1.2 Historical references

GPM was an important ancestor of m4. See C. Strachey: “A General Purpose Macro generator”, Computer Journal 8,3 (1965), pp. 225 ff. GPM is also succinctly described into David Gries classic “Compiler Construction for Digital Computers”.

The classic B. Kernighan and P.J. Plauger: “Software Tools”, Addison-Wesley, Inc. (1976) describes and implements a Unix macro-processor language, which inspired Dennis Ritchie to write m3, a macro processor for the AP-3 minicomputer.

Kernighan and Ritchie then joined forces to develop the original m4, as described in “The M4 Macro Processor”, Bell Laboratories (1977). It had only 21 builtin macros.

While GPM was more pure, m4 is meant to deal with the true intricacies of real life: macros can be recognized without being pre-announced, skipping whitespace or end-of-lines is easier, more constructs are builtin instead of derived, etc.

Originally, the Kernighan and Plauger macro-processor, and then m3, formed the engine for the Rational FORTRAN preprocessor, that is, the Ratfor equivalent of cpp. Later, m4 was used as a front-end for Ratfor, C and Cobol.

René Seindal released his implementation of m4, GNU m4, in 1990, with the aim of removing the artificial limitations in many of the traditional m4 implementations, such as maximum line length, macro size, or number of macros.

The late Professor A. Dain Samples described and implemented a further evolution in the form of M5: “User’s Guide to the M5 Macro Language: 2nd edition”, Electronic Announcement on comp.compilers newsgroup (1992).

François Pinard took over maintenance of GNU m4 in 1992, until 1994 when he released GNU m4 1.4, which was the stable release for 10 years. It was at this time that GNU Autoconf decided to require GNU m4 as its underlying engine, since all other implementations of m4 had too many limitations.

More recently, in 2004, Paul Eggert released 1.4.1 and 1.4.2 which addressed some long standing bugs in the venerable 1.4 release. Then in 2005, Gary V. Vaughan collected together the many patches to GNU m4 1.4 that were floating around the net and released 1.4.3 and 1.4.4. And in 2006, Eric Blake joined the team and prepared patches for the release of 1.4.5, 1.4.6, 1.4.7, and 1.4.8. More bug fixes were incorporated in 2007, with releases 1.4.9 and 1.4.10. Eric continued with some portability fixes for 1.4.11 and 1.4.12 in 2008, 1.4.13 in 2009, 1.4.14 and 1.4.15 in 2010, and 1.4.16 in 2011.

Meanwhile, development has continued on new features for m4, such as dynamic module loading and additional builtins. When complete, GNU m4 2.0 will start a new series of releases.