Header questions

[wizoverloadfroze]

I've been reading source headers. A few enigmas have appeared that have baffled me.
One of them is a bizarre declaration:

DECL(p1, p2, pN);
DECL(p1, p2, pN);

A bunch more will be like this with different parameters.

The DECL will be a specific name that is all the same. I've looked at the other headers to see if this DECL is defined to give more hints to what it exactly is.

These are scattered across multiple header files.

Thanks.