When the option arises, it is nice to run the test vectors against the diversity of generated output, C, Ruby, Etc. One of those backends could have very well alerted on the error.
Although Ragel can emit a variety of code, it's non-trivial to rework your own code that's a part of that from C to Ruby or Rust or whatever. You'd basically have to implement the same thing N times.
ANTLR has the same problem. Where any non-trivial grammar will require embedded code, forking it away from ever being supported by more than one backend.
It might be nice to have Lua or a Scheme embedded in the generator platform so that, one can truly target multiple backends.
