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Re: [PATCH] ctype: Fix bitfield types on 16-bit targets
> On Jul 20, 2018, at 1:37 PM, Hans-Bernhard Bröker <HBBroeker@t-online.de> wrote:
>
> Am 20.07.2018 um 13:07 schrieb Sebastian Huber:
>> - unsigned int first: 24; - unsigned short delta; + uint_least32_t
>> first: 24; + uint_least16_t delta;
>
> Unfortunately that makes the code's correctness implementation-defined,
> because it now depends on what the underlying implementation's take on
> the constraint C99 6.7.2.1p4 is:
>
> A bit-field shall have a type that is a qualified or unqualified
> version of _Bool, signed int, unsigned int, or some other
> implementation-defined type.
>
> I.e. compilers are not required to allow uint32_least_t in this place.
Yes, but the original code was just as implementation-dependent, because it depended on "int" having at least 24 bits. And indeed that is not true (or not necessarily true) on 16-bit targets.
Does "qualified" mean "long int" is allowed? If so, that would be an alternative. But the proposed patch has the advantage that it explicitly calls for a long-enough type.
While legally speaking the standard doesn't require that to work, is it plausible that any real world compiler would object?
paul