80 lines
2.3 KiB
C
80 lines
2.3 KiB
C
/* Once-only initialization in multithreaded situations.
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Copyright (C) 2005-2025 Free Software Foundation, Inc.
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This file is free software: you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as
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published by the Free Software Foundation; either version 2.1 of the
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License, or (at your option) any later version.
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This file is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with this program. If not, see <https://www.gnu.org/licenses/>. */
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/* Written by Bruno Haible <bruno@clisp.org>, 2005.
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Based on GCC's gthr-posix.h, gthr-posix95.h. */
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#include <config.h>
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#include "glthread/once.h"
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/* ========================================================================= */
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#if USE_ISOC_THREADS || USE_ISOC_AND_POSIX_THREADS
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#endif
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/* ========================================================================= */
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#if USE_POSIX_THREADS
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static const pthread_once_t fresh_once = PTHREAD_ONCE_INIT;
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int
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glthread_once_singlethreaded (pthread_once_t *once_control)
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{
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/* We don't know whether pthread_once_t is an integer type, a floating-point
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type, a pointer type, or a structure type. */
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char *firstbyte = (char *)once_control;
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if (*firstbyte == *(const char *)&fresh_once)
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{
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/* First time use of once_control. Invert the first byte. */
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*firstbyte = ~ *(const char *)&fresh_once;
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return 1;
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}
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else
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return 0;
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}
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# if !(PTHREAD_IN_USE_DETECTION_HARD || USE_POSIX_THREADS_WEAK)
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int
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glthread_once_multithreaded (pthread_once_t *once_control,
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void (*init_function) (void))
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{
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int err = pthread_once (once_control, init_function);
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if (err == ENOSYS)
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{
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/* This happens on FreeBSD 11: The pthread_once function in libc returns
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ENOSYS. */
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if (glthread_once_singlethreaded (once_control))
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init_function ();
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return 0;
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}
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return err;
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}
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# endif
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#endif
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/* ========================================================================= */
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#if USE_WINDOWS_THREADS
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#endif
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/* ========================================================================= */
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