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Groups > comp.lang.c > #167002
| From | Keith Thompson <Keith.S.Thompson+u@gmail.com> |
|---|---|
| Newsgroups | comp.lang.c |
| Subject | Re: New features added into C23 standard |
| Date | 2022-07-30 16:46 -0700 |
| Organization | None to speak of |
| Message-ID | <87ilnew4dn.fsf@nosuchdomain.example.com> (permalink) |
| References | (2 earlier) <fb562391-0bbe-488d-a89f-edc676e703b7n@googlegroups.com> <87mtcwzwt9.fsf@nosuchdomain.example.com> <40f5c874-ba25-4020-98a0-b6ce01b38dban@googlegroups.com> <tc3903$3rs12$1@dont-email.me> <87wnbu8sv1.fsf@bsb.me.uk> |
Ben Bacarisse <ben.usenet@bsb.me.uk> writes:
> David Brown <david.brown@hesbynett.no> writes:
>
>> On 26/07/2022 00:51, Thiago Adams wrote:
>>> On Monday, July 25, 2022 at 6:50:41 PM UTC-3, Keith Thompson wrote:
>>>> Thiago Adams <thiago...@gmail.com> writes:
>>>>> On Monday, July 25, 2022 at 5:49:30 PM UTC-3, Thiago Adams wrote:
>>>>>> It's hard to believe how nullptr was accepted.
>>>>>> https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3039.htm
>>>>>> The same for auto and constexpr.
>>>>>
>>>>> In 2018 I suggested nullptr
>>>>>
>>>>> https://groups.google.com/g/comp.lang.c/c/YJmom4rC2FI/m/DJzGmwXmCQAJ
>>>>>
>>>>> In 2019 I replied my own message saying that was a bad idea.
>>>>> https://groups.google.com/g/comp.lang.c/c/YJmom4rC2FI/m/Daz0AvxHAwAJ
>>>>>
>>>>> I agree with myself from 2019.
>>>>> "
>>>>> One difference between adding _Bool into the language is that BOOL
>>>>> was never added into the language headers. (Am I right? I didn't find
>>>>> BOOL or TRUE FALSE at the language specification).
>>>>>
>>>>> On the other hand if you search for NULL at the standard you will
>>>>> find that NULL is defined in stddef.h
>>>>>
>>>>> This means that adding _Bool didn't added a new way to declare booleans,
>>>>> but adding nullptr will create this confusion that is two ways of
>>>>> writing code that means NULL.
>>>>>
>>>>> In C we also have different ((void*)0) conversion rules compared with
>>>>> C++ that is more strict.
>>>>>
>>>>> Then for C, I believe that the literal that corresponds nullptr already
>>>>> exists and it is ((void*)0).
>>>>>
>>>>> What could be done is adding flags to static analysis to decide what
>>>>> to do with ((void*)0) conversions.
>>>>> "
>>>> I don't see the problem. There are already arbitrarily many ways to
>>>> write a null pointer constant in C. For example, '\0' '-'-'-', and
>>>> 0x0ULL are all null pointer constants.
>>>>
>>>> A null pointer constant can be of any integer type, or of type void*.
>>>>
>>>> Adding nullptr and nullptr_t adds one more form of null pointer
>>>> constant, and an unambiguous type for nullptr. Of course NULL and
>>>> (void*)0 are still valid, because invalidating them would break tons of
>>>> existing code -- but nullptr is the new preferred way to write a null
>>>> pointer constant. Old code is still valid, but new code can be cleaner
>>>> -- and if a user writes nullptr, there's no question that it was
>>>> *intended* to be a null pointer constant, which could result in clearer
>>>> diagnostic messages.
>>>>
>>>> (It's likely that if the language were being defined from scratch,
>>>> nullptr would be the *only* way to write a null pointer constant. The
>>>> stuff about using integer constant expressions exists only for backward
>>>> compatibility, and we're stuck with it.)
>>>>
>>> I cannot see any problem with (void*) 0.
>>> Apparently this was considered but I didn't found details about the problem.
>>> "After WG14 refused a specification for a simple macro with value (void*)0, as well as a sophisticated
>>> version with an incomplete type and with a rewriting approach for many contexts, this new version tries
>>> a middle ground."
>>> I never see anyone complaining or having bugs with NULL. And the original motivation
>>> for C++ was different.
>>
>> As I see it, the point of "nullptr" is not because there is something
>> wrong with NULL, 0, or "(void*) 0". It is because "nullptr" is
>> /better/, and gives you a clearer way to write your code, more
>> opportunities for checking, and thus lower risk of errors in your code
>> (for those that take advantage of the new feature and appropriate
>> tools). It does this without affecting existing code.
>
> Except for those programs that have decided to use that perfectly
> ordinary name!
Right. I wonder how much code defines nullptr as an identifer. I
suspect it's not much, especially given that it's a keyword in C++.
Except that I can imagine some programmers might do something like
#define nullptr ((void*)0)
just because they like the name. But a macro definition likely
wouldn't cause any problems.
[...]
>> "nullptr" is not as useful in C as it is in C++, since there is no
>> function overloading and thus no need to determine if "foo(0)" meant
>> an integer parameter or a pointer parameter, but it might still be
>> handy with _Generic.
>
> How? (I've not see the new draft so there may be something I',
> missing...)
nullptr is of the distinct type nullptr_t, which is a scalar type but
not a pointer or integer type, so a generic selection might have to
account for it.
(nullptr_t is not a keyword; rather it's defined in <stddef.h> as
something like `typeof(nullptr)`).
--
Keith Thompson (The_Other_Keith) Keith.S.Thompson+u@gmail.com
Working, but not speaking, for Philips
void Void(void) { Void(); } /* The recursive call of the void */
Back to comp.lang.c | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread
New features added into C23 standard Thiago Adams <thiago.adams@gmail.com> - 2022-07-22 12:32 -0700
Re: New features added into C23 standard Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-07-22 23:15 +0100
Re: New features added into C23 standard Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2022-07-23 01:31 -0700
Re: New features added into C23 standard gazelle@shell.xmission.com (Kenny McCormack) - 2022-07-23 10:10 +0000
Re: New features added into C23 standard Thiago Adams <thiago.adams@gmail.com> - 2022-07-25 13:49 -0700
Re: New features added into C23 standard Thiago Adams <thiago.adams@gmail.com> - 2022-07-25 13:57 -0700
Re: New features added into C23 standard Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-07-25 14:50 -0700
Re: New features added into C23 standard Thiago Adams <thiago.adams@gmail.com> - 2022-07-25 15:51 -0700
Re: New features added into C23 standard Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-07-25 18:04 -0700
Re: New features added into C23 standard Thiago Adams <thiago.adams@gmail.com> - 2022-07-25 19:23 -0700
Re: New features added into C23 standard Opus <ifonly@youknew.org> - 2022-07-26 05:13 +0200
Re: New features added into C23 standard Richard Damon <Richard@Damon-Family.org> - 2022-07-25 23:36 -0400
Re: New features added into C23 standard Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-07-25 21:52 -0700
Re: New features added into C23 standard Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-07-26 11:44 -0700
Re: New features added into C23 standard Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-07-26 11:39 -0700
Re: New features added into C23 standard David Brown <david.brown@hesbynett.no> - 2022-07-30 14:42 +0200
Re: New features added into C23 standard scott@slp53.sl.home (Scott Lurndal) - 2022-07-30 15:18 +0000
Re: New features added into C23 standard Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2022-07-30 09:13 -0700
Re: New features added into C23 standard Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-07-30 17:31 +0100
Re: New features added into C23 standard Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-07-30 16:46 -0700
Re: New features added into C23 standard Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-07-30 14:36 -0700
Re: New features added into C23 standard Richard Damon <Richard@Damon-Family.org> - 2022-07-30 18:15 -0400
Re: New features added into C23 standard Kaz Kylheku <480-992-1380@kylheku.com> - 2022-07-30 23:28 +0000
Re: New features added into C23 standard Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-07-31 16:48 -0700
Re: New features added into C23 standard Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2022-07-31 22:42 -0700
Re: New features added into C23 standard Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-07-31 23:25 -0700
Re: New features added into C23 standard Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2022-08-01 00:10 -0700
Re: New features added into C23 standard David Brown <david.brown@hesbynett.no> - 2022-08-01 09:55 +0200
Re: New features added into C23 standard Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-08-01 20:17 +0100
Re: New features added into C23 standard Kaz Kylheku <480-992-1380@kylheku.com> - 2022-07-30 23:21 +0000
Re: New features added into C23 standard Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2022-07-25 22:59 -0700
Re: New features added into C23 standard Öö Tiib <ootiib@hot.ee> - 2022-07-26 00:48 -0700
Re: New features added into C23 standard Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2022-07-26 02:08 -0700
Re: New features added into C23 standard Richard Damon <Richard@Damon-Family.org> - 2022-07-26 06:59 -0400
Re: New features added into C23 standard Öö Tiib <ootiib@hot.ee> - 2022-07-26 04:02 -0700
Re: New features added into C23 standard Vir Campestris <vir.campestris@invalid.invalid> - 2022-07-29 21:18 +0100
Re: New features added into C23 standard Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-07-29 16:55 -0700
Re: New features added into C23 standard Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-07-26 11:51 -0700
Re: New features added into C23 standard David Brown <david.brown@hesbynett.no> - 2022-07-31 11:12 +0200
Re: New features added into C23 standard Richard Damon <Richard@Damon-Family.org> - 2022-07-31 07:40 -0400
Re: New features added into C23 standard Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-07-31 17:40 +0100
Re: New features added into C23 standard Richard Damon <Richard@Damon-Family.org> - 2022-07-31 12:56 -0400
Re: New features added into C23 standard Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-07-31 19:28 +0100
Re: New features added into C23 standard Richard Damon <Richard@Damon-Family.org> - 2022-07-31 14:52 -0400
Re: New features added into C23 standard Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-07-31 21:35 +0100
Re: New features added into C23 standard Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-08-15 23:24 -0700
Re: New features added into C23 standard Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-07-31 16:57 -0700
Re: New features added into C23 standard Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-07-31 16:55 -0700
Re: New features added into C23 standard Richard Damon <Richard@Damon-Family.org> - 2022-07-31 20:09 -0400
Re: New features added into C23 standard Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-08-15 22:52 -0700
Re: New features added into C23 standard David Brown <david.brown@hesbynett.no> - 2022-08-16 09:21 +0200
Re: New features added into C23 standard Philipp Klaus Krause <pkk@spth.de> - 2022-08-16 09:32 +0200
Re: New features added into C23 standard David Brown <david.brown@hesbynett.no> - 2022-08-16 11:06 +0200
Re: New features added into C23 standard Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-08-15 23:17 -0700
Re: New features added into C23 standard Richard Damon <Richard@Damon-Family.org> - 2022-08-17 20:11 -0400
Re: New features added into C23 standard Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-08-17 20:08 -0700
Re: New features added into C23 standard Richard Damon <Richard@Damon-Family.org> - 2022-08-17 23:19 -0400
Re: New features added into C23 standard Kaz Kylheku <480-992-1380@kylheku.com> - 2022-08-18 07:03 +0000
Re: New features added into C23 standard Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-08-23 09:43 -0700
Re: New features added into C23 standard Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-08-23 11:02 -0700
Re: New features added into C23 standard Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-08-23 13:40 -0700
Re: New features added into C23 standard Richard Damon <Richard@Damon-Family.org> - 2022-07-26 07:04 -0400
Re: New features added into C23 standard Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2022-07-26 05:24 -0700
Re: New features added into C23 standard Richard Damon <Richard@Damon-Family.org> - 2022-07-26 22:30 -0400
Re: New features added into C23 standard Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-07-29 00:02 +0100
Re: New features added into C23 standard Richard Damon <Richard@Damon-Family.org> - 2022-07-28 21:20 -0400
Re: New features added into C23 standard William Ahern <william@25thandClement.com> - 2022-07-28 19:36 -0700
Re: New features added into C23 standard scott@slp53.sl.home (Scott Lurndal) - 2022-07-29 16:39 +0000
Re: New features added into C23 standard Richard Damon <Richard@Damon-Family.org> - 2022-07-29 18:55 -0400
Re: New features added into C23 standard Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-07-29 15:17 +0100
Re: New features added into C23 standard scott@slp53.sl.home (Scott Lurndal) - 2022-07-26 13:27 +0000
Re: New features added into C23 standard Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-07-26 11:47 -0700
Re: New features added into C23 standard Kaz Kylheku <480-992-1380@kylheku.com> - 2022-07-26 20:27 +0000
Re: New features added into C23 standard Philipp Klaus Krause <pkk@spth.de> - 2022-08-16 08:42 +0200
Re: New features added into C23 standard Bonita Montero <Bonita.Montero@gmail.com> - 2022-07-26 05:37 +0200
Re: New features added into C23 standard Lynn McGuire <lynnmcguire5@gmail.com> - 2022-07-28 16:47 -0500
Re: New features added into C23 standard Bonita Montero <Bonita.Montero@gmail.com> - 2022-07-29 07:14 +0200
Re: New features added into C23 standard Vir Campestris <vir.campestris@invalid.invalid> - 2022-07-29 21:21 +0100
Re: New features added into C23 standard Grant Mulholland <grantlmul@gmail.com> - 2022-08-13 22:21 -0700
Re: New features added into C23 standard Lynn McGuire <lynnmcguire5@gmail.com> - 2022-08-15 21:21 -0500
Re: New features added into C23 standard Bonita Montero <Bonita.Montero@gmail.com> - 2022-08-16 08:39 +0200
Re: New features added into C23 standard Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-08-15 22:54 -0700
Re: New features added into C23 standard Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-08-18 12:03 -0700
Re: New features added into C23 standard "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2022-08-18 12:56 -0700
Re: New features added into C23 standard William Ahern <william@25thandClement.com> - 2022-08-18 16:07 -0700
Re: New features added into C23 standard Thiago Adams <thiago.adams@gmail.com> - 2022-08-18 18:47 -0700
Re: New features added into C23 standard Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-08-18 20:23 -0700
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