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From: Keith Thompson <Keith.S.Thompson+u@gmail.com>
Newsgroups: comp.lang.c
Subject: Re: How About Disallowing Assignments In Expressions?
Date: Mon, 12 Feb 2024 08:20:41 -0800
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David Brown <david.brown@hesbynett.no> writes:
[...]
>>>> On 12/02/2024 11:26, David Brown wrote:
[...]
>>>>>      int * p;
[...]
>>>>>      _Bool b = p;
[...]
>>>>>      int x = p;
[...]
> Conversions of a pointer to "int" or to "_Bool" are both allowed by
> the C standards.  So a conforming C compiler has to accept them and
> generate appropriate code for them.
> 
> If the pointer's value cannot be represented in the target type when
> converting to an integer type, then it is undefined behaviour - but
> the compiler usually can't know that for sure at compile time.  Thus
> it has to generate code that accepts this and will work if the address
> happens to be small enough.  The compiler can, however, issue a
> warning that the programmer is probably doing something silly.
>
> Conversion of any scaler (including pointers) to _Bool is done by
> comparison to 0.  And since that is often a sensible thing to do,
> there is no warning in gcc - it would give too many false positives.

Conversion of a pointer to int behaves as you describe, but cannot be
done implicitly.  A cast is required to avoid a constraint violation.

-- 
Keith Thompson (The_Other_Keith) Keith.S.Thompson+u@gmail.com
Working, but not speaking, for Medtronic
void Void(void) { Void(); } /* The recursive call of the void */