Ken Moffat wrote: > On Tue, Jun 05, 2012 at 09:51:23PM +0100, Matt Burgess wrote: >> Why is sedding configure not enough? I don't doubt it isn't, but >> can't think why. My understanding is that configure.ac is used as >> input to generate configure. Therefore, whatever Makefile rules >> are in place to regenerate configure should be triggered if >> configure.ac has a modification time later than configure. By >> sedding configure, you ensure that isn't the case and therefore the >> rebuild rules shouldn't be triggered, right? > > Well, Bryan explained some of the details earlier this month > (autotooled Makefiles contain tests to see if things changed, and run > various commands as-necessary). I didn't interpret that as > regenerating configure in this case, but I was wrong - that might be > a change with newer autotools. Probably the key is that we're also > changing Makefile.in to get rid of the manpage.
I think it's been in automake for quite a while. autoconf gets run if configure.ac is newer than configure. automake gets run if Makefile.in is newer than Makefile.am. Both configure and config.status get run if Makefile.in is newer than Makefile. Etc., etc. (Though the specific files in these cases are affected by configure.ac m4 macros: AC_OUTPUT and whatever else.) That doesn't explain why it gets run in this particular case though. We're editing configure, which should set its mtime to "right now", which should be later than configure.ac. Unless configure.ac is shipping with an mtime in the future? We don't sed aclocal.m4, so that's not the issue... AHA! configure.ac is shipped newer than aclocal.m4, so aclocal gets run, which causes automake and autoconf to both be required. This would have happened whether or not we did any patching or anything. To stop it from running entirely, we could also teach a new syntax for touch, and: touch -d '2011-05-07 13:30' configure.ac at any point during the configuration (during patching or sedding or whatever), although that will only work for the current kbd release.
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