How can I fold #ifdef/#ifndef blocks in Emacs?

Question

I want to hide blocks of #ifdef and #ifndef blocks in C. Looks like I'd either need to use Folding mode or the Outline minor mode.

Answer 1

hide-ifdef-mode should do something like that. I have not used it myself though, but turn it on and read it's description with the commands below. It should be included with emacs.

M-x hide-ifdef-mode
C-h m

Answer 2

You can use folding-mode from Cedet