regex: Make configure test more maintainable

[Bruno Haible]

Since M_CHECK_ACTION is only defined in <malloc.h>, it is confusing that the
test program tests it _before_ having included <malloc.h>. (Fortunately this
does not produce a bug, since HAVE_DECL_ALARM is 1 on glibc.) But anyway,
it's better written like this:


2024-10-26  Bruno Haible  <bruno@clisp.org>

        regex: Make configure test more maintainable.
        * m4/regex.m4 (gl_REGEX): Include <malloc.h> before testing for
        M_CHECK_ACTION.

diff --git a/m4/regex.m4 b/m4/regex.m4
index 64fa7e9146..18f36804c4 100644
--- a/m4/regex.m4
+++ b/m4/regex.m4
@@ -1,5 +1,5 @@
 # regex.m4
-# serial 75
+# serial 76
 dnl Copyright (C) 1996-2001, 2003-2024 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -40,15 +40,15 @@ AC_DEFUN([gl_REGEX]
             #include <limits.h>
             #include <string.h>
 
+            #if HAVE_MALLOC_H
+            # include <malloc.h> /* defines M_CHECK_ACTION on glibc */
+            #endif
+
             #if defined M_CHECK_ACTION || HAVE_DECL_ALARM
             # include <signal.h>
             # include <unistd.h>
             #endif
 
-            #if HAVE_MALLOC_H
-            # include <malloc.h>
-            #endif
-
             #ifdef M_CHECK_ACTION
             /* Exit with distinguishable exit code.  */
             static void sigabrt_no_core (int sig) { raise (SIGTERM); }