If in C++, LLVM + Flex/Bison still the most productive for me. I've tried lots of other compiler compilers, but they're still the best once you learn them. If anybody is bored, I put together a simple word count example a long time ago that has taken on a life of its own: https://github.com/jonathan-beard/simple_wc_example

> If you are serious about making your own programming language, I would strongly suggest to target the LLVM.

Strange advice given the state of LLVM on platforms such as windows. Both Swift and Crystal, LLVM based don't run on windows for instance. LLVM gives you more quickly but at the cost of portability.