[Reproducible-builds] Bug#792687: gettext: please support timestamps from environment

[Dhole]

Source: gettext
Version: 0.19.4-1
Severity: wishlist
Tags: patch
User: reproducible-builds at lists.alioth.debian.org
Usertags: toolchain timestamps
X-Debbugs-Cc: reproducible-builds at lists.alioth.debian.org

Hi,

While working on the "reproducible builds" effort [1], we have noticed
that the xgettext tool from gettext embeds timestamps on the creation of
PO files.

For the Reproducible Builds effort we are proposing an environment
variable (SOURCE_DATE_EPOCH) [2] that will contain a deterministic epoch
timestamp (based on the latest debian/changelog entry) that could be
used, which should be automatically exported by debhelper in the future [3].

The attached patch proposes a way to use this variable to get
reproducible timestamps in the PO files generated by xgettext, if the
variable has been set (if not, it falls back to the old behavior).
With the attached patch packages using xgettext would then automatically
generate reproducible translation files.


[1]: https://wiki.debian.org/ReproducibleBuilds
[2]: https://wiki.debian.org/ReproducibleBuilds/TimestampsProposal
[3]: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=791815

Regards,
-- 
Dhole
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diff -Nru gettext-0.19.4/debian/changelog gettext-0.19.4/debian/changelog
--- gettext-0.19.4/debian/changelog	2015-05-15 18:01:14.000000000 +0200
+++ gettext-0.19.4/debian/changelog	2015-07-17 15:47:54.000000000 +0200
@@ -1,3 +1,11 @@
+gettext (0.19.4-1.1) UNRELEASED; urgency=medium
+
+  * Non-maintainer upload.
+  * Add support for reproducible builds by using $SOURCE_DATE_EPOCH as the
+    date on creation of PO files with xgettext.
+
+ -- Dhole <dhole at openmailbox.org>  Fri, 17 Jul 2015 15:47:41 +0200
+
 gettext (0.19.4-1) unstable; urgency=low
 
   * New upstream release.
diff -Nru gettext-0.19.4/debian/patches/03-Replace-timestamp-with-SOURCE_DATE_EPOCH gettext-0.19.4/debian/patches/03-Replace-timestamp-with-SOURCE_DATE_EPOCH
--- gettext-0.19.4/debian/patches/03-Replace-timestamp-with-SOURCE_DATE_EPOCH	1970-01-01 01:00:00.000000000 +0100
+++ gettext-0.19.4/debian/patches/03-Replace-timestamp-with-SOURCE_DATE_EPOCH	2015-07-17 15:56:22.000000000 +0200
@@ -0,0 +1,47 @@
+Description: Replace date timestamp by SOURCE_DATE_EPOCH env var in xgettext
+ .
+ gettext (0.19.4-1.1) UNRELEASED; urgency=medium
+ .
+   * Non-maintainer upload.
+   * Add support for reproducible builds by using $SOURCE_DATE_EPOCH as the
+     date on creation of PO files with xgettext.
+Author: Dhole <dhole at openmailbox.org>
+
+---
+
+--- gettext-0.19.4.orig/gettext-tools/src/xgettext.c
++++ gettext-0.19.4/gettext-tools/src/xgettext.c
+@@ -3410,6 +3410,7 @@ construct_header ()
+   message_ty *mp;
+   char *msgstr;
+   char *comment;
++  char *source_date_epoch;
+   static lex_pos_ty pos = { __FILE__, __LINE__ };
+ 
+   if (package_name != NULL)
+@@ -3431,7 +3432,24 @@ the MSGID_BUGS_ADDRESS variable there; o
+ specify an --msgid-bugs-address command line option.\n\
+ ")));
+ 
+-  time (&now);
++  /* Allow the date and time to be set externally by an exported
++     environment variable to enable reproducible builds. */
++  source_date_epoch = getenv ("SOURCE_DATE_EPOCH");
++  if (source_date_epoch)
++    {
++      errno = 0;
++      now = (time_t) strtol (source_date_epoch, NULL, 10);
++      if (errno != 0)
++        error (EXIT_FAILURE, errno, _("\
++SOURCE_DATE_EPOCH=\"%s\" is not a valid number"), source_date_epoch);
++
++      /* The function po_strftime uses localtime() to parse the timestamp, so 
++         we need to fix the environment timezone to get reproducible results */
++      setenv("TZ", "UTC", 1);
++    }
++  else
++    time (&now);
++
+   timestring = po_strftime (&now);
+ 
+   msgstr = xasprintf ("\
diff -Nru gettext-0.19.4/debian/patches/series gettext-0.19.4/debian/patches/series
--- gettext-0.19.4/debian/patches/series	2015-05-15 17:19:58.000000000 +0200
+++ gettext-0.19.4/debian/patches/series	2015-07-17 15:55:50.000000000 +0200
@@ -1,2 +1,3 @@
 01-do-not-use-java-in-urlget
 02-msgfmt-default-little-endian
+03-Replace-timestamp-with-SOURCE_DATE_EPOCH
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