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From: Keith Thompson <Keith.S.Thompson+u@gmail.com>
Newsgroups: comp.lang.c
Subject: Re: how cast works?
Date: Fri, 09 Aug 2024 12:18:29 -0700
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David Brown <david.brown@hesbynett.no> writes:
> On 09/08/2024 01:14, Keith Thompson wrote:
>> David Brown <david.brown@hesbynett.no> writes:
>> [...]
>>> A _Bool is always either 0 or 1.  The conversion is whatever the
>>> compiler needs to give an int of value 0 or 1.
>> 
>> The value of a _Bool object is always either 0 or 1 *unless* the
>> program does something weird.
>
> True.  But attempting to use a _Bool object (as a _Bool) that does not
> contain either 0 or 1 is going to be undefined behaviour (at least it
> was on the platform where I saw this happen as a code bug).

It depends on whether representations with non-zero padding bits are
treated as trap representations (non-value representations in C23) or
not.

[...]

>> It doesn't specify whether setting the padding bits to 1 results in a
>> non-value representation.
>
> That's probably an implementation-defined issue, is it not?

I'm not sure whether it's implementation-defined or unspecified.
I don't see any mention of trap/non-value representations in Annex J.

[...]

-- 
Keith Thompson (The_Other_Keith) Keith.S.Thompson+u@gmail.com
void Void(void) { Void(); } /* The recursive call of the void */