Re: [PATCH] libgfortran: Disable gthreads weak symbols for glibc 2.34

[Andrew Pinski <pinskia@gmail.com>]

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On Tue, Apr 9, 2024, 10:07 H.J. Lu <hjl.tools@gmail.com> wrote:

> Since Glibc 2.34 all pthreads symbols are defined directly in libc not
> libpthread, and since Glibc 2.32 we have used __libc_single_threaded to
> avoid unnecessary locking in single-threaded programs. This means there
> is no reason to avoid linking to libpthread now, and so no reason to use
> weak symbols defined in gthr-posix.h for all the pthread_xxx functions.
>


First you forgot to cc fortran@. Second the issue is in gthrd-posix.h which
should be fixed instead of libgfortran since the issue will also be seen
with libobjc, and the other users of gthrd.

Note the fix for libstdc++ was also done in the wrong location too and
should have done once and for all in gthrd-posix.h.


Thanks,
Andrew


> Also add prune_warnings to libgomp.exp to prune glibc static link warning:
>
> .*: warning: Using 'dlopen' in statically linked applications requires at
> runtime the shared libraries from the glibc version us ed for linking
>
> libgfortran/
>
>         PR libgfortran/114646
>         * acinclude.m4: Define GTHREAD_USE_WEAK 0 for glibc 2.34 or
>         above on Linux.
>         * configure: Regenerated.
>
> libgomp/
>
>         PR libgfortran/114646
>         * testsuite/lib/libgomp.exp (prune_warnings): New.
>         * testsuite/libgomp.fortran/pr114646-1.f90: New test.
>         * testsuite/libgomp.fortran/pr114646-2.f90: Likewise.
> ---
>  libgfortran/acinclude.m4                      | 14 +++++++++
>  libgfortran/configure                         | 29 +++++++++++++++++++
>  libgomp/testsuite/lib/libgomp.exp             | 14 +++++++++
>  .../testsuite/libgomp.fortran/pr114646-1.f90  | 11 +++++++
>  .../testsuite/libgomp.fortran/pr114646-2.f90  | 22 ++++++++++++++
>  5 files changed, 90 insertions(+)
>  create mode 100644 libgomp/testsuite/libgomp.fortran/pr114646-1.f90
>  create mode 100644 libgomp/testsuite/libgomp.fortran/pr114646-2.f90
>
> diff --git a/libgfortran/acinclude.m4 b/libgfortran/acinclude.m4
> index a73207e5465..f4642494c4f 100644
> --- a/libgfortran/acinclude.m4
> +++ b/libgfortran/acinclude.m4
> @@ -92,6 +92,20 @@ void foo (void);
>        AC_DEFINE(GTHREAD_USE_WEAK, 0,
>                 [Define to 0 if the target shouldn't use #pragma weak])
>        ;;
> +    *-*-linux*)
> +      AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
> +#include <features.h>
> +#if !__GLIBC_PREREQ(2, 34)
> +#error glibc version is too old
> +#endif
> +]], [[]])],
> +                       libgfor_cv_use_pragma_weak=no,
> +                       libgfor_cv_use_pragma_weak=yes)
> +      if test $libgfor_cv_use_pragma_weak = no; then
> +        AC_DEFINE(GTHREAD_USE_WEAK, 0,
> +                 [Define to 0 if the target shouldn't use #pragma weak])
> +      fi
> +      ;;
>    esac])
>
>  dnl Check whether target effectively supports weakref
> diff --git a/libgfortran/configure b/libgfortran/configure
> index 774dd52fc95..1f477256b75 100755
> --- a/libgfortran/configure
> +++ b/libgfortran/configure
> @@ -31057,6 +31057,35 @@ $as_echo "#define SUPPORTS_WEAK 1" >>confdefs.h
>
>  $as_echo "#define GTHREAD_USE_WEAK 0" >>confdefs.h
>
> +      ;;
> +    *-*-linux*)
> +      cat confdefs.h - <<_ACEOF >conftest.$ac_ext
> +/* end confdefs.h.  */
> +
> +#include <features.h>
> +#if !__GLIBC_PREREQ(2, 34)
> +#error glibc version is too old
> +#endif
> +
> +int
> +main ()
> +{
> +
> +  ;
> +  return 0;
> +}
> +_ACEOF
> +if ac_fn_c_try_compile "$LINENO"; then :
> +  libgfor_cv_use_pragma_weak=no
> +else
> +  libgfor_cv_use_pragma_weak=yes
> +fi
> +rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
> +      if test $libgfor_cv_use_pragma_weak = no; then
> +
> +$as_echo "#define GTHREAD_USE_WEAK 0" >>confdefs.h
> +
> +      fi
>        ;;
>    esac
>
> diff --git a/libgomp/testsuite/lib/libgomp.exp
> b/libgomp/testsuite/lib/libgomp.exp
> index cab926a798b..9cfa6d7b31d 100644
> --- a/libgomp/testsuite/lib/libgomp.exp
> +++ b/libgomp/testsuite/lib/libgomp.exp
> @@ -54,6 +54,20 @@ set dg-do-what-default run
>
>  set libgomp_compile_options ""
>
> +# Prune messages that aren't useful.
> +
> +proc prune_warnings { text } {
> +
> +    verbose "prune_warnings: entry: $text" 2
> +
> +    # Ignore warning from -static: warning: Using 'dlopen' in statically
> linked applications requires at runtime the shared libraries from the glibc
> version used for linking
> +    regsub -all "(^|\n)\[^\n\]*: warning: Using 'dlopen' in statically
> linked\[^\n\]*" $text "" text
> +
> +    verbose "prune_warnings: exit: $text" 2
> +
> +    return $text
> +}
> +
>  #
>  # libgomp_init
>  #
> diff --git a/libgomp/testsuite/libgomp.fortran/pr114646-1.f90
> b/libgomp/testsuite/libgomp.fortran/pr114646-1.f90
> new file mode 100644
> index 00000000000..a48e6103343
> --- /dev/null
> +++ b/libgomp/testsuite/libgomp.fortran/pr114646-1.f90
> @@ -0,0 +1,11 @@
> +! PR libgfortran/114646
> +! { dg-do run }
> +! { dg-additional-options "-static" }
> +
> +!$OMP PARALLEL
> +!$OMP CRITICAL
> + write(6,*) "Hello world"
> +!$OMP END CRITICAL
> +!$OMP END PARALLEL
> + write(6,*) "Done!"
> +END
> diff --git a/libgomp/testsuite/libgomp.fortran/pr114646-2.f90
> b/libgomp/testsuite/libgomp.fortran/pr114646-2.f90
> new file mode 100644
> index 00000000000..8c0d7526f95
> --- /dev/null
> +++ b/libgomp/testsuite/libgomp.fortran/pr114646-2.f90
> @@ -0,0 +1,22 @@
> +! PR libgfortran/114646
> +! { dg-do run }
> +! { dg-additional-options "-static" }
> +
> +      use omp_lib
> +      implicit none
> +      integer, parameter :: NT = 4
> +      integer :: nThreads(NT)
> +
> +      print *, 'Call omp_set_dynamic'
> +!$    call omp_set_dynamic(.false.)
> +      print *, 'Call omp_set_num_threads'
> +!$    call omp_set_num_threads(NT)
> +      print *, 'Now enter the parallel region'
> +
> +!$omp parallel default(none) shared(nThreads)
> +      nThreads(omp_get_thread_num()+1) = omp_get_num_threads()
> +!$omp end parallel
> +
> +      print*, nThreads
> +
> +      END
> --
> 2.44.0
>
>