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List:       gcc
Subject:    Re: AMD64. sign extension correct?
From:       Andreas Schwab <schwab () suse ! de>
Date:       2005-02-27 21:20:37
Message-ID: jeis4d3dju.fsf () sykes ! suse ! de
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Claus-Justus Heine <ch@dot-heine.de> writes:

> 3.
> (signed long) = (signed int) x (unsigned int)
>
> Surprisingly the sign is not promoted in this case:
>
> a = -1 * 20, then a = 0x0000 0000 ffff ffec
>
>
> IMHO, this is a bug.

No, it's correct.  The type of the multiplication expression is unsigned
int, because signed int and unsigned int have the same integer conversion
rank, thus the common type is unsigned int and the signed int operand is
converted to unsigned int.  See 6.3.1.8 "Usual arithmetic conversions" in
the C standard.

Andreas.

-- 
Andreas Schwab, SuSE Labs, schwab@suse.de
SuSE Linux Products GmbH, Maxfeldstraße 5, 90409 Nürnberg, Germany
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