1  // Exception Handling support header for -*- C++ -*-
       2  
       3  // Copyright (C) 2016-2023 Free Software Foundation, Inc.
       4  //
       5  // This file is part of GCC.
       6  //
       7  // GCC is free software; you can redistribute it and/or modify
       8  // it under the terms of the GNU General Public License as published by
       9  // the Free Software Foundation; either version 3, or (at your option)
      10  // any later version.
      11  //
      12  // GCC is distributed in the hope that it will be useful,
      13  // but WITHOUT ANY WARRANTY; without even the implied warranty of
      14  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
      15  // GNU General Public License for more details.
      16  //
      17  // Under Section 7 of GPL version 3, you are granted additional
      18  // permissions described in the GCC Runtime Library Exception, version
      19  // 3.1, as published by the Free Software Foundation.
      20  
      21  // You should have received a copy of the GNU General Public License and
      22  // a copy of the GCC Runtime Library Exception along with this program;
      23  // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
      24  // <http://www.gnu.org/licenses/>.
      25  
      26  /** @file eh_atomics.h
      27   *  This is an internal header file, included by library source files.
      28   *  Do not attempt to use it directly.
      29   */
      30  
      31  #ifndef _EH_ATOMICS_H
      32  #define _EH_ATOMICS_H 1
      33  
      34  #include <bits/c++config.h>
      35  #include <bits/atomic_word.h>
      36  #include <bits/atomic_lockfree_defines.h>
      37  #if ATOMIC_INT_LOCK_FREE <= 1
      38  # include <ext/atomicity.h>
      39  #endif
      40  
      41  #pragma GCC visibility push(default)
      42  extern "C++" {
      43  namespace __gnu_cxx
      44  {
      45    void
      46    __eh_atomic_inc (_Atomic_word* __count) __attribute__((always_inline));
      47  
      48    bool
      49    __eh_atomic_dec (_Atomic_word* __count) __attribute__((always_inline));
      50  
      51    // Increments the count.
      52    inline void
      53    __eh_atomic_inc (_Atomic_word* __count)
      54    {
      55  #if ATOMIC_INT_LOCK_FREE > 1
      56      __atomic_add_fetch (__count, 1, __ATOMIC_ACQ_REL);
      57  #else
      58      _GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE (__count);
      59      __gnu_cxx::__atomic_add_dispatch (__count, 1);
      60      _GLIBCXX_SYNCHRONIZATION_HAPPENS_AFTER (__count);
      61  #endif
      62    }
      63  
      64    // Decrements the count and returns true if it reached zero.
      65    inline bool
      66    __eh_atomic_dec (_Atomic_word* __count)
      67    {
      68  #if ATOMIC_INT_LOCK_FREE > 1
      69      return __atomic_sub_fetch (__count, 1, __ATOMIC_ACQ_REL) == 0;
      70  #else
      71      _GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE (__count);
      72      if (__gnu_cxx::__exchange_and_add_dispatch (__count, -1) == 1)
      73        {
      74  	_GLIBCXX_SYNCHRONIZATION_HAPPENS_AFTER (__count);
      75  	return true;
      76        }
      77      return false;
      78  #endif
      79    }
      80  } // namespace __gnu_cxx
      81  }
      82  #pragma GCC visibility pop
      83  
      84  #endif // _EH_ATOMICS_H