lsg.c: Make the output of lopsubgen reproducible.

Whilst working on the Reproducible Builds effort [0], we noticed that
liblopsub generates output that is not reproducible. The lopsubgen
utility does not respect SOURCE_DATE_EPOCH [1] and thus packages such
as src:tfortune are rendered unreproducible as they then encode the
build date and time.

This patch makes lopsubgen honour SOURCE_DATE_EPOCH.

[0] https://reproducible-builds.org/
[1] https://reproducible-builds.org/specs/source-date-epoch/

Signed-off-by: Andre Noll <maan@tuebingen.mpg.de>

diff --git a/lsg.c b/lsg.c
index 54b7816eae94fa99e4b145706403a6d7823abf99..83a72da5b3b26b949a09f83d251086fed5a9e02d 100644 (file)
--- a/lsg.c
+++ b/lsg.c
@@ -610,7 +610,7 @@ static char *get_output_path(const char *suffix, const char *arg,
 static void gen_man(struct lls_parse_result *lpr, const char *cmdline)
 {
        int i;
-       time_t t;
+       time_t t = 0;
        struct tm *tmp;
        FILE *out;
        char *outpath = get_output_path("man",
@@ -626,12 +626,22 @@ static void gen_man(struct lls_parse_result *lpr, const char *cmdline)
        if (suite.commands[0].name.orig) {
                char date[200];
                const char *version_string;
-
                if (!suite.date) {
-                       t = time(NULL);
-                       tmp = localtime(&t);
+                       /*
+                        * If the SOURCE_DATE_EPOCH environment variable
+                        * contains a positive integer in the time_t range, use
+                        * that instead of the current time. See:
+                        * <https://reproducible-builds.org/specs/source-date-epoch/>
+                        * for more information.
+                        */
+                       char *source_date_epoch = getenv("SOURCE_DATE_EPOCH");
+                       if (source_date_epoch != NULL)
+                               t = strtoll(source_date_epoch, NULL, 10);
+                       if (t <= 0)
+                               t = time(NULL);
+                       tmp = gmtime(&t);
                        if (tmp == NULL) {
-                               perror("localtime");
+                               perror("gmtime");
                                exit(EXIT_FAILURE);
                        }
                        if (strftime(date, sizeof(date), "%B %Y", tmp) == 0) {