ntdll: Don't use strncasecmp for _strnicmp implementation

[Jacek Caban]

On 10/16/12 13:16, Marcus Meissner wrote:
> On Tue, Oct 16, 2012 at 01:12:50PM +0200, Jacek Caban wrote:
>> On 10/16/12 13:08, Marcus Meissner wrote:
>>> On Tue, Oct 16, 2012 at 12:38:51PM +0200, Jacek Caban wrote:
>>>> ---
>>>>  dlls/ntdll/string.c       |   12 +++++++++++-
>>>>  dlls/ntdll/tests/string.c |   33 +++++++++++++++++++++++++++++++++
>>>>  2 files changed, 44 insertions(+), 1 deletions(-)
>>>>
>>>>
>>>> diff --git a/dlls/ntdll/string.c b/dlls/ntdll/string.c
>>>> index 716dbdf..288e910 100644
>>>> --- a/dlls/ntdll/string.c
>>>> +++ b/dlls/ntdll/string.c
>>>> @@ -254,7 +254,17 @@ int __cdecl _stricmp( LPCSTR str1, LPCSTR str2 )
>>>>   */
>>>>  int __cdecl _strnicmp( LPCSTR str1, LPCSTR str2, size_t n )
>>>>  {
>>>> -    return strncasecmp( str1, str2, n );
>>>> +    int ret = 0;
>>>> +
>>>> +    /* 32-bit Windows return only -1,0,1 values */
>>>> +    while(n--) {
>>>> +        if(!*str1)
>>>> +            return sizeof(void*) == 4 ? (*str2 ? -1 : 0) : -(unsigned char)*str2;
>>>> +        if((ret = tolower(*str1++) - tolower(*str2++)))
>>>> +            return sizeof(void*) == 4 ? (ret > 0 ? 1 : -1) : ret;
>>>> +    }
>>> Errm. Why not
>>>
>>> int ret = strncasecmp( str1, str2, n );
>>>
>>> if (ret < 0 ) return -1;
>>> if (ret > 0 ) return 1;
>>> return 0;
>> That wasn't the original reason for writing this patch. It seems like
>> some distros (well, at least some Gentoo installations) have broken
>> strncasecmp.
> How exactly? Do you know more details / urls?
>
> Does it return -n ... +n values? Like the memcmp optimization that caused mysql security issue?
> In that case my patch should work.

>From what I know following call crashes:
strncasecmp("", "", 1);
It's probably a corner case for some optimizations.

Jacek