Re: Footnote in section on Address-Of Operator

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From	Ben Bacarisse <ben.usenet@bsb.me.uk>
Newsgroups	comp.std.c
Subject	Re: Footnote in section on Address-Of Operator
Date	Thu, 24 Nov 2022 13:26:13 +0000
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Tim Rentsch <tr.17687@z991.linuxsc.com> writes:

> Ben Bacarisse <ben.usenet@bsb.me.uk> writes:
>
>> JoJoModding <jojohostert@gmail.com> writes:
>>
>>> in the paragraph on address and indirection operators (6.5.3.2 in the
>>> C23 draft N3047), there is a footnote (footnote 117 in that draft),
>>> which says that
>>>
>>>> &*E is equivalent to E (even if E is a null pointer)
>>
>> This seems to be a case where a footnote might add confusion rather than
>> clarity.  The normative text makes it clear that &*E can't be equivalent
>> to E in every way because &*E is not an lvalue.  And &*E has type
>> constraints that E does not have.
>>
>>> This seems to imply that sizeof(&*E) == sizeof(E), which is unexpected
>>> if E is an array.
>>
>> There are much simpler examples if the apparent non-equivalence.  If p
>> is a pointer object, p can be assigned to by &*p can't be.  And due to
>> the clause about constraints.  &*(void *)0 is a constraint violation,
>> but (void *)0 is obviously fine.
>
> What makes you say &*(void*)0 is a constraint violation?  I
> don't see any constraints that are violated.

Isn't * applied to a pointer to an incomplete type a constraint?  Let me
go look...  ah, no it is not!  Thanks.

-- 
Ben.

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Footnote in section on Address-Of Operator JoJoModding <jojohostert@gmail.com> - 2022-11-23 14:40 -0800
  Re: Footnote in section on Address-Of Operator Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-11-24 00:05 +0000
    Re: Footnote in section on Address-Of Operator Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-11-23 18:48 -0800
      Re: Footnote in section on Address-Of Operator Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-11-24 13:26 +0000

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