From 6bdb0ec1bf5f771b7a2e7bfac5b08f128e4697a8 Mon Sep 17 00:00:00 2001
From: Chris Lamb <address@hidden>
Date: Mon, 29 Oct 2018 16:38:39 -0400
Subject: [PATCH] misc.c: Make the output reproducible

Whilst working on the Reproducible Builds effort [0], we noticed
that mtools generates non-reproducible output.

This is because it uses the current time of day as a default
timestamp, such as when adding files to an existing file.

Patch attached that uses the SOURCE_DATE_EPOCH [1] environment
variables. It was initially filed in Debian bug #900410 [2]) and has
been incorporated into the version distributed by that operating
system seemingly without issue.

 [0] https://reproducible-builds.org/
 [1] https://https://reproducible-builds.org/specs/source-date-epoch/
 [2] https://bugs.debian.org/900410
---
 misc.c | 27 +++++++++++++++++++++++++--
 1 file changed, 25 insertions(+), 2 deletions(-)

diff --git a/misc.c b/misc.c
index 6adf33b..d6bcee1 100644
--- a/misc.c
+++ b/misc.c
@@ -109,7 +109,8 @@ FILE *open_mcwd(const char *mode)
 		 * Ignore the info, if the file is more than 6 hours old
 		 */
 		getTimeNow(&now);
-		if (now - sbuf.st_mtime > 6 * 60 * 60) {
+		if (now - sbuf.st_mtime > 6 * 60 * 60
+		    && getenv("SOURCE_DATE_EPOCH") == NULL) {
 			fprintf(stderr,
 				"Warning: \"%s\" is out of date, removing it\n",
 				file);
@@ -159,11 +160,33 @@ void print_sector(const char *message, unsigned char *data, int size)
 
 time_t getTimeNow(time_t *now)
 {
+	char *endptr;
+	char *source_date_epoch;
+	unsigned long long epoch;
 	static int haveTime = 0;
 	static time_t sharedNow;
 
 	if(!haveTime) {
-		time(&sharedNow);
+		source_date_epoch = getenv("SOURCE_DATE_EPOCH");
+		if (source_date_epoch) {
+			epoch = strtoull(source_date_epoch, &endptr, 10);
+
+			if (endptr == source_date_epoch)
+				fprintf(stderr, "SOURCE_DATE_EPOCH invalid\n");
+			else if ((errno == ERANGE && (epoch == ULLONG_MAX || epoch == 0))
+					|| (errno != 0 && epoch == 0))
+				fprintf(stderr, "SOURCE_DATE_EPOCH: strtoull: %s: %llu\n",
+				strerror(errno), epoch);
+			else if (*endptr != '\0')
+				fprintf(stderr, "SOURCE_DATE_EPOCH has trailing garbage\n");
+			else if (epoch > ULONG_MAX)
+				fprintf(stderr, "SOURCE_DATE_EPOCH must be <= %lu but saw: %llu\n", ULONG_MAX, epoch);
+			else {
+				sharedNow = epoch;
+			}
+		} else {
+			time(&sharedNow);
+		}
 		haveTime = 1;
 	}
 	if(now)
-- 
2.19.1