How to show function prototype in Emacs?

Question

While in C-mode I can jump to a function using M-. on the function name....is there a way i can simply display the function prototype? (preferably as a tooltip or so) I often struggle to remember the exact order and types required by a given function.

Answer 1

c-eldoc-mode is a mode that is not as heavyweight as CEDET that will do precisely what you want.

Answer 2

CEDET (there are rumors that it is finally going to become part of Emacs starting with 23.2) is your friend. After installation, look up semantic-ia-show-summary.