don't use timespeccmp()/timespecsub()

There's no compat library for OS X that provides them yet.

configure.ac

@@ -42,16 +42,7 @@ AC_ARG_ENABLE([libbsd-feature-test],
 AC_CHECK_FUNCS([err errx warn warnx],,
     [LIBBSD_NEEDED=yes])
 AC_CHECK_HEADERS([sys/queue.h],, [LIBBSD_NEEDED=yes])
-AC_CHECK_FUNCS([clock_nanosleep],, [
-    AC_COMPILE_IFELSE([
-        AC_LANG_SOURCE([
-            #include <sys/time.h>
-            #if !defined(timespecsub) || !defined(timespeccmp)
-                #error "timespecsub or timespeccmp not found"
-            #endif
-        ])
-    ],, [LIBBSD_NEEDED=yes])
-])
+AC_CHECK_FUNCS([clock_nanosleep])
 # libbsd is obligatory on systems that don't have the BSD functions we use.
 # Pass "--enable-libbsd-feature-test" to ./configure, and the configure script
 # will tell you whether the library is a dependency. This option is intended to

src/util.c

@@ -102,9 +102,22 @@ clock_nanosleep(clockid_t clock, int flags, const struct timespec *timeout,
     if (flags == TIMER_ABSTIME) {
         if (clock_gettime(clock, &tmp) == -1)
             return -1;
-        if (timespeccmp(&tmp, timeout, >=))
+
+        /* XXX: Use timespeccmp(). OS X doesn't have that BSD macro, and libbsd
+         * doesn't support OS X save for an unmaintained fork. libobsd supports
+         * OS X but doesn't have the macro yet.
+         */
+        if (tmp.tv_sec == timeout->tv_sec ?
+            tmp.tv_nsec >= timeout->tv_nsec : tmp.tv_sec >= timeout->tv_sec)
             return 0;
-        timespecsub(timeout, &tmp, &tmp);
+        /* XXX: Use timespecsub(). Same issues as timespeccmp(). */
+        tmp.tv_sec -= timeout->tv_sec;
+        tmp.tv_nsec -= timeout->tv_nsec;
+        if (tmp.tv_nsec < 0) {
+            tmp.tv_sec--;
+            tmp.tv_nsec += 1000000000;
+        }
+
         remainder = NULL;
     }
     return nanosleep(&tmp, remainder);