Help in understanding small code for FreeBSD implementation of the C library

Hello guys, here is the code in reference:

Code:

/* sys/cdef.h */ 
#if     defined(__STDC__) || defined(__cplusplus) 
#define __P(protos)   protos 
#else 
#define __P(protos)   () 
#endif 
/* stdio.h */ 
#include <sys/cdefs.h> 
div_t div __P((int, int));

i cannot understand some parts in the code like
1.> why is there space between div and __P in

Code:

div_t div __P((int, int));

and why are there double braces around

Code:

__P((int,int))

.
2.> what is #define doing, i know these are preprocessor directives and i have seen the common implementations but i don't understand this.

Thanks

 

Thanks Guys but i got it. See what the code

Code:

div_t div __P((int, int));

does is replace __P((int,int)) simply with () or (int,int), so that the code now becomes

Code:

div_t div ()

or

Code:

div_t div (int,int)

.
A good way for making variable argument functions.

Good day

 

@Everyone: I would like to point out that when i said "I got it" in the above reply, i didn't mean that i solved it myself but what i meant was that i understood it, from a reply on another forum and so i have posted it here so that others who read it can benefit from the reply.

Thanls