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Groups > comp.lang.c > #166997
| From | Ben Bacarisse <ben.usenet@bsb.me.uk> |
|---|---|
| Newsgroups | comp.lang.c |
| Subject | Re: New features added into C23 standard |
| Date | 2022-07-30 17:31 +0100 |
| Organization | A noiseless patient Spider |
| Message-ID | <87wnbu8sv1.fsf@bsb.me.uk> (permalink) |
| References | (1 earlier) <a500a595-29ee-47b2-a5c0-e725c76b5a39n@googlegroups.com> <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> |
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! > The key problem with null pointers in C code is that "0" is a null > pointer as well as an integer constant. So it's easy to mix up these > very different purposes when writing or reading code. The only problem I see is not really a case of confusing the two, and that's using 0 in variable arguments where a pointer is expected. Here, nullptr wins over the NULL because, at least technically, NULL might be plain 0 (or some other constant integer expression) The lowest impact change would have been to require the expansion of NULL to be an expression of type void *. But I think the new committee is inclined to go the C++ route: more changes, and more alignment, even at the cost of some code breakage. > (Let's be honest here - most null pointers in real code are written > "0", not "NULL".) Technically, using NULL is not a fix, since NULL /could/ expand to 0. No implementation I know of does this (because of the var args problem) but it's possible. Using NULL might avoid what you see as the possibility of confusing the two uses, but then I don't think I've come across that. > If you get in the habit of using "nullptr" as your null pointer, that > mixup is gone. And your tools can check this, giving a warning > whenever "0" is used in the context of a pointer. Bu the only case that really matters can't be warned against. > "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...) -- Ben.
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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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