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| From | Keith Thompson <Keith.S.Thompson+u@gmail.com> |
|---|---|
| Newsgroups | comp.lang.c |
| Subject | Re: Bart's Language |
| Date | 2025-04-27 14:29 -0700 |
| Organization | None to speak of |
| Message-ID | <877c35pa37.fsf@nosuchdomain.example.com> (permalink) |
| References | (3 earlier) <vrc2d5$1jjrf$1@paganini.bofh.team> <vrc4eb$2p28t$1@dont-email.me> <vri6co$26v8m$2@paganini.bofh.team> <87a59fs2xm.fsf@nosuchdomain.example.com> <86wmb58mi6.fsf@linuxsc.com> |
Tim Rentsch <tr.17687@z991.linuxsc.com> writes:
> Keith Thompson <Keith.S.Thompson+u@gmail.com> writes:
>> antispam@fricas.org (Waldek Hebisch) writes:
>> [...]
>>> Well, it is rather easy to see if variable is used within its
>>> own initialization, so practically it is minor gap. Of course,
>>> there is problem with C standard: IIUC depending on rest of
>>> the code declarations as above are merely undefined behaviour
>>> or even produce unspecified value. So C compiler is
>>> forbidden to stop compilation are report compile time error.
>>
>> Valid responses to undefined behavior include "terminating a translation
>> or execution (with the issuance of a diagnostic message)".
>
> That's true, but doing so is allowed only if the circumstances
> of undefined behavior have occurred. In the case of compiling
> a declaration such as
>
> int a = a;
>
> no undefined behavior has as yet occurred.
N3096 6.3.2.1p2 (lvalue conversion):
If the lvalue designates an object of automatic storage duration
that could have been declared with the register storage class (never
had its address taken), and that object is uninitialized (not
declared with an initializer and no assignment to it has been
performed prior to use), the behavior is undefined.
Strictly speaking, `a` doesn't meet the definition of
"uninitialized", since it is declared with an initializer, but
its value is accessed before the initialization has been executed.
I'm not entirely certain that `int a = a;` has undefined behavior,
but it's unclear that the behavior is defined.
>> In other
>> words, if a compiler is able to prove that a program has undefined
>> behavior (that will occur on each execution), it can reject it at
>> compile time.
>
> The program can be rejected, but not because of the rule about
> terminating a translation. The program can be rejected because
> the program is not strictly conforming, and implementations are
> not required to accept programs that are not strictly conforming.
I disagree, but we've gone over this before with no resolution.
--
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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Bart's Language bart <bc@freeuk.com> - 2025-03-17 23:51 +0000
Re: Bart's Language antispam@fricas.org (Waldek Hebisch) - 2025-03-18 12:17 +0000
Re: Bart's Language bart <bc@freeuk.com> - 2025-03-18 13:54 +0000
Re: Bart's Language antispam@fricas.org (Waldek Hebisch) - 2025-03-18 15:10 +0000
Re: Bart's Language bart <bc@freeuk.com> - 2025-03-18 15:45 +0000
Re: Bart's Language David Brown <david.brown@hesbynett.no> - 2025-03-18 17:31 +0100
int a = a (Was: Bart's Language) gazelle@shell.xmission.com (Kenny McCormack) - 2025-03-18 18:04 +0000
Re: int a = a (Was: Bart's Language) Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-03-18 19:36 +0100
Re: int a = a (Was: Bart's Language) Kaz Kylheku <643-408-1753@kylheku.com> - 2025-03-18 19:11 +0000
Re: int a = a (Was: Bart's Language) David Brown <david.brown@hesbynett.no> - 2025-03-19 15:56 +0100
Re: int a = a (Was: Bart's Language) scott@slp53.sl.home (Scott Lurndal) - 2025-03-19 16:38 +0000
Re: int a = a (Was: Bart's Language) "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2025-03-19 14:29 -0700
Re: int a = a (Was: Bart's Language) David Brown <david.brown@hesbynett.no> - 2025-03-20 09:39 +0100
Re: int a = a (Was: Bart's Language) bart <bc@freeuk.com> - 2025-03-20 11:59 +0000
Re: int a = a (Was: Bart's Language) David Brown <david.brown@hesbynett.no> - 2025-03-20 15:46 +0100
Re: int a = a (Was: Bart's Language) wij <wyniijj5@gmail.com> - 2025-03-20 23:13 +0800
Re: int a = a (Was: Bart's Language) Tim Rentsch <tr.17687@z991.linuxsc.com> - 2025-03-20 02:02 -0700
Re: int a = a (Was: Bart's Language) David Brown <david.brown@hesbynett.no> - 2025-03-20 15:57 +0100
Re: int a = a (Was: Bart's Language) Kaz Kylheku <643-408-1753@kylheku.com> - 2025-03-19 17:07 +0000
Re: int a = a Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-03-19 13:34 -0700
Re: int a = a Tim Rentsch <tr.17687@z991.linuxsc.com> - 2025-03-20 02:54 -0700
Re: int a = a Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-03-20 03:20 -0700
Re: int a = a David Brown <david.brown@hesbynett.no> - 2025-03-20 16:22 +0100
Re: int a = a Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-03-20 12:46 -0700
Re: int a = a David Brown <david.brown@hesbynett.no> - 2025-03-21 10:44 +0100
Re: int a = a Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-03-21 12:23 -0700
Re: int a = a David Brown <david.brown@hesbynett.no> - 2025-03-21 21:46 +0100
Re: int a = a Tim Rentsch <tr.17687@z991.linuxsc.com> - 2025-03-22 13:59 -0700
Re: int a = a Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-03-22 15:37 -0700
Re: int a = a Tim Rentsch <tr.17687@z991.linuxsc.com> - 2025-04-28 09:39 -0700
Re: int a = a Tim Rentsch <tr.17687@z991.linuxsc.com> - 2025-04-29 13:12 -0700
Re: int a = a Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-04-29 13:34 -0700
Re: int a = a David Brown <david.brown@hesbynett.no> - 2025-03-20 15:42 +0100
Re: int a = a (Was: Bart's Language) scott@slp53.sl.home (Scott Lurndal) - 2025-03-18 19:37 +0000
Re: int a = a (Was: Bart's Language) David Brown <david.brown@hesbynett.no> - 2025-03-18 20:51 +0100
Re: int a = a (Was: Bart's Language) Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2025-03-18 23:27 +0100
Re: int a = a (Was: Bart's Language) David Brown <david.brown@hesbynett.no> - 2025-03-19 11:40 +0100
Re: int a = a (Was: Bart's Language) Tim Rentsch <tr.17687@z991.linuxsc.com> - 2025-03-18 23:52 -0700
Re: int a = a Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-03-19 01:55 -0700
Re: int a = a Tim Rentsch <tr.17687@z991.linuxsc.com> - 2025-04-27 13:41 -0700
Re: int a = a (Was: Bart's Language) David Brown <david.brown@hesbynett.no> - 2025-03-19 11:43 +0100
Re: int a = a (Was: Bart's Language) Rosario19 <Ros@invalid.invalid> - 2025-03-19 13:23 +0100
Re: int a = a (Was: Bart's Language) Tim Rentsch <tr.17687@z991.linuxsc.com> - 2025-03-20 01:32 -0700
Re: Bart's Language antispam@fricas.org (Waldek Hebisch) - 2025-03-20 22:55 +0000
Re: Bart's Language Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-03-20 16:22 -0700
Re: Bart's Language antispam@fricas.org (Waldek Hebisch) - 2025-03-22 14:37 +0000
Re: Bart's Language James Kuyper <jameskuyper@alumni.caltech.edu> - 2025-03-22 11:41 -0400
Re: Bart's Language antispam@fricas.org (Waldek Hebisch) - 2025-03-22 16:52 +0000
Re: Bart's Language James Kuyper <jameskuyper@alumni.caltech.edu> - 2025-03-22 20:12 -0400
By definition... (Was: Bart's Language) gazelle@shell.xmission.com (Kenny McCormack) - 2025-03-23 17:20 +0000
Re: Bart's Language Tim Rentsch <tr.17687@z991.linuxsc.com> - 2025-04-27 11:53 -0700
Re: Bart's Language Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-04-27 14:29 -0700
Re: Bart's Language Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-01-06 14:04 -0800
Re: Bart's Language Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-01-06 17:12 -0800
Re: Bart's Language Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-03-06 09:04 -0800
Re: Bart's Language bart <bc@freeuk.com> - 2025-03-18 22:19 +0000
Re: Bart's Language antispam@fricas.org (Waldek Hebisch) - 2025-03-20 22:38 +0000
Re: Bart's Language Kaz Kylheku <643-408-1753@kylheku.com> - 2025-03-20 23:45 +0000
Re: Bart's Language bart <bc@freeuk.com> - 2025-03-21 00:56 +0000
Re: Bart's Language Kaz Kylheku <643-408-1753@kylheku.com> - 2025-03-21 17:47 +0000
Re: Bart's Language Tim Rentsch <tr.17687@z991.linuxsc.com> - 2025-03-22 07:12 -0700
Re: Bart's Language bart <bc@freeuk.com> - 2025-03-21 00:33 +0000
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