don't use timespecsub() because it isn't on OS X

configure.ac

@@ -42,16 +42,6 @@ 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])
-])
 # 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
@@ -78,9 +68,10 @@ AC_SUBST([CPPFLAGS], ["$X11_CFLAGS $XCOMPOSITE_CFLAGS $XEXT_CFLAGS \
 # Checks for header files.
 AC_CHECK_HEADERS([stdint.h sys/time.h unistd.h])
 
-# Required: Checks for library functions.
+# Checks for library functions.
 AC_CHECK_FUNCS([getopt_long getsubopt gethostname strdup strerror strndup strtol],,
     AC_MSG_ERROR([required functions are not present.]))
+AC_CHECK_FUNCS([clock_nanosleep])
 
 AC_CONFIG_FILES([Makefile src/Makefile])
 AC_OUTPUT

src/scrot.c

@@ -43,7 +43,6 @@ CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */
 
 #include <sys/stat.h>
-#include <sys/time.h>
 #include <sys/wait.h>
 
 #include <assert.h>
@@ -323,7 +322,17 @@ static void scrotWaitUntil(const struct timespec *time)
     struct timespec tmp;
     do {
         clock_gettime(CLOCK_MONOTONIC, &tmp);
-        timespecsub(time, &tmp, &tmp);
+
+        /* XXX: Use timespecsub(). 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.
+         */
+        tmp.tv_sec = time->tv_sec - tmp.tv_sec;
+        tmp.tv_nsec = time->tv_nsec - tmp.tv_nsec;
+        if (tmp.tv_nsec < 0) {
+            tmp.tv_sec--;
+            tmp.tv_nsec += 1000000000L;
+        }
     } while (nanosleep(&tmp, &tmp) == -1 && errno == EINTR);
 #endif
     errno = savedErrno;