Re: [Xen-devel] [PATCH URGENT] common/vsprintf: Fix signed->unsigned error, causing glacial performance.

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 12/11/13 16:23, Jan Beulich wrote:
>>>> On 12.11.13 at 17:10, Andrew Cooper <andrew.cooper3@xxxxxxxxxx> wrote:
>> The original patch for
>>
>>   c/s 67a3542c5bc356e6452d8305991617c875f87de4
>>   "common/vsprintf: Refactor string() out of vsnprintf()"
>>
>> specifically used signed integers, identical to the code copied out of 
>> vsprintf.
>>
>> When committed, these had changed to unsigned integers, which causes a
>> functional change.  This causes glacial boot performance and an excessive
>> quantity of spaces printed to the serial console, as we loop to the upper
>> bound of a 32bit integer.
>>
>> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> Considering that I had changed those on the fly while committing,
> I committed this one without waiting for an ack. But ...
>
>> --- a/xen/common/vsprintf.c
>> +++ b/xen/common/vsprintf.c
>> @@ -239,7 +239,7 @@ static char *number(
>>  static char *string(char *str, char *end, const char *s,
>>                      int field_width, int precision, int flags)
>>  {
>> -    unsigned int i, len = strnlen(s, precision);
>> +    int i, len = strnlen(s, precision);
> ... this just looks _so_ wrong (and whenever I'll come across
> this again, I'll just be tempted again to adjust it)!
>
> Jan
>

I agree in general, and do err on the side of unsigned whenever
possible.  In this case, I went with exactly what was present before.

~Andrew

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