Passage: As of 2018 many applications continue to use m4 as part of the GNU Project's autoconf. It also appears in the configuration process of sendmail (a widespread mail transfer agent) and for generating footprints in the gEDA toolsuite. The SELinux Reference Policy relies heavily on the m4 macro processor.

Question: The m4 can be used for?
generating footprints in the gEDA toolsuite