Noob Question... Typedef Struct Redefination error when I include the header in more than one c source file

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typedef struct NOTEPAD_GLOBALS;

typedef struct 
 {
  HINSTANCE hInstance;
  HWND    hMainWnd;
}NOTEPAD_GLOBALS;

extern NOTEPAD_GLOBALS Globals;

This is my def.h when I #include it in only main.c it works fine, but when I #include it in the main.h, as well, it gives me this error.

def.h(12) : error C2371: 'NOTEPAD_GLOBALS' : redefinition; different basic types<br />
def.h(12) : see declaration of 'NOTEPAD_GLOBALS'

I have no idea what is wrong with it. Any help would be greatly appreciated. I am using Visual C++ 6

Posted 28-Dec-09 22:58pm

drkwlf

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CPallini · Accepted Answer · 2009-12-28T23:05:00

You should add the directive

#pragma once

at the top of your header.

If VC6 compiler doesn't support it (I don't remember...), use the oldie goldie #if !defined(), for instance:

#if !defined( __MYHEADER__)
#define __MYHEADER__

typedef struct NOTEPAD_GLOBALS;

typedef struct 
 {
  HINSTANCE hInstance;
  HWND    hMainWnd;
}NOTEPAD_GLOBALS;

extern NOTEPAD_GLOBALS Globals;

#endif// __MYHEADER__

These meachanism avoid multiple inclusion issues.
:)