67dc6ce5fd
R=bmeurer@chromium.org Committed: https://crrev.com/15f36b2b1e166a511966a9991fddea94f890a755 Cr-Commit-Position: refs/heads/master@{#31566} Review URL: https://codereview.chromium.org/1423833003 Cr-Commit-Position: refs/heads/master@{#31576}
411 lines
13 KiB
C++
411 lines
13 KiB
C++
// Copyright 2011 the V8 project authors. All rights reserved.
|
|
// Use of this source code is governed by a BSD-style license that can be
|
|
// found in the LICENSE file.
|
|
|
|
#ifndef V8_HANDLES_H_
|
|
#define V8_HANDLES_H_
|
|
|
|
#include "include/v8.h"
|
|
#include "src/base/functional.h"
|
|
#include "src/base/macros.h"
|
|
#include "src/checks.h"
|
|
#include "src/globals.h"
|
|
#include "src/zone.h"
|
|
|
|
namespace v8 {
|
|
namespace internal {
|
|
|
|
// Forward declarations.
|
|
class DeferredHandles;
|
|
class HandleScopeImplementer;
|
|
class Isolate;
|
|
class Object;
|
|
|
|
|
|
// ----------------------------------------------------------------------------
|
|
// Base class for Handle instantiations. Don't use directly.
|
|
class HandleBase {
|
|
public:
|
|
V8_INLINE explicit HandleBase(Object** location) : location_(location) {}
|
|
V8_INLINE explicit HandleBase(Object* object, Isolate* isolate);
|
|
|
|
// Check if this handle refers to the exact same object as the other handle.
|
|
V8_INLINE bool is_identical_to(const HandleBase that) const {
|
|
// Dereferencing deferred handles to check object equality is safe.
|
|
SLOW_DCHECK((this->location_ == nullptr ||
|
|
this->IsDereferenceAllowed(NO_DEFERRED_CHECK)) &&
|
|
(that.location_ == nullptr ||
|
|
that.IsDereferenceAllowed(NO_DEFERRED_CHECK)));
|
|
if (this->location_ == that.location_) return true;
|
|
if (this->location_ == NULL || that.location_ == NULL) return false;
|
|
return *this->location_ == *that.location_;
|
|
}
|
|
|
|
V8_INLINE bool is_null() const { return location_ == nullptr; }
|
|
|
|
protected:
|
|
// Provides the C++ dereference operator.
|
|
V8_INLINE Object* operator*() const {
|
|
SLOW_DCHECK(IsDereferenceAllowed(INCLUDE_DEFERRED_CHECK));
|
|
return *location_;
|
|
}
|
|
|
|
// Returns the address to where the raw pointer is stored.
|
|
V8_INLINE Object** location() const {
|
|
SLOW_DCHECK(location_ == nullptr ||
|
|
IsDereferenceAllowed(INCLUDE_DEFERRED_CHECK));
|
|
return location_;
|
|
}
|
|
|
|
enum DereferenceCheckMode { INCLUDE_DEFERRED_CHECK, NO_DEFERRED_CHECK };
|
|
#ifdef DEBUG
|
|
bool IsDereferenceAllowed(DereferenceCheckMode mode) const;
|
|
#else
|
|
V8_INLINE
|
|
bool IsDereferenceAllowed(DereferenceCheckMode mode) const { return true; }
|
|
#endif // DEBUG
|
|
|
|
Object** location_;
|
|
};
|
|
|
|
|
|
// ----------------------------------------------------------------------------
|
|
// A Handle provides a reference to an object that survives relocation by
|
|
// the garbage collector.
|
|
//
|
|
// Handles are only valid within a HandleScope. When a handle is created
|
|
// for an object a cell is allocated in the current HandleScope.
|
|
//
|
|
// Also note that Handles do not provide default equality comparison or hashing
|
|
// operators on purpose. Such operators would be misleading, because intended
|
|
// semantics is ambiguous between Handle location and object identity. Instead
|
|
// use either {is_identical_to} or {location} explicitly.
|
|
template <typename T>
|
|
class Handle final : public HandleBase {
|
|
public:
|
|
V8_INLINE explicit Handle(T** location = nullptr)
|
|
: HandleBase(reinterpret_cast<Object**>(location)) {
|
|
Object* a = nullptr;
|
|
T* b = nullptr;
|
|
a = b; // Fake assignment to enforce type checks.
|
|
USE(a);
|
|
}
|
|
V8_INLINE explicit Handle(T* object) : Handle(object, object->GetIsolate()) {}
|
|
V8_INLINE Handle(T* object, Isolate* isolate) : HandleBase(object, isolate) {}
|
|
|
|
// Allocate a new handle for the object, do not canonicalize.
|
|
V8_INLINE static Handle<T> New(T* object, Isolate* isolate);
|
|
|
|
// Constructor for handling automatic up casting.
|
|
// Ex. Handle<JSFunction> can be passed when Handle<Object> is expected.
|
|
template <typename S>
|
|
V8_INLINE Handle(Handle<S> handle)
|
|
: HandleBase(handle) {
|
|
T* a = nullptr;
|
|
S* b = nullptr;
|
|
a = b; // Fake assignment to enforce type checks.
|
|
USE(a);
|
|
}
|
|
|
|
V8_INLINE T* operator->() const { return operator*(); }
|
|
|
|
// Provides the C++ dereference operator.
|
|
V8_INLINE T* operator*() const {
|
|
return reinterpret_cast<T*>(HandleBase::operator*());
|
|
}
|
|
|
|
// Returns the address to where the raw pointer is stored.
|
|
V8_INLINE T** location() const {
|
|
return reinterpret_cast<T**>(HandleBase::location());
|
|
}
|
|
|
|
template <typename S>
|
|
static const Handle<T> cast(Handle<S> that) {
|
|
T::cast(*reinterpret_cast<T**>(that.location_));
|
|
return Handle<T>(reinterpret_cast<T**>(that.location_));
|
|
}
|
|
|
|
// TODO(yangguo): Values that contain empty handles should be declared as
|
|
// MaybeHandle to force validation before being used as handles.
|
|
static const Handle<T> null() { return Handle<T>(); }
|
|
|
|
// Provide function object for location equality comparison.
|
|
struct equal_to : public std::binary_function<Handle<T>, Handle<T>, bool> {
|
|
V8_INLINE bool operator()(Handle<T> lhs, Handle<T> rhs) const {
|
|
return lhs.location() == rhs.location();
|
|
}
|
|
};
|
|
|
|
// Provide function object for location hashing.
|
|
struct hash : public std::unary_function<Handle<T>, size_t> {
|
|
V8_INLINE size_t operator()(Handle<T> const& handle) const {
|
|
return base::hash<void*>()(handle.location());
|
|
}
|
|
};
|
|
|
|
private:
|
|
// Handles of different classes are allowed to access each other's location_.
|
|
template <typename>
|
|
friend class Handle;
|
|
// MaybeHandle is allowed to access location_.
|
|
template <typename>
|
|
friend class MaybeHandle;
|
|
};
|
|
|
|
template <typename T>
|
|
inline std::ostream& operator<<(std::ostream& os, Handle<T> handle);
|
|
|
|
template <typename T>
|
|
V8_INLINE Handle<T> handle(T* object, Isolate* isolate) {
|
|
return Handle<T>(object, isolate);
|
|
}
|
|
|
|
template <typename T>
|
|
V8_INLINE Handle<T> handle(T* object) {
|
|
return Handle<T>(object);
|
|
}
|
|
|
|
|
|
// ----------------------------------------------------------------------------
|
|
// A Handle can be converted into a MaybeHandle. Converting a MaybeHandle
|
|
// into a Handle requires checking that it does not point to NULL. This
|
|
// ensures NULL checks before use.
|
|
//
|
|
// Do not use MaybeHandle as argument type.
|
|
//
|
|
// Also note that Handles do not provide default equality comparison or hashing
|
|
// operators on purpose. Such operators would be misleading, because intended
|
|
// semantics is ambiguous between Handle location and object identity.
|
|
template <typename T>
|
|
class MaybeHandle final {
|
|
public:
|
|
V8_INLINE MaybeHandle() {}
|
|
V8_INLINE ~MaybeHandle() {}
|
|
|
|
// Constructor for handling automatic up casting from Handle.
|
|
// Ex. Handle<JSArray> can be passed when MaybeHandle<Object> is expected.
|
|
template <typename S>
|
|
V8_INLINE MaybeHandle(Handle<S> handle)
|
|
: location_(reinterpret_cast<T**>(handle.location_)) {
|
|
T* a = nullptr;
|
|
S* b = nullptr;
|
|
a = b; // Fake assignment to enforce type checks.
|
|
USE(a);
|
|
}
|
|
|
|
// Constructor for handling automatic up casting.
|
|
// Ex. MaybeHandle<JSArray> can be passed when Handle<Object> is expected.
|
|
template <typename S>
|
|
V8_INLINE MaybeHandle(MaybeHandle<S> maybe_handle)
|
|
: location_(reinterpret_cast<T**>(maybe_handle.location_)) {
|
|
T* a = nullptr;
|
|
S* b = nullptr;
|
|
a = b; // Fake assignment to enforce type checks.
|
|
USE(a);
|
|
}
|
|
|
|
V8_INLINE void Assert() const { DCHECK_NOT_NULL(location_); }
|
|
V8_INLINE void Check() const { CHECK_NOT_NULL(location_); }
|
|
|
|
V8_INLINE Handle<T> ToHandleChecked() const {
|
|
Check();
|
|
return Handle<T>(location_);
|
|
}
|
|
|
|
// Convert to a Handle with a type that can be upcasted to.
|
|
template <typename S>
|
|
V8_INLINE bool ToHandle(Handle<S>* out) const {
|
|
if (location_ == nullptr) {
|
|
*out = Handle<T>::null();
|
|
return false;
|
|
} else {
|
|
*out = Handle<T>(location_);
|
|
return true;
|
|
}
|
|
}
|
|
|
|
bool is_null() const { return location_ == nullptr; }
|
|
|
|
protected:
|
|
T** location_ = nullptr;
|
|
|
|
// MaybeHandles of different classes are allowed to access each
|
|
// other's location_.
|
|
template <typename>
|
|
friend class MaybeHandle;
|
|
};
|
|
|
|
|
|
// ----------------------------------------------------------------------------
|
|
// A stack-allocated class that governs a number of local handles.
|
|
// After a handle scope has been created, all local handles will be
|
|
// allocated within that handle scope until either the handle scope is
|
|
// deleted or another handle scope is created. If there is already a
|
|
// handle scope and a new one is created, all allocations will take
|
|
// place in the new handle scope until it is deleted. After that,
|
|
// new handles will again be allocated in the original handle scope.
|
|
//
|
|
// After the handle scope of a local handle has been deleted the
|
|
// garbage collector will no longer track the object stored in the
|
|
// handle and may deallocate it. The behavior of accessing a handle
|
|
// for which the handle scope has been deleted is undefined.
|
|
class HandleScope {
|
|
public:
|
|
explicit inline HandleScope(Isolate* isolate);
|
|
|
|
inline ~HandleScope();
|
|
|
|
// Counts the number of allocated handles.
|
|
static int NumberOfHandles(Isolate* isolate);
|
|
|
|
// Create a new handle or lookup a canonical handle.
|
|
V8_INLINE static Object** GetHandle(Isolate* isolate, Object* value);
|
|
|
|
// Creates a new handle with the given value.
|
|
V8_INLINE static Object** CreateHandle(Isolate* isolate, Object* value);
|
|
|
|
// Deallocates any extensions used by the current scope.
|
|
static void DeleteExtensions(Isolate* isolate);
|
|
|
|
static Address current_next_address(Isolate* isolate);
|
|
static Address current_limit_address(Isolate* isolate);
|
|
static Address current_level_address(Isolate* isolate);
|
|
|
|
// Closes the HandleScope (invalidating all handles
|
|
// created in the scope of the HandleScope) and returns
|
|
// a Handle backed by the parent scope holding the
|
|
// value of the argument handle.
|
|
template <typename T>
|
|
Handle<T> CloseAndEscape(Handle<T> handle_value);
|
|
|
|
Isolate* isolate() { return isolate_; }
|
|
|
|
// Limit for number of handles with --check-handle-count. This is
|
|
// large enough to compile natives and pass unit tests with some
|
|
// slack for future changes to natives.
|
|
static const int kCheckHandleThreshold = 30 * 1024;
|
|
|
|
private:
|
|
// Prevent heap allocation or illegal handle scopes.
|
|
HandleScope(const HandleScope&);
|
|
void operator=(const HandleScope&);
|
|
void* operator new(size_t size);
|
|
void operator delete(void* size_t);
|
|
|
|
Isolate* isolate_;
|
|
Object** prev_next_;
|
|
Object** prev_limit_;
|
|
|
|
// Close the handle scope resetting limits to a previous state.
|
|
static inline void CloseScope(Isolate* isolate,
|
|
Object** prev_next,
|
|
Object** prev_limit);
|
|
|
|
// Extend the handle scope making room for more handles.
|
|
static Object** Extend(Isolate* isolate);
|
|
|
|
#ifdef ENABLE_HANDLE_ZAPPING
|
|
// Zaps the handles in the half-open interval [start, end).
|
|
static void ZapRange(Object** start, Object** end);
|
|
#endif
|
|
|
|
friend class v8::HandleScope;
|
|
friend class DeferredHandles;
|
|
friend class DeferredHandleScope;
|
|
friend class HandleScopeImplementer;
|
|
friend class Isolate;
|
|
};
|
|
|
|
|
|
// Forward declarations for CanonicalHandleScope.
|
|
template <typename V>
|
|
class IdentityMap;
|
|
class RootIndexMap;
|
|
|
|
|
|
// A CanonicalHandleScope does not open a new HandleScope. It changes the
|
|
// existing HandleScope so that Handles created within are canonicalized.
|
|
// This does not apply to nested inner HandleScopes unless a nested
|
|
// CanonicalHandleScope is introduced. Handles are only canonicalized within
|
|
// the same CanonicalHandleScope, but not across nested ones.
|
|
class CanonicalHandleScope final {
|
|
public:
|
|
explicit CanonicalHandleScope(Isolate* isolate);
|
|
~CanonicalHandleScope();
|
|
|
|
private:
|
|
Object** Lookup(Object* object);
|
|
|
|
Isolate* isolate_;
|
|
Zone zone_;
|
|
RootIndexMap* root_index_map_;
|
|
IdentityMap<Object**>* identity_map_;
|
|
// Ordinary nested handle scopes within the current one are not canonical.
|
|
int canonical_level_;
|
|
// We may have nested canonical scopes. Handles are canonical within each one.
|
|
CanonicalHandleScope* prev_canonical_scope_;
|
|
|
|
friend class HandleScope;
|
|
};
|
|
|
|
|
|
class DeferredHandleScope final {
|
|
public:
|
|
explicit DeferredHandleScope(Isolate* isolate);
|
|
// The DeferredHandles object returned stores the Handles created
|
|
// since the creation of this DeferredHandleScope. The Handles are
|
|
// alive as long as the DeferredHandles object is alive.
|
|
DeferredHandles* Detach();
|
|
~DeferredHandleScope();
|
|
|
|
private:
|
|
Object** prev_limit_;
|
|
Object** prev_next_;
|
|
HandleScopeImplementer* impl_;
|
|
|
|
#ifdef DEBUG
|
|
bool handles_detached_;
|
|
int prev_level_;
|
|
#endif
|
|
|
|
friend class HandleScopeImplementer;
|
|
};
|
|
|
|
|
|
// Seal off the current HandleScope so that new handles can only be created
|
|
// if a new HandleScope is entered.
|
|
class SealHandleScope final {
|
|
public:
|
|
#ifndef DEBUG
|
|
explicit SealHandleScope(Isolate* isolate) {}
|
|
~SealHandleScope() {}
|
|
#else
|
|
explicit inline SealHandleScope(Isolate* isolate);
|
|
inline ~SealHandleScope();
|
|
private:
|
|
Isolate* isolate_;
|
|
Object** prev_limit_;
|
|
int prev_sealed_level_;
|
|
#endif
|
|
};
|
|
|
|
|
|
struct HandleScopeData final {
|
|
Object** next;
|
|
Object** limit;
|
|
int level;
|
|
int sealed_level;
|
|
CanonicalHandleScope* canonical_scope;
|
|
|
|
void Initialize() {
|
|
next = limit = NULL;
|
|
sealed_level = level = 0;
|
|
canonical_scope = NULL;
|
|
}
|
|
};
|
|
|
|
} // namespace internal
|
|
} // namespace v8
|
|
|
|
#endif // V8_HANDLES_H_
|