Re: [PATCH] Add cast to unsigned char to strverscmp

Hans-Bernhard Bröker wrote:
> Am 08.11.2024 um 12:41 schrieb Christian Franke:
>> Corinna Vinschen wrote:
>>> On Nov  7 13:58, Joel Sherrill wrote:
>
>>> Given that l and r are unsigned char anyway, the entire expression
>>> is unsigned, so there shouldn't be a sign-compare error in newlib's
>>> version.
>
>> It's actually signed, IIRC due to changing 'unsigned preserving' (K&R 
>> C) to 'value preserving' (C89) implicit conversions.
>
> The reason it's signed is because '1' is a signed integer, so this 
> expression has a type train of:
>
>   ((unsigned char) - (signed int)) < (unsigned int)

The LHS of '<' is signed because both arguments are signed after 
implicit integer promotion:

   ((signed int)(unsigned char) - (signed int)) < (unsigned int)

In traditional K&R C, it was unsigned:

   ((unsigned int)(unsigned char) - (signed int)) < (unsigned int)