regex: port to mingw's recent addition of undeclared alarm On mingw (at least, when cross-compiling with Fedora 18's mingw32-headers-2.0.999-0.15.trunk.20121110.fc18.noarch build), compilation of test-regex fails: test-regex.c: In function 'main': test-regex.c:42:11: error: 'SIGALRM' undeclared (first use in this function) test-regex.c:42:11: note: each undeclared identifier is reported only once for each function it appears in test-regex.c:43:3: warning: implicit declaration of function 'alarm' It turns out that recent mingw64 added an export of alarm() and SIGALRM, but guarded their declarations behind __USE_MINGW_ALARM (default off, and with alarm() only in the non-standard <io.h>); so the m4 tests were setting HAVE_ALARM to 1 based on link success but then failing to compile. * doc/posix-functions/alarm.texi (alarm): Document that alarm exists but still doesn't work in newer mingw. * m4/frexp.m4 (gl_FUNC_FREXP_WORKS): Check for alarm declaration, not existence. Ensure SIGALRM is not trapped. * m4/mktime.m4 (gl_FUNC_MKTIME): Likewise. * m4/regex.m4 (gl_REGEX): Likewise. * m4/remainderf.m4 (gl_FUNC_REMAINDERF_WORKS): Likewise. * tests/test-regex.c (main): Use correct probe for alarm. Signed-off-by: Eric Blake <eblake@redhat.com>

--- a/m4/regex.m4
+++ b/m4/regex.m4
@@ -1,4 +1,4 @@
-# serial 63
+# serial 64
 
 # Copyright (C) 1996-2001, 2003-2013 Free Software Foundation, Inc.
 #
@@ -27,7 +27,7 @@
     # following run test, then default to *not* using the included regex.c.
     # If cross compiling, assume the test would fail and use the included
     # regex.c.
-    AC_CHECK_FUNCS_ONCE([alarm])
+    AC_CHECK_DECLS_ONCE([alarm])
     AC_CACHE_CHECK([for working re_compile_pattern],
                    [gl_cv_func_re_compile_pattern_working],
       [AC_RUN_IFELSE(
@@ -37,7 +37,7 @@
             #include <locale.h>
             #include <limits.h>
             #include <string.h>
-            #if HAVE_ALARM
+            #if HAVE_DECL_ALARM
             # include <unistd.h>
             # include <signal.h>
             #endif
@@ -49,7 +49,7 @@
             const char *s;
             struct re_registers regs;
 
-#if HAVE_ALARM
+#if HAVE_DECL_ALARM
             /* Some builds of glibc go into an infinite loop on this test.  */
             signal (SIGALRM, SIG_DFL);
             alarm (2);