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* [PATCH] libgfortran: Disable gthreads weak symbols for glibc 2.34
@ 2024-04-09 17:06 H.J. Lu
  2024-04-09 17:25 ` Andrew Pinski
  0 siblings, 1 reply; 3+ messages in thread
From: H.J. Lu @ 2024-04-09 17:06 UTC (permalink / raw)
  To: gcc-patches; +Cc: fweimer, jakub

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.

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


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2024-04-09 17:06 [PATCH] libgfortran: Disable gthreads weak symbols for glibc 2.34 H.J. Lu
2024-04-09 17:25 ` Andrew Pinski
2024-04-09 17:30   ` H.J. Lu

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