The Tor Browser: js/src/frontend/SharedContext.h@6474c204b198 (annotated)

js/src/frontend/SharedContext.h@6474c204b198 (annotated)

js/src/frontend/SharedContext.h

Wed, 31 Dec 2014 06:09:35 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Wed, 31 Dec 2014 06:09:35 +0100
changeset 0: 6474c204b198
permissions: -rw-r--r--

Cloned upstream origin tor-browser at tor-browser-31.3.0esr-4.5-1-build1
revision ID fc1c9ff7c1b2defdbc039f12214767608f46423f for hacking purpose.

 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
  * vim: set ts=8 sts=4 et sw=4 tw=99:
  * 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 frontend_SharedContext_h
 #define frontend_SharedContext_h
 #include "jsatom.h"
 #include "jsopcode.h"
 #include "jspubtd.h"
 #include "jsscript.h"
 #include "jstypes.h"
 #include "frontend/ParseMaps.h"
 #include "frontend/ParseNode.h"
 #include "frontend/TokenStream.h"
 #include "vm/ScopeObject.h"
 namespace js {
 namespace frontend {
 // These flags apply to both global and function contexts.
 class AnyContextFlags
 {
     // This class's data is all private and so only visible to these friends.
     friend class SharedContext;
     // True if "use strict"; appears in the body instead of being inherited.
     bool            hasExplicitUseStrict:1;
     // The (static) bindings of this script need to support dynamic name
     // read/write access. Here, 'dynamic' means dynamic dictionary lookup on
     // the scope chain for a dynamic set of keys. The primary examples are:
     //  - direct eval
     //  - function::
     //  - with
     // since both effectively allow any name to be accessed. Non-examples are:
     //  - upvars of nested functions
     //  - function statement
     // since the set of assigned name is known dynamically. 'with' could be in
     // the non-example category, provided the set of all free variables within
     // the with block was noted. However, we do not optimize 'with' so, for
     // simplicity, 'with' is treated like eval.
     //
     // Note: access through the arguments object is not considered dynamic
     // binding access since it does not go through the normal name lookup
     // mechanism. This is debatable and could be changed (although care must be
     // taken not to turn off the whole 'arguments' optimization). To answer the
     // more general "is this argument aliased" question, script->needsArgsObj
     // should be tested (see JSScript::argIsAlised).
     //
     bool            bindingsAccessedDynamically:1;
     // Whether this script, or any of its inner scripts contains a debugger
     // statement which could potentially read or write anywhere along the
     // scope chain.
     bool            hasDebuggerStatement:1;
   public:
     AnyContextFlags()
      :  hasExplicitUseStrict(false),
         bindingsAccessedDynamically(false),
         hasDebuggerStatement(false)
     { }
 };
 class FunctionContextFlags
 {
     // This class's data is all private and so only visible to these friends.
     friend class FunctionBox;
     // The function or a function that encloses it may define new local names
     // at runtime through means other than calling eval.
     bool mightAliasLocals:1;
     // This function does something that can extend the set of bindings in its
     // call objects --- it does a direct eval in non-strict code, or includes a
     // function statement (as opposed to a function definition).
     //
     // This flag is *not* inherited by enclosed or enclosing functions; it
     // applies only to the function in whose flags it appears.
     //
     bool hasExtensibleScope:1;
     // This function refers directly to its name in a way which requires the
     // name to be a separate object on the scope chain.
     bool needsDeclEnvObject:1;
     // Technically, every function has a binding named 'arguments'. Internally,
     // this binding is only added when 'arguments' is mentioned by the function
     // body. This flag indicates whether 'arguments' has been bound either
     // through implicit use:
     //   function f() { return arguments }
     // or explicit redeclaration:
     //   function f() { var arguments; return arguments }
     //
     // Note 1: overwritten arguments (function() { arguments = 3 }) will cause
     // this flag to be set but otherwise require no special handling:
     // 'arguments' is just a local variable and uses of 'arguments' will just
     // read the local's current slot which may have been assigned. The only
     // special semantics is that the initial value of 'arguments' is the
     // arguments object (not undefined, like normal locals).
     //
     // Note 2: if 'arguments' is bound as a formal parameter, there will be an
     // 'arguments' in Bindings, but, as the "LOCAL" in the name indicates, this
     // flag will not be set. This is because, as a formal, 'arguments' will
     // have no special semantics: the initial value is unconditionally the
     // actual argument (or undefined if nactual < nformal).
     //
     bool argumentsHasLocalBinding:1;
     // In many cases where 'arguments' has a local binding (as described above)
     // we do not need to actually create an arguments object in the function
     // prologue: instead we can analyze how 'arguments' is used (using the
     // simple dataflow analysis in analyzeSSA) to determine that uses of
     // 'arguments' can just read from the stack frame directly. However, the
     // dataflow analysis only looks at how JSOP_ARGUMENTS is used, so it will
     // be unsound in several cases. The frontend filters out such cases by
     // setting this flag which eagerly sets script->needsArgsObj to true.
     //
     bool definitelyNeedsArgsObj:1;
   public:
     FunctionContextFlags()
      :  mightAliasLocals(false),
         hasExtensibleScope(false),
         needsDeclEnvObject(false),
         argumentsHasLocalBinding(false),
         definitelyNeedsArgsObj(false)
     { }
 };
 class GlobalSharedContext;
 // List of directives that may be encountered in a Directive Prologue (ES5 15.1).
 class Directives
 {
     bool strict_;
     bool asmJS_;
   public:
     explicit Directives(bool strict) : strict_(strict), asmJS_(false) {}
     template <typename ParseHandler> explicit Directives(ParseContext<ParseHandler> *parent);
     void setStrict() { strict_ = true; }
     bool strict() const { return strict_; }
     void setAsmJS() { asmJS_ = true; }
     bool asmJS() const { return asmJS_; }
     Directives &operator=(Directives rhs) {
         strict_ = rhs.strict_;
         asmJS_ = rhs.asmJS_;
         return *this;
     }
     bool operator==(const Directives &rhs) const {
         return strict_ == rhs.strict_ && asmJS_ == rhs.asmJS_;
     }
     bool operator!=(const Directives &rhs) const {
         return !(*this == rhs);
     }
 };
 /*
  * The struct SharedContext is part of the current parser context (see
  * ParseContext). It stores information that is reused between the parser and
  * the bytecode emitter. Note however, that this information is not shared
  * between the two; they simply reuse the same data structure.
  */
 class SharedContext
 {
   public:
     ExclusiveContext *const context;
     AnyContextFlags anyCxFlags;
     bool strict;
     bool extraWarnings;
     // If it's function code, funbox must be non-nullptr and scopeChain must be
     // nullptr. If it's global code, funbox must be nullptr.
     SharedContext(ExclusiveContext *cx, Directives directives, bool extraWarnings)
       : context(cx),
         anyCxFlags(),
         strict(directives.strict()),
         extraWarnings(extraWarnings)
     {}
     virtual ObjectBox *toObjectBox() = 0;
     inline bool isGlobalSharedContext() { return toObjectBox() == nullptr; }
     inline bool isFunctionBox() { return toObjectBox() && toObjectBox()->isFunctionBox(); }
     inline GlobalSharedContext *asGlobalSharedContext();
     inline FunctionBox *asFunctionBox();
     bool hasExplicitUseStrict()        const { return anyCxFlags.hasExplicitUseStrict; }
     bool bindingsAccessedDynamically() const { return anyCxFlags.bindingsAccessedDynamically; }
     bool hasDebuggerStatement()        const { return anyCxFlags.hasDebuggerStatement; }
     void setExplicitUseStrict()           { anyCxFlags.hasExplicitUseStrict        = true; }
     void setBindingsAccessedDynamically() { anyCxFlags.bindingsAccessedDynamically = true; }
     void setHasDebuggerStatement()        { anyCxFlags.hasDebuggerStatement        = true; }
     inline bool allLocalsAliased();
     // JSOPTION_EXTRA_WARNINGS warnings or strict mode errors.
     bool needStrictChecks() {
         return strict || extraWarnings;
     }
 };
 class GlobalSharedContext : public SharedContext
 {
   private:
     const RootedObject scopeChain_; /* scope chain object for the script */
   public:
     GlobalSharedContext(ExclusiveContext *cx, JSObject *scopeChain,
                         Directives directives, bool extraWarnings)
       : SharedContext(cx, directives, extraWarnings),
         scopeChain_(cx, scopeChain)
     {}
     ObjectBox *toObjectBox() { return nullptr; }
     JSObject *scopeChain() const { return scopeChain_; }
 };
 inline GlobalSharedContext *
 SharedContext::asGlobalSharedContext()
 {
     JS_ASSERT(isGlobalSharedContext());
     return static_cast<GlobalSharedContext*>(this);
 }
 class FunctionBox : public ObjectBox, public SharedContext
 {
   public:
     Bindings        bindings;               /* bindings for this function */
     uint32_t        bufStart;
     uint32_t        bufEnd;
     uint32_t        startLine;
     uint32_t        startColumn;
     uint16_t        length;
     uint8_t         generatorKindBits_;     /* The GeneratorKind of this function. */
     bool            inWith:1;               /* some enclosing scope is a with-statement */
     bool            inGenexpLambda:1;       /* lambda from generator expression */
     bool            hasDestructuringArgs:1; /* arguments list contains destructuring expression */
     bool            useAsm:1;               /* function contains "use asm" directive */
     bool            insideUseAsm:1;         /* nested function of function of "use asm" directive */
     // Fields for use in heuristics.
     bool            usesArguments:1;  /* contains a free use of 'arguments' */
     bool            usesApply:1;      /* contains an f.apply() call */
     FunctionContextFlags funCxFlags;
     template <typename ParseHandler>
     FunctionBox(ExclusiveContext *cx, ObjectBox* traceListHead, JSFunction *fun,
                 ParseContext<ParseHandler> *pc, Directives directives,
                 bool extraWarnings, GeneratorKind generatorKind);
     ObjectBox *toObjectBox() { return this; }
     JSFunction *function() const { return &object->as<JSFunction>(); }
     GeneratorKind generatorKind() const { return GeneratorKindFromBits(generatorKindBits_); }
     bool isGenerator() const { return generatorKind() != NotGenerator; }
     bool isLegacyGenerator() const { return generatorKind() == LegacyGenerator; }
     bool isStarGenerator() const { return generatorKind() == StarGenerator; }
     void setGeneratorKind(GeneratorKind kind) {
         // A generator kind can be set at initialization, or when "yield" is
         // first seen.  In both cases the transition can only happen from
         // NotGenerator.
         JS_ASSERT(!isGenerator());
         generatorKindBits_ = GeneratorKindAsBits(kind);
     }
     bool mightAliasLocals()         const { return funCxFlags.mightAliasLocals; }
     bool hasExtensibleScope()       const { return funCxFlags.hasExtensibleScope; }
     bool needsDeclEnvObject()       const { return funCxFlags.needsDeclEnvObject; }
     bool argumentsHasLocalBinding() const { return funCxFlags.argumentsHasLocalBinding; }
     bool definitelyNeedsArgsObj()   const { return funCxFlags.definitelyNeedsArgsObj; }
     void setMightAliasLocals()             { funCxFlags.mightAliasLocals         = true; }
     void setHasExtensibleScope()           { funCxFlags.hasExtensibleScope       = true; }
     void setNeedsDeclEnvObject()           { funCxFlags.needsDeclEnvObject       = true; }
     void setArgumentsHasLocalBinding()     { funCxFlags.argumentsHasLocalBinding = true; }
     void setDefinitelyNeedsArgsObj()       { JS_ASSERT(funCxFlags.argumentsHasLocalBinding);
                                              funCxFlags.definitelyNeedsArgsObj   = true; }
     bool hasDefaults() const {
         return length != function()->nargs() - function()->hasRest();
     }
     // Return whether this function has either specified "use asm" or is
     // (transitively) nested inside a function that has.
     bool useAsmOrInsideUseAsm() const {
         return useAsm || insideUseAsm;
     }
     void setStart(const TokenStream &tokenStream) {
         bufStart = tokenStream.currentToken().pos.begin;
         startLine = tokenStream.getLineno();
         startColumn = tokenStream.getColumn();
     }
     bool isHeavyweight()
     {
         // Note: this should be kept in sync with JSFunction::isHeavyweight().
         return bindings.hasAnyAliasedBindings() ||
                hasExtensibleScope() ||
                needsDeclEnvObject() ||
                isGenerator();
     }
 };
 inline FunctionBox *
 SharedContext::asFunctionBox()
 {
     JS_ASSERT(isFunctionBox());
     return static_cast<FunctionBox*>(this);
 }
 // In generators, we treat all locals as aliased so that they get stored on the
 // heap.  This way there is less information to copy off the stack when
 // suspending, and back on when resuming.  It also avoids the need to create and
 // invalidate DebugScope proxies for unaliased locals in a generator frame, as
 // the generator frame will be copied out to the heap and released only by GC.
 inline bool
 SharedContext::allLocalsAliased()
 {
     return bindingsAccessedDynamically() || (isFunctionBox() && asFunctionBox()->isGenerator());
 }
 /*
  * NB: If you add a new type of statement that is a scope, add it between
  * STMT_WITH and STMT_CATCH, or you will break StmtInfoBase::linksScope. If you
  * add a non-looping statement type, add it before STMT_DO_LOOP or you will
  * break StmtInfoBase::isLoop().
  *
  * Also remember to keep the statementName array in BytecodeEmitter.cpp in
  * sync.
  */
 enum StmtType {
     STMT_LABEL,                 /* labeled statement:  L: s */
     STMT_IF,                    /* if (then) statement */
     STMT_ELSE,                  /* else clause of if statement */
     STMT_SEQ,                   /* synthetic sequence of statements */
     STMT_BLOCK,                 /* compound statement: { s1[;... sN] } */
     STMT_SWITCH,                /* switch statement */
     STMT_WITH,                  /* with statement */
     STMT_CATCH,                 /* catch block */
     STMT_TRY,                   /* try block */
     STMT_FINALLY,               /* finally block */
     STMT_SUBROUTINE,            /* gosub-target subroutine body */
     STMT_DO_LOOP,               /* do/while loop statement */
     STMT_FOR_LOOP,              /* for loop statement */
     STMT_FOR_IN_LOOP,           /* for/in loop statement */
     STMT_FOR_OF_LOOP,           /* for/of loop statement */
     STMT_WHILE_LOOP,            /* while loop statement */
     STMT_LIMIT
 };
 /*
  * A comment on the encoding of the js::StmtType enum and StmtInfoBase
  * type-testing methods:
  *
  * StmtInfoBase::maybeScope() tells whether a statement type is always, or may
  * become, a lexical scope. It therefore includes block and switch (the two
  * low-numbered "maybe" scope types) and excludes with (with has dynamic scope
  * pending the "reformed with" in ES4/JS2). It includes all try-catch-finally
  * types, which are high-numbered maybe-scope types.
  *
  * StmtInfoBase::linksScope() tells whether a js::StmtInfo{PC,BCE} of the given
  * type eagerly links to other scoping statement info records. It excludes the
  * two early "maybe" types, block and switch, as well as the try and both
  * finally types, since try and the other trailing maybe-scope types don't need
  * block scope unless they contain let declarations.
  *
  * We treat WITH as a static scope because it prevents lexical binding from
  * continuing further up the static scope chain. With the lost "reformed with"
  * proposal for ES4, we would be able to model it statically, too.
  */
 // StmtInfoPC is used by the Parser.  StmtInfoBCE is used by the
 // BytecodeEmitter.  The two types have some overlap, encapsulated by
 // StmtInfoBase.  Several functions below (e.g. PushStatement) are templated to
 // work with both types.
 struct StmtInfoBase {
     // Statement type (StmtType).
     uint16_t        type;
     // True if type is STMT_BLOCK, STMT_TRY, STMT_SWITCH, or STMT_FINALLY and
     // the block contains at least one let-declaration, or if type is
     // STMT_CATCH.
     bool isBlockScope:1;
     // True if isBlockScope or type == STMT_WITH.
     bool isNestedScope:1;
     // for (let ...) induced block scope
     bool isForLetBlock:1;
     // Block label.
     RootedAtom      label;
     // Compile-time scope chain node for this scope.  Only set if
     // isNestedScope.
     Rooted<NestedScopeObject *> staticScope;
     StmtInfoBase(ExclusiveContext *cx)
         : isBlockScope(false), isNestedScope(false), isForLetBlock(false),
           label(cx), staticScope(cx)
     {}
     bool maybeScope() const {
         return STMT_BLOCK <= type && type <= STMT_SUBROUTINE && type != STMT_WITH;
     }
     bool linksScope() const {
         return isNestedScope;
     }
     StaticBlockObject& staticBlock() const {
         JS_ASSERT(isNestedScope);
         JS_ASSERT(isBlockScope);
         return staticScope->as<StaticBlockObject>();
     }
     bool isLoop() const {
         return type >= STMT_DO_LOOP;
     }
     bool isTrying() const {
         return STMT_TRY <= type && type <= STMT_SUBROUTINE;
     }
 };
 // Push the C-stack-allocated struct at stmt onto the StmtInfoPC stack.
 template <class ContextT>
 void
 PushStatement(ContextT *ct, typename ContextT::StmtInfo *stmt, StmtType type)
 {
     stmt->type = type;
     stmt->isBlockScope = false;
     stmt->isNestedScope = false;
     stmt->isForLetBlock = false;
     stmt->label = nullptr;
     stmt->staticScope = nullptr;
     stmt->down = ct->topStmt;
     ct->topStmt = stmt;
     if (stmt->linksScope()) {
         stmt->downScope = ct->topScopeStmt;
         ct->topScopeStmt = stmt;
     } else {
         stmt->downScope = nullptr;
     }
 }
 template <class ContextT>
 void
 FinishPushNestedScope(ContextT *ct, typename ContextT::StmtInfo *stmt, NestedScopeObject &staticScope)
 {
     stmt->isNestedScope = true;
     stmt->downScope = ct->topScopeStmt;
     ct->topScopeStmt = stmt;
     ct->staticScope = &staticScope;
     stmt->staticScope = &staticScope;
 }
 // Pop pc->topStmt. If the top StmtInfoPC struct is not stack-allocated, it
 // is up to the caller to free it.  The dummy argument is just to make the
 // template matching work.
 template <class ContextT>
 void
 FinishPopStatement(ContextT *ct)
 {
     typename ContextT::StmtInfo *stmt = ct->topStmt;
     ct->topStmt = stmt->down;
     if (stmt->linksScope()) {
         ct->topScopeStmt = stmt->downScope;
         if (stmt->isNestedScope) {
             JS_ASSERT(stmt->staticScope);
             ct->staticScope = stmt->staticScope->enclosingNestedScope();
         }
     }
 }
 /*
  * Find a lexically scoped variable (one declared by let, catch, or an array
  * comprehension) named by atom, looking in sc's compile-time scopes.
  *
  * If a WITH statement is reached along the scope stack, return its statement
  * info record, so callers can tell that atom is ambiguous. If slotp is not
  * null, then if atom is found, set *slotp to its stack slot, otherwise to -1.
  * This means that if slotp is not null, all the block objects on the lexical
  * scope chain must have had their depth slots computed by the code generator,
  * so the caller must be under EmitTree.
  *
  * In any event, directly return the statement info record in which atom was
  * found. Otherwise return null.
  */
 template <class ContextT>
 typename ContextT::StmtInfo *
 LexicalLookup(ContextT *ct, HandleAtom atom, int *slotp, typename ContextT::StmtInfo *stmt);
 } // namespace frontend
 } // namespace js
 #endif /* frontend_SharedContext_h */

The Tor Browser / annotate

js/src/frontend/SharedContext.h@6474c204b198 (annotated)

js/src/frontend/SharedContext.h