GNU Make: double-expandA few days ago I stumbled upon this article
late in the evening and it kept me awake the whole night! It describes a cool trick that
allows to "double-expand" a macro without using eval. The following is a summary of
the main idea, a reflection of why it works and a small extension.
GNU Make: double-colon rulesConsider an integration testing setup where the command to test appears on the first line of a text file, followed by the expected output. I used to run all tests using:
TESTS := test-html test-latex test-semicolon ...
.PHONY: $(TESTS)
$(TESTS): COMMAND = $(shell head -n 1 $(TEST_DIR/$@))
$(TESTS): EXPECTED = ... $(TEST_DIR/$@)
$(TESTS): RESULT = ...
$(TESTS):
compare $(EXPECTED) with $(RESULT)
but the other day I had the following problem: one of the tests required additional post-processing.
After having spent years documenting my Makefiles using (a variation of)
this awk one-liner, I decided to factor
things out in a library makefile-doc. This
turned out to be a nice small project with awk. The following is a short overview.