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Subject: Re: Performance improvement to strnlen().
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Date: Sun, 26 May 2013 15:01:33 -0400
From: Lee Thomas <lee_thomas@aslantools.com>
Organization: Aslan Tools
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On 2013-05-26 08:00, Václav Zeman wrote:
> On 05/25/2013 10:27 PM, Lee Thomas wrote:
>> +	lp = (const unsigned long *)((uintptr_t)str & ~LONGPTR_MASK);
>> +	va = (*lp - mask01);
>> +	vb = ((~*lp) & mask80);
> I do not think that this correct C. This is type punning violating 
> the
> rules of the language.

Hello Václav,

The aliasing here is safe, because there are no writes through either 
of the pointers, and the reads are correctly aligned.

Regards,
Lee Thomas