1 // Exception Handling support header for -*- C++ -*-
2 
3 // Copyright (C) 2016-2020 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
__eh_atomic_inc(_Atomic_word * __count)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
__eh_atomic_dec(_Atomic_word * __count)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
85