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ACCESS_ONCE()ACCESS_ONCE()Posted Aug 13, 2012 12:11 UTC (Mon) by nye (guest, #51576)In reply to: ACCESS_ONCE() by dgm Parent article: ACCESS_ONCE()
>> How can the compiler possibly know what you meant when you wrote something outside the language spec?
> The code we are arguing about, the one with ACCESS_ONCE(), is NOT outside the spec in any way, is it?
No it isn't. The point is that, absent the ACCESS_ONCE() macro, the assumption that the compiler shouldn't pull that access out of the loop is what's outside the language spec, because the spec says it can safely do so.
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ACCESS_ONCE() Posted Aug 17, 2012 10:57 UTC (Fri) by dgm (subscriber, #49227) [Link]
> the spec says it can safely do so.
But does the spec say it _has_ to do so? Does it more good or harm?
Not everything that is allowed is good. For example, the compiler is (in theory) allowed to do anything it wants when presented with code that raises undefined behavior. Anything. "rm -rf /" for instance would be 100% correct. Are GCC developers planing this "feature" for gcc 4.8? Of course not, that would be stupid when you could be playing nethack instead...
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