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Compatibility with other versions of m4

This chapter describes the differences between this implementation of m4, and the implementation found under Unix, notably System V, Release 3.

Extensions in GNU m4

This version of m4 contains a few facilities, that do not exist in System V m4. These extra facilities are all suppressed by using the `-G' command line option, unless overridden by other command line options.

In addition to the above extensions, GNU m4 implements the following command line options: `-G', `-I', `-L', `-N', `-V', `-W', `-d', `-l', `-o' and `-t'. See section Invoking m4, for a description of these options.

Also, the debugging and tracing facilities in GNU m4 are much more extensive than in most other versions of m4.

Facilities in System V m4 not in GNU m4

The version of m4 from System V contains a few facilities that have not been implemented in GNU m4 yet.

Other incompatibilities

There are a few other incompatibilities between this implementation of m4, and the System V version.

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