Simon Thum wrote: > > newtail = (oldtail + 1) % QUEUE_SIZE; > > miEventQueue.tail = newtail; > > > > becoming > > > > miEventQueue.tail++; > > miEventQueue.tail |= QUEUE_SIZE - 1;
Er, shouldn't this be "&=" ? > 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. Unless an lvalue is declared "volatile", the compiler is free to generate code which modifies it as and when it sees fit, so long as it has the correct value "in the end". In the meantime, it can freely store arbitrary data there if it wishes. This is why the "volatile" keyword was added to the ANSI C standard: so that the compiler could optimise memory access as it saw fit, while providing an opt-out for the cases where "intermediate" values are significant (signals, interrupts, memory-mapped I/O, threads, etc). -- Glynn Clements <[EMAIL PROTECTED]> _______________________________________________ xorg mailing list xorg@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/xorg
