`asm' in natObject.cc

Mon Dec 3 11:33:00 GMT 2001

Boehm, Hans writes:
 > I think the memory clobber is necessary, since it's used to acquire or
 > release a lock. Thus gcc shouldn't move other memory operations across the
 > compare_and_swap, since that might move them out of the region in which the
 > lock is held.
Yes, I see. The argument is that even though other memory references
aren't volatile they still must never be moved across the locking
code. Clobbering all of memory acheives this.
 > To be honest, I'm not sure why the __volatile__ is needed, or whether it has
 > any real effect beyond the memory clobber.
It's probably unnecessary and does no harm.
Andrew.