E.g. in a Makefile to have
obj-$(CONFIG_FOO) += common-thing.o foo.o obj-$(CONFIG_BAR) += common-thing.o bar.o
where both FOO and BAR can be enabled at the same time?
Looks a bit suspect to me. My instinct would be to invent CONFIG_BAZ to compile common-thing.o and make FOO and BAR select it. Or possibly some makefile conditional OR expression I can't think of off the top of my head.