How to test if preprocessor symbol is #define'd but has no value?

Question

Using C++ preprocessor directives, is it possible to test if a preprocessor symbol has been defined but has no value? Something like that:

#define MYVARIABLE         


        

Answer 1

I don't think that this can be done. That being said, I don't see a need for it. When you make a preprocessor #define symbol, you should establish a convention that either you define it as 1 or 0 for use in #if, or you leave it blank.