A problem with the C preprocessor.

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Hello Daniweb,

I've ran against an issue in my code and i'm not sure why I receive an error. I've managed to reproduce the error with the following code:

C Syntax (Toggle Plain Text)
#ifdef _WIN32
#define PERFORMANCE_METING
#endif
 
#ifdef PERFORMANCE_METING
#include <windows.h>
#endif
 
#include <stdio.h>
#include <stdlib.h>
 
typedef enum { FALSE, TRUE } Boolean;
 
int main()
{
    return 0;
}
#ifdef _WIN32
#define PERFORMANCE_METING
#endif

#ifdef PERFORMANCE_METING
#include <windows.h>
#endif

#include <stdio.h>
#include <stdlib.h>

typedef enum { FALSE, TRUE } Boolean;

int main()
{
    return 0;
}

This code gives me the following error for the line where the typedef is:

C Syntax (Toggle Plain Text)

error: syntax error before numeric constant

Could anyone tell me why what I did is not allowed?
Besides that I was wondering if it was possible to check 2 symbols in 1 line with ifdef. (e.g. ifdef _WIN32 && PERFORMANCE_METING or something) or can I only use #if defined(_WIN32) && defined(PERFORMANCE_METING) for that?

Thanks in advance,

Gonbe.

-edit-
It doesn't seem to like include <windows.h> for some reason.
Do not know why though.

-edit-
Windef.h has a definition for FALSE and TRUE.. guess that's the issue.

Last edited by Gonbe; Feb 24th, 2010 at 1:56 pm.

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Gonbe

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Feb 24th, 2010

Re: A problem with the C preprocessor.

>>This code gives me the following error for the line where the typedef is:

windows.h already defines TRUE and FALSE, which are #define's, not typedefs. I suppose you could undefine them before that typedef, but that could cause many other problems with win32 api functions.

>>or can I only use #if defined(_WIN32) && defined(PERFORMANCE_METING) for that?

Yes. But then you could have tried it yourself to find out.

Last edited by Ancient Dragon; Feb 24th, 2010 at 3:20 pm.

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