libgcc: Don't use weakrefs for glibc 2.34
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Commit Message
Hi!
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.
Bootstrapped/regtested on x86_64-linux and i686-linux (with glibc 2.35), ok
for trunk?
2024-04-25 Jakub Jelinek <jakub@redhat.com>
* gthr.h (GTHREAD_USE_WEAK): Redefine to 0 for GLIBC 2.34 or later.
Jakub
Comments
> Am 25.04.2024 um 20:24 schrieb Jakub Jelinek <jakub@redhat.com>:
>
> Hi!
>
> 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.
>
> Bootstrapped/regtested on x86_64-linux and i686-linux (with glibc 2.35), ok
> for trunk?
Ok
Richard
> 2024-04-25 Jakub Jelinek <jakub@redhat.com>
>
> * gthr.h (GTHREAD_USE_WEAK): Redefine to 0 for GLIBC 2.34 or later.
>
> --- libgcc/gthr.h.jj 2024-01-03 12:07:28.623363560 +0100
> +++ libgcc/gthr.h 2024-04-25 12:09:39.708622613 +0200
> @@ -141,6 +141,15 @@ see the files COPYING3 and COPYING.RUNTI
> #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
>
> Jakub
>
On Thu, 25 Apr 2024, Jakub Jelinek wrote:
> Hi!
>
> 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).
I suspect this has caused link failures in the glibc testsuite for Hurd,
which still has separate libpthread.
https://sourceware.org/pipermail/libc-testresults/2024q2/012556.html
@@ -141,6 +141,15 @@ see the files COPYING3 and COPYING.RUNTI
#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