Tweaking discovery of Pthreads C flags

1 files changed, 12 insertions, 0 deletions

diff --git a/m4/m4_ax_pthread.m4 b/m4/m4_ax_pthread.m4
index d383ad5c..f0717ada 100644
--- a/m4/m4_ax_pthread.m4
+++ b/m4/m4_ax_pthread.m4
@@ -204,11 +204,22 @@ for flag in $ax_pthread_flags; do
                 ;;
         esac
 
+        save_LDFLAGS="$LDFLAGS"
         save_LIBS="$LIBS"
         save_CFLAGS="$CFLAGS"
         LIBS="$PTHREAD_LIBS $LIBS"
         CFLAGS="$CFLAGS $PTHREAD_CFLAGS $ax_pthread_extra_flags"
 
+        # This check added by Adam Chlipala on January 16, 2016.
+        # The documentation at the top of this file said that PTHREAD_CFLAGS needs to
+        # be used at link-time, too, but this test didn't seem to do so.
+        # For now, I'm patching just for the common case of '-pthread'.
+        case $flag in
+             -pthread)
+             LDFLAGS="$LDFLAGS -pthread"
+             ;;
+        esac
+
         # Check for various functions.  We must include pthread.h,
         # since some functions may be macros.  (On the Sequent, we
         # need a special flag -Kthread to make this header compile.)
@@ -230,6 +241,7 @@ for flag in $ax_pthread_flags; do
                 [ax_pthread_ok=yes],
                 [])
 
+        LDFLAGS="$save_LDFLAGS"
         LIBS="$save_LIBS"
         CFLAGS="$save_CFLAGS"