On Feb 5, 2008, at 11:40 AM, Paul Smith wrote:
On Tue, 2008-02-05 at 11:32 -0800, Derek Clegg wrote:
Given this simple makefile
start: dir/a.c
dir/%.c: %.c | dir ; cp $< $@
dir/%.c: foo.h
dir: ; mkdir $@
a.c foo.h: ; touch $@
I'm seeing the following when I run make:
touch a.c
mkdir dir
cp a.c dir/a.c
This is surprising; my expectation is that the dependency "dir/%c.:
foo.h" would force "foo.h" to be created as well. Is this a bug or
correct behavior?
This is correct.
Pattern rules are not the same as explicit rules: only one pattern
rule
will ever match a given target. Make goes through them in the order
you
define them and whichever one matches first will be used; the rest
will
be ignored.
I responded to Mike Shal in a similar vein. If you're correct,
changing the order of the "dir/%.c:" lines would change the behavior,
but it doesn't appear to.
Anyway, I don't think you really want the .c file to depend on the .h
file, do you? That's pretty unusual. You don't need to copy the .c
file again just because the .h file changes?!?!
This is a trivial makefile for illustration purposes only. Best not
to take it literally :-)
Derek
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