make -d C no-op?

I was looking for the definition of ${.CURDIR} and the C flag was giving
nothing.

$ cd /usr/src/usr.bin/make
$ egrep "DEBUG[1-5]?\(CWD" *
$
$  fgrep debug.DEBUG_CWD *
main.c:                 debug.DEBUG_CWD = true;

Am I right in concluding that the C flag is not implemented / a no-op?
or am I looking at the wrong place or not invoking it correctly?
-- 
        Thierry Laronde <tlaronde +AT+ polynum +dot+ com>
                     http://www.kergis.com/
                    http://kertex.kergis.com/
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