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-rw-r--r--xpcom/base/StaticPtr.h275
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diff --git a/xpcom/base/StaticPtr.h b/xpcom/base/StaticPtr.h
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+/* -*- 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
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