There's a bunch of "plugins" for Emacs (and vim, I guess, that provide that, but I wouldn't know). xcscope largely does what I want and I've successfully used i

There's a bunch of "plugins" for Emacs (and vim, I guess, that provide that, but I wouldn't know). xcscope largely does what I want and I've successfully used it on very large codebases (think Linux kernel + vendor-supplied HAL + a very large amount of userspace code). It's hard to beat an IDE on a large, disorganised codebase though, I'd lie if I said I only use Emacs and never reach out for an IDE.