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A.5.3 Development Steps

To write support for a language, you’ll want to do the following steps:

1. Clone one of the existing skeletons. If the language you are supporting is named foo, you should create a file named foo-flex.skl.
2. Modify skeleton.c to ass the digested form of your skeleton to the backends list.
3. Add the name of your skeleton file to EXTRA_DIST.
4. Add a production to src/Makefile.am parallel to the one that produces cpp-skel.h. Your objective is to make a string list initializer from your skeleton file that can be linked with flex and is pointed at by the skel nember of your language back end.
5. The interesting part: mutate your new back end and skeleton so they produce code in your desired target language.
6. Add a test suite for your back end. You should be able to clone one of the existing sets of test loads to get good coverage. Note that is highly unlikely your back end will be accepted into the flex distribution without a test suite. Fortunately, adapting the existing tests should not be difficult. There is some guidance in the tests/README file of the source distrbution.

Syntactically C-like languages such as Go, Rust, and Java should be easy targets. Almost anything generally descended from Algol shouldn’t be much more difficult; this certainly includes the whole Pascal/Modula/Oberon family.

The C99 back end can be used for production, but it is really intended as a launch point to be cloned by people writing support for additional languages. Accordingly, it omits support for some features that can’t be practically ported out of C in order to lower the complexity of what needs to be translated to a new target language. These features are: the Bison bridge, header generation, and loadable tables.