Good tools for creating a C/C++ parser/analyzer

The ANTLR parser generator has a grammar for C/C++ as well as the preprocessor. I've never used it so I can't say how complete its parsing of C++ is going to be. ANTLR itself has been a useful tool for me on a couple of occasions for parsing much simpler languages.

You can look at clang that uses llvm for parsing.

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Parsing C++ is extremely hard because the grammar is undecidable. To quote Yossi Kreinin:

Outstandingly complicated grammar

"Outstandingly" should be interpreted literally, because all popular languages have context-free (or "nearly" context-free) grammars, while C++ has undecidable grammar. If you like compilers and parsers, you probably know what this means. If you're not into this kind of thing, there's a simple example showing the problem with parsing C++: is AA BB(CC); an object definition or a function declaration? It turns out that the answer depends heavily on the code before the statement - the "context". This shows (on an intuitive level) that the C++ grammar is quite context-sensitive.