Avoid compiler warnings in some configure tests

[Bruno Haible]

In some config.log I was seeing this warning:

configure:24322: checking for pthread_mutex_timedlock
configure:24346: gcc -o conftest -g -O2 -I/inst-x86_64-64/include -Wall 
-L/inst-x86_64-64/lib conftest.c   >&5
conftest.c: In function 'main':
conftest.c:149:25: warning: argument 2 null where non-null expected [-Wnonnull]
  149 |                  return pthread_mutex_timedlock (&lock, (struct 
timespec *) 0);
      |                         ^~~~~~~~~~~~~~~~~~~~~~~

This patch fixes it.


2024-08-07  Bruno Haible  <br...@clisp.org>

        Avoid compiler warnings in some configure tests.
        * m4/pthread-rwlock.m4 (gl_PTHREAD_RWLOCK): Allocate more room for local
        array 'name'.
        * m4/pthread_mutex_timedlock.m4 (gl_FUNC_PTHREAD_MUTEX_TIMEDLOCK): Don't
        pass a NULL pointer to pthread_mutex_timedlock.

diff --git a/m4/pthread-rwlock.m4 b/m4/pthread-rwlock.m4
index 51d84419c7..cbd08790e1 100644
--- a/m4/pthread-rwlock.m4
+++ b/m4/pthread-rwlock.m4
@@ -1,5 +1,5 @@
 # pthread-rwlock.m4
-# serial 5
+# serial 6
 dnl Copyright (C) 2019-2024 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -249,7 +249,7 @@ AC_DEFUN([gl_PTHREAD_RWLOCK]
   char **names = (char **) malloc (n * sizeof (char *));
   for (size_t i = 0; i < n; i++)
     {
-      char name[10];
+      char name[12];
       sprintf (name, "%c%u", rw_string[i], (unsigned int) (i+1));
       names[i] = strdup (name);
     }
diff --git a/m4/pthread_mutex_timedlock.m4 b/m4/pthread_mutex_timedlock.m4
index 46b59d793c..9b175d5474 100644
--- a/m4/pthread_mutex_timedlock.m4
+++ b/m4/pthread_mutex_timedlock.m4
@@ -1,5 +1,5 @@
 # pthread_mutex_timedlock.m4
-# serial 5
+# serial 6
 dnl Copyright (C) 2019-2024 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -28,7 +28,8 @@ AC_DEFUN([gl_FUNC_PTHREAD_MUTEX_TIMEDLOCK]
                  #include <time.h>
                ]],
                [[pthread_mutex_t lock;
-                 return pthread_mutex_timedlock (&lock, (struct timespec *) 0);
+                 struct timespec ts = { 0 };
+                 return pthread_mutex_timedlock (&lock, &ts);
                ]])
             ],
             [gl_cv_func_pthread_mutex_timedlock_in_LIBMULTITHREAD=yes],