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      1 /* atomic.c -- Support for atomic functions if not present.
      2    Copyright (C) 2013-2024 Free Software Foundation, Inc.
      3    Written by Ian Lance Taylor, Google.
      4 
      5 Redistribution and use in source and binary forms, with or without
      6 modification, are permitted provided that the following conditions are
      7 met:
      8 
      9     (1) Redistributions of source code must retain the above copyright
     10     notice, this list of conditions and the following disclaimer.
     11 
     12     (2) Redistributions in binary form must reproduce the above copyright
     13     notice, this list of conditions and the following disclaimer in
     14     the documentation and/or other materials provided with the
     15     distribution.
     16 
     17     (3) The name of the author may not be used to
     18     endorse or promote products derived from this software without
     19     specific prior written permission.
     20 
     21 THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
     22 IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
     23 WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
     24 DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
     25 INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
     26 (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
     27 SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     28 HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
     29 STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
     30 IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     31 POSSIBILITY OF SUCH DAMAGE.  */
     32 
     33 #include "config.h"
     34 
     35 #include <sys/types.h>
     36 
     37 #include "backtrace.h"
     38 #include "backtrace-supported.h"
     39 #include "internal.h"
     40 
     41 /* This file holds implementations of the atomic functions that are
     42    used if the host compiler has the sync functions but not the atomic
     43    functions, as is true of versions of GCC before 4.7.  */
     44 
     45 #if !defined (HAVE_ATOMIC_FUNCTIONS) && defined (HAVE_SYNC_FUNCTIONS)
     46 
     47 /* Do an atomic load of a pointer.  */
     48 
     49 void *
     50 backtrace_atomic_load_pointer (void *arg)
     51 {
     52   void **pp;
     53   void *p;
     54 
     55   pp = (void **) arg;
     56   p = *pp;
     57   while (!__sync_bool_compare_and_swap (pp, p, p))
     58     p = *pp;
     59   return p;
     60 }
     61 
     62 /* Do an atomic load of an int.  */
     63 
     64 int
     65 backtrace_atomic_load_int (int *p)
     66 {
     67   int i;
     68 
     69   i = *p;
     70   while (!__sync_bool_compare_and_swap (p, i, i))
     71     i = *p;
     72   return i;
     73 }
     74 
     75 /* Do an atomic store of a pointer.  */
     76 
     77 void
     78 backtrace_atomic_store_pointer (void *arg, void *p)
     79 {
     80   void **pp;
     81   void *old;
     82 
     83   pp = (void **) arg;
     84   old = *pp;
     85   while (!__sync_bool_compare_and_swap (pp, old, p))
     86     old = *pp;
     87 }
     88 
     89 /* Do an atomic store of a size_t value.  */
     90 
     91 void
     92 backtrace_atomic_store_size_t (size_t *p, size_t v)
     93 {
     94   size_t old;
     95 
     96   old = *p;
     97   while (!__sync_bool_compare_and_swap (p, old, v))
     98     old = *p;
     99 }
    100 
    101 /* Do an atomic store of a int value.  */
    102 
    103 void
    104 backtrace_atomic_store_int (int *p, int v)
    105 {
    106   size_t old;
    107 
    108   old = *p;
    109   while (!__sync_bool_compare_and_swap (p, old, v))
    110     old = *p;
    111 }
    112 
    113 #endif
    114