Re: Question about pattern rule with multiple targets

[Philip Guenther]

On Fri, Jun 27, 2014 at 11:24 AM, Tom Varga <address@hidden> wrote:

On page 120 of the gnumake manual, it mentions support for pattern

rules with multiple targets.

This pattern rule has two targets:

%.tab.c %.tab.h: %.y

bison -d $<

So, if I have a simple rule that looks like:

%.bar1 %.bar2 : %.foo

touch $(*F).bar1

touch $(*F).bar2

and then do:

> touch a.foo

> make a.bar1

touch a.bar1

touch a.bar2

> make a.bar1

make: 'a.bar1' is up to date.

> rm a.bar2

> make a.bar1

make: 'a.bar1' is up to date.

> make a.bar2

touch a.bar1

touch a.bar2

What I was really hoping is that make would consider both a.bar1 and

a.bar2 to be required outputs of the rule and if one of them is

deleted, then both the .bar1 and .bar2 targets should be considered

out-of-date.  But when I manually remove the a.bar2 file, the a.bar1

file is still considered to be up-to-date.  Yet, when I then ask to

build the a.bar2 target, both the a.bar1 and a.bar2 targets are

re-built.

Umm, why isn't this solved by having a correct dependency on a.bar2 where necessary?

Philip Guenther