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From: Tim Rentsch <tr.17687@z991.linuxsc.com>
Newsgroups: comp.lang.c
Subject: Re: UB or not UB? was: On Undefined Behavior
Date: Mon, 12 Jan 2026 12:03:36 -0800
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Michael S <already5chosen@yahoo.com> writes:

> On Mon, 12 Jan 2026 08:03:31 -0800
> Andrey Tarasevich <noone@noone.net> wrote:
>
>> On Mon 1/12/2026 6:28 AM, Michael S wrote:
>>
>>> According to C Standard, access to p->table[4] in foo1() is UB.
>>> ...
>>> Now the question.
>>> What The Standard says about foo2() ? Is there UB in foo2() as
>>> well?
>>
>> Yes, in the same sense as in `foo1`.
>>
>>> gcc code generator does not think so.
>>
>> It definitely does.

Right.

> Do you have citation from the Standard?

The short answer is section 6.5.6 paragraph 8.

There is amplification in Annex J.2, roughly three pages
after the start of J.2.  You can search for "an array
subscript is out of range", where there is a clarifying
example.