[Bug libstdc++/95989] Segmentation fault compiling with static libraries and using jthread::request_stop

["redi at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95989

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           See Also|                            |https://sourceware.org/bugz
                   |                            |illa/show_bug.cgi?id=22635

--- Comment #13 from Jonathan Wakely <redi at gcc dot gnu.org> ---
I'm testing this:

diff --git a/libgcc/gthr-posix.h b/libgcc/gthr-posix.h
index 965247602ac..0af84a781e5 100644
--- a/libgcc/gthr-posix.h
+++ b/libgcc/gthr-posix.h
@@ -684,7 +684,12 @@ __gthread_equal (__gthread_t __t1, __gthread_t __t2)
 static inline __gthread_t
 __gthread_self (void)
 {
+#if __GLIBC_PREREQ(2, 27)
+  /* See PR libstdc++/95989  */
+  return pthread_self ();
+#else
   return __gthrw_(pthread_self) ();
+#endif
 }

 static inline int
diff --git a/libstdc++-v3/include/std/thread b/libstdc++-v3/include/std/thread
index 0445ab1e319..2772dd3950e 100644
--- a/libstdc++-v3/include/std/thread
+++ b/libstdc++-v3/include/std/thread
@@ -364,13 +364,14 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     inline thread::id
     get_id() noexcept
     {
-#ifdef __GLIBC__
+#if defined __GLIBC__ && ! __GLIBC_PREREQ(2, 27)
       // For the GNU C library pthread_self() is usable without linking to
-      // libpthread.so but returns 0, so we cannot use it in single-threaded
-      // programs, because this_thread::get_id() != thread::id{} must be true.
-      // We know that pthread_t is an integral type in the GNU C library.
+      // libpthread, but prior to version 2.27 the version in libc returns 0,
+      // which breaks the invariant this_thread::get_id() != thread::id{}.
+      // We know that pthread_t is a scalar type in the GNU C library,
+      // so just use (__gthread_t)1 as the ID of the main (and only) thread.
       if (!__gthread_active_p())
-       return thread::id(1);
+       return thread::id((__gthread_t)1);
 #endif
       return thread::id(__gthread_self());
     }