What does "$$?" mean in this makefile snippet?

Question

What does "$$?" mean in below Makefile snippet?

$(PROGS): FORCE
    @cd $(BUILD_DIRECTORY_PATH)/$@; \
    mkdir -p obj; \
    $(MAKE) || exit "$$?"; \  <====== HERE

ADD 1

I guess it means exit "$?" in bash since $$ in makefile escapes to $ .

But what does exit "$?" mean then?

Answer 1

$? is the return code when a program exits or finishes. Therefore, in your line

$(MAKE) || exit "$$?"

It will execute $(MAKE) . If this program does not finish correctly, it will have a return code different from 0 and then the exit "$$?" will be executed. which will make the current process to exit to shell with the same return code as the $(MAKE) program, which you will be able to show executing echo $? in the shell.

Answer 2

Said another way, $$? is the Makefile equivalent of $? . In Make, to escape $? you need to use $$? . More info: Shell status codes in make