Ismail Badawi wrote:
> I'm trying to define new targets with eval during secondary expansion, but
> apparently this is not allowed -- with make 4.2.1 I get an error like
> this:
>
> Makefile:94: *** prerequisites cannot be defined in recipes. Stop.
>
> I found bugs #24588 and #24622 related to this.
>
> My use case is as follows. I have a bunch of targets which can be nested
> arbitrarily deeply in subdirectories within my build directory. For each
> target, I'd like to have an order-only prerequisite on the existence of
> its parent directory. So something like this:
>
> build/foo/bar/baz/mytarget: | build/foo/bar/baz
> touch $@
>
> build/foo/bar/baz:
> mkdir -p $@
>
> The issue is that if I have many targets in many different directories,
> then I
> need to write lots of 'mkdir' rules like this. I can save some typing with
> a template and a foreach/eval/call, but that's still a bit awkward because
> I have
> to maintain a list of all the directories I need.
I don't have a solution to your general problem but for your specific
requirement of creating directories this is what I do:
1. All directories must end in the '/' character.
2. Use secondary expansion to determine the target directory. Note trailing
'/'.
build/foo/bar/baz/mytarget: | $$(@D))/
touch '$(@)'
3. Define pattern rule for directories.
$(build_dir)%/ :
mkdir -p '$(@)'
4. You may need to mark the pattern as precious
.PRECIOUS : $(build_dir)%/
Works well for me for 4.1 and later. No need to list directories. Only one
rule required.
--
JP
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