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/* Once-only initialization in multithreaded situations.
Copyright (C) 2005-2024 Free Software Foundation, Inc.
This file is free software: you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as
published by the Free Software Foundation; either version 2.1 of the
License, or (at your option) any later version.
This file is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with this program. If not, see <https://www.gnu.org/licenses/>. */
/* Written by Bruno Haible <bruno@clisp.org>, 2005.
Based on GCC's gthr-posix.h, gthr-posix95.h. */
#include <config.h>
#include "glthread/once.h"
/* ========================================================================= */
#if USE_ISOC_THREADS || USE_ISOC_AND_POSIX_THREADS
#endif
/* ========================================================================= */
#if USE_POSIX_THREADS
static const pthread_once_t fresh_once = PTHREAD_ONCE_INIT;
int
glthread_once_singlethreaded (pthread_once_t *once_control)
{
/* We don't know whether pthread_once_t is an integer type, a floating-point
type, a pointer type, or a structure type. */
char *firstbyte = (char *)once_control;
if (*firstbyte == *(const char *)&fresh_once)
{
/* First time use of once_control. Invert the first byte. */
*firstbyte = ~ *(const char *)&fresh_once;
return 1;
}
else
return 0;
}
# if !(PTHREAD_IN_USE_DETECTION_HARD || USE_POSIX_THREADS_WEAK)
int
glthread_once_multithreaded (pthread_once_t *once_control,
void (*init_function) (void))
{
int err = pthread_once (once_control, init_function);
if (err == ENOSYS)
{
/* This happens on FreeBSD 11: The pthread_once function in libc returns
ENOSYS. */
if (glthread_once_singlethreaded (once_control))
init_function ();
return 0;
}
return err;
}
# endif
#endif
/* ========================================================================= */
#if USE_WINDOWS_THREADS
#endif
/* ========================================================================= */
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