1 files changed, 536 insertions, 0 deletions
diff --git a/js/src/vm/BoundFunctionObject.cpp b/js/src/vm/BoundFunctionObject.cpp
new file mode 100644
index 0000000000..1b80415598
--- /dev/null
+++ b/js/src/vm/BoundFunctionObject.cpp
@@ -0,0 +1,536 @@
+/* -*- 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 "vm/BoundFunctionObject.h"
+
+#include <string_view>
+
+#include "util/StringBuffer.h"
+#include "vm/Interpreter.h"
+#include "vm/Shape.h"
+#include "vm/Stack.h"
+
+#include "gc/ObjectKind-inl.h"
+#include "vm/JSFunction-inl.h"
+#include "vm/JSObject-inl.h"
+#include "vm/NativeObject-inl.h"
+#include "vm/Shape-inl.h"
+
+using namespace js;
+
+// Helper function to initialize `args` with all bound arguments + the arguments
+// supplied in `callArgs`.
+template <typename Args>
+static MOZ_ALWAYS_INLINE void FillArguments(Args& args,
+                                            BoundFunctionObject* bound,
+                                            size_t numBoundArgs,
+                                            const CallArgs& callArgs) {
+  MOZ_ASSERT(args.length() == numBoundArgs + callArgs.length());
+
+  if (numBoundArgs <= BoundFunctionObject::MaxInlineBoundArgs) {
+    for (size_t i = 0; i < numBoundArgs; i++) {
+      args[i].set(bound->getInlineBoundArg(i));
+    }
+  } else {
+    ArrayObject* boundArgs = bound->getBoundArgsArray();
+    for (size_t i = 0; i < numBoundArgs; i++) {
+      args[i].set(boundArgs->getDenseElement(i));
+    }
+  }
+
+  for (size_t i = 0; i < callArgs.length(); i++) {
+    args[numBoundArgs + i].set(callArgs[i]);
+  }
+}
+
+// ES2023 10.4.1.1 [[Call]]
+// https://tc39.es/ecma262/#sec-bound-function-exotic-objects-call-thisargument-argumentslist
+// static
+bool BoundFunctionObject::call(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+  Rooted<BoundFunctionObject*> bound(cx,
+                                     &args.callee().as<BoundFunctionObject>());
+
+  // Step 1.
+  Rooted<Value> target(cx, bound->getTargetVal());
+
+  // Step 2.
+  Rooted<Value> boundThis(cx, bound->getBoundThis());
+
+  // Steps 3-4.
+  size_t numBoundArgs = bound->numBoundArgs();
+  InvokeArgs args2(cx);
+  if (!args2.init(cx, uint64_t(numBoundArgs) + args.length())) {
+    return false;
+  }
+  FillArguments(args2, bound, numBoundArgs, args);
+
+  // Step 5.
+  return Call(cx, target, boundThis, args2, args.rval());
+}
+
+// ES2023 10.4.1.2 [[Construct]]
+// https://tc39.es/ecma262/#sec-bound-function-exotic-objects-construct-argumentslist-newtarget
+// static
+bool BoundFunctionObject::construct(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+  Rooted<BoundFunctionObject*> bound(cx,
+                                     &args.callee().as<BoundFunctionObject>());
+
+  MOZ_ASSERT(bound->isConstructor(),
+             "shouldn't have called this hook if not a constructor");
+
+  // Step 1.
+  Rooted<Value> target(cx, bound->getTargetVal());
+
+  // Step 2.
+  MOZ_ASSERT(IsConstructor(target));
+
+  // Steps 3-4.
+  size_t numBoundArgs = bound->numBoundArgs();
+  ConstructArgs args2(cx);
+  if (!args2.init(cx, uint64_t(numBoundArgs) + args.length())) {
+    return false;
+  }
+  FillArguments(args2, bound, numBoundArgs, args);
+
+  // Step 5.
+  Rooted<Value> newTarget(cx, args.newTarget());
+  if (newTarget == ObjectValue(*bound)) {
+    newTarget = target;
+  }
+
+  // Step 6.
+  Rooted<JSObject*> res(cx);
+  if (!Construct(cx, target, args2, newTarget, &res)) {
+    return false;
+  }
+  args.rval().setObject(*res);
+  return true;
+}
+
+// static
+JSString* BoundFunctionObject::funToString(JSContext* cx, Handle<JSObject*> obj,
+                                           bool isToSource) {
+  // Implementation of the funToString hook used by Function.prototype.toString.
+
+  // For the non-standard toSource extension, we include "bound" to indicate
+  // it's a bound function.
+  if (isToSource) {
+    static constexpr std::string_view nativeCodeBound =
+        "function bound() {\n    [native code]\n}";
+    return NewStringCopy<CanGC>(cx, nativeCodeBound);
+  }
+
+  static constexpr std::string_view nativeCode =
+      "function() {\n    [native code]\n}";
+  return NewStringCopy<CanGC>(cx, nativeCode);
+}
+
+// static
+SharedShape* BoundFunctionObject::assignInitialShape(
+    JSContext* cx, Handle<BoundFunctionObject*> obj) {
+  MOZ_ASSERT(obj->empty());
+
+  constexpr PropertyFlags propFlags = {PropertyFlag::Configurable};
+  if (!NativeObject::addPropertyInReservedSlot(cx, obj, cx->names().length,
+                                               LengthSlot, propFlags)) {
+    return nullptr;
+  }
+  if (!NativeObject::addPropertyInReservedSlot(cx, obj, cx->names().name,
+                                               NameSlot, propFlags)) {
+    return nullptr;
+  }
+
+  SharedShape* shape = obj->sharedShape();
+  if (shape->proto() == TaggedProto(&cx->global()->getFunctionPrototype())) {
+    cx->global()->setBoundFunctionShapeWithDefaultProto(shape);
+  }
+  return shape;
+}
+
+static MOZ_ALWAYS_INLINE bool ComputeLengthValue(
+    JSContext* cx, Handle<BoundFunctionObject*> bound, Handle<JSObject*> target,
+    size_t numBoundArgs, double* length) {
+  *length = 0.0;
+
+  // Try to avoid invoking the JSFunction resolve hook.
+  if (target->is<JSFunction>() &&
+      !target->as<JSFunction>().hasResolvedLength()) {
+    uint16_t targetLength;
+    if (!JSFunction::getUnresolvedLength(cx, target.as<JSFunction>(),
+                                         &targetLength)) {
+      return false;
+    }
+
+    if (size_t(targetLength) > numBoundArgs) {
+      *length = size_t(targetLength) - numBoundArgs;
+    }
+    return true;
+  }
+
+  // Use a fast path for getting the .length value if the target is a bound
+  // function with its initial shape.
+  Value targetLength;
+  if (target->is<BoundFunctionObject>() && target->shape() == bound->shape()) {
+    BoundFunctionObject* targetFn = &target->as<BoundFunctionObject>();
+    targetLength = targetFn->getLengthForInitialShape();
+  } else {
+    bool hasLength;
+    Rooted<PropertyKey> key(cx, NameToId(cx->names().length));
+    if (!HasOwnProperty(cx, target, key, &hasLength)) {
+      return false;
+    }
+
+    if (!hasLength) {
+      return true;
+    }
+
+    Rooted<Value> targetLengthRoot(cx);
+    if (!GetProperty(cx, target, target, key, &targetLengthRoot)) {
+      return false;
+    }
+    targetLength = targetLengthRoot;
+  }
+
+  if (targetLength.isNumber()) {
+    *length = std::max(
+        0.0, JS::ToInteger(targetLength.toNumber()) - double(numBoundArgs));
+  }
+  return true;
+}
+
+static MOZ_ALWAYS_INLINE JSAtom* AppendBoundFunctionPrefix(JSContext* cx,
+                                                           JSString* str) {
+  auto& cache = cx->zone()->boundPrefixCache();
+
+  JSAtom* strAtom = str->isAtom() ? &str->asAtom() : nullptr;
+  if (strAtom) {
+    if (auto p = cache.lookup(strAtom)) {
+      return p->value();
+    }
+  }
+
+  StringBuffer sb(cx);
+  if (!sb.append("bound ") || !sb.append(str)) {
+    return nullptr;
+  }
+  JSAtom* atom = sb.finishAtom();
+  if (!atom) {
+    return nullptr;
+  }
+
+  if (strAtom) {
+    (void)cache.putNew(strAtom, atom);
+  }
+  return atom;
+}
+
+static MOZ_ALWAYS_INLINE JSAtom* ComputeNameValue(
+    JSContext* cx, Handle<BoundFunctionObject*> bound,
+    Handle<JSObject*> target) {
+  // Try to avoid invoking the JSFunction resolve hook.
+  JSString* name = nullptr;
+  if (target->is<JSFunction>() && !target->as<JSFunction>().hasResolvedName()) {
+    JSFunction* targetFn = &target->as<JSFunction>();
+    name = targetFn->getUnresolvedName(cx);
+    if (!name) {
+      return nullptr;
+    }
+  } else {
+    // Use a fast path for getting the .name value if the target is a bound
+    // function with its initial shape.
+    Value targetName;
+    if (target->is<BoundFunctionObject>() &&
+        target->shape() == bound->shape()) {
+      BoundFunctionObject* targetFn = &target->as<BoundFunctionObject>();
+      targetName = targetFn->getNameForInitialShape();
+    } else {
+      Rooted<Value> targetNameRoot(cx);
+      if (!GetProperty(cx, target, target, cx->names().name, &targetNameRoot)) {
+        return nullptr;
+      }
+      targetName = targetNameRoot;
+    }
+    if (!targetName.isString()) {
+      return cx->names().boundWithSpace_;
+    }
+    name = targetName.toString();
+  }
+
+  return AppendBoundFunctionPrefix(cx, name);
+}
+
+// ES2023 20.2.3.2 Function.prototype.bind
+// https://tc39.es/ecma262/#sec-function.prototype.bind
+// static
+bool BoundFunctionObject::functionBind(JSContext* cx, unsigned argc,
+                                       Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  // Steps 1-2.
+  if (!IsCallable(args.thisv())) {
+    ReportIncompatibleMethod(cx, args, &FunctionClass);
+    return false;
+  }
+
+  if (MOZ_UNLIKELY(args.length() > ARGS_LENGTH_MAX)) {
+    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                              JSMSG_TOO_MANY_ARGUMENTS);
+    return false;
+  }
+
+  Rooted<JSObject*> target(cx, &args.thisv().toObject());
+
+  BoundFunctionObject* bound =
+      functionBindImpl(cx, target, args.array(), args.length(), nullptr);
+  if (!bound) {
+    return false;
+  }
+
+  // Step 11.
+  args.rval().setObject(*bound);
+  return true;
+}
+
+// ES2023 20.2.3.2 Function.prototype.bind
+// https://tc39.es/ecma262/#sec-function.prototype.bind
+//
+// ES2023 10.4.1.3 BoundFunctionCreate
+// https://tc39.es/ecma262/#sec-boundfunctioncreate
+//
+// BoundFunctionCreate has been inlined in Function.prototype.bind for
+// performance reasons.
+//
+// static
+BoundFunctionObject* BoundFunctionObject::functionBindImpl(
+    JSContext* cx, Handle<JSObject*> target, Value* args, uint32_t argc,
+    Handle<BoundFunctionObject*> maybeBound) {
+  MOZ_ASSERT(target->isCallable());
+
+  // Make sure the arguments on the stack are rooted when we're called directly
+  // from JIT code.
+  RootedExternalValueArray argsRoot(cx, argc, args);
+
+  size_t numBoundArgs = argc > 0 ? argc - 1 : 0;
+  MOZ_ASSERT(numBoundArgs <= ARGS_LENGTH_MAX, "ensured by callers");
+
+  // If this assertion fails, make sure we use the correct AllocKind and that we
+  // use all of its slots (consider increasing MaxInlineBoundArgs).
+  static_assert(gc::GetGCKindSlots(allocKind) == SlotCount);
+
+  // ES2023 10.4.1.3 BoundFunctionCreate
+  // Steps 1-5.
+  Rooted<BoundFunctionObject*> bound(cx);
+  if (maybeBound) {
+    // We allocated a bound function in JIT code. In the uncommon case of the
+    // target not having Function.prototype as proto, we have to set the right
+    // proto here.
+    bound = maybeBound;
+    if (MOZ_UNLIKELY(bound->staticPrototype() != target->staticPrototype())) {
+      Rooted<JSObject*> proto(cx, target->staticPrototype());
+      if (!SetPrototype(cx, bound, proto)) {
+        return nullptr;
+      }
+    }
+  } else {
+    // Step 1.
+    Rooted<JSObject*> proto(cx);
+    if (!GetPrototype(cx, target, &proto)) {
+      return nullptr;
+    }
+
+    // Steps 2-5.
+    if (proto == &cx->global()->getFunctionPrototype() &&
+        cx->global()->maybeBoundFunctionShapeWithDefaultProto()) {
+      Rooted<SharedShape*> shape(
+          cx, cx->global()->maybeBoundFunctionShapeWithDefaultProto());
+      bound = NativeObject::create<BoundFunctionObject>(
+          cx, allocKind, gc::Heap::Default, shape);
+      if (!bound) {
+        return nullptr;
+      }
+    } else {
+      bound = NewObjectWithGivenProto<BoundFunctionObject>(cx, proto);
+      if (!bound) {
+        return nullptr;
+      }
+      if (!SharedShape::ensureInitialCustomShape<BoundFunctionObject>(cx,
+                                                                      bound)) {
+        return nullptr;
+      }
+    }
+  }
+
+  MOZ_ASSERT(bound->lookupPure(cx->names().length)->slot() == LengthSlot);
+  MOZ_ASSERT(bound->lookupPure(cx->names().name)->slot() == NameSlot);
+
+  // Steps 6 and 9.
+  bound->initFlags(numBoundArgs, target->isConstructor());
+
+  // Step 7.
+  bound->initReservedSlot(TargetSlot, ObjectValue(*target));
+
+  // Step 8.
+  if (argc > 0) {
+    bound->initReservedSlot(BoundThisSlot, args[0]);
+  }
+
+  if (numBoundArgs <= MaxInlineBoundArgs) {
+    for (size_t i = 0; i < numBoundArgs; i++) {
+      bound->initReservedSlot(BoundArg0Slot + i, args[i + 1]);
+    }
+  } else {
+    ArrayObject* arr = NewDenseCopiedArray(cx, numBoundArgs, args + 1);
+    if (!arr) {
+      return nullptr;
+    }
+    bound->initReservedSlot(BoundArg0Slot, ObjectValue(*arr));
+  }
+
+  // ES2023 20.2.3.2 Function.prototype.bind
+  // Step 4.
+  double length = 0.0;
+
+  // Steps 5-6.
+  if (!ComputeLengthValue(cx, bound, target, numBoundArgs, &length)) {
+    return nullptr;
+  }
+
+  // Step 7.
+  bound->initLength(length);
+
+  // Steps 8-9.
+  JSAtom* name = ComputeNameValue(cx, bound, target);
+  if (!name) {
+    return nullptr;
+  }
+
+  // Step 10.
+  bound->initName(name);
+
+  // Step 11.
+  return bound;
+}
+
+// static
+BoundFunctionObject* BoundFunctionObject::createWithTemplate(
+    JSContext* cx, Handle<BoundFunctionObject*> templateObj) {
+  Rooted<SharedShape*> shape(cx, templateObj->sharedShape());
+  auto* bound = NativeObject::create<BoundFunctionObject>(
+      cx, allocKind, gc::Heap::Default, shape);
+  if (!bound) {
+    return nullptr;
+  }
+  bound->initFlags(templateObj->numBoundArgs(), templateObj->isConstructor());
+  bound->initLength(templateObj->getLengthForInitialShape().toInt32());
+  bound->initName(&templateObj->getNameForInitialShape().toString()->asAtom());
+  return bound;
+}
+
+// static
+BoundFunctionObject* BoundFunctionObject::functionBindSpecializedBaseline(
+    JSContext* cx, Handle<JSObject*> target, Value* args, uint32_t argc,
+    Handle<BoundFunctionObject*> templateObj) {
+  // Root the Values on the stack.
+  RootedExternalValueArray argsRoot(cx, argc, args);
+
+  MOZ_ASSERT(target->is<JSFunction>() || target->is<BoundFunctionObject>());
+  MOZ_ASSERT(target->isCallable());
+  MOZ_ASSERT(target->isConstructor() == templateObj->isConstructor());
+  MOZ_ASSERT(target->staticPrototype() == templateObj->staticPrototype());
+
+  size_t numBoundArgs = argc > 0 ? argc - 1 : 0;
+  MOZ_ASSERT(numBoundArgs <= MaxInlineBoundArgs);
+
+  BoundFunctionObject* bound = createWithTemplate(cx, templateObj);
+  if (!bound) {
+    return nullptr;
+  }
+
+  MOZ_ASSERT(bound->lookupPure(cx->names().length)->slot() == LengthSlot);
+  MOZ_ASSERT(bound->lookupPure(cx->names().name)->slot() == NameSlot);
+
+  bound->initReservedSlot(TargetSlot, ObjectValue(*target));
+  if (argc > 0) {
+    bound->initReservedSlot(BoundThisSlot, args[0]);
+  }
+  for (size_t i = 0; i < numBoundArgs; i++) {
+    bound->initReservedSlot(BoundArg0Slot + i, args[i + 1]);
+  }
+  return bound;
+}
+
+// static
+BoundFunctionObject* BoundFunctionObject::createTemplateObject(JSContext* cx) {
+  Rooted<JSObject*> proto(cx, &cx->global()->getFunctionPrototype());
+  Rooted<BoundFunctionObject*> bound(
+      cx, NewTenuredObjectWithGivenProto<BoundFunctionObject>(cx, proto));
+  if (!bound) {
+    return nullptr;
+  }
+  if (!SharedShape::ensureInitialCustomShape<BoundFunctionObject>(cx, bound)) {
+    return nullptr;
+  }
+  return bound;
+}
+
+bool BoundFunctionObject::initTemplateSlotsForSpecializedBind(
+    JSContext* cx, uint32_t numBoundArgs, bool targetIsConstructor,
+    uint32_t targetLength, JSAtom* targetName) {
+  size_t len = 0;
+  if (targetLength > numBoundArgs) {
+    len = targetLength - numBoundArgs;
+  }
+
+  JSAtom* name = AppendBoundFunctionPrefix(cx, targetName);
+  if (!name) {
+    return false;
+  }
+
+  initFlags(numBoundArgs, targetIsConstructor);
+  initLength(len);
+  initName(name);
+  return true;
+}
+
+static const JSClassOps classOps = {
+    nullptr,                         // addProperty
+    nullptr,                         // delProperty
+    nullptr,                         // enumerate
+    nullptr,                         // newEnumerate
+    nullptr,                         // resolve
+    nullptr,                         // mayResolve
+    nullptr,                         // finalize
+    BoundFunctionObject::call,       // call
+    BoundFunctionObject::construct,  // construct
+    nullptr,                         // trace
+};
+
+static const ObjectOps objOps = {
+    nullptr,                           // lookupProperty
+    nullptr,                           // qdefineProperty
+    nullptr,                           // hasProperty
+    nullptr,                           // getProperty
+    nullptr,                           // setProperty
+    nullptr,                           // getOwnPropertyDescriptor
+    nullptr,                           // deleteProperty
+    nullptr,                           // getElements
+    BoundFunctionObject::funToString,  // funToString
+};
+
+const JSClass BoundFunctionObject::class_ = {
+    "BoundFunctionObject",
+    // Note: bound functions don't have their own constructor or prototype (they
+    // use the prototype of the target object), but we give them a JSProtoKey
+    // because that's what Xray wrappers use to identify builtin objects.
+    JSCLASS_HAS_CACHED_PROTO(JSProto_BoundFunction) |
+        JSCLASS_HAS_RESERVED_SLOTS(BoundFunctionObject::SlotCount),
+    &classOps,
+    JS_NULL_CLASS_SPEC,
+    JS_NULL_CLASS_EXT,
+    &objOps,
+};