core.sys.posix.setjmp unavailable for OS X?

[bpr via Digitalmars-d-learn]

Is there a reason that it's unavailable on OS X when it works 
fine on Linux? The functions exist on OS X, and it's easy enough 
to compile C programs using setjmp there; but not D programs. I 
don't think I'm getting a betterC experience on the Mac.

I'd also ask why the there are no D docs for core.sys.posix but I 
read the responses to the last time the question was asked and 
now I'm D-pressed. :-(