including header file

Question

hello everyone, I have some question about header files(I'm talking about c, but I think it will be the same for c++), let's assume I have some my_ADT.c file (inside I have implementation of the functions and actual struct) and also my_ADT.h inside I have pointer for my struct Question: if I use ADT Set for implementation my_ADT do I need to include set.h to both files my_ADT.h and my_ADT.c or including only to my_ADT.h will be sufficient (inside my_ADT.c I have #include "my_ADT.h") thanks in advance

Answer 1

If my_ADT.h is included in the my_ADT.c file, then you should include set.h only in my_ADT.h.

Answer 2

There are 3 scenarios

1. set.h is needed ONLY in my_ADT.h
2. set.h is needed ONLY in my_ADT.c
3. set.h is needed in both my_ADT.h and my_ADT.c
4. set.h is not needed at all :-)

For scenario 3) add the #include "set.h" to the file my_ADT.h, document that fact, and #include "my_ADT.h" in my_ADT.c (with proper include guards, you lose nothing by including set.h also to the C file).

For scenario 2) include set.h only in my_ADT.c

For scenario 1) include set.h only in my_ADT.h

Answer 3

In addiction to pmg answer you must know that a good way of avoiding #include problem is to surround all header file with a precomplier instruction that check if the .h file has been already included.

#ifndef __my_ADT_header
#define __my_ADT_header
/*
 * your header declaration here
 */
#endif

this prevent error caused by multiple header inclusion

hope this helps