Gnulib fails to detect nanosleep in MinGW runtime

[Bruno Haible]

While building the latest pretest of wget2, I saw that the Gnulib's
detection of nanosleep fails to detect its presence in mingw.org's
MinGW runtime. The test program used for that fails for unrelated
reason: it uses SIGALRM, which is unavailable on MS-Windows.
I'm guessing that SIGALRM is used to guard against buggy nanosleep
implementations

Yes, when SIGALRM was introduced in this test, it was in the commit
2006-08-31 "Work around a bug in both the Linux and SunOS 64-bit kernels".

perhaps the test program could be modified
to avoid using SIGALRM on Windows.

Indeed. I'm pushing this patch. Please complain if it does not work.


2018-05-12 Bruno Haible <***@clisp.org>

nanosleep: Avoid test failure on mingw when it has nanosleep.
Reported by Eli Zaretskii <***@gnu.org>.
* m4/nanosleep.m4 (gl_FUNC_NANOSLEEP): Check whether alarm() exists.
If it does not exist, use a simpler test program that does not call
alarm().

diff --git a/m4/nanosleep.m4 b/m4/nanosleep.m4
index 8903734..7c945cc 100644
--- a/m4/nanosleep.m4
+++ b/m4/nanosleep.m4
@@ -1,4 +1,4 @@
-# serial 37
+# serial 38

dnl From Jim Meyering.
dnl Check for the nanosleep function.
@@ -22,6 +22,8 @@ AC_DEFUN([gl_FUNC_NANOSLEEP],
AC_CHECK_HEADERS_ONCE([sys/time.h])
AC_REQUIRE([gl_FUNC_SELECT])

+ AC_CHECK_DECLS_ONCE([alarm])
+
nanosleep_save_libs=$LIBS

# Solaris 2.5.1 needs -lposix4 to get the nanosleep function.
@@ -62,40 +64,49 @@ AC_DEFUN([gl_FUNC_NANOSLEEP],
? (t) -1 \
: ((((t) 1 << (sizeof (t) * CHAR_BIT - 2)) - 1) * 2 + 1)))

+ #if HAVE_DECL_ALARM
static void
check_for_SIGALRM (int sig)
{
if (sig != SIGALRM)
_exit (1);
}
+ #endif

int
main ()
{
static struct timespec ts_sleep;
static struct timespec ts_remaining;
- static struct sigaction act;
/* Test for major problems first. */
if (! nanosleep)
return 2;
- act.sa_handler = check_for_SIGALRM;
- sigemptyset (&act.sa_mask);
- sigaction (SIGALRM, &act, NULL);
ts_sleep.tv_sec = 0;
ts_sleep.tv_nsec = 1;
- alarm (1);
- if (nanosleep (&ts_sleep, NULL) != 0)
+ #if HAVE_DECL_ALARM
+ {
+ static struct sigaction act;
+ act.sa_handler = check_for_SIGALRM;
+ sigemptyset (&act.sa_mask);
+ sigaction (SIGALRM, &act, NULL);
+ alarm (1);
+ if (nanosleep (&ts_sleep, NULL) != 0)
+ return 3;
+ /* Test for a minor problem: the handling of large arguments. */
+ ts_sleep.tv_sec = TYPE_MAXIMUM (time_t);
+ ts_sleep.tv_nsec = 999999999;
+ alarm (1);
+ if (nanosleep (&ts_sleep, &ts_remaining) != -1)
+ return 4;
+ if (errno != EINTR)
+ return 5;
+ if (ts_remaining.tv_sec <= TYPE_MAXIMUM (time_t) - 10)
+ return 6;
+ }
+ #else /* A simpler test for native Windows. */
+ if (nanosleep (&ts_sleep, &ts_remaining) < 0)
return 3;
- /* Test for a minor problem: the handling of large arguments. */
- ts_sleep.tv_sec = TYPE_MAXIMUM (time_t);
- ts_sleep.tv_nsec = 999999999;
- alarm (1);
- if (nanosleep (&ts_sleep, &ts_remaining) != -1)
- return 4;
- if (errno != EINTR)
- return 5;
- if (ts_remaining.tv_sec <= TYPE_MAXIMUM (time_t) - 10)
- return 6;
+ #endif
return 0;
}]])],
[gl_cv_func_nanosleep=yes],