File: autoconf.info,  Node: Why GNU M4,  Next: Bootstrapping,  Prev: Distributing,  Up: FAQ

20.2 Why Require GNU M4?
========================

     Why does Autoconf require GNU M4?

   Many M4 implementations have hard-coded limitations on the size and
number of macros that Autoconf exceeds.  They also lack several builtin
macros that it would be difficult to get along without in a
sophisticated application like Autoconf, including:

     m4_builtin
     m4_indir
     m4_bpatsubst
     __file__
     __line__

   Autoconf requires version 1.4.8 or later of GNU M4.  It works better
with version 1.4.16 or later.

   Since only software maintainers need to use Autoconf, and since GNU
M4 is simple to configure and install, it seems reasonable to require
GNU M4 to be installed also.  Many maintainers of GNU and other free
software already have most of the GNU utilities installed, since they
prefer them.