On Thu, Aug 21, 2014 at 4:57 PM, Ray Donnelly <mingw.android@xxxxxxxxx> wrote: > On Thu, Aug 21, 2014 at 4:32 PM, Eric Blake <eblake@xxxxxxxxxx> wrote: >> Make folks: >> You may want to check out http://austingroupbugs.net/view.php?id=857 and >> add comments and/or change GNU make behavior accordingly. There, the >> argument is made that HP-UX make behavior is nicer than GNU's current >> behavior when two files have identical timestamps: HP-UX considers the >> file as out-of-date, while GNU make considers it up-to-date. A strict >> reading of POSIX can argue that GNU's behavior was required, but this >> reading has been called into question. >> >> GNU's behavior is an optimization that avoids needless churn on file >> systems with course timestamps (well, FAT still exists, but these days, >> MOST file systems have sub-second resolution, so it is harder to get >> files with identical timestamps without actually touch'ing them that >> way) - but it risks leaving a tree in an incomplete state. HP-UX >> behavior guarantees the rules are run, even if they were not strictly >> necessary, but has the nice property that the tree is never left in an >> incomplete state due to unfortunate timing on a file system with course >> timestamps. >> >> The POSIX recommendation was therefore that GNU should change its >> behavior to act like HP-UX, and consider identical timestamps as >> out-of-date, because the standard will be fixed to allow HP-UX behavior. >> >> Autoconf folks: >> The section of the autoconf manual that discusses this should probably >> be modernized, particularly if changes to POSIX and/or GNU make result >> from this discussion. >> https://www.gnu.org/software/autoconf/manual/autoconf.html#Timestamps-and-Make >> > > Some projects that want to have deterministic builds by using the > gitian builder [1] use libfaketime to set the timestamps to a known > constant, and gnu make trips up on this, occasionally causing broken > builds and othertimes autoconf declares suck a build system "insane". Freudian slip? I meant "such", not "suck". > There was a bug in libfaketime so that the nanosecond field wasn't > cleared and this allowed you to avoid both these bugs if the planets > were aligned correctly (which has since been fixed). I agree that > these issues should be fixed in make and autoconf. > > [1] https://gitian.org/ > >> -- >> Eric Blake eblake redhat com +1-919-301-3266 >> Libvirt virtualization library http://libvirt.org >> >> >> _______________________________________________ >> Bug-make mailing list >> Bug-make@xxxxxxx >> https://lists.gnu.org/mailman/listinfo/bug-make >> _______________________________________________ Autoconf mailing list Autoconf@xxxxxxx https://lists.gnu.org/mailman/listinfo/autoconf
