I've lived with the old definition so long that I didn't notice Plan 9's definition, which is not a problem on today's architectures because there are two equally efficient instructions to choose from. 

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> On Nov 23, 2015, at 7:05 AM, Charles Forsyth <charles.forsyth@gmail.com> wrote:
> 
> 
>> On 23 November 2015 at 11:50, Brantley Coile <brantleycoile@me.com> wrote:
>> It is undefined in C whether or not it sign extends or not. Some machines do it one way, some another. To force the language to one behavior requires more code on some architectures.
> 
> Ironically for its use as an example, that's another case where Plan 9 C defines the effect: char is always signed, unsigned char is the only unsigned form, on all targets, just like int/unsigned int, short/unsigned short. The abbreviation "uchar" makes it relatively painless.
> It's just a pity that string literals must be char*, not uchar*, and all the str* functions take char*.