make conditionally including other makefiles

Question

I want to conditionally include makefiles depending on the contents of a xml file and product.
My xml file (myxml.xml):

<product1>
  <component1 dirname=dir1 />
  <component2 dirname=dir2 />
</product1>
<product2>
  <component1 dirname=dir1 />
  <component3 dirname=dir3 />
</product2>

In dir1 I have a config.mk file which looks like this:

SRC_JS+=dir1/file1.js
SRC_JS+=dir1/file2.js
SRC_HTML+=dir1/file3.html

Same for dir2 and dir3 which are all subdirs of the makefile dir.

Now I want depending on the specified product include certain config.mk files according to what is in the xml file.
So my makefile:

myjscode.js: myxml.xml
  read_dirs.py -p $PRODUCT $< > mydirs.txt
  while read mydir; do \
    include $$mydir/config.mk ; \
  done < mydirs.txt;
  js-compiler $(addprexis --js ,$SRC_JS) -output $@

Can this be done? FYI: I'm using bash and the read_dirs.py script outputs a 'one-line-per-directory' list.

Beta Beta · Accepted Answer · 2013-01-09T15:54:19

First the easy part. The include directive cannot be in a command in a rule. Modify read_dirs.py to produce something like this (when PRODUCT="product2"):

include dir1/config.mk
include dir3/config.mk

Then in your makefile:

mydirs.mk: myxml.xml
    read_dirs.py -p $PRODUCT $< > $@

include mydirs.mk

There is no need for anything else to depend on mydirs.mk; since this makefile includes it, Make will rebuild it if necessary.

Now the hard part. I presume you want the choice of included makefiles to change not just when myxml.xml changes, but also when PRODUCT changes. But PRODUCT is not a file, so we have some choices. We could have a file product.mk that contains the PRODUCT variable. Or instead of mydirs.mk we could have a different file for each PRODUCT. Or we could force the building of mydirs.mk every time. It depends on how you set PRODUCT and what your priorities are.

make conditionally including other makefiles

2 Answers