libcxx/src/mutex_destructor.cpp

   1 //===----------------------------------------------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 // Define ~mutex.
  10 //
  11 // On some platforms ~mutex has been made trivial and the definition is only
  12 // provided for ABI compatibility.
  13 //
  14 // In order to avoid ODR violations within libc++ itself, we need to ensure
  15 // that *nothing* sees the non-trivial mutex declaration. For this reason
  16 // we re-declare the entire class in this file instead of using
  17 // _LIBCPP_BUILDING_LIBRARY to change the definition in the headers.
  18
  19 #include <__config>
  20 #include <__threading_support>
  21
  22 #if _LIBCPP_ABI_VERSION == 1 || !defined(_LIBCPP_HAS_TRIVIAL_MUTEX_DESTRUCTION)
  23 #  define NEEDS_MUTEX_DESTRUCTOR
  24 #endif
  25
  26 _LIBCPP_BEGIN_NAMESPACE_STD
  27
  28 #ifdef NEEDS_MUTEX_DESTRUCTOR
  29 class _LIBCPP_EXPORTED_FROM_ABI mutex {
  30   __libcpp_mutex_t __m_ = _LIBCPP_MUTEX_INITIALIZER;
  31
  32 public:
  33   _LIBCPP_ALWAYS_INLINE _LIBCPP_HIDE_FROM_ABI constexpr mutex() = default;
  34   mutex(const mutex&)                                           = delete;
  35   mutex& operator=(const mutex&)                                = delete;
  36   ~mutex() noexcept;
  37 };
  38
  39 mutex::~mutex() noexcept { __libcpp_mutex_destroy(&__m_); }
  40 #endif // !NEEDS_MUTEX_DESTRUCTOR
  41
  42 _LIBCPP_END_NAMESPACE_STD