I've made groff's build as reproducible as I can get it, as noted in the comments to Savannah #57218[1]. The fix to pdfroff turned out to be gentle and simple--just stop telling it to preserve temporary files during the groff build. That neatly reduced the size of a build diff by 99%. What remains between successive builds using the same SOURCE_DATE_EPOCH is less than 3 KiB of `diff -u` and easily eyeballed.
This issue is still open and tagged as a blocker for release, however. To resolve it we should settle on the time zone semantics of the system time retrieved by groff components (the formatter, the output drivers). We should also attempt to resolve these differing semantics between groff as distributed by GNU and by the Debian Project (and its many derivatives, none of which--to my knowledge--reverse the patch). It appears to me that the consensus on this list is for groff to represent the system time in the local time zone, as date(1) does, whatever that may be. People requiring reproducible builds should set TZ=UTC as well as SOURCE_EPOCH_DATE. If that is true, then our documentation of the several date/time (g)roff registers should be reviewed to see where and how this fact should be recorded. Off the top of my head, I see this affecting our Texinfo manual, groff(7), possibly groff_diff(7), and the man pages for the output drivers that embed timestamp information (grohtml, grops, gropdf). Colin, what can groff do to make life easier for reproducible build efforts in general and for this time zone issue in particular? I will also note, since it's the perfect time of year to do so, that the only component of a conventional date rendering (Y M D h m s) that _isn't_ affected by time zone is the seconds field. It will take 26 hours[2] for every time zone in the world to roll over to 1 January 2021, and some unfortunate millions of people live in places where the time zone offset from UTC is a non-integral number of hours[3]. Regards, Branden [1] https://savannah.gnu.org/bugs/index.php?57218 [2] https://en.wikipedia.org/wiki/Line_Islands [3] Doubtless some bureaucrat somewhere would innovate a sub-minute time zone offset if doing so would facilitate tracking the mobile devices of suspected dissidents. Fortunately(?) this is not necessary; such tracking is already available upon request thanks to the heroic entrepreneurs of Silicon Valley.
signature.asc
Description: PGP signature
