Thread: Defining and using a macro

Hello! I am trying to create a small set of filepath functions that I intend to compile across linux and windows (I prefer not to use a big library).

I want to have a global constant PATH_SEPARATOR that depends on the OS environment. This is what I set at the top of header file.

Code:

#include <stdio.h>
const char PATH_SEPARATOR =      
#ifdef _WIN32     
'\\';     
#else     
'/';     
#endif

I was hoping to test this while compiling this in a linux environment using gcc, thusly:

Code:

int main (int argc, char const* argv[])     
{       
    printf("OSNAME not defined. Separator is: %c\n", PATH_SEPARATOR);          
#define _WIN32       
    printf("OSNAME defined. Separator is: %c\n", PATH_SEPARATOR);     
#undef _WIN32 
    return 0;     
}

which gives me the following:

Code:

_WIN32 not defined. Separator is: /     
_WIN32 defined. Separator is: /

where apparently, I seem not to be able to "set" a part of the code to have "_WIN32" defined. I don't know if I explained this clearly. I'm not even sure I got the title correct.

C macros are applied compiletime, not runtime. Once your PATH_SEPARATOR is defined in can't be changed.

Thanks Yarin for your reply. However, I still get the same result. I think my problem is how to set "_WIN32" defined in that part of the code printing the PATH_SEPARATOR.

Originally Posted by Yarin

C macros are applied compiletime, not runtime. Once your PATH_SEPARATOR is defined in can't be changed.

I am not trying to change the value at runtime. I was just hoping to test the value of PATH_SEPARATOR set at compile time by making a #define at parts of the code. Is this possible?

Originally Posted by champen

I am not trying to change the value at runtime. I was just hoping to test the value of PATH_SEPARATOR set at compile time by making a #define at parts of the code. Is this possible?

No.
It shouldn't be much of a problem, though. You'll need to compile it for (or on) either platform when testing, anyway.

Originally Posted by Yarin

No.
It shouldn't be much of a problem, though. You'll need to compile it for (or on) either platform when testing, anyway.

Thanks! I got it working by compiling it with MinGW's gcc compiler.