[bug #63098] make-4.3.90 regression of unexpected dependencies in pattern rules with multiple targets

[Paul D. Smith]

Follow-up Comment #4, bug #63098 (project make):

Yes, I saw that behavior when I looked at the repo.  I agree it's difficult to
see how to map that onto make's current behavior.  I'll take a look through
the manual to see if that change (which was somewhat last-minute) might be
going against some previously-guaranteed behavior.

In general it's very hard to express a situation like "the set of output files
being generated depends on the contents of the input file" in make; it wasn't
really designed that way (as an extreme example this is why you can't use make
with Java very well).

If only some of the msg files generate .cxx files then my last option below,
splitting into two different pattern rules, would probably work best.

Another option of course is (since they already require GNU make) to simply
use a $(shell ...) function to grep out which msg files contain the special
marking, and use a static pattern rule to handle those differently with a
different set of outputs.  Unfortunately without GNU make 4.3's grouped
targets it's tricky to get this right; if you want to run with older versions
of GNU make this won't work well.


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