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From: Keith Thompson <kst-u@mib.org>
Newsgroups: comp.lang.c
Subject: Re: counting bytes
Date: Mon, 20 Jul 2015 11:18:16 -0700
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Tim Rentsch <txr@alumni.caltech.edu> writes:
> Keith Thompson <kst-u@mib.org> writes:
>> Tim Rentsch <txr@alumni.caltech.edu> writes:
[...]
>>> It is possible to have a conforming implementation with
>>> CHAR_BIT > 8 but still having a type that occupies only eight
>>> bits.  AFAIK there is no reason such an implementation
>>> could not use that type to provide the [u]int8_t types.
>>
>> I'm skeptical.
>
> The combination of undefined behavior resulting from trap
> representatons and the Standard allowing an extremely wide
> range of extensions is enormously powerful.  In some sense
> it's an academic question since such an implementation will
> in all likelihood never be produced.  But I think it's
> interesting to consider the possibility.

Sure -- but I still don't think it's a possibility.

Extensions can take advantage of undefined behavior, but your proposed
extension (using padding bits and trap representations in size_t to
represent fractional values) introduces undefined behavior where it
doesn't currently exist.  I believe it is therefore non-conforming.

I believe that this program:

#include <stdio.h>
#include <stdint.h>

int main(void) {
#ifdef UINT8_MAX
    if (sizeof (uint8_t) < (size_t)1) {
        puts("I am confused");
    }
    else {
        puts("ok");
    }
#else
    puts("ok");
#endif
    return 0;
}

is strictly conforming (subject to the usual caveats about the puts call
failing) and must print "ok".

-- 
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
Working, but not speaking, for JetHead Development, Inc.
"We must do something.  This is something.  Therefore, we must do this."
    -- Antony Jay and Jonathan Lynn, "Yes Minister"