c which include contains function

Question

I received a large code file, that I didn't write. There's a function being used in that code that I want to use myself in a separate code file. Is there a quick and simple way to find which of the (many) includes in the original code file makes this function available?

Answer 1

The fastest way is usually to grep for the function name (pro tip: use grep -rw to search recursively and for whole-word matches only). That assumes you have some idea which directories the header file may be in.

If that won't work, you can preprocess the file. With GCC that's the -E option instead of -c. This will output what the actual compiler sees, after #includes are resolved. Then you can easily search in the preprocessed file for the function declaration and look above that for which file it came from.

Answer 2

This completely depends on your developmnet environment. I often use ack tool (consider it as "better grep" for programmers) for that purpose, beside that I know that some IDEs have "go to definition" or "go to declaration" feature, so you can directly look for function's definition or its prototype.