what is #define __P(proto) proto in C

Hi friends.

I was reading a program ( C language) in an article.

It has defined this macro...

#define __P(proto) proto

what is significance of this macro.

Thanks..

It means that whenever you see __P(proto), that the result of that will be proto. Outside of reading the article, how are we supposed to know what it means?

Nevertheless, if you had bothered to google to figure this one out, you might have discovered it is part of a macro combination to provide backwards compatibility with K&R C.