libstdc++-v3/libsupc++/eh_atomics.h

   1 // Exception Handling support header for -*- C++ -*-
   2
   3 // Copyright (C) 2016-2018 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