Fix signals delivery fail in find-leak mode if init from non-main thread

Issue #542 (bdwgc).

The scenario of the failure (on Linux):
- Find-leak mode is on
- pthread_create/join primitives are not redirected
- GC is initialized from a thread other than primordial
- that thread is terminated (but not unregistered as the 1st one in GC)
- the primordial thread exits and launches GC_exit_check
- GC_gcollect tries to suspend the terminated thread by sending a signal
- the signal is not delivered but pthread_kill just returns zero
- the signal sending is retried until aborting with the proper message.

The proposed solution (workaround) is not to call GC_gcollect at
the process exit (in the find-leak mode) if GC_init was called from
a thread other than primordial one.

Check in GC_exit_check() (which is called if GC_find_leak) that the
thread executing at-exit functions is the same as the one performed
the GC initialization, otherwise the latter thread might already be
dead but still registered and this, as a consequence, might cause
a signal delivery fail when suspending the threads on platforms that
do not guarantee ESRCH returned if the signal is not delivered (as
observed on Ubuntu 22).

* include/private/gc_priv.h [THREADS && !DONT_USE_ATEXIT]
(GC_is_main_thread): Declare GC_INNER function.
* include/private/pthread_support.h [GC_WIN32_THREADS
&& !DONT_USE_ATEXIT] (GC_main_thread_id): Declare variable.
* include/private/pthread_support.h [GC_WIN32_THREADS
&& !GC_NO_THREADS_DISCOVERY] (GC_main_thread_id): Do not depend on
GC_ASSERTIONS.
* misc.c [!DONT_USE_ATEXIT && THREADS] (GC_exit_check): If not
GC_is_main_thread() or not GC_thread_is_registered() then do not call
GC_gcollect(); add comment; do not set and clear GC_in_thread_creation.
* pthread_support.c [!GC_NO_THREADS_DISCOVERY && GC_WIN32_THREADS
|| !DONT_USE_ATEXIT] (GC_main_thread_id): Define variable.
* pthread_support.c [!DONT_USE_ATEXIT] (GC_is_main_thread): Implement.
* pthread_support.c [!GC_WIN32_THREADS] (GC_thr_init): Define self_id
local variable.
* pthread_support.c [!GC_WIN32_THREADS && !DONT_USE_ATEXIT]
(GC_thr_init): Set GC_main_thread_id.
* win32_threads.c [!DONT_USE_ATEXIT] (GC_thr_init): Likewise.
* win32_threads.c [!GC_NO_THREADS_DISCOVERY] (GC_main_thread_id): Do
not define variable.

1 files changed, 1 insertions, 8 deletions

diff --git a/win32_threads.c b/win32_threads.c
index 91a2a037..d7cbf89b 100644
--- a/win32_threads.c
+++ b/win32_threads.c
@@ -109,13 +109,6 @@ GC_API void GC_CALL GC_use_threads_discovery(void)
 }
 
 #ifndef GC_NO_THREADS_DISCOVERY
-# ifdef GC_ASSERTIONS
-    GC_INNER
-# else
-    STATIC
-# endif
-  thread_id_t GC_main_thread_id;
-
   /* We track thread attachments while the world is supposed to be      */
   /* stopped.  Unfortunately, we cannot stop them from starting, since  */
   /* blocking in DllMain seems to cause the world to deadlock.  Thus,   */
@@ -1642,7 +1635,7 @@ GC_INNER void GC_thr_init(void)
 # ifdef GC_ASSERTIONS
     GC_thr_initialized = TRUE;
 # endif
-# ifndef GC_NO_THREADS_DISCOVERY
+# if !defined(DONT_USE_ATEXIT) || !defined(GC_NO_THREADS_DISCOVERY)
     GC_main_thread_id = self_id;
 # endif
 # ifdef CAN_HANDLE_FORK