Re: [PATCH] Fix error: array subscript has type 'char' [and 1 more messages]

[Jan Beulich <jbeulich@xxxxxxxx>]

On 27.01.2021 14:53, Ian Jackson wrote:
> Jan Beulich writes ("Re: [PATCH] Fix error: array subscript has type 'char'"):
>> On 27.01.2021 09:31, Jan Beulich wrote:
>>> But yes, I'm not the maintainer of this code, so if you're
>>> happy with such risks, so be it.
>>
>> And actually I was only partly right here - there's one hunk
>> here affecting code I'm the maintainer just as much as you
>> are. At least there I'd like to ask that ...
>>
>>> For the record, to me the less risky approach here would seem
>>> to have been to make use of compilers allowing to choose
>>> whether plain char is signed or unsigned, and force it to
>>> unsigned for at least the affected components.
>>
>> ... this be considered as an alternative, before I maybe
>> withdraw my de-facto nak.
> 
> Whether char is signed or unsigned is generally specified in the
> platform API/ABI.  Deviating from this for userland code is not
> possible or reasonable since it would involve processing the system
> headers with a deviant langauge definition!

I don't think I've ever come across that part of a platform
API/ABI spec. Instead my understanding so far was that good
platform headers would be ignorant of the user's choice of
char's signed-ness (wherever compilers offer such a choice,
but I think all that I've ever worked with did). At the very
least gcc's doc doesn't warn about any possible
incompatibilities resulting from use of -fsigned-char or
-funsigned-char (or their bitfield equivalents, for that
matter).

Jan