c++ - How to use #include directive correctly?

Question

Is there any material about how to use #include correctly? I didn't find any C/C++ text book that explains this usage in detail. In formal project, I always get confused in dealing with it.

Answer 1

The big one that always tripped me up was this:

This searches in the header path:

#include <stdio.h>

This searches in your local directory:

#include "myfile.h"

Second thing you should do with EVERY header is this:

myfilename.h:

#ifndef MYFILENAME_H
#define MYFILENAME_H
//put code here
#endif

This pattern means that you cannot fall over on redefining the headers in your compilation (Cheers to orsogufo for pointing out to me this is called an "include guard"). Do some reading on how the C compiler actually compiles the files (before linking) because that will make the world of #define and #include make a whole lot of sense to you, the C compiler when it comes to parsing text isn't very intelligent. (The C compiler itself however is another matter)