how to find the value of a macro?

George2 · 07-11-2006, 01:15 AM

Hello everyone,

I am wondering what is the easiest and safest way to find the value of a macro? For example, if I,

#define FOO "value1"

The value of FOO I can get is "value1" and if then I,

#undef FOO
#define FOO "value2",

then the value of FOO I can get is "value2".

thanks in advance,
George

jim mcnamara · 07-11-2006, 06:14 AM

#define creates a permanent, hard-coded value at compile time, not run time.

This means that if you have a test in your code for a value, it will fail at compile time if the value is not there ie.,

Code:

#define VALUE
printf("%s\n,VALUE);

Normally you test a #define with another directive like #ifdef or #ifndef not "regular" C code:

Code:

#ifndef __MYINCLUDE_H_
#define __MYINCLUDE_H_
#include "myinclude.h"
#endif

What are you trying to do?