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devel / comp.std.c / N2838: Types and sizes: "This changes the specification when the operand of sizeof is not an lvalue of VLA type"???

SubjectAuthor
* N2838: Types and sizes: "This changes the specification when theAndrey Tarasevich
`- N2838: Types and sizes: "This changes the specification when the operand of sizeTim Rentsch

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N2838: Types and sizes: "This changes the specification when the operand of sizeof is not an lvalue of VLA type"???

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From: andreytarasevich@hotmail.com (Andrey Tarasevich)
Newsgroups: comp.std.c
Subject: N2838: Types and sizes: "This changes the specification when the
operand of sizeof is not an lvalue of VLA type"???
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 by: Andrey Tarasevich - Sat, 12 Nov 2022 04:49 UTC

https://open-std.org/jtc1/sc22/wg14/www/docs/n2838.htm

Section "3.2.1. Rationale" of that proposal begins with

"This changes the specification when the operand of sizeof is *not*
an lvalue of VLA type [...]"

Note the "not" in the above sentence: "not an lvalue of VLA type".

And then it proceeds to demonstrate the proposed change with an example
in 3.2.2 where the `sizeof` in question (whose behavior will supposedly
change) is clearly applied to an lvalue of VLA type!

So, what is that "not" doing in the initial sentence of 3.2.1? Is this
just a typo/miswording? Or am I missing something about the intended
meaning of that sentence?

--
Best regards,
Andrey

Re: N2838: Types and sizes: "This changes the specification when the operand of sizeof is not an lvalue of VLA type"???

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From: tr.17687@z991.linuxsc.com (Tim Rentsch)
Newsgroups: comp.std.c
Subject: Re: N2838: Types and sizes: "This changes the specification when the operand of sizeof is not an lvalue of VLA type"???
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 by: Tim Rentsch - Sun, 13 Nov 2022 14:42 UTC

Andrey Tarasevich <andreytarasevich@hotmail.com> writes:

> https://open-std.org/jtc1/sc22/wg14/www/docs/n2838.htm
>
> Section "3.2.1. Rationale" of that proposal begins with
>
> "This changes the specification when the operand of sizeof is
> *not* an lvalue of VLA type [...]"
>
> Note the "not" in the above sentence: "not an lvalue of VLA type".
>
> And then it proceeds to demonstrate the proposed change with an
> example in 3.2.2 where the `sizeof` in question (whose behavior will
> supposedly change) is clearly applied to an lvalue of VLA type!
>
> So, what is that "not" doing in the initial sentence of 3.2.1? Is
> this just a typo/miswording? Or am I missing something about the
> intended meaning of that sentence?

My reading of that statement in 3.2.1 is that it is wrong. The
change proposed in 3.2 /does/ affect the semantics of sizeof with
an operand that is an lvalue of VLA type, and also, AFAICT, does
/not/ affect the semantics of sizeof with any other kind of
operand. As to what may have caused it, I have nothing new to
offer.

<editorial-comment>
The proposal document is poorly written. The changes proposed
are either poorly written or poorly thought out, perhaps both.
Sadly I believe the overall quality of the proposal is indicative
of what is going on in the ISO C standard more generally.
</editorial-comment>

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