>Believe me, it left me scratching mine when I first saw it, and yes, it goes against everything I thought I knew about compile time constants. If I were to hazard a SWAG, it looks like if a function call is used, we've got our old macro business going on. If literals are used, then I'd suspect they're treated like any other (normal) compile time constant.

I think we're confusing "pre-processing" and "compiling"; these are simply "code substitutions" performed during the pre-processor stage. The substituted code (ie. .... SYS( n ) ....) is what is getting compiled.