Getting the name of the makefile from the makefile

(Should you have any questions, refer to amazingly written GNU make manual. But remember, that, just like Makefile, this manual should be read completely before putting the concepts into practice).

I couldn't figure out how it is done easily. As far as I understand, you'll have to do some manual job.

Later I will describe how it could be done and show scripts that introduce current_makefile variable. But I would like to stress an important concept at the first place.

You should understand that if we had some kind of variable current_makefile, that expands to the current makefile name, then it will have to change during the process of reading makefiles. That means that it should be used withinin "immediate" expansion context -- i.e. within commands that are executed during reading the makefile. Most commands, however, are executed after makefiles are read. Therefore, some commands will print the correct value smoothly, while in certain places, where "deferred" expansion is used, it will always expand to the root makefile name.

If you would want to use this variable within rule text, for example, you'll have to do tricks, because rule text always has deferred expansion. So, if your have the rule

rule:
        echo In makefile $(current_makefile):
        echo Making target $@

it will always print the name of the root makefile. Instead, to force immediate expansion, you will have to create another variable with makefile-specific name (i.e. names of such variables should be different in each makefile):

this_makefile_unique_name := $(current_makefile)
rule:
        echo In makefile $(current_makefile):
        echo Making target $@

or use eval:.

define make_rule
rule:
        echo In makefile $(1):
        echo Making target $$@

$(eval $(call make_rule,$(current_makefile)))

If you want to use the name of current makefile for debug purpose only, consider special debugging functions, like warning or info:.

$(warning We're in makefile $(current_makefile))

These functions use "immediate" expansion and will print the correct value.

How to define such a $(current_makefile)?

You have to manually maintain stack of makefile inclusions. When you include a makefile, its name is placed to the top of the stack; when you return from included makefile to the outer one, the topmost name is popped out of stack. This is achieved by inserting special calls to the beginning and the end of makefile:

# Beginning of makefile
$(eval $(makefile_names_push))
#... makefile text
$(warning $(current_makefile))
#...
$(eval $(makefile_names_pop))
#End of file

Now define the functions at the beginning of your root makefile.

lastword=$(word $(words $(1)),$(1))

define makefile_names_push
current_makefile := $$(CURDIR)/$$(call lastword,$$(MAKEFILE_LIST))
makefile_stack :=$$(makefile_stack) $$(current_makefile)
endef

define makefile_names_pop
makefile_stack := $$(filter-out $$(current_makefile),$$(makefile_stack))
current_makefile := $$(call lastword,$$(makefile_stack))
endef

If you're sure your make is new enough (version 3.81+), replace lastword call with builtin function:.

#inctead of $$(call lastword,$$(MAKEFILE_LIST))
$$(lastword $$(MAKEFILE_LIST))

Is it useful?

Totally useless. An only use that might be useful here is to make 100 makefiles that are symlinks to one makefile, the rules in these makefiles depending on their names. But it can be achieved within one makefile and foreach-eval technique described in the manual. So my post was a complete waste of time, though I had some fun :-)


location = $(CURDIR)/$(word $(words $(MAKEFILE_LIST)),$(MAKEFILE_LIST))
WHERE_ART_THOU := $(location)
$(warning $(WHERE_ART_THOU))

I also believe this is GNU make-specific, but I'm not too sure.

Tags:

Makefile

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