1 files changed, 80 insertions, 0 deletions

diff --git a/gl/glthread/once.c b/gl/glthread/once.c
new file mode 100644
index 00000000..53211af8
--- /dev/null
+++ b/gl/glthread/once.c
@@ -0,0 +1,80 @@
+/* Once-only initialization in multithreaded situations.
+   Copyright (C) 2005-2025 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
+
+/* ========================================================================= */