How come it only reran the rule once the second time? All three targets were invalid.
On Fri, Apr 12, 2013 at 6:41 AM, Reinier Post <reinp...@win.tue.nl> wrote: > 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 >
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