libcxx/src/mutex_destructor.cpp

//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

// Define ~mutex.
//
// On some platforms ~mutex has been made trivial and the definition is only
// provided for ABI compatibility.
//
// In order to avoid ODR violations within libc++ itself, we need to ensure
// that *nothing* sees the non-trivial mutex declaration. For this reason
// we re-declare the entire class in this file instead of using
// _LIBCPP_BUILDING_LIBRARY to change the definition in the headers.

#include <__config>
#include <__thread/support.h>

#if _LIBCPP_ABI_VERSION == 1 || !_LIBCPP_HAS_TRIVIAL_MUTEX_DESTRUCTION
#  define NEEDS_MUTEX_DESTRUCTOR
#endif

_LIBCPP_BEGIN_NAMESPACE_STD

#ifdef NEEDS_MUTEX_DESTRUCTOR
class _LIBCPP_EXPORTED_FROM_ABI mutex {
  __libcpp_mutex_t __m_ = _LIBCPP_MUTEX_INITIALIZER;

public:
  _LIBCPP_ALWAYS_INLINE _LIBCPP_HIDE_FROM_ABI constexpr mutex() = default;
  mutex(const mutex&)                                           = delete;
  mutex& operator=(const mutex&)                                = delete;
  ~mutex() noexcept;
};

mutex::~mutex() noexcept { __libcpp_mutex_destroy(&__m_); }
#endif // !NEEDS_MUTEX_DESTRUCTOR

_LIBCPP_END_NAMESPACE_STD