On Sun, 21 Jan 2024 14:30:00 +0100
ASSI wrote:
> Takashi Yano via Cygwin writes:
> > I found the cause. In pthread.h of cygwin, PTHREAD_ONCE_INIT is defined as:
> > #define PTHREAD_ONCE_INIT { PTHREAD_MUTEX_INITIALIZER, 0 }
> > however, libstdc++ initializes non-static pthread_once_t using this macro.
>
> https://www.ibm.com/docs/en/aix/7.3?topic=p-pthread-once-init-macro
> https://pubs.opengroup.org/onlinepubs/9699919799/functions/pthread_once.html
>
> "The behavior of pthread_once() is undefined if once_control has
> automatic storage duration or is not initialized by PTHREAD_ONCE_INIT."
>
> > I cannot find the POSIX statement that only static pthread_once_t can be
> > initialized using PTHREAD_ONCE_INIT. If I do not overlook something,
> > this is the problem of cygwin side, isn't it?
>
> You can initialize just about anything with PTHREAD_ONCE_INIT, but you
> cannot expect the resulting structure to work as intended if there is
> more than instance per library / program, so the libstdc++ object should
> be a singleton, not automatic.
>
> Still looks like ATWIL to me…
Thanks for the information.
Anyway, I confirmed the two patches (one is for gcc, the other is for cygwin)
resolve the issue.
PATCH1: (for gcc)
Do not use PTHREAD_MUTEX_INITIALIZER etc. for non-static pthread_mutex_t.
diff -ur origsrc/gcc-13-20230902/libgcc/gthr-posix.h
src/gcc-13-20230902/libgcc/gthr-posix.h
--- origsrc/gcc-13-20230902/libgcc/gthr-posix.h 2023-09-03 07:32:49.000000000
+0900
+++ src/gcc-13-20230902/libgcc/gthr-posix.h 2024-01-22 09:04:54.342189600
+0900
@@ -34,6 +34,12 @@
#include <pthread.h>
+#ifdef __CYGWIN__
+#define _GTHREAD_USE_MUTEX_INIT_FUNC 1
+#define _GTHREAD_USE_RECURSIVE_MUTEX_INIT_FUNC 1
+#define _GTHREAD_USE_COND_INIT_FUNC 1
+#endif
+
#if ((defined(_LIBOBJC) || defined(_LIBOBJC_WEAK)) \
|| !defined(_GTHREAD_USE_MUTEX_TIMEDLOCK))
# include <unistd.h>
PATCH2: (for cygwin)
Avoid handle leak caused when non-static pthread_once_t is initialized
with PTHREAD_ONCE_INIT
diff --git a/winsup/cygwin/thread.cc b/winsup/cygwin/thread.cc
index 7bb4f9fc8..127569160 100644
--- a/winsup/cygwin/thread.cc
+++ b/winsup/cygwin/thread.cc
@@ -2060,6 +2060,9 @@ pthread::once (pthread_once_t *once_control, void
(*init_routine) (void))
{
init_routine ();
once_control->state = 1;
+ pthread_mutex_unlock (&once_control->mutex);
+ while (pthread_mutex_destroy (&once_control->mutex) == EBUSY);
+ return 0;
}
/* Here we must remove our cancellation handler */
pthread_mutex_unlock (&once_control->mutex);
--
Takashi Yano <takashi.y...@nifty.ne.jp>
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