Re: [PATCH] Fix CPU bitmask truncation

Andreas Schwab (schwab@suse.de)
Fri, 20 Dec 2002 21:00:23 +0100


Jeremy Fitzhardinge <jeremy@goop.org> writes:

|> On Fri, 2002-12-20 at 04:17, Andreas Schwab wrote:
|> > This is useless. Assigning -1 to any unsigned type is garanteed to give
|> > you all bits one, and with two's complement this also holds for any signed
|> > type.
|>
|> Only if the -1 is the same size as the unsigned type. Otherwise it will
|> be 0-extended.

Wrong. Unsigned arithmetics is defined as modulo MAX+1, and -1 equals MAX
modulo MAX+1 for every MAX.

Andreas.

-- 
Andreas Schwab, SuSE Labs, schwab@suse.de
SuSE Linux AG, Deutschherrnstr. 15-19, D-90429 Nürnberg
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