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Old 06-25-2004, 08:39 AM   #1
tuxfood
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help with #ifdef #undef etc


hi...

read a prgm with this #ifdef #undef etc ...got some idea but now so clear ....

can anyone hellp me out with this

thnks

tuxfood
 
Old 06-25-2004, 08:45 AM   #2
acid_kewpie
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please try to write well defined questions when you post.... what are you after? you're question is far too vague and short...
 
Old 06-29-2004, 09:04 AM   #3
tuxfood
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hi..

sorry but i just need to know when and where to use #ifdef #undef etc..

thnks

tuxfood
 
Old 06-29-2004, 09:12 AM   #4
deiussum
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You can use #ifdef (if defined) to conditionally compile features into your application. You can use #ifndef (if not defined) for various things, but it is ofen used as guards in your header so that they do not get included more than once in any single .c/.cpp file. You use #undef to undefine a symbol or macro, and #define to define a symbol or create a macro:

Code:
#ifndef __SOME_HEADER_H__
#define __SOME_HEADER_H__

#ifdef WIN32  // if we are compiling on a Windows system...
#include <windows.h>
#endif

#ifdef DEBUG  // Could possibly pass to compiler using -DDEBUG parameter
#define TRACE(msg)    printf(msg);
#else
#define TRACE(msg)
#endif

#undef SOME_MACRO_OR_CONSTANT_YOU_NO_LONGER_WANT_DEFINED

#endif  // __SOME_HEADER_H__
 
  


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