Hi, First a bit of context: for the GTK+ port of WebKit (www.webkitgtk.org) we are using autotools as our build system (autoconf+automake+libtool, the whole lot). We have a *lot* of files, so the resulting Makefile is about 9MB in size and takes, in my system, about 55s to go through a null-build (that is, just typing 'make' when there's nothing to do).
Today I was looking at ways of reducing this, and I managed to save 10s by getting rid of some implicit rules we don't need (the win is essentially the same than using -r in Make). After that I found that for each target in the build a .Plo file with the dependencies is generated, and that an empty rule for each dependency of that target is added to that file. This adds up *really* quickly in size, and I found that by removing all those I can go from ~43s (the time without the implicit rules) to ~20s. I realize this has some uses (as the -MP doc explains), but 23 seconds per build seems excessive, so I think we can try to live without it. Problem is, apparently it's totally hardcoded in am/depend2.am, so: any idea on how to get rid of it in some kind of prost-processing step? (Even grepping/replacing the whole Makefile after is generated will very likely take a fraction of those 23s). Alternatively, is there some well-known way to reduce either the size or the processing time for the Makefile in huge automake projects?[1] Cheers, Xan [1]: I found this thread, http://lists.gnu.org/archive/html/automake/2003-12/msg00103.html, from years ago, but I'm not sure there was any definitive conclusion, and gcj nowadays seems different than how the mail implies it was back then.