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behavior is nicer than GNU's current behavior when two files have identical timestamps: HP-UX considers the file as out-of-date, while GNU make considers it up-to-date.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was therefore that GNU should change its behavior to act like HP-UX, and consider identical timestamps as out-of-date, because the standard will be fixed to allow HP-UX behavior.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 -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org
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