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In-Reply-To: <jeish9vh43.fsf@sykes.suse.de>
References: <87wu5pwyg7.fsf@aladdin.de> <jeish9vh43.fsf@sykes.suse.de>
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Cc: Dale Johannesen <dalej@apple.com>, Andreas Schwab <schwab@suse.de>,
        GCC List <gcc@gcc.gnu.org>
From: Dale Johannesen <dalej@apple.com>
Subject: Re: signed/unsigned right shift
Date: Fri, 12 Mar 2004 22:37:00 -0000
To: Christian Groessler <cpg@aladdin.de>
X-SW-Source: 2004-03/txt/msg00594.txt.bz2

On Mar 12, 2004, at 2:24 PM, Andreas Schwab wrote:
> Christian Groessler <cpg@aladdin.de> writes:
>> I have the following program which takes 2 unsigned short values,
>> multiplies them and shifts the result right.
>>
>> This right shift gives a value with 1s bits at the high end.
>
> This is correct.  The promotion rules let unsigned short promote to 
> int,
> since the latter can represent all values of the former.

Correct, the multiplication is done as signed int.  And it is 
implementation
defined whether right shift of a negative signed int does sign fill or 
not.
So both compilers are right; it is only your code that's wrong.

C89 references: 3.3.7, 3.2.1.5, 3.2.1.1.