xquartz dereferencing a NULL pointer (patch 2)

[Simon Thum]

> newtail = (oldtail + 1) % QUEUE_SIZE; 
> miEventQueue.tail = newtail;
> 
> becoming
> 
> miEventQueue.tail++;
> miEventQueue.tail |= QUEUE_SIZE - 1;
I don't think a compiler should be doing this to a non-local store. It
could probably be considered a bug. C doesn't really have a memory model
but few rules likely to forbid this. I didn't check, but I'd be highly
surprised by this being legal. Do you have a case where it happens?

Cheers,

Simon