Le 27/05/2013 10:37, Václav Zeman a écrit : > On 26 May 2013 21:01, Lee Thomas wrote: >> 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. > I disagree. IANALL but AFAIK, this is simply not allowed by the > language => UB => even though it seems to work in this instance, you > are just lucky the UB is actually doing what you expect.
In that case we should rewrite strlen, it's the same code. That doesn't mean it's a good code but I really don't think it's bad. Using signedness is totally valid and what is done here appears valid too. > -- > VZ -- Florent Peterschmitt | /"\ ASCII Ribbon Campaign flor...@peterschmitt.fr | \ / - No HTML/RTF in E-mail +33 (0)6 64 33 97 92 | X - No proprietary attachments http://florent.peterschmitt.fr | / \ - Respect for open standards
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