Abort makefile if variable not set

Question

How could I abort a make/makefile execution based on a makefile\'s variable not being set/valued?

I came up with this, but works only if caller doesn\'t explicitly r

Answer 1

For simplicity and brevity:

$ cat Makefile
check-%:
        @: $(if $(value $*),,$(error $* is undefined))

bar:| check-foo
        echo "foo is $$foo"

With outputs:

$ make bar
Makefile:2: *** foo is undefined. Stop.
$ make bar foo="something"
echo "foo is $$foo"
foo is something