Should I use #include in headers?

Question

Is it necessary to #include some file, if inside a header (*.h), types defined in this file are used?

For instance, if I use GLib and wish to use the

Answer 1

You need to include the header from your header, and there's no need to include it in the .c. Includes should go after the #define so they are not unnecessarily included multiple times. For example:

/* myHeader.h */
#ifndef MY_HEADER_H
#define MY_HEADER_H

#include 

struct S
{
    gchar c;
};

#endif /* MY_HEADER_H */

and

/* myCode.c */
#include "myHeader.h"

void myFunction()
{
    struct S s;
    /* really exciting code goes here */
}