Jump to function definition in vim

Use ctags. Generate a tags file, and tell vim where it is using the :tags command. Then you can just jump to the function definition using Ctrl-]

There are more tags tricks and tips in this question.

If everything is contained in one file, there's the command gd (as in 'goto definition'), which will take you to the first occurrence in the file of the word under the cursor, which is often the definition.

g* does a decent job without ctags being set up.

That is, type g,* (or just * - see below) to search for the word under the cursor (in this case, the function name). Then press n to go to the next (or Shift-n for previous) occurrence.

It doesn't jump directly to the definition, given that this command just searches for the word under the cursor, but if you don't want to deal with setting up ctags at the moment, you can at least save yourself from having to re-type the function name to search for its definition.

--Edit-- Although I've been using g* for a long time, I've recently discovered two shortcuts for these shortcuts!

(a) * will jump to the next occurrence of the word under the cursor. (No need to type the g, the 'goto' command in vi).

(b) # goes to the previous occurrence, in similar fashion.

N and n still work, but '#' is often very useful to start the search initially in the reverse direction, for example, when looking for the declaration of a variable under the cursor.