Messages in this thread | | | Date | Wed, 9 Jan 2002 23:37:26 -0500 | From | Tim Hollebeek <> | Subject | Re: [PATCH] C undefined behavior fix |
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> Nope, that's not enough, it's not that simple. Yes your > example of a-a is of course straightforward but what about > > b = (a & 1) | (b & 1); > > if a is volatile and b is known to be odd, can the read of a be eliminated? > The answer should be no (and I think the standard guarantees this), but the > reasoning is completely different from thinking about the fact that a may > change unexpectedly, since obviously no matter what value comes from > reading a, b will be set to 1 if b is known to be odd.
But presumably the transformation to:
a; b = 1;
is ok. where 'a;' represents the operation "read the value a into a register and then let that register die". - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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