On Thu Apr 11 12:47:56 2013, psm...@gnu.org (Paul Smith) wrote: > On Thu, 2013-04-11 at 12:14 +0200, Reinier Post wrote: > > > It's just a shorthand for writing a lot of identical rules; it does NOT > > > mean that a single invocation if the rule will generate all three > > > targets, which is what you are expecting. > > > > Incidentally: other workflow/inference languages can express this > > distinction perfectly and still allow the resulting specifications to > > be analyzed for proper termination (e.g. safe Petri nets, Datalog); > > I'd love to know of an alternative to make that is based on such a > > language, but it seems too much to ask for make to be extended > > in this way. > > I'm not sure exactly what you mean by "this distinction", but GNU make > already supports multi-target generators with pattern rules, as > mentioned in the part of the email you clipped. So the basic > infrastructure exists. There were proof-of-concept patches floating > around to support it for explicit rules as well.
Hmm, indeed: | /tmp % cat Makefile | %.1:; echo $*.1 for $@ > $@ | %.e.1 %.f.1:; echo $*.1 for $@ > $@ | %.c.1 %.d.1:; for f in $*.c.1 $*.d.1; do echo $$f for $@ > $$f; done | %.ab.2: %.a.1 %.b.1; cat $+ > $@ | %.cd.2: %.c.1 %.d.1; cat $+ > $@ | %.ef.2: %.e.1 %.f.1; cat $+ > $@ | /tmp % make -rR stage.ab.2 stage.cd.2 stage.ef.2 | echo stage.a.1 for stage.a.1 > stage.a.1 | echo stage.b.1 for stage.b.1 > stage.b.1 | cat stage.a.1 stage.b.1 > stage.ab.2 | for f in stage.c.1 stage.d.1; do echo $f for stage.d.1 > $f; done | cat stage.c.1 stage.d.1 > stage.cd.2 | echo stage.1 for stage.f.1 > stage.f.1 | cat stage.e.1 stage.f.1 > stage.ef.2 | cat: stage.e.1: No such file or directory | make: *** [stage.ef.2] Error 1 | rm stage.a.1 stage.b.1 stage.c.1 | /tmp % I didn't realise make would skip the creation of stage.e.1; yet this is documented very clearly: http://www.gnu.org/software/make/manual/html_node/Pattern-Intro.html I thought this was just describing an optimization; I didn't realize it would actually affect the build process. Why does it work this way? What is a possible use case? I use symbolic intermediate targets a lot, but my targets in pattern rules are always real files. Or is it just intended as an optimization to avoid a stat() call? (I tried cvs annotate to find this out, but this documentation text is in r1.1 already.) In any case, it may be useful to also be able to state that a multi-target pattern rule only makes its actual target. With :: we can already have alternative rules for the same targets. Considering these features together, the rule selection and execution mechanism becomes difficult to understand; a formal model might help. > Really the trickiest part is the user interface (makefile syntax): it > must be backward-compatible with existing makefiles, or at least be sure > to break virtually none of them. -- Reinier Post _______________________________________________ Bug-make mailing list Bug-make@gnu.org https://lists.gnu.org/mailman/listinfo/bug-make
