Source code

Revision control

Other Tools

/* -*- 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/. */
#ifndef mozilla_StaticPtr_h
#define mozilla_StaticPtr_h
#include "mozilla/AlreadyAddRefed.h"
#include "mozilla/Assertions.h"
#include "mozilla/Attributes.h"
#include "mozilla/RefPtr.h"
namespace mozilla {
/**
* StaticAutoPtr and StaticRefPtr are like UniquePtr and RefPtr, except they
* are suitable for use as global variables.
*
* In particular, a global instance of Static{Auto,Ref}Ptr doesn't cause the
* compiler to emit a static initializer (in release builds, anyway).
*
* In order to accomplish this, Static{Auto,Ref}Ptr must have a trivial
* constructor and destructor. As a consequence, it cannot initialize its raw
* pointer to 0 on construction, and it cannot delete/release its raw pointer
* upon destruction.
*
* Since the compiler guarantees that all global variables are initialized to
* 0, these trivial constructors are safe. Since we rely on this, the clang
* plugin, run as part of our "static analysis" builds, makes it a compile-time
* error to use Static{Auto,Ref}Ptr as anything except a global variable.
*
* Static{Auto,Ref}Ptr have a limited interface as compared to ns{Auto,Ref}Ptr;
* this is intentional, since their range of acceptable uses is smaller.
*/
template <class T>
class MOZ_ONLY_USED_TO_AVOID_STATIC_CONSTRUCTORS StaticAutoPtr {
public:
// In debug builds, check that mRawPtr is initialized for us as we expect
// by the compiler. In non-debug builds, don't declare a constructor
// so that the compiler can see that the constructor is trivial.
#ifdef DEBUG
StaticAutoPtr() {
# ifdef __GNUC__
# pragma GCC diagnostic push
# pragma GCC diagnostic ignored "-Wuninitialized"
// False positive with gcc. See bug 1430729
# endif
MOZ_ASSERT(!mRawPtr);
# ifdef __GNUC__
# pragma GCC diagnostic pop
# endif
}
#endif
StaticAutoPtr<T>& operator=(T* aRhs) {
Assign(aRhs);
return *this;
}
T* get() const { return mRawPtr; }
operator T*() const { return get(); }
T* operator->() const {
MOZ_ASSERT(mRawPtr);
return get();
}
T& operator*() const { return *get(); }
T* forget() {
T* temp = mRawPtr;
mRawPtr = nullptr;
return temp;
}
private:
// Disallow copy constructor, but only in debug mode. We only define
// a default constructor in debug mode (see above); if we declared
// this constructor always, the compiler wouldn't generate a trivial
// default constructor for us in non-debug mode.
#ifdef DEBUG
StaticAutoPtr(StaticAutoPtr<T>& aOther);
#endif
void Assign(T* aNewPtr) {
MOZ_ASSERT(!aNewPtr || mRawPtr != aNewPtr);
T* oldPtr = mRawPtr;
mRawPtr = aNewPtr;
delete oldPtr;
}
T* mRawPtr;
};
template <class T>
class MOZ_ONLY_USED_TO_AVOID_STATIC_CONSTRUCTORS StaticRefPtr {
public:
// In debug builds, check that mRawPtr is initialized for us as we expect
// by the compiler. In non-debug builds, don't declare a constructor
// so that the compiler can see that the constructor is trivial.
#ifdef DEBUG
StaticRefPtr() {
# ifdef __GNUC__
# pragma GCC diagnostic push
# pragma GCC diagnostic ignored "-Wuninitialized"
// False positive with gcc. See bug 1430729
# endif
MOZ_ASSERT(!mRawPtr);
# ifdef __GNUC__
# pragma GCC diagnostic pop
# endif
}
#endif
StaticRefPtr<T>& operator=(T* aRhs) {
AssignWithAddref(aRhs);
return *this;
}
StaticRefPtr<T>& operator=(const StaticRefPtr<T>& aRhs) {
return (this = aRhs.mRawPtr);
}
StaticRefPtr<T>& operator=(already_AddRefed<T>& aRhs) {
AssignAssumingAddRef(aRhs.take());
return *this;
}
template <typename U>
StaticRefPtr<T>& operator=(RefPtr<U>&& aRhs) {
AssignAssumingAddRef(aRhs.forget().take());
return *this;
}
StaticRefPtr<T>& operator=(already_AddRefed<T>&& aRhs) {
AssignAssumingAddRef(aRhs.take());
return *this;
}
already_AddRefed<T> forget() {
T* temp = mRawPtr;
mRawPtr = nullptr;
return already_AddRefed<T>(temp);
}
T* get() const { return mRawPtr; }
operator T*() const { return get(); }
T* operator->() const {
MOZ_ASSERT(mRawPtr);
return get();
}
T& operator*() const { return *get(); }
private:
void AssignWithAddref(T* aNewPtr) {
if (aNewPtr) {
aNewPtr->AddRef();
}
AssignAssumingAddRef(aNewPtr);
}
void AssignAssumingAddRef(T* aNewPtr) {
T* oldPtr = mRawPtr;
mRawPtr = aNewPtr;
if (oldPtr) {
oldPtr->Release();
}
}
T* MOZ_OWNING_REF mRawPtr;
};
namespace StaticPtr_internal {
class Zero;
} // namespace StaticPtr_internal
#define REFLEXIVE_EQUALITY_OPERATORS(type1, type2, eq_fn, ...) \
template <__VA_ARGS__> \
inline bool operator==(type1 lhs, type2 rhs) { \
return eq_fn; \
} \
\
template <__VA_ARGS__> \
inline bool operator==(type2 lhs, type1 rhs) { \
return rhs == lhs; \
} \
\
template <__VA_ARGS__> \
inline bool operator!=(type1 lhs, type2 rhs) { \
return !(lhs == rhs); \
} \
\
template <__VA_ARGS__> \
inline bool operator!=(type2 lhs, type1 rhs) { \
return !(lhs == rhs); \
}
// StaticAutoPtr (in)equality operators
template <class T, class U>
inline bool operator==(const StaticAutoPtr<T>& aLhs,
const StaticAutoPtr<U>& aRhs) {
return aLhs.get() == aRhs.get();
}
template <class T, class U>
inline bool operator!=(const StaticAutoPtr<T>& aLhs,
const StaticAutoPtr<U>& aRhs) {
return !(aLhs == aRhs);
}
REFLEXIVE_EQUALITY_OPERATORS(const StaticAutoPtr<T>&, const U*,
lhs.get() == rhs, class T, class U)
REFLEXIVE_EQUALITY_OPERATORS(const StaticAutoPtr<T>&, U*, lhs.get() == rhs,
class T, class U)
// Let us compare StaticAutoPtr to 0.
REFLEXIVE_EQUALITY_OPERATORS(const StaticAutoPtr<T>&, StaticPtr_internal::Zero*,
lhs.get() == nullptr, class T)
// StaticRefPtr (in)equality operators
template <class T, class U>
inline bool operator==(const StaticRefPtr<T>& aLhs,
const StaticRefPtr<U>& aRhs) {
return aLhs.get() == aRhs.get();
}
template <class T, class U>
inline bool operator!=(const StaticRefPtr<T>& aLhs,
const StaticRefPtr<U>& aRhs) {
return !(aLhs == aRhs);
}
REFLEXIVE_EQUALITY_OPERATORS(const StaticRefPtr<T>&, const U*, lhs.get() == rhs,
class T, class U)
REFLEXIVE_EQUALITY_OPERATORS(const StaticRefPtr<T>&, U*, lhs.get() == rhs,
class T, class U)
// Let us compare StaticRefPtr to 0.
REFLEXIVE_EQUALITY_OPERATORS(const StaticRefPtr<T>&, StaticPtr_internal::Zero*,
lhs.get() == nullptr, class T)
#undef REFLEXIVE_EQUALITY_OPERATORS
} // namespace mozilla
// Declared in mozilla/RefPtr.h
template <class T>
template <class U>
RefPtr<T>::RefPtr(const mozilla::StaticRefPtr<U>& aOther)
: RefPtr(aOther.get()) {}
template <class T>
template <class U>
RefPtr<T>& RefPtr<T>::operator=(const mozilla::StaticRefPtr<U>& aOther) {
return operator=(aOther.get());
}
template <class T>
inline already_AddRefed<T> do_AddRef(const mozilla::StaticRefPtr<T>& aObj) {
RefPtr<T> ref(aObj);
return ref.forget();
}
#endif