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From: Tim Rentsch <tr.17687@z991.linuxsc.com>
Newsgroups: comp.lang.c
Subject: Re: _BitInt(N)
Date: Mon, 15 Dec 2025 08:21:44 -0800
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Keith Thompson <Keith.S.Thompson+u@gmail.com> writes:

> David Brown <david.brown@hesbynett.no> writes:
> [...]
>
>> (I am not entirely sure, but I think it is standards-conforming for
>> an implementation to haev BITINT_MAXWIDTH set to 64 and support all
>> _BitInts up size 64, and then also support _BitInts of multiples of
>> 64 thereafter.  Use of _BitInt greater than BITINT_MAXWIDTH is UB
>> in the standard - so an implementation can choose to give that a
>> defined behaviour for specific sizes.)
>
> [...]
>
> No, _BitInt(N) where N > BITINT_MAXWIDTH is a constraint violation.
>
> N3220 6.7.3.1p2 ("Constraints") :
>
>     The parenthesized constant expression that follows the _BitInt
>     keyword shall be an integer constant expression N that specifies
>     the width (6.2.6.2) of the type.  The value of N for unsigned
>     _BitInt shall be greater than or equal to 1.  The value of N
>     for _BitInt shall be greater than or equal to 2.  The value of
>     N shall be less than or equal to the value of BITINT_MAXWIDTH
>     (see 5.2.5.3.2).
>
> As I mentioned before, there's a proposal for C2y to allow
> signed _BitInt(1).

Yay!  Sanity prevails.