Finding makefile dependencies

Question

I have several widgets denoted by a config.xml in their root in a directory layout.

The GNUmakefile I have here is able to build them. Though if I update the folders, the dependencies aren't tracked. I don't want to depend on a clean target obviously, so how do I track the contents of each folder?

WGTS := $(shell find -name 'config.xml' | while read wgtdir; do echo `dirname $$wgtdir`.wgt; done )
all: $(WGTS)
%.wgt: 
    @cd $* && zip -q -r ../$(shell basename $*).wgt .
    @echo Created $@
clean:
     rm -f $(WGTS)

I hoped something like:

 %.wgt: $(shell find $* -type f)

Would work, but it doesn't. Help.

Answer 1

Combining Beta's idea with mine:

WGTS := $(shell find -name config.xml)
WGTS := $(WGTS:/config.xml=.wgt)
WGTS_d := $(WGTS:.wgt=.wgt.d)

all: $(WGTS)
clean:
    rm -f $(WGTS) $(WGTS_d)

-include $(WGTS_d)

define WGT_RULE
$(1): $(shell find $(1:.wgt=))
$(1:.wgt=)/%:
    @
endef
$(foreach targ,$(WGTS),$(eval $(call WGT_RULE,$(targ))))
%.wgt:
    @echo Creating $@
    @(echo -n "$@: "; find $* -type f | tr '\n' ' ') > [email protected]
    @cd $* && zip -q -r ../$(shell basename $*).wgt .

Example:

$ mkdir -p foo bar/nested
$ touch {foo,bar/nested}/config.xml
$ make
Creating bar/nested.wgt
Creating foo.wgt
$ make
make: Nothing to be done for `all'.
$ touch foo/a
$ make
Creating foo.wgt
$ rm foo/a
$ make
Creating foo.wgt
$ make
make: Nothing to be done for `all'.

The only potential problem here is the dummy rule that lets make ignore targets it doesn't know how to build which are nested inside the directories. (foo/a in my example.) If those are real targets that make needs to know how to build, the duplicate recipe definition may be a problem.