Re: [PATCH 2/2] Simplify (and warn about) right shifts that result in zero

[Josh Triplett <josh@freedesktop.org>]

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Linus Torvalds wrote:
> On Thu, 24 Apr 2008, Pavel Roskin wrote:
>> So I would suggest a similar warning is this case.  Maybe "right shift
>> too big (%u) for source type %s" (if the source type is readily
>> available) or "right shift count (%d) >= width of type (%d)"
> 
> That's fine, except we shouldn't talk about "type", since we're really 
> doing some really stupid value analysis (the *type* will generally have 
> been cast to a bigger one by the implicit C type evaluation rules).

Pavel, it sounds like you agree with the semantic of the warning, and
just want an different wording.  Thus, I've applied and pushed the patch;
feel free to propose a change to the wording in a subsequent patch.

>> By the way, your patch has caught something interesting in
>> net/mac80211/tkip.c:
>>
>>         iv32 = data[hdr_len + 4] +
>>                 (data[hdr_len + 5] >> 8) +
>>                 (data[hdr_len + 6] >> 16) +
>>                 (data[hdr_len + 7] >> 24);
>>
>> Wow!
> 
> Heh. That does look like somebody is shifting the wrong way, and 
> apparently the new warning was worth something ;)

Nice.

- Josh Triplett



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