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Re: Regarding assignment to struct

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Tim Rentsch <tr.17687@z991.linuxsc.com> writes:
> Keith Thompson <Keith.S.Thompson+u@gmail.com> writes:
>> Tim Rentsch <tr.17687@z991.linuxsc.com> writes:
>>> Keith Thompson <Keith.S.Thompson+u@gmail.com> writes:
>>>> Andrey Tarasevich <noone@noone.net> writes:
>>>> [...]
>>>>
>>>>>   #include <stdio.h>
>>>>>
>>>>>   struct S { int a[10]; };
>>>>>
>>>>>   int main()
>>>>>   {
>>>>>     struct S a, b = { 0 };
>>>>>     int *pa, *pb, *pc;
>>>>>
>>>>>     pa = &a.a[5],
>>>>>     pb = &b.a[5],
>>>>>     pc = &(a = b).a[5],
>>>>>     printf("%p %p %p\n", (void *) pa, (void *) pb, (void *) pc);
>>>>>   }
>>>>>
>>>>> This version has no UB.
>>>>
>>>> I believe it does.  [...]
>>>
>>> If you look again carefully, I expect you will reach a
>>> different conclusion.
>>
>> Please explain.  Or don't.
>>
>> I explained, in text that you snipped, why I think it has UB.
>> If there's a flaw in my reasoning, I invite you to point it out
>> without being mysterious.
>
> I wasn't thinking about your reasoning or what flaw there may have
> been in it.  My intention was to suggest a course of action that
> would be helpful rather than to point out any sort of mistake.  But
> since you ask, I think the mistake you made was jumping to a
> conclusion without looking carefully enough at the problem.

The mistake I made was failing to notice that the line with the
assignment to pc ends with a comma operator rather than a semicolon.

The code was deliberately obfuscated, and I fell for it.

I acknowledged that nearly a year ago.  Why bring it up now?
I find it extremely annoying.

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

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Re: Regarding assignment to struct Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-03-01 18:54 -0800
  Re: Regarding assignment to struct Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-03-01 19:36 -0800

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