m4: sync ax_pthread.m4 with autoconf archive

Sync with [1].

In particular, this lets us configure with -Wunused-but-set-parameter.

[1] https://raw.githubusercontent.com/autoconf-archive/autoconf-archive/62e8491dbc174113a04fe910cad1e92e8a9e2164/m4/ax_pthread.m4

Signed-off-by: Simon Marchi <simon.marchi@efficios.com>
Change-Id: Id9a6eb7cd0b8c7597ae6abb5587078afdaa420f6
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>

diff --git a/m4/ax_pthread.m4 b/m4/ax_pthread.m4
index 4920e073bf5a21e2a728576e138fa2f8181b05f2..0300e4ed882b999b361b4556c4afa2535acf628c 100644 (file)
--- a/m4/ax_pthread.m4
+++ b/m4/ax_pthread.m4
@@ -82,7 +82,7 @@
 #   modified version of the Autoconf Macro, you may extend this special
 #   exception to the GPL to apply to your modified version as well.
 
-#serial 25
+#serial 26
 
 AU_ALIAS([ACX_PTHREAD], [AX_PTHREAD])
 AC_DEFUN([AX_PTHREAD], [
@@ -371,7 +371,13 @@ for ax_pthread_try_flag in $ax_pthread_flags; do
 #                       if $ax_pthread_check_cond
 #                        error "$ax_pthread_check_macro must be defined"
 #                       endif
-                        static void routine(void *a) { a = 0; }
+                        static void *some_global = NULL;
+                        static void routine(void *a)
+                          {
+                             /* To avoid any unused-parameter or
+                                unused-but-set-parameter warning.  */
+                             some_global = a;
+                          }
                         static void *start_routine(void *a) { return a; }],
                        [pthread_t th; pthread_attr_t attr;
                         pthread_create(&th, 0, start_routine, 0);