When looking at function signatures such as

EXPORT _foo_bar_handle_restricted _foo_common_alloc_restricted( … )

it’s often hard to quickly see what the function name is among all the spaces and underscores. To help with this, many editors support highlighting function names. Vim can also do this, e.g. by using a tags file, but for large code bases this can be quite slow. The following syntax definitions use a simple heuristic to highlight function names in C code by making their names boldface. In my experience it works quite well.

(The original version came from a stackoverflow answer, but Albert Lee posted a better version in the comments.)

" Highlight all function names
syntax match cCustomFunc /\w\+\s*(/me=e-1,he=e-1
highlight def link cCustomFunc Function

To use this, put it in ~/.vim/after/syntax/c/highlight_functions.vim. (All files in ~/.vim/after/syntax/[filetype]/ will be sourced when vim opens a file of type [filetype].)