Ask HN: C/C++ AST generation tools?

Anybody know of any tools that will generate AST class definitions for you, from a grammar, or another spec? For example, if I'm writing a parser using flex/bison (which in itself is often frustrating), I have to write the AST classes by hand. So all in all, if you're trying to make a compiler or simple analyzer, you can easily pour hours into a step that has long been a solved problem.

I'm aware of ANTLR, and have used it a lot, but am not a fan of v4's C++ generation.

Thanks in advance... If none exists, I might end up writing one.