[gcc r14-10133] libgcc: Don't use weakrefs for glibc 2.34

[Jakub Jelinek <jakub@gcc.gnu.org>]

https://gcc.gnu.org/g:fe02f6caac2d9b51ad311889e76ba0c484356ea1

commit r14-10133-gfe02f6caac2d9b51ad311889e76ba0c484356ea1
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Thu Apr 25 20:43:13 2024 +0200

    libgcc: Don't use weakrefs for glibc 2.34
    
    glibc 2.34 and later doesn't have separate libpthread (libpthread.so.0 is a
    dummy shared library with just some symbol versions for compatibility, but
    all the pthread_* APIs are in libc.so.6).
    So, we don't need to do the .weakref dances to check whether a program
    has been linked with -lpthread or not, in dynamically linked apps those
    will be always true anyway.
    In -static linking, this fixes various issues people had when only linking
    some parts of libpthread.a and getting weird crashes.  A hack for that was
    what e.g. some Fedora glibcs used, where libpthread.a was a library
    containing just one giant *.o file which had all the normal libpthread.a
    *.o files linked with -r together.
    
    libstdc++-v3 actually does something like this already since r10-10928,
    the following patch is meant to fix it even for libgfortran, libobjc and
    whatever else uses gthr.h.
    
    2024-04-25  Jakub Jelinek  <jakub@redhat.com>
    
            * gthr.h (GTHREAD_USE_WEAK): Redefine to 0 for GLIBC 2.34 or later.

Diff:
---
 libgcc/gthr.h | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/libgcc/gthr.h b/libgcc/gthr.h
index 31c404250b8..53a5f0f7458 100644
--- a/libgcc/gthr.h
+++ b/libgcc/gthr.h
@@ -141,6 +141,15 @@ see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
 #define GTHREAD_USE_WEAK 0
 #endif
 
+#ifdef __GLIBC_PREREQ
+#if __GLIBC_PREREQ(2, 34)
+/* glibc 2.34 and later has all pthread_* APIs inside of libc,
+   no need to link separately with -lpthread.  */
+#undef GTHREAD_USE_WEAK
+#define GTHREAD_USE_WEAK 0
+#endif
+#endif
+
 #ifndef GTHREAD_USE_WEAK
 #define GTHREAD_USE_WEAK 1
 #endif