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da618cf0a7
This set usage of operator& instead of std::addressof seems not be easy to "abuse". Some seem easy to misuse, like basic_ostream::operator<<, trying to do that results in compilation errors since the `widen` function is not specialized for the hijacking character type. Hence there are no tests.
138 lines
4.6 KiB
C++
138 lines
4.6 KiB
C++
//===----------------------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#ifndef _LIBCPP___MEMORY_SHARED_COUNT_H
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#define _LIBCPP___MEMORY_SHARED_COUNT_H
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#include <__config>
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#include <__memory/addressof.h>
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#include <typeinfo>
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#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
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# pragma GCC system_header
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#endif
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_LIBCPP_BEGIN_NAMESPACE_STD
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// NOTE: Relaxed and acq/rel atomics (for increment and decrement respectively)
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// should be sufficient for thread safety.
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// See https://llvm.org/PR22803
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#if (defined(__clang__) && __has_builtin(__atomic_add_fetch) && defined(__ATOMIC_RELAXED) && \
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defined(__ATOMIC_ACQ_REL)) || \
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defined(_LIBCPP_COMPILER_GCC)
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# define _LIBCPP_HAS_BUILTIN_ATOMIC_SUPPORT 1
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#else
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# define _LIBCPP_HAS_BUILTIN_ATOMIC_SUPPORT 0
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#endif
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template <class _ValueType>
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inline _LIBCPP_HIDE_FROM_ABI _ValueType __libcpp_relaxed_load(_ValueType const* __value) {
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#if _LIBCPP_HAS_THREADS && defined(__ATOMIC_RELAXED) && \
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(__has_builtin(__atomic_load_n) || defined(_LIBCPP_COMPILER_GCC))
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return __atomic_load_n(__value, __ATOMIC_RELAXED);
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#else
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return *__value;
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#endif
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}
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template <class _ValueType>
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inline _LIBCPP_HIDE_FROM_ABI _ValueType __libcpp_acquire_load(_ValueType const* __value) {
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#if _LIBCPP_HAS_THREADS && defined(__ATOMIC_ACQUIRE) && \
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(__has_builtin(__atomic_load_n) || defined(_LIBCPP_COMPILER_GCC))
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return __atomic_load_n(__value, __ATOMIC_ACQUIRE);
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#else
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return *__value;
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#endif
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}
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template <class _Tp>
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inline _LIBCPP_HIDE_FROM_ABI _Tp __libcpp_atomic_refcount_increment(_Tp& __t) _NOEXCEPT {
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#if _LIBCPP_HAS_BUILTIN_ATOMIC_SUPPORT && _LIBCPP_HAS_THREADS
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return __atomic_add_fetch(std::addressof(__t), 1, __ATOMIC_RELAXED);
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#else
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return __t += 1;
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#endif
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}
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template <class _Tp>
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inline _LIBCPP_HIDE_FROM_ABI _Tp __libcpp_atomic_refcount_decrement(_Tp& __t) _NOEXCEPT {
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#if _LIBCPP_HAS_BUILTIN_ATOMIC_SUPPORT && _LIBCPP_HAS_THREADS
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return __atomic_add_fetch(std::addressof(__t), -1, __ATOMIC_ACQ_REL);
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#else
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return __t -= 1;
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#endif
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}
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class _LIBCPP_EXPORTED_FROM_ABI __shared_count {
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__shared_count(const __shared_count&);
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__shared_count& operator=(const __shared_count&);
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protected:
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long __shared_owners_;
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virtual ~__shared_count();
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private:
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virtual void __on_zero_shared() _NOEXCEPT = 0;
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public:
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_LIBCPP_HIDE_FROM_ABI explicit __shared_count(long __refs = 0) _NOEXCEPT : __shared_owners_(__refs) {}
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#if defined(_LIBCPP_SHARED_PTR_DEFINE_LEGACY_INLINE_FUNCTIONS)
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void __add_shared() noexcept;
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bool __release_shared() noexcept;
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#else
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_LIBCPP_HIDE_FROM_ABI void __add_shared() _NOEXCEPT { __libcpp_atomic_refcount_increment(__shared_owners_); }
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_LIBCPP_HIDE_FROM_ABI bool __release_shared() _NOEXCEPT {
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if (__libcpp_atomic_refcount_decrement(__shared_owners_) == -1) {
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__on_zero_shared();
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return true;
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}
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return false;
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}
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#endif
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_LIBCPP_HIDE_FROM_ABI long use_count() const _NOEXCEPT { return __libcpp_relaxed_load(&__shared_owners_) + 1; }
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};
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class _LIBCPP_EXPORTED_FROM_ABI __shared_weak_count : private __shared_count {
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long __shared_weak_owners_;
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public:
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_LIBCPP_HIDE_FROM_ABI explicit __shared_weak_count(long __refs = 0) _NOEXCEPT
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: __shared_count(__refs),
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__shared_weak_owners_(__refs) {}
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protected:
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~__shared_weak_count() override;
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public:
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#if defined(_LIBCPP_SHARED_PTR_DEFINE_LEGACY_INLINE_FUNCTIONS)
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void __add_shared() noexcept;
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void __add_weak() noexcept;
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void __release_shared() noexcept;
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#else
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_LIBCPP_HIDE_FROM_ABI void __add_shared() _NOEXCEPT { __shared_count::__add_shared(); }
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_LIBCPP_HIDE_FROM_ABI void __add_weak() _NOEXCEPT { __libcpp_atomic_refcount_increment(__shared_weak_owners_); }
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_LIBCPP_HIDE_FROM_ABI void __release_shared() _NOEXCEPT {
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if (__shared_count::__release_shared())
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__release_weak();
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}
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#endif
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void __release_weak() _NOEXCEPT;
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_LIBCPP_HIDE_FROM_ABI long use_count() const _NOEXCEPT { return __shared_count::use_count(); }
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__shared_weak_count* lock() _NOEXCEPT;
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virtual const void* __get_deleter(const type_info&) const _NOEXCEPT;
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private:
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virtual void __on_zero_shared_weak() _NOEXCEPT = 0;
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};
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_LIBCPP_END_NAMESPACE_STD
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#endif // _LIBCPP___MEMORY_SHARED_COUNT_H
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