We have a really big C++ codebase at work and I find codesearch[1] to be the best way to search through the code, although the UX is terrible compared to Ack/Ag. Another problem is that it's written in go; so hard to get builds for the AIX PPC machines. Faster than everything though -- running a complex regex against 2-3 million SLOC and getting an answer within a second is certainly worth something.