[prog] Solution

[Mary]

On Sat, Feb 01, 2003, Jenn Vesperman wrote:
> I can't see a need to have separate header files for each set of
> #included code, nor to surround the #included code in #ifdefs. C will
> only link the headers once, it should be fine to multiply include them
> if you do wind up doing so. 

Really? In the following situation:

A.h:
        #define A
 
        typedef int a;

B.h

        #include "A.h"
        #define B

C.h
        #include "A.h"
        #define C

A.c
        #include "B.h"
        #include "C.h"

where A.c is including A.h through two different header files, I get the
following error:

In file included from C.h:1,
                 from A.c:2:
                 A.h:3: redefinition of `a'
                 A.h:3: `a' previously declared here

Hence, major system libraries all use ifndefs to protect from multiple
inclusion, for example, /usr/include/stdio.h on my system begins:

#ifndef _STDIO_H
# define _STDIO_H       1

.
.
.


It's fine to multply include function definitions I believe (as long as
they have the same signature) but definitions will cause an error.

-Mary