Finite State Machine compiler

Question

What is the best Opensource FSM compiler which can generate c++ code ?

Answer 1

I don't know about the best, but you could look at Ragel:

Ragel compiles executable finite state machines from regular languages. Ragel targets C, C++, Objective-C, D, Java and Ruby. Ragel state machines can not only recognize byte sequences as regular expression machines do, but can also execute code at arbitrary points in the recognition of a regular language.

Answer 2

Please refer to the answer I gave to this question, SMC can also generate C++ code. I can't comment on the quality of the generated C++ but for C# it's satisfactory.