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Groups > comp.lang.c > #151903
| From | Keith Thompson <Keith.S.Thompson+u@gmail.com> |
|---|---|
| Newsgroups | comp.lang.c |
| Subject | Re: longer 'char literals' meaning in c |
| Date | 2020-04-30 18:55 -0700 |
| Organization | None to speak of |
| Message-ID | <87lfmc4dwh.fsf@nosuchdomain.example.com> (permalink) |
| References | (5 earlier) <znHqG.187261$vn2.19120@fx34.am4> <874kt061yl.fsf@nosuchdomain.example.com> <oNIqG.282039$QJp.69102@fx08.am4> <87tv104ij2.fsf@nosuchdomain.example.com> <4lKqG.254784$mk2.321@fx21.am4> |
Bart <bc@freeuk.com> writes:
> On 01/05/2020 01:15, Keith Thompson wrote:
>> Bart <bc@freeuk.com> writes:
>>> On 30/04/2020 23:30, Keith Thompson wrote:
>> [...]
>>>> There is no specified limit on the number of characters in a
>>>> multi-character constant.
>>>
>>> I don't agree with that. If the extra characters can't be used and
>>> shouldn't be there, then that's an error in my book. DMC agrees, and
>>> further it explicitly states a maximum of 4 characters.
>>
>> What exactly do you disagree with?
>>
>> The C standard does not impose a limit on the number of characters in a
>> multi-character constant. If you disagree with that, cite the wording
>> in the standard that imposes such a limit.
>
> '6.4.4.4p10 An integer character constant has type int.'
>
> That suggests that you cannot practically have more than sizeof(int)
> characters in a character constant. Practically in being able to store
> and remember the values.
If the C standard were to impose a limit, it wouldn't and shouldn't
do so by some vague suggestion. For there to be an actual limit
on the number of characters in a multi-character constant, there
would have to be either a syntax rule or a constraint that 'ABCDE'
would violate. There isn't.
Imagine an implementation in which the value of '11001001' is 201 (i.e.,
it's binary). That might be silly, but it would be conforming. So
would an implementation where 'three' == 3. It's well within what
"implementation-defined" means, as long as it's documented.
The reason the standard makes the value implementation-defined is
that, when the standard was being written, there were implementations
that did it differently. Requiring the value to be sensible,
say by restricting it a choice from what actual compilers did,
would have been substantially more effort with no real benefit.
Making the value simply implementation-defined means that (a) you
can use multi-character constants in non-portable code, and (b)
you can't meaningfully use them in portable code. Banning 'ABCDE'
when int is 32 bits would not have changed that.
From a programmer's point of view, the solution is simple: Don't use
multi-character constants. From an implementer's point of view, the
solution is equally simple: Implement the requirements from the
standard, and document how the value is determined.
> You're probably thinking of being allowed to write any number of
> characters between '...' quotes, subject to receiving or inhibiting a
> warning, but you can only store and remember 4 or those, either the
> first 4 or the last 4.
Sure, that's one possibility. But what I was actually thinking of is
simply that the value of a multi-character constant is
implementation-defined. The standard doesn't even suggest that the
value should be computed from the values of the characters. I
understand that you *want* the value to be computed in some sensible way
from the values of the individual characters, but the standard doesn't
require or suggest it.
Just in case you misunderstood, I am *not* suggesting that a character
constant like 'ABCDEFGHIJKLMNOPQRSTUVWXYZ' is useful, merely that the
language standard does not permit a conforming compiler to reject it.
I don't want my compiler to reject code because it thinks it's icky --
unless I've asked it to.
> My compiler and at least DMC don't allow that, in my case as I can't
> see the point. (I do allow 8, as then the type is 'long long int', but
> that makes code non-portable outside my compiler, so it's not useful,
> other than to show off.)
Again, you're under no obligation to make your C compiler conforming.
You snipped my questions about exactly what DMC does. I'm still curious
about that.
--
Keith Thompson (The_Other_Keith) Keith.S.Thompson+u@gmail.com
Working, but not speaking, for Philips Healthcare
void Void(void) { Void(); } /* The recursive call of the void */
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longer 'char literals' meaning in c fir <profesor.fir@gmail.com> - 2020-04-30 04:43 -0700
Re: longer 'char literals' meaning in c Bonita Montero <Bonita.Montero@gmail.com> - 2020-04-30 13:55 +0200
Re: longer 'char literals' meaning in c fir <profesor.fir@gmail.com> - 2020-04-30 05:17 -0700
Re: longer 'char literals' meaning in c fir <profesor.fir@gmail.com> - 2020-04-30 05:22 -0700
Re: longer 'char literals' meaning in c fir <profesor.fir@gmail.com> - 2020-04-30 05:24 -0700
Re: longer 'char literals' meaning in c fir <profesor.fir@gmail.com> - 2020-04-30 05:29 -0700
Re: longer 'char literals' meaning in c fir <profesor.fir@gmail.com> - 2020-04-30 06:16 -0700
Re: longer 'char literals' meaning in c fir <profesor.fir@gmail.com> - 2020-04-30 05:44 -0700
Re: longer 'char literals' meaning in c Bart <bc@freeuk.com> - 2020-04-30 14:00 +0100
Re: longer 'char literals' meaning in c fir <profesor.fir@gmail.com> - 2020-04-30 06:13 -0700
Re: longer 'char literals' meaning in c Bart <bc@freeuk.com> - 2020-04-30 14:41 +0100
Re: longer 'char literals' meaning in c fir <profesor.fir@gmail.com> - 2020-04-30 07:18 -0700
Re: longer 'char literals' meaning in c fir <profesor.fir@gmail.com> - 2020-04-30 07:31 -0700
Re: longer 'char literals' meaning in c Spiros Bousbouras <spibou@gmail.com> - 2020-04-30 15:49 +0000
Re: longer 'char literals' meaning in c fir <profesor.fir@gmail.com> - 2020-04-30 09:12 -0700
Re: longer 'char literals' meaning in c Bart <bc@freeuk.com> - 2020-04-30 15:49 +0100
Re: longer 'char literals' meaning in c fir <profesor.fir@gmail.com> - 2020-04-30 08:31 -0700
Re: longer 'char literals' meaning in c Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-04-30 14:00 -0700
Re: longer 'char literals' meaning in c Spiros Bousbouras <spibou@gmail.com> - 2020-04-30 21:16 +0000
Re: longer 'char literals' meaning in c Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-04-30 15:22 -0700
Re: longer 'char literals' meaning in c James Kuyper <jameskuyper@alumni.caltech.edu> - 2020-04-30 18:36 -0400
Re: longer 'char literals' meaning in c Bart <bc@freeuk.com> - 2020-04-30 22:25 +0100
Re: longer 'char literals' meaning in c Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-04-30 15:30 -0700
Re: longer 'char literals' meaning in c Bart <bc@freeuk.com> - 2020-05-01 00:01 +0100
Re: longer 'char literals' meaning in c fir <profesor.fir@gmail.com> - 2020-04-30 16:15 -0700
Re: longer 'char literals' meaning in c fir <profesor.fir@gmail.com> - 2020-04-30 16:29 -0700
Re: longer 'char literals' meaning in c Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-04-30 17:15 -0700
Re: longer 'char literals' meaning in c Bart <bc@freeuk.com> - 2020-05-01 01:47 +0100
Re: longer 'char literals' meaning in c James Kuyper <jameskuyper@alumni.caltech.edu> - 2020-04-30 18:38 -0700
Re: longer 'char literals' meaning in c Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-04-30 18:55 -0700
Re: longer 'char literals' meaning in c Bart <bc@freeuk.com> - 2020-05-01 11:35 +0100
Re: longer 'char literals' meaning in c James Kuyper <jameskuyper@alumni.caltech.edu> - 2020-05-01 05:47 -0700
Re: longer 'char literals' meaning in c fir <profesor.fir@gmail.com> - 2020-05-01 06:15 -0700
Re: longer 'char literals' meaning in c Bart <bc@freeuk.com> - 2020-05-01 15:53 +0100
Re: longer 'char literals' meaning in c Richard Damon <Richard@Damon-Family.org> - 2020-05-01 12:38 -0400
Re: longer 'char literals' meaning in c Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-05-01 09:57 -0700
Re: longer 'char literals' meaning in c Bart <bc@freeuk.com> - 2020-05-01 20:50 +0100
Re: longer 'char literals' meaning in c Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-05-01 13:11 -0700
Re: longer 'char literals' meaning in c jameskuyper@stellarscience.com - 2020-05-01 12:05 -0700
Re: longer 'char literals' meaning in c James Kuyper <jameskuyper@alumni.caltech.edu> - 2020-05-01 19:08 -0400
Re: longer 'char literals' meaning in c Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-05-01 09:51 -0700
Re: longer 'char literals' meaning in c David Brown <david.brown@hesbynett.no> - 2020-05-02 15:22 +0200
Re: longer 'char literals' meaning in c Richard Damon <Richard@Damon-Family.org> - 2020-05-02 12:13 -0400
Re: longer 'char literals' meaning in c Les Cargill <lcargill99@comcast.com> - 2020-05-04 00:17 -0500
Re: longer 'char literals' meaning in c James Kuyper <jameskuyper@alumni.caltech.edu> - 2020-05-04 10:51 -0400
Re: longer 'char literals' meaning in c James Kuyper <jameskuyper@alumni.caltech.edu> - 2020-05-04 10:23 -0400
Re: longer 'char literals' meaning in c David Brown <david.brown@hesbynett.no> - 2020-05-04 16:48 +0200
Re: longer 'char literals' meaning in c James Kuyper <jameskuyper@alumni.caltech.edu> - 2020-05-04 12:39 -0400
Re: longer 'char literals' meaning in c David Brown <david.brown@hesbynett.no> - 2020-05-04 19:37 +0200
Re: longer 'char literals' meaning in c James Kuyper <jameskuyper@alumni.caltech.edu> - 2020-05-04 15:03 -0400
Re: longer 'char literals' meaning in c David Brown <david.brown@hesbynett.no> - 2020-05-05 08:33 +0200
Re: longer 'char literals' meaning in c James Kuyper <jameskuyper@alumni.caltech.edu> - 2020-05-05 09:47 -0400
Re: longer 'char literals' meaning in c David Brown <david.brown@hesbynett.no> - 2020-05-05 16:22 +0200
Re: longer 'char literals' meaning in c Tim Rentsch <tr.17687@z991.linuxsc.com> - 2020-05-04 10:27 -0700
Re: longer 'char literals' meaning in c antispam@math.uni.wroc.pl - 2020-05-05 00:47 +0000
Re: longer 'char literals' meaning in c Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-05-04 20:08 -0700
Re: longer 'char literals' meaning in c James Kuyper <jameskuyper@alumni.caltech.edu> - 2020-05-04 23:52 -0400
Re: longer 'char literals' meaning in c antispam@math.uni.wroc.pl - 2020-05-05 17:10 +0000
Re: longer 'char literals' meaning in c Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-05-05 13:41 -0700
Re: longer 'char literals' meaning in c antispam@math.uni.wroc.pl - 2020-05-05 22:29 +0000
Re: longer 'char literals' meaning in c Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-05-05 16:18 -0700
Re: longer 'char literals' meaning in c antispam@math.uni.wroc.pl - 2020-05-06 02:33 +0000
Re: longer 'char literals' meaning in c Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-05-05 20:06 -0700
Re: longer 'char literals' meaning in c antispam@math.uni.wroc.pl - 2020-05-06 18:57 +0000
Re: longer 'char literals' meaning in c Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-05-06 13:37 -0700
Re: longer 'char literals' meaning in c Spiros Bousbouras <spibou@gmail.com> - 2020-05-07 13:48 +0000
Re: longer 'char literals' meaning in c Spiros Bousbouras <spibou@gmail.com> - 2020-05-07 13:58 +0000
Re: longer 'char literals' meaning in c Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-05-07 18:01 -0700
Re: longer 'char literals' meaning in c James Kuyper <jameskuyper@alumni.caltech.edu> - 2020-05-05 20:18 -0400
Re: longer 'char literals' meaning in c antispam@math.uni.wroc.pl - 2020-05-06 20:01 +0000
Re: longer 'char literals' meaning in c James Kuyper <jameskuyper@alumni.caltech.edu> - 2020-05-06 18:20 -0400
Re: longer 'char literals' meaning in c Siri Cruise <chine.bleu@yahoo.com> - 2020-04-30 20:13 -0700
Re: longer 'char literals' meaning in c Bonita Montero <Bonita.Montero@gmail.com> - 2020-04-30 16:58 +0200
Re: longer 'char literals' meaning in c Bonita Montero <Bonita.Montero@gmail.com> - 2020-04-30 16:59 +0200
Re: longer 'char literals' meaning in c Bonita Montero <Bonita.Montero@gmail.com> - 2020-04-30 17:14 +0200
Re: longer 'char literals' meaning in c fir <profesor.fir@gmail.com> - 2020-04-30 08:33 -0700
Re: longer 'char literals' meaning in c Bonita Montero <Bonita.Montero@gmail.com> - 2020-04-30 18:15 +0200
Re: longer 'char literals' meaning in c James Kuyper <jameskuyper@alumni.caltech.edu> - 2020-04-30 08:33 -0700
Re: longer 'char literals' meaning in c David Brown <david.brown@hesbynett.no> - 2020-04-30 17:49 +0200
Re: longer 'char literals' meaning in c Bart <bc@freeuk.com> - 2020-04-30 17:23 +0100
Re: longer 'char literals' meaning in c fir <profesor.fir@gmail.com> - 2020-04-30 09:38 -0700
Re: longer 'char literals' meaning in c Bart <bc@freeuk.com> - 2020-04-30 17:56 +0100
Re: longer 'char literals' meaning in c fir <profesor.fir@gmail.com> - 2020-04-30 10:04 -0700
Re: longer 'char literals' meaning in c Bart <bc@freeuk.com> - 2020-04-30 18:28 +0100
Re: longer 'char literals' meaning in c fir <profesor.fir@gmail.com> - 2020-04-30 10:39 -0700
Re: longer 'char literals' meaning in c Bart <bc@freeuk.com> - 2020-04-30 19:16 +0100
Re: longer 'char literals' meaning in c fir <profesor.fir@gmail.com> - 2020-04-30 11:24 -0700
Re: longer 'char literals' meaning in c Bart <bc@freeuk.com> - 2020-04-30 19:58 +0100
Re: longer 'char literals' meaning in c fir <profesor.fir@gmail.com> - 2020-04-30 12:08 -0700
Re: longer 'char literals' meaning in c Bart <bc@freeuk.com> - 2020-04-30 20:16 +0100
Re: longer 'char literals' meaning in c fir <profesor.fir@gmail.com> - 2020-04-30 12:29 -0700
Re: longer 'char literals' meaning in c fir <profesor.fir@gmail.com> - 2020-04-30 12:10 -0700
Re: longer 'char literals' meaning in c fir <profesor.fir@gmail.com> - 2020-04-30 11:17 -0700
Re: longer 'char literals' meaning in c fir <profesor.fir@gmail.com> - 2020-04-30 10:31 -0700
Re: longer 'char literals' meaning in c Bart <bc@freeuk.com> - 2020-04-30 19:20 +0100
Re: longer 'char literals' meaning in c fir <profesor.fir@gmail.com> - 2020-04-30 11:28 -0700
Re: longer 'char literals' meaning in c Richard Damon <Richard@Damon-Family.org> - 2020-04-30 13:48 -0400
Re: longer 'char literals' meaning in c fir <profesor.fir@gmail.com> - 2020-04-30 09:01 -0700
Re: longer 'char literals' meaning in c Vir Campestris <vir.campestris@invalid.invalid> - 2020-04-30 21:32 +0100
Re: longer 'char literals' meaning in c fir <profesor.fir@gmail.com> - 2020-04-30 13:43 -0700
Re: longer 'char literals' meaning in c Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2020-04-30 16:54 -0400
Re: longer 'char literals' meaning in c Vir Campestris <vir.campestris@invalid.invalid> - 2020-05-03 21:23 +0100
Re: longer 'char literals' meaning in c Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2020-05-03 16:48 -0400
Re: longer 'char literals' meaning in c fir <profesor.fir@gmail.com> - 2020-04-30 11:38 -0700
Re: longer 'char literals' meaning in c fir <profesor.fir@gmail.com> - 2020-04-30 11:57 -0700
Re: longer 'char literals' meaning in c Bonita Montero <Bonita.Montero@gmail.com> - 2020-04-30 21:01 +0200
Re: longer 'char literals' meaning in c Bart <bc@freeuk.com> - 2020-04-30 20:07 +0100
Re: longer 'char literals' meaning in c fir <profesor.fir@gmail.com> - 2020-04-30 12:41 -0700
Re: longer 'char literals' meaning in c Tim Rentsch <tr.17687@z991.linuxsc.com> - 2020-05-04 10:30 -0700
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