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>

@node alarm
@section @code{alarm}
@findex alarm

POSIX specification:@* @url{http://www.opengroup.org/onlinepubs/9699919799/functions/alarm.html}

Gnulib module: ---

Portability problems fixed by Gnulib:
@itemize
@end itemize

Portability problems not fixed by Gnulib:
@itemize
@item
This function has no impact if <code>SIGALRM</code> is inherited as
ignored; programs should use <code>signal (SIGALRM, SIG_DFL)</code> if
it is important to ensure the alarm will fire.
@item
Use of this function in multi-threaded applications is not advised.
@item
This function is missing on some platforms:
mingw (2011), MSVC 9.
@item
This function is conditionally declared in the non-standard
@code{<io.h>} header on some platforms:
mingw (2012 or newer).
@end itemize