Editing M4 (computer language) (section)

==Implementations==
[[FreeBSD]], [[NetBSD]], and [[OpenBSD]] provide independent implementations of the m4 language. Furthermore, the [[Heirloom Project]] Development Tools includes a free version of the m4 language, derived from [[OpenSolaris]].

M4 has been included in the [[Inferno (operating system)|Inferno]] operating system. This implementation is more closely related to the original m4 developed by Kernighan and Ritchie in [[Version 7 Unix]] than its more sophisticated relatives in [[UNIX System V]] and [[POSIX]].<ref>{{man|1|m4|Inferno}}</ref>

''GNU m4'' is an implementation of m4 for the [[GNU Project]].<ref name='GNUm4web'>GNU m4 web site [https://www.gnu.org/software/m4/ "GNU M4"], accessed January 25, 2020.</ref><ref name='GNUm4manual'>GNU m4 manual, online and for download in HTML, PDF, and other forms. [https://www.gnu.org/software/m4/manual/index.html "GNU M4 &mdash; GNU macro processor"], accessed January 25, 2020.</ref>  It is designed to avoid many kinds of arbitrary limits found in traditional m4 implementations, such as maximum line lengths, maximum size of a macro and number of macros. Removing such arbitrary limits is one of the stated goals of the GNU Project.<ref>[https://www.gnu.org/prep/standards/html_node/Semantics.html "GNU Coding Standards: Writing Robust Programs"].
quote: "Avoid arbitrary limits on the length or number of any data structure".
</ref>

The GNU [[Autoconf]] package makes extensive use of the features of GNU m4.

GNU m4 is currently maintained by Gary V. Vaughan and Eric Blake.<ref name='GNUm4web'/> GNU m4 is [[free software]], released under the terms of the [[GNU General Public License]].