Question

In an automake and autoconf project how would you add a custom pre-build step. I need to run a command before make is ran to update a files timestamp to ensure it gets built on every build.

Thanks

Answer 1

If you need a file to be regenerated on every ‘make’ invocation, this makefile idiom will do the job:

always_build_me: FORCE
        # commands

FORCE: # no dependencies or commands
.PHONY: FORCE # hint for gnu make, ignored by others

However, that you need this suggests that always_build_me changes each time it is rebuilt, which is a bad practice. Your build process should be fully deterministic — that is, if you haven’t changed the sources, rebuilding from scratch should produce exactly the same bits it did the last time.