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diff --git a/js/public/CompileOptions.h b/js/public/CompileOptions.h
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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* 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/. */
+
+/*
+ * Options for JavaScript compilation.
+ *
+ * In the most common use case, a CompileOptions instance is allocated on the
+ * stack, and holds non-owning references to non-POD option values: strings,
+ * principals, objects, and so on.  The code declaring the instance guarantees
+ * that such option values will outlive the CompileOptions itself: objects are
+ * otherwise rooted, principals have had their reference counts bumped, and
+ * strings won't be freed until the CompileOptions goes out of scope.  In this
+ * situation, CompileOptions only refers to things others own, so it can be
+ * lightweight.
+ *
+ * In some cases, however, we need to hold compilation options with a
+ * non-stack-like lifetime.  For example, JS::CompileOffThread needs to save
+ * compilation options where a worker thread can find them, then return
+ * immediately.  The worker thread will come along at some later point, and use
+ * the options.
+ *
+ * The compiler itself just needs to be able to access a collection of options;
+ * it doesn't care who owns them, or what's keeping them alive.  It does its
+ * own addrefs/copies/tracing/etc.
+ *
+ * Furthermore, in some cases compile options are propagated from one entity to
+ * another (e.g. from a script to a function defined in that script).  This
+ * involves copying over some, but not all, of the options.
+ *
+ * So we have a class hierarchy that reflects these four use cases:
+ *
+ * - TransitiveCompileOptions is the common base class, representing options
+ *   that should get propagated from a script to functions defined in that
+ *   script.  This class is abstract and is only ever used as a subclass.
+ *
+ * - ReadOnlyCompileOptions is the only subclass of TransitiveCompileOptions,
+ *   representing a full set of compile options.  It can be used by code that
+ *   simply needs to access options set elsewhere, like the compiler.  This
+ *   class too is abstract and is only ever used as a subclass.
+ *
+ * - The usual CompileOptions class must be stack-allocated, and holds
+ *   non-owning references to the filename, element, and so on. It's derived
+ *   from ReadOnlyCompileOptions, so the compiler can use it.
+ *
+ * - OwningCompileOptions roots / copies / reference counts of all its values,
+ *   and unroots / frees / releases them when it is destructed. It too is
+ *   derived from ReadOnlyCompileOptions, so the compiler accepts it.
+ */
+
+#ifndef js_CompileOptions_h
+#define js_CompileOptions_h
+
+#include "mozilla/Attributes.h"       // MOZ_MUST_USE
+#include "mozilla/MemoryReporting.h"  // mozilla::MallocSizeOf
+
+#include <stddef.h>  // size_t
+#include <stdint.h>  // uint8_t
+
+#include "jstypes.h"  // JS_PUBLIC_API
+
+#include "js/RootingAPI.h"  // JS::PersistentRooted, JS::Rooted
+#include "js/Value.h"
+
+struct JS_PUBLIC_API JSContext;
+class JS_PUBLIC_API JSObject;
+class JS_PUBLIC_API JSScript;
+class JS_PUBLIC_API JSString;
+
+namespace JS {
+
+enum class AsmJSOption : uint8_t {
+  Enabled,
+  Disabled,
+  DisabledByDebugger,
+};
+
+/**
+ * The common base class for the CompileOptions hierarchy.
+ *
+ * Use this in code that needs to propagate compile options from one
+ * compilation unit to another.
+ */
+class JS_PUBLIC_API TransitiveCompileOptions {
+ protected:
+  /**
+   * The Web Platform allows scripts to be loaded from arbitrary cross-origin
+   * sources. This allows an attack by which a malicious website loads a
+   * sensitive file (say, a bank statement) cross-origin (using the user's
+   * cookies), and sniffs the generated syntax errors (via a window.onerror
+   * handler) for juicy morsels of its contents.
+   *
+   * To counter this attack, HTML5 specifies that script errors should be
+   * sanitized ("muted") when the script is not same-origin with the global
+   * for which it is loaded. Callers should set this flag for cross-origin
+   * scripts, and it will be propagated appropriately to child scripts and
+   * passed back in JSErrorReports.
+   */
+  bool mutedErrors_ = false;
+
+  // Either the Realm configuration or specialized VM operating modes may
+  // disallow syntax-parse altogether. These conditions are checked in the
+  // CompileOptions constructor.
+  bool forceFullParse_ = false;
+
+  // Either the Realm configuration or the compile request may force
+  // strict-mode.
+  bool forceStrictMode_ = false;
+
+  // The context has specified that source pragmas should be parsed.
+  bool sourcePragmas_ = true;
+
+  const char* filename_ = nullptr;
+  const char* introducerFilename_ = nullptr;
+  const char16_t* sourceMapURL_ = nullptr;
+
+  // Flag used to bypass the filename validation callback.
+  // See also SetFilenameValidationCallback.
+  bool skipFilenameValidation_ = false;
+
+ public:
+  // POD options.
+  bool selfHostingMode = false;
+  AsmJSOption asmJSOption = AsmJSOption::Disabled;
+  bool throwOnAsmJSValidationFailureOption = false;
+  bool forceAsync = false;
+  bool discardSource = false;
+  bool sourceIsLazy = false;
+  bool allowHTMLComments = true;
+  bool hideScriptFromDebugger = false;
+  bool nonSyntacticScope = false;
+  bool privateClassFields = false;
+  bool privateClassMethods = false;
+  bool topLevelAwait = false;
+
+  // True if transcoding to XDR should use Stencil instead of JSScripts.
+  bool useStencilXDR = false;
+
+  // True if off-thread parsing should use a parse GlobalObject in order to
+  // directly allocate to the GC from a helper thread. If false, transfer the
+  // CompilationStencil back to main thread before allocating GC objects.
+  bool useOffThreadParseGlobal = true;
+
+  /**
+   * |introductionType| is a statically allocated C string: one of "eval",
+   * "Function", or "GeneratorFunction".
+   */
+  const char* introductionType = nullptr;
+
+  unsigned introductionLineno = 0;
+  uint32_t introductionOffset = 0;
+  bool hasIntroductionInfo = false;
+
+  // Mask of operation kinds which should be instrumented.
+  uint32_t instrumentationKinds = 0;
+
+ protected:
+  TransitiveCompileOptions() = default;
+
+  // Set all POD options (those not requiring reference counts, copies,
+  // rooting, or other hand-holding) to their values in |rhs|.
+  void copyPODTransitiveOptions(const TransitiveCompileOptions& rhs);
+
+ public:
+  // Read-only accessors for non-POD options. The proper way to set these
+  // depends on the derived type.
+  bool mutedErrors() const { return mutedErrors_; }
+  bool forceFullParse() const { return forceFullParse_; }
+  bool forceStrictMode() const { return forceStrictMode_; }
+  bool skipFilenameValidation() const { return skipFilenameValidation_; }
+  bool sourcePragmas() const { return sourcePragmas_; }
+  const char* filename() const { return filename_; }
+  const char* introducerFilename() const { return introducerFilename_; }
+  const char16_t* sourceMapURL() const { return sourceMapURL_; }
+  virtual Value privateValue() const = 0;
+  virtual JSString* elementAttributeName() const = 0;
+  virtual JSScript* introductionScript() const = 0;
+
+  // For some compilations the spec requires the ScriptOrModule field of the
+  // resulting script to be set to the currently executing script. This can be
+  // achieved by setting this option with setScriptOrModule() below.
+  //
+  // Note that this field doesn't explicitly exist in our implementation;
+  // instead the ScriptSourceObject's private value is set to that associated
+  // with the specified script.
+  virtual JSScript* scriptOrModule() const = 0;
+
+  TransitiveCompileOptions(const TransitiveCompileOptions&) = delete;
+  TransitiveCompileOptions& operator=(const TransitiveCompileOptions&) = delete;
+};
+
+/**
+ * The class representing a full set of compile options.
+ *
+ * Use this in code that only needs to access compilation options created
+ * elsewhere, like the compiler.  Don't instantiate this class (the constructor
+ * is protected anyway); instead, create instances only of the derived classes:
+ * CompileOptions and OwningCompileOptions.
+ */
+class JS_PUBLIC_API ReadOnlyCompileOptions : public TransitiveCompileOptions {
+ public:
+  // POD options.
+  unsigned lineno = 1;
+  unsigned column = 0;
+
+  // The offset within the ScriptSource's full uncompressed text of the first
+  // character we're presenting for compilation with this CompileOptions.
+  //
+  // When we compile a lazy script, we pass the compiler only the substring of
+  // the source the lazy function occupies. With chunked decompression, we may
+  // not even have the complete uncompressed source present in memory. But parse
+  // node positions are offsets within the ScriptSource's full text, and
+  // BaseScript indicate their substring of the full source by its starting and
+  // ending offsets within the full text. This scriptSourceOffset field lets the
+  // frontend convert between these offsets and offsets within the substring
+  // presented for compilation.
+  unsigned scriptSourceOffset = 0;
+
+  // These only apply to non-function scripts.
+  bool isRunOnce = false;
+  bool noScriptRval = false;
+
+ protected:
+  ReadOnlyCompileOptions() = default;
+
+  void copyPODNonTransitiveOptions(const ReadOnlyCompileOptions& rhs);
+
+  ReadOnlyCompileOptions(const ReadOnlyCompileOptions&) = delete;
+  ReadOnlyCompileOptions& operator=(const ReadOnlyCompileOptions&) = delete;
+};
+
+/**
+ * Compilation options, with dynamic lifetime. An instance of this type
+ * makes a copy of / holds / roots all dynamically allocated resources
+ * (principals; elements; strings) that it refers to. Its destructor frees
+ * / drops / unroots them. This is heavier than CompileOptions, below, but
+ * unlike CompileOptions, it can outlive any given stack frame.
+ *
+ * Note that this *roots* any JS values it refers to - they're live
+ * unconditionally. Thus, instances of this type can't be owned, directly
+ * or indirectly, by a JavaScript object: if any value that this roots ever
+ * comes to refer to the object that owns this, then the whole cycle, and
+ * anything else it entrains, will never be freed.
+ */
+class JS_PUBLIC_API OwningCompileOptions final : public ReadOnlyCompileOptions {
+  PersistentRooted<JSString*> elementAttributeNameRoot;
+  PersistentRooted<JSScript*> introductionScriptRoot;
+  PersistentRooted<JSScript*> scriptOrModuleRoot;
+  PersistentRooted<Value> privateValueRoot;
+
+ public:
+  // A minimal constructor, for use with OwningCompileOptions::copy.
+  explicit OwningCompileOptions(JSContext* cx);
+  ~OwningCompileOptions();
+
+  Value privateValue() const override { return privateValueRoot; }
+  JSString* elementAttributeName() const override {
+    return elementAttributeNameRoot;
+  }
+  JSScript* introductionScript() const override {
+    return introductionScriptRoot;
+  }
+  JSScript* scriptOrModule() const override { return scriptOrModuleRoot; }
+
+  /** Set this to a copy of |rhs|.  Return false on OOM. */
+  bool copy(JSContext* cx, const ReadOnlyCompileOptions& rhs);
+
+  size_t sizeOfExcludingThis(mozilla::MallocSizeOf mallocSizeOf) const;
+
+  OwningCompileOptions& setIsRunOnce(bool once) {
+    isRunOnce = once;
+    return *this;
+  }
+
+  OwningCompileOptions& setForceStrictMode() {
+    forceStrictMode_ = true;
+    return *this;
+  }
+
+  OwningCompileOptions& setModule() {
+    // ES6 10.2.1 Module code is always strict mode code.
+    setForceStrictMode();
+    setIsRunOnce(true);
+    allowHTMLComments = false;
+    return *this;
+  }
+
+ private:
+  void release();
+
+  OwningCompileOptions(const OwningCompileOptions&) = delete;
+  OwningCompileOptions& operator=(const OwningCompileOptions&) = delete;
+};
+
+/**
+ * Compilation options stored on the stack. An instance of this type
+ * simply holds references to dynamically allocated resources (element;
+ * filename; source map URL) that are owned by something else. If you
+ * create an instance of this type, it's up to you to guarantee that
+ * everything you store in it will outlive it.
+ */
+class MOZ_STACK_CLASS JS_PUBLIC_API CompileOptions final
+    : public ReadOnlyCompileOptions {
+ private:
+  Rooted<JSString*> elementAttributeNameRoot;
+  Rooted<JSScript*> introductionScriptRoot;
+  Rooted<JSScript*> scriptOrModuleRoot;
+  Rooted<Value> privateValueRoot;
+
+ public:
+  // Default options determined using the JSContext.
+  explicit CompileOptions(JSContext* cx);
+
+  // Copy both the transitive and the non-transitive options from another
+  // options object.
+  CompileOptions(JSContext* cx, const ReadOnlyCompileOptions& rhs)
+      : ReadOnlyCompileOptions(),
+        elementAttributeNameRoot(cx),
+        introductionScriptRoot(cx),
+        scriptOrModuleRoot(cx),
+        privateValueRoot(cx) {
+    copyPODNonTransitiveOptions(rhs);
+    copyPODTransitiveOptions(rhs);
+
+    filename_ = rhs.filename();
+    introducerFilename_ = rhs.introducerFilename();
+    sourceMapURL_ = rhs.sourceMapURL();
+    privateValueRoot = rhs.privateValue();
+    elementAttributeNameRoot = rhs.elementAttributeName();
+    introductionScriptRoot = rhs.introductionScript();
+    scriptOrModuleRoot = rhs.scriptOrModule();
+  }
+
+  Value privateValue() const override { return privateValueRoot; }
+
+  JSString* elementAttributeName() const override {
+    return elementAttributeNameRoot;
+  }
+
+  JSScript* introductionScript() const override {
+    return introductionScriptRoot;
+  }
+
+  JSScript* scriptOrModule() const override { return scriptOrModuleRoot; }
+
+  CompileOptions& setFile(const char* f) {
+    filename_ = f;
+    return *this;
+  }
+
+  CompileOptions& setLine(unsigned l) {
+    lineno = l;
+    return *this;
+  }
+
+  CompileOptions& setFileAndLine(const char* f, unsigned l) {
+    filename_ = f;
+    lineno = l;
+    return *this;
+  }
+
+  CompileOptions& setSourceMapURL(const char16_t* s) {
+    sourceMapURL_ = s;
+    return *this;
+  }
+
+  CompileOptions& setPrivateValue(const Value& v) {
+    privateValueRoot = v;
+    return *this;
+  }
+
+  CompileOptions& setElementAttributeName(JSString* p) {
+    elementAttributeNameRoot = p;
+    return *this;
+  }
+
+  CompileOptions& setScriptOrModule(JSScript* s) {
+    scriptOrModuleRoot = s;
+    return *this;
+  }
+
+  CompileOptions& setMutedErrors(bool mute) {
+    mutedErrors_ = mute;
+    return *this;
+  }
+
+  CompileOptions& setColumn(unsigned c) {
+    column = c;
+    return *this;
+  }
+
+  CompileOptions& setScriptSourceOffset(unsigned o) {
+    scriptSourceOffset = o;
+    return *this;
+  }
+
+  CompileOptions& setIsRunOnce(bool once) {
+    isRunOnce = once;
+    return *this;
+  }
+
+  CompileOptions& setNoScriptRval(bool nsr) {
+    noScriptRval = nsr;
+    return *this;
+  }
+
+  CompileOptions& setSkipFilenameValidation(bool b) {
+    skipFilenameValidation_ = b;
+    return *this;
+  }
+
+  CompileOptions& setSelfHostingMode(bool shm) {
+    selfHostingMode = shm;
+    return *this;
+  }
+
+  CompileOptions& setSourceIsLazy(bool l) {
+    sourceIsLazy = l;
+    return *this;
+  }
+
+  CompileOptions& setNonSyntacticScope(bool n) {
+    nonSyntacticScope = n;
+    return *this;
+  }
+
+  CompileOptions& setIntroductionType(const char* t) {
+    introductionType = t;
+    return *this;
+  }
+
+  CompileOptions& setIntroductionInfo(const char* introducerFn,
+                                      const char* intro, unsigned line,
+                                      JSScript* script, uint32_t offset) {
+    introducerFilename_ = introducerFn;
+    introductionType = intro;
+    introductionLineno = line;
+    introductionScriptRoot = script;
+    introductionOffset = offset;
+    hasIntroductionInfo = true;
+    return *this;
+  }
+
+  // Set introduction information according to any currently executing script.
+  CompileOptions& setIntroductionInfoToCaller(JSContext* cx,
+                                              const char* introductionType);
+
+  CompileOptions& setForceFullParse() {
+    forceFullParse_ = true;
+    return *this;
+  }
+
+  CompileOptions& setForceStrictMode() {
+    forceStrictMode_ = true;
+    return *this;
+  }
+
+  CompileOptions& setModule() {
+    // ES6 10.2.1 Module code is always strict mode code.
+    setForceStrictMode();
+    setIsRunOnce(true);
+    allowHTMLComments = false;
+    return *this;
+  }
+
+  CompileOptions(const CompileOptions& rhs) = delete;
+  CompileOptions& operator=(const CompileOptions& rhs) = delete;
+};
+
+}  // namespace JS
+
+#endif /* js_CompileOptions_h */