This chapter describes the many of the differences between this
m4, and of other implementations found under
UNIX, such as System V Release 4, Solaris, and BSD flavors.
In particular, it lists the known differences and extensions to
POSIX. However, the list is not necessarily comprehensive.
At the time of this writing, POSIX 2001 (also known as IEEE
Std 1003.1-2001) is the latest standard, although a new version of
POSIX is under development and includes several proposals for
m4 is required to do. The requirements for
m4 are shared between SUSv3 and POSIX, and
can be viewed at
|• Extensions||Extensions in GNU M4|
|• Incompatibilities||Facilities in System V m4 not in GNU M4|
|• Other Incompatibilities||Other incompatibilities|