bug#16232: [PATCH] grep: make --ignore-case (-i) faster (sometimes 10x) in multibyte locales

[Jim Meyering]

On Mon, Dec 23, 2013 at 2:52 PM, Eric Blake <address@hidden> wrote:
> On 12/23/2013 03:39 PM, Jim Meyering wrote:
>> FYI, here is a quick and clean/safe performance improvement for grep -i.
>> I expect to push this commit right after the upcoming bug-fix release.
>> Currently, this optimization is enabled when the search string is
>> ASCII and contains neither of '\' (backslash) nor '['.  I expect to
>> eliminate the latter two constraints in a follow-on commit including
>> tests to exercise all of the corner cases.
>>
>
>> +
>> +  /* Worst case is that every byte of keys will be alpha,
>> +     so every byte B will map to the sequence of 4 bytes [Bb].  */
>
> Umm, is this always true?  Consider the UTF-8 Turkish locale, where

Hi Eric,

Thanks for the review.
Did you miss the "isascii" check in the new trivial_case_convert function?
If you can describe circumstances in which the new patch malfunctions,
please do,
but everything you wrote seems to rely on a false assumption.
E.g., your turkish-I example works fine with my patch.