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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 */
* 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/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 {
* 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 {
* 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;
// POD options.
bool selfHostingMode = false;
AsmJSOption asmJSOption = AsmJSOption::DisabledByAsmJSPref;
bool throwOnAsmJSValidationFailureOption = false;
bool forceAsync = false;
bool discardSource = false;
bool sourceIsLazy = false;
bool allowHTMLComments = true;
bool hideScriptFromDebugger = false;
// If set, this script will be hidden from the debugger. The requirement
// is that once compilation is finished, a call to UpdateDebugMetadata will
// be made, which will update the SSO with the appropiate debug metadata,
// and expose the script to the debugger (if hideScriptFromDebugger isn't set)
bool deferDebugMetadata = false;
bool hideFromNewScriptInitial() const {
return deferDebugMetadata || hideScriptFromDebugger;
bool nonSyntacticScope = false;
bool privateClassFields = false;
bool privateClassMethods = false;
bool topLevelAwait = true;
bool classStaticBlocks = 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;
// When decoding from XDR, borrow ImmutableScriptData from the XDR buffer
// instead of copying out of it.
// NOTE: When using this mode, the XDR buffer must live until JS_Shutdown is
// called. There is currently no mechanism to release the data sooner.
bool usePinnedBytecode = false;
* |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;
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);
// 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_; }
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 {
// 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;
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 {
// A minimal constructor, for use with OwningCompileOptions::copy.
explicit OwningCompileOptions(JSContext* cx);
/** 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.
allowHTMLComments = false;
return *this;
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 {
// 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() {
filename_ = rhs.filename();
introducerFilename_ = rhs.introducerFilename();
sourceMapURL_ = rhs.sourceMapURL();
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& 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& setdeferDebugMetadata(bool v = true) {
deferDebugMetadata = v;
return *this;
CompileOptions& setIntroductionInfo(const char* introducerFn,
const char* intro, unsigned line,
uint32_t offset) {
introducerFilename_ = introducerFn;
introductionType = intro;
introductionLineno = line;
introductionOffset = offset;
hasIntroductionInfo = true;
return *this;
// Set introduction information according to any currently executing script.
CompileOptions& setIntroductionInfoToCaller(
JSContext* cx, const char* introductionType,
JS::MutableHandle<JSScript*> introductionScript);
CompileOptions& setDiscardSource() {
discardSource = true;
return *this;
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.
allowHTMLComments = false;
return *this;
CompileOptions(const CompileOptions& rhs) = delete;
CompileOptions& operator=(const CompileOptions& rhs) = delete;
} // namespace JS
#endif /* js_CompileOptions_h */