only* optional arguments may be added.
+ */
+class OptionParser {
+ public:
+  enum Result {
+    Okay = 0,
+    Fail,       /* As in, allocation fail. */
+    ParseError, /* Successfully parsed but with an error. */
+    EarlyExit   /* Successfully parsed but exits the program,
+                 * for example with --help and --version. */
+  };
+
+ private:
+  typedef Vector<detail::Option*, 0, detail::OptionAllocPolicy> Options;
+  typedef detail::Option Option;
+  typedef detail::BoolOption BoolOption;
+
+  Options options;
+  Options arguments;
+  BoolOption helpOption;
+  BoolOption versionOption;
+  const char* usage;
+  const char* version;
+  const char* descr;
+  size_t descrWidth;
+  size_t helpWidth;
+  size_t nextArgument;
+
+  // If '--' is passed, all remaining arguments should be interpreted as the
+  // argument at index 'restArgument'. Defaults to the next unassigned
+  // argument.
+  int restArgument;
+
+  Option* findOption(char shortflag);
+  const Option* findOption(char shortflag) const;
+  const Option* tryFindOption(char shortflag) const;
+  Option* findOption(const char* longflag);
+  const Option* findOption(const char* longflag) const;
+  const Option* tryFindOption(const char* longflag) const;
+  int findArgumentIndex(const char* name) const;
+  Option* findArgument(const char* name);
+  const Option* findArgument(const char* name) const;
+
+  Result error(const char* fmt, ...) MOZ_FORMAT_PRINTF(2, 3);
+  Result extractValue(size_t argc, char** argv, size_t* i, char** value);
+  Result handleArg(size_t argc, char** argv, size_t* i, bool* optsAllowed);
+  Result handleOption(Option* opt, size_t argc, char** argv, size_t* i,
+                      bool* optsAllowed);
+
+ public:
+  explicit OptionParser(const char* usage)
+      : helpOption('h', "help", "Display help information"),
+        versionOption('v', "version", "Display version information and exit"),
+        usage(usage),
+        version(nullptr),
+        descr(nullptr),
+        descrWidth(80),
+        helpWidth(80),
+        nextArgument(0),
+        restArgument(-1) {}
+
+  ~OptionParser();
+
+  Result parseArgs(int argc, char** argv);
+  Result printHelp(const char* progname);
+  Result printVersion();
+
+  /* Metadata */
+
+  void setVersion(const char* v) { version = v; }
+  void setHelpWidth(size_t width) { helpWidth = width; }
+  void setDescriptionWidth(size_t width) { descrWidth = width; }
+  void setDescription(const char* description) { descr = description; }
+  void setHelpOption(char shortflag, const char* longflag, const char* help);
+  void setArgTerminatesOptions(const char* name, bool enabled);
+  void setArgCapturesRest(const char* name);
+
+  /* Arguments: no further arguments may be added after a variadic argument. */
+
+  bool addOptionalStringArg(const char* name, const char* help);
+  bool addOptionalMultiStringArg(const char* name, const char* help);
+
+  const char* getStringArg(const char* name) const;
+  MultiStringRange getMultiStringArg(const char* name) const;
+
+  /* Options */
+
+  bool addBoolOption(char shortflag, const char* longflag, const char* help);
+  bool addStringOption(char shortflag, const char* longflag, const char* help,
+                       const char* metavar);
+  bool addIntOption(char shortflag, const char* longflag, const char* help,
+                    const char* metavar, int defaultValue);
+  bool addMultiStringOption(char shortflag, const char* longflag,
+                            const char* help, const char* metavar);
+  bool addOptionalVariadicArg(const char* name);
+
+  int getIntOption(char shortflag) const;
+  int getIntOption(const char* longflag) const;
+  const char* getStringOption(char shortflag) const;
+  const char* getStringOption(const char* longflag) const;
+  bool getBoolOption(char shortflag) const;
+  bool getBoolOption(const char* longflag) const;
+  MultiStringRange getMultiStringOption(char shortflag) const;
+  MultiStringRange getMultiStringOption(const char* longflag) const;
+
+  /*
+   * Return whether the help option was present (and thus help was already
+   * displayed during parse_args).
+   */
+  bool getHelpOption() const;
+};
+
+} /* namespace cli */
+} /* namespace js */
+
+#endif /* shell_jsoptparse_h */
diff --git a/js/src/shell/jsrtfuzzing/jsrtfuzzing-example.js b/js/src/shell/jsrtfuzzing/jsrtfuzzing-example.js
new file mode 100644
index 0000000000..2ea9dd95ae
--- /dev/null
+++ b/js/src/shell/jsrtfuzzing/jsrtfuzzing-example.js
@@ -0,0 +1,42 @@
+/* -*- Mode: javascript; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+// This global will hold the current fuzzing buffer for each iteration.
+var fuzzBuf;
+
+function JSFuzzIterate() {
+  // This function is called per iteration. You must ensure that:
+  //
+  //   1) Each of your actions/decisions is only based on fuzzBuf,
+  //      in particular not on Math.random(), Date/Time or other
+  //      external inputs.
+  //
+  //   2) Your actions should be deterministic. The same fuzzBuf
+  //      should always lead to the same set of actions/decisions.
+  //
+  //   3) You can modify the global where needed, but ensure that
+  //      each iteration is isolated from one another by cleaning
+  //      any modifications to the global after each iteration.
+  //      In particular, iterations must not depend on or influence
+  //      each other in any way (see also 1)).
+  //
+  //   4) You must catch all exceptions.
+
+  try {
+    // This is a very simple UTF-16 string conversion for example purposes only.
+    let input = String.fromCharCode.apply(
+      null,
+      new Uint16Array(fuzzBuf.buffer)
+    );
+
+    // Pass the input through the JSON code as an example. Note that this
+    // particular example could probably be implemented more efficiently
+    // directly in fuzz-tests on a C++ level. This is purely for demonstration
+    // purposes.
+    print(JSON.stringify(JSON.parse(input)));
+  } catch (exc) {
+    print(exc);
+  }
+}
diff --git a/js/src/shell/jsrtfuzzing/jsrtfuzzing.cpp b/js/src/shell/jsrtfuzzing/jsrtfuzzing.cpp
new file mode 100644
index 0000000000..0b6f505fb6
--- /dev/null
+++ b/js/src/shell/jsrtfuzzing/jsrtfuzzing.cpp
@@ -0,0 +1,139 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "shell/jsrtfuzzing/jsrtfuzzing.h"
+
+#include "mozilla/Assertions.h"  // MOZ_CRASH
+#include "mozilla/Utf8.h"        // mozilla::Utf8Unit
+
+#include <stdio.h>  // fflush, fprintf, fputs
+
+#include "FuzzerDefs.h"
+#include "FuzzingInterface.h"
+#include "jsapi.h"  // JS_ClearPendingException, JS_IsExceptionPending
+
+#include "js/CompilationAndEvaluation.h"  // JS::Evaluate
+#include "js/CompileOptions.h"            // JS::CompileOptions
+#include "js/Conversions.h"               // JS::ToInt32
+#include "js/ErrorReport.h"               // JS::PrintError
+#include "js/Exception.h"                 // JS::StealPendingExceptionStack
+#include "js/experimental/TypedData.h"  // JS_GetUint8ClampedArrayData, JS_NewUint8ClampedArray
+#include "js/PropertyAndElement.h"  // JS_SetProperty
+#include "js/RootingAPI.h"          // JS::Rooted
+#include "js/SourceText.h"          // JS::Source{Ownership,Text}
+#include "js/Value.h"               // JS::Value
+#include "shell/jsshell.h"  // js::shell::{reportWarnings,PrintStackTrace,sArg{c,v}}
+#include "util/Text.h"
+#include "vm/Interpreter.h"
+#include "vm/TypedArrayObject.h"
+
+#include "vm/ArrayBufferObject-inl.h"
+#include "vm/JSContext-inl.h"
+
+static JSContext* gCx = nullptr;
+static std::string gFuzzModuleName;
+
+static void CrashOnPendingException() {
+  if (JS_IsExceptionPending(gCx)) {
+    JS::ExceptionStack exnStack(gCx);
+    (void)JS::StealPendingExceptionStack(gCx, &exnStack);
+
+    JS::ErrorReportBuilder report(gCx);
+    if (!report.init(gCx, exnStack, JS::ErrorReportBuilder::WithSideEffects)) {
+      fprintf(stderr, "out of memory initializing JS::ErrorReportBuilder\n");
+      fflush(stderr);
+    } else {
+      JS::PrintError(stderr, report, js::shell::reportWarnings);
+      if (!js::shell::PrintStackTrace(gCx, exnStack.stack())) {
+        fputs("(Unable to print stack trace)\n", stderr);
+      }
+    }
+
+    MOZ_CRASH("Unhandled exception from JS runtime!");
+  }
+}
+
+int js::shell::FuzzJSRuntimeStart(JSContext* cx, int* argc, char*** argv) {
+  gCx = cx;
+  gFuzzModuleName = getenv("FUZZER");
+
+  int ret = FuzzJSRuntimeInit(argc, argv);
+  if (ret) {
+    fprintf(stderr, "Fuzzing Interface: Error: Initialize callback failed\n");
+    return ret;
+  }
+
+#ifdef LIBFUZZER
+  fuzzer::FuzzerDriver(&shell::sArgc, &shell::sArgv, FuzzJSRuntimeFuzz);
+#elif AFLFUZZ
+  MOZ_CRASH("AFL is unsupported for JS runtime fuzzing integration");
+#endif
+  return 0;
+}
+
+int js::shell::FuzzJSRuntimeInit(int* argc, char*** argv) {
+  JS::Rooted<JS::Value> v(gCx);
+  JS::CompileOptions opts(gCx);
+
+  // Load the fuzzing module specified in the FUZZER environment variable
+  JS::EvaluateUtf8Path(gCx, opts, gFuzzModuleName.c_str(), &v);
+
+  // Any errors while loading the fuzzing module should be fatal
+  CrashOnPendingException();
+
+  return 0;
+}
+
+int js::shell::FuzzJSRuntimeFuzz(const uint8_t* buf, size_t size) {
+  if (!size) {
+    return 0;
+  }
+
+  JS::Rooted<JSObject*> arr(gCx, JS_NewUint8ClampedArray(gCx, size));
+  if (!arr) {
+    MOZ_CRASH("OOM");
+  }
+
+  do {
+    JS::AutoCheckCannotGC nogc;
+    bool isShared;
+    uint8_t* data = JS_GetUint8ClampedArrayData(arr, &isShared, nogc);
+    MOZ_RELEASE_ASSERT(!isShared);
+    memcpy(data, buf, size);
+  } while (false);
+
+  JS::RootedValue arrVal(gCx, JS::ObjectValue(*arr));
+  if (!JS_SetProperty(gCx, gCx->global(), "fuzzBuf", arrVal)) {
+    MOZ_CRASH("JS_SetProperty failed");
+  }
+
+  JS::Rooted<JS::Value> v(gCx);
+  JS::CompileOptions opts(gCx);
+
+  static const char data[] = "JSFuzzIterate();";
+
+  JS::SourceText<mozilla::Utf8Unit> srcBuf;
+  if (!srcBuf.init(gCx, data, js_strlen(data), JS::SourceOwnership::Borrowed)) {
+    return 1;
+  }
+
+  if (!JS::Evaluate(gCx, opts.setFileAndLine(__FILE__, __LINE__), srcBuf, &v) &&
+      !JS_IsExceptionPending(gCx)) {
+    // A return value of `false` without a pending exception indicates
+    // a timeout as triggered by the `timeout` shell function.
+    return 1;
+  }
+
+  // The fuzzing module is required to handle any exceptions
+  CrashOnPendingException();
+
+  int32_t ret = 0;
+  if (!JS::ToInt32(gCx, v, &ret)) {
+    MOZ_CRASH("Must return an int32 compatible return value!");
+  }
+
+  return ret;
+}
diff --git a/js/src/shell/jsrtfuzzing/jsrtfuzzing.h b/js/src/shell/jsrtfuzzing/jsrtfuzzing.h
new file mode 100644
index 0000000000..9216aa91a1
--- /dev/null
+++ b/js/src/shell/jsrtfuzzing/jsrtfuzzing.h
@@ -0,0 +1,28 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+// jsrtfuzzing.h - Functionality for JS runtime fuzzing
+
+#ifndef shell_jsrtfuzzing_h
+#define shell_jsrtfuzzing_h
+
+#include "vm/JSContext.h"
+
+namespace js {
+namespace shell {
+
+// This is the entry point of the JS runtime fuzzing code from the JS shell
+int FuzzJSRuntimeStart(JSContext* cx, int* argc, char*** argv);
+
+// These are the traditional libFuzzer-style functions for initialization
+// and fuzzing iteration.
+int FuzzJSRuntimeInit(int* argc, char*** argv);
+int FuzzJSRuntimeFuzz(const uint8_t* buf, size_t size);
+
+}  // namespace shell
+}  // namespace js
+
+#endif /* shell_jsrtfuzzing_h */
diff --git a/js/src/shell/jsshell.cpp b/js/src/shell/jsshell.cpp
new file mode 100644
index 0000000000..fe4b7488dc
--- /dev/null
+++ b/js/src/shell/jsshell.cpp
@@ -0,0 +1,128 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+// jsshell.cpp - Utilities for the JS shell
+
+#include "shell/jsshell.h"
+
+#include "mozilla/Sprintf.h"
+
+#include "jsfriendapi.h"
+
+#include "js/GlobalObject.h"
+#include "js/PropertyAndElement.h"  // JS_DefineProperty, JS_GetProperty, JS_GetPropertyById
+#include "util/StringBuffer.h"
+
+using namespace JS;
+
+namespace js {
+namespace shell {
+
+// Generate 'usage' and 'help' properties for the given object.
+// JS_DefineFunctionsWithHelp will define individual function objects with both
+// of those properties (eg getpid.usage = "getpid()" and getpid.help = "return
+// the process id"). This function will generate strings for an "interface
+// object", eg os.file, which contains some number of functions.
+//
+// .usage will be set to "<name> - interface object".
+//
+// .help will be set to a newline-separated list of functions that have either
+// 'help' or 'usage' properties. Functions are described with their usage
+// strings, if they have them, else with just their names.
+//
+bool GenerateInterfaceHelp(JSContext* cx, HandleObject obj, const char* name) {
+  RootedIdVector idv(cx);
+  if (!GetPropertyKeys(cx, obj, JSITER_OWNONLY | JSITER_HIDDEN, &idv)) {
+    return false;
+  }
+
+  JSStringBuilder buf(cx);
+  int numEntries = 0;
+  for (size_t i = 0; i < idv.length(); i++) {
+    RootedId id(cx, idv[i]);
+    RootedValue v(cx);
+    if (!JS_GetPropertyById(cx, obj, id, &v)) {
+      return false;
+    }
+    if (!v.isObject()) {
+      continue;
+    }
+    RootedObject prop(cx, &v.toObject());
+
+    RootedValue usage(cx);
+    RootedValue help(cx);
+    if (!JS_GetProperty(cx, prop, "usage", &usage)) {
+      return false;
+    }
+    if (!JS_GetProperty(cx, prop, "help", &help)) {
+      return false;
+    }
+    if (!usage.isString() && !help.isString()) {
+      continue;
+    }
+
+    if (numEntries && !buf.append("\n")) {
+      return false;
+    }
+    numEntries++;
+
+    if (!buf.append("  ")) {
+      return false;
+    }
+
+    if (!buf.append(usage.isString() ? usage.toString() : id.toString())) {
+      return false;
+    }
+  }
+
+  RootedString s(cx, buf.finishString());
+  if (!s || !JS_DefineProperty(cx, obj, "help", s, 0)) {
+    return false;
+  }
+
+  buf.clear();
+  if (!buf.append(name, strlen(name)) ||
+      !buf.append(" - interface object with ")) {
+    return false;
+  }
+  char cbuf[100];
+  SprintfLiteral(cbuf, "%d %s", numEntries,
+                 numEntries == 1 ? "entry" : "entries");
+  if (!buf.append(cbuf, strlen(cbuf))) {
+    return false;
+  }
+  s = buf.finishString();
+  if (!s || !JS_DefineProperty(cx, obj, "usage", s, 0)) {
+    return false;
+  }
+
+  return true;
+}
+
+bool CreateAlias(JSContext* cx, const char* dstName,
+                 JS::HandleObject namespaceObj, const char* srcName) {
+  RootedObject global(cx, JS::GetNonCCWObjectGlobal(namespaceObj));
+
+  RootedValue val(cx);
+  if (!JS_GetProperty(cx, namespaceObj, srcName, &val)) {
+    return false;
+  }
+
+  if (!val.isObject()) {
+    JS_ReportErrorASCII(cx, "attempted to alias nonexistent function");
+    return false;
+  }
+
+  RootedObject function(cx, &val.toObject());
+  if (!JS_DefineProperty(cx, global, dstName, function, 0)) {
+    return false;
+  }
+
+  return true;
+}
+
+}  // namespace shell
+}  // namespace js
diff --git a/js/src/shell/jsshell.h b/js/src/shell/jsshell.h
new file mode 100644
index 0000000000..a5be15cb35
--- /dev/null
+++ b/js/src/shell/jsshell.h
@@ -0,0 +1,264 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef jsshell_js_h
+#define jsshell_js_h
+
+#include "mozilla/Atomics.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/TimeStamp.h"
+
+#include "builtin/MapObject.h"
+#include "js/CompileOptions.h"
+#include "js/GCVector.h"
+#include "shell/ModuleLoader.h"
+#include "threading/ConditionVariable.h"
+#include "threading/LockGuard.h"
+#include "threading/Mutex.h"
+#include "threading/Thread.h"
+#include "vm/GeckoProfiler.h"
+#include "vm/Monitor.h"
+
+// Some platform hooks must be implemented for single-step profiling.
+#if defined(JS_SIMULATOR_ARM) || defined(JS_SIMULATOR_MIPS64) || \
+    defined(JS_SIMULATOR_MIPS32)
+#  define SINGLESTEP_PROFILING
+#endif
+
+namespace js {
+namespace shell {
+
+// Define use of application-specific slots on the shell's global object.
+enum GlobalAppSlot { GlobalAppSlotModuleRegistry, GlobalAppSlotCount };
+static_assert(GlobalAppSlotCount <= JSCLASS_GLOBAL_APPLICATION_SLOTS,
+              "Too many applications slots defined for shell global");
+
+enum JSShellErrNum {
+#define MSG_DEF(name, count, exception, format) name,
+#include "jsshell.msg"
+#undef MSG_DEF
+  JSShellErr_Limit
+};
+
+const JSErrorFormatString* my_GetErrorMessage(void* userRef,
+                                              const unsigned errorNumber);
+
+void WarningReporter(JSContext* cx, JSErrorReport* report);
+
+class MOZ_STACK_CLASS AutoReportException {
+  JSContext* cx;
+
+ public:
+  explicit AutoReportException(JSContext* cx) : cx(cx) {}
+  ~AutoReportException();
+};
+
+bool GenerateInterfaceHelp(JSContext* cx, JS::HandleObject obj,
+                           const char* name);
+
+JSString* FileAsString(JSContext* cx, JS::HandleString pathnameStr);
+
+class AutoCloseFile {
+ private:
+  FILE* f_;
+
+ public:
+  explicit AutoCloseFile(FILE* f) : f_(f) {}
+  ~AutoCloseFile() { (void)release(); }
+  bool release() {
+    bool success = true;
+    if (f_ && f_ != stdin && f_ != stdout && f_ != stderr) {
+      success = !fclose(f_);
+    }
+    f_ = nullptr;
+    return success;
+  }
+};
+
+// Reference counted file.
+struct RCFile {
+  FILE* fp;
+  uint32_t numRefs;
+
+  RCFile() : fp(nullptr), numRefs(0) {}
+  explicit RCFile(FILE* fp) : fp(fp), numRefs(0) {}
+
+  void acquire() { numRefs++; }
+
+  // Starts out with a ref count of zero.
+  static RCFile* create(JSContext* cx, const char* filename, const char* mode);
+
+  void close();
+  bool isOpen() const { return fp; }
+  bool release();
+};
+
+// Shell command-line arguments and count.
+extern int sArgc;
+extern char** sArgv;
+
+// Shell state set once at startup.
+extern const char* selfHostedXDRPath;
+extern bool encodeSelfHostedCode;
+extern bool enableCodeCoverage;
+extern bool enableDisassemblyDumps;
+extern bool offthreadCompilation;
+extern JS::DelazificationOption defaultDelazificationMode;
+extern bool enableAsmJS;
+extern bool enableWasm;
+extern bool enableSharedMemory;
+extern bool enableWasmBaseline;
+extern bool enableWasmOptimizing;
+
+#define WASM_FEATURE(NAME, ...) extern bool enableWasm##NAME;
+JS_FOR_WASM_FEATURES(WASM_FEATURE, WASM_FEATURE, WASM_FEATURE);
+#undef WASM_FEATURE
+
+extern bool enableWasmVerbose;
+extern bool enableTestWasmAwaitTier2;
+extern bool enableSourcePragmas;
+extern bool enableAsyncStacks;
+extern bool enableAsyncStackCaptureDebuggeeOnly;
+extern bool enableWeakRefs;
+extern bool enableToSource;
+extern bool enablePropertyErrorMessageFix;
+extern bool enableIteratorHelpers;
+extern bool enableShadowRealms;
+extern bool enableArrayGrouping;
+extern bool enableArrayFromAsync;
+extern bool enablePrivateClassFields;
+extern bool enablePrivateClassMethods;
+#ifdef ENABLE_CHANGE_ARRAY_BY_COPY
+extern bool enableChangeArrayByCopy;
+#endif
+#ifdef ENABLE_NEW_SET_METHODS
+extern bool enableNewSetMethods;
+#endif
+extern bool enableClassStaticBlocks;
+extern bool enableImportAssertions;
+#ifdef JS_GC_ZEAL
+extern uint32_t gZealBits;
+extern uint32_t gZealFrequency;
+#endif
+extern bool printTiming;
+extern RCFile* gErrFile;
+extern RCFile* gOutFile;
+extern bool reportWarnings;
+extern bool compileOnly;
+extern bool disableOOMFunctions;
+extern bool defaultToSameCompartment;
+
+#ifdef DEBUG
+extern bool dumpEntrainedVariables;
+extern bool OOM_printAllocationCount;
+#endif
+
+extern bool useFdlibmForSinCosTan;
+
+extern UniqueChars processWideModuleLoadPath;
+
+// Alias the global dstName to namespaceObj.srcName. For example, if dstName is
+// "snarf", namespaceObj represents "os.file", and srcName is "readFile", then
+// this is equivalent to the JS code:
+//
+//   snarf = os.file.readFile;
+//
+// This provides a mechanism for namespacing the various JS shell helper
+// functions without breaking backwards compatibility with things that use the
+// global names.
+bool CreateAlias(JSContext* cx, const char* dstName,
+                 JS::HandleObject namespaceObj, const char* srcName);
+
+class NonshrinkingGCObjectVector
+    : public GCVector<HeapPtr<JSObject*>, 0, SystemAllocPolicy> {
+ public:
+  bool traceWeak(JSTracer* trc) {
+    for (HeapPtr<JSObject*>& obj : *this) {
+      TraceWeakEdge(trc, &obj, "NonshrinkingGCObjectVector element");
+    }
+    return true;
+  }
+};
+
+using MarkBitObservers = JS::WeakCache<NonshrinkingGCObjectVector>;
+
+#ifdef SINGLESTEP_PROFILING
+using StackChars = Vector<char16_t, 0, SystemAllocPolicy>;
+#endif
+
+class OffThreadJob;
+
+// Per-context shell state.
+struct ShellContext {
+  explicit ShellContext(JSContext* cx);
+  ~ShellContext();
+
+  bool isWorker;
+  bool lastWarningEnabled;
+
+  // Track promise rejections and report unhandled rejections.
+  bool trackUnhandledRejections;
+
+  double timeoutInterval;
+  double startTime;
+  mozilla::Atomic<bool> serviceInterrupt;
+  mozilla::Atomic<bool> haveInterruptFunc;
+  JS::PersistentRootedValue interruptFunc;
+  JS::PersistentRootedValue lastWarning;
+  JS::PersistentRootedValue promiseRejectionTrackerCallback;
+
+  // Rejected promises that are not yet handled. Added when rejection
+  // happens, and removed when rejection is handled. This uses SetObject to
+  // report unhandled rejections in the rejected order.
+  JS::PersistentRooted<SetObject*> unhandledRejectedPromises;
+
+#ifdef SINGLESTEP_PROFILING
+  Vector<StackChars, 0, SystemAllocPolicy> stacks;
+#endif
+
+  /*
+   * Watchdog thread state.
+   */
+  js::Mutex watchdogLock MOZ_UNANNOTATED;
+  js::ConditionVariable watchdogWakeup;
+  mozilla::Maybe<js::Thread> watchdogThread;
+  mozilla::Maybe<mozilla::TimeStamp> watchdogTimeout;
+
+  js::ConditionVariable sleepWakeup;
+
+  int exitCode;
+  bool quitting;
+
+  JS::UniqueChars readLineBuf;
+  size_t readLineBufPos;
+
+  js::shell::RCFile** errFilePtr;
+  js::shell::RCFile** outFilePtr;
+
+  UniquePtr<ProfilingStack> geckoProfilingStack;
+
+  UniquePtr<ModuleLoader> moduleLoader;
+
+  UniquePtr<MarkBitObservers> markObservers;
+
+  // Off-thread parse state.
+  js::Monitor offThreadMonitor MOZ_UNANNOTATED;
+  Vector<OffThreadJob*, 0, SystemAllocPolicy> offThreadJobs;
+
+  // Queued finalization registry cleanup jobs.
+  using FunctionVector = GCVector<JSFunction*, 0, SystemAllocPolicy>;
+  JS::PersistentRooted<FunctionVector> finalizationRegistryCleanupCallbacks;
+};
+
+extern ShellContext* GetShellContext(JSContext* cx);
+
+[[nodiscard]] extern bool PrintStackTrace(JSContext* cx,
+                                          JS::Handle<JSObject*> stackObj);
+
+} /* namespace shell */
+} /* namespace js */
+
+#endif
diff --git a/js/src/shell/moz.build b/js/src/shell/moz.build
new file mode 100644
index 0000000000..ed8551f1ec
--- /dev/null
+++ b/js/src/shell/moz.build
@@ -0,0 +1,59 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+GeckoProgram("js", linkage=None)
+if CONFIG["JS_BUNDLED_EDITLINE"]:
+    DIRS += ["../editline"]
+    USE_LIBS += ["editline"]
+USE_LIBS += ["static:js"]
+
+include("../js-config.mozbuild")
+include("../js-cxxflags.mozbuild")
+include("../js-standalone.mozbuild")
+
+UNIFIED_SOURCES += [
+    "js.cpp",
+    "jsoptparse.cpp",
+    "jsshell.cpp",
+    "ModuleLoader.cpp",
+    "OSObject.cpp",
+    "ShellModuleObjectWrapper.cpp",
+    "WasmTesting.cpp",
+]
+
+if CONFIG["FUZZING_INTERFACES"]:
+    UNIFIED_SOURCES += ["jsrtfuzzing/jsrtfuzzing.cpp"]
+    USE_LIBS += [
+        "static:fuzzer",
+    ]
+
+if CONFIG["FUZZING_JS_FUZZILLI"]:
+    OS_LIBS += ["rt"]
+
+DEFINES["EXPORT_JS_API"] = True
+
+LOCAL_INCLUDES += [
+    "!..",
+    "..",
+]
+
+OS_LIBS += CONFIG["EDITLINE_LIBS"]
+
+# Place a GDB Python auto-load file next to the shell executable, both in
+# the build directory and in the dist/bin directory.
+FINAL_TARGET_FILES += ["js-gdb.py"]
+OBJDIR_FILES.js.src.shell += ["!/dist/bin/js-gdb.py"]
+
+# People expect the js shell to wind up in the top-level JS dir.
+OBJDIR_FILES.js.src += ["!/dist/bin/js%s" % CONFIG["BIN_SUFFIX"]]
+
+# Stack size on Wasm/WASI
+# ==================================
+# Increase the default stack size (64KB) to 1MB.
+# Also make the stack grow towards 0 so that if SpiderMonkey's stack limiter is buggy, overflow will likely trap.
+if CONFIG["OS_ARCH"] == "WASI":
+    LDFLAGS += ["-Wl,-z,stack-size=1048576", "-Wl,--stack-first"]
+    OS_LIBS += ["wasi-emulated-process-clocks", "wasi-emulated-getpid"]