main: Use difftime() instead of comparing time_t

C99 § 7.23.1 defines time_t as an "arithmetic [type] capable of
representing times" with "implementation-defined" "range and precision
of times representable".  It doesn't require that time1 > time0 for
time1 later than time0.

See also:
http://computer-programming-forum.com/47-c-language/8d7dec65bd1ddafe.htm

1 files changed, 4 insertions, 4 deletions

diff --git a/src/main.c b/src/main.c
index 10630e8..4abf977 100644
--- a/src/main.c
+++ b/src/main.c
@@ -172,7 +172,7 @@ main(int argc, char * const argv[])
 	char   *buf;
 	time_t  arg;
 	time_t  now;
-	time_t  dif;
+	double  dif;
 
 	optind = 1;
 	opterr = 0;
@@ -218,14 +218,14 @@ main(int argc, char * const argv[])
 	free(buf);
 
 	time(&now);
-	dif = arg - now;
+	dif = difftime(arg, now);
 	if (dif >= 1000 * 24 * 60 * 60) {
 		fputs("Date too far in the future\n", stderr);
 		return EXIT_FAILURE;
 	}
 
 	setvbuf(stdout, NULL, _IONBF, 0);
-	while (arg > now) {
+	while (dif > 0) {
 		printf("\r%03d:%02d:%02d:%02d",
 				(int) dif / 60 / 60 / 24,
 				(int) dif / 60 / 60 % 24,
@@ -233,7 +233,7 @@ main(int argc, char * const argv[])
 				(int) dif % 60);
 		sleep(1);
 		time(&now);
-		dif = arg - now;
+		dif = difftime(arg, now);
 	}
 	printf("\r000:00:00:00\n");