CODEWITHSUNDEEP
makefile
nv317
nv317

Reputation: 180

Multiple rules for one target

I have large project and it's compiled on-demand on several different machines with different OS'es. One of targets has foo.res in it's dependencies. This resource file can be compiled using either one of 2 different rules:

First rule requires text file foo.txt to be present. This rule also requires some of the non-cross platform software to be installed in the system. This rule can not be used in-field by the our engineers, as it won't run under old MacOS.

Second rule uses pre-compiled resource file foo.res in resources directory and simply copies it to build/. Obviously, this is unwanted workaround, but i have no other choice.

I've tried to describe 2 rules in one Makefile, but i've got such error:

Makefile:78: warning: overriding recipe for target 'build/foo.res'
Makefile:75: warning: ignoring old recipe for target 'build/foo.res'

Currently I use Makefile with one of the rules commented-out:

.PHONY: compile
build/app.bin: some_files... build/foo.res
    (Here is compiler call)

build/:
    -mkdir build/

.PHONY: clear
clear:
    -rm -rf ./build

... Lots of stuff here ...

# build/foo.res: res/foo.res | build/.
#     cp res/foo.res build/foo.res

build/foo.res: res/foo.txt | build/.
    some_app -o build/foo.res res/foo.txt

I deploy pre-compiled res/foo.res to some machines and then I swap commented rules, so regular cp is used. This works fine, until some changes are introduced to Makefile in some of commits. Then it blocks fast-forward update in git.

How can I configure make to fire only one of the rules, based on matched dependencies?

Upvotes: 3

Views: 1331

Answers (1)

MadScientist
MadScientist

Reputation: 100781

You can't do this with explicit rules. An explicit rule tells make THIS is how you build this target. You can create two different pattern rules that can build the same target. A pattern rule says this is one way you can build that target.

So, change your makefile to:

build/%.res: res/%.res | build/.
        cp $< $@

build/%.res: res/%.txt | build/.
        some_app -o $@ $<

Upvotes: 2

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