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| From | Ben Bacarisse <ben.usenet@bsb.me.uk> |
|---|---|
| Newsgroups | comp.lang.c |
| Subject | Re: Pointers as error values |
| Date | 2015-10-30 11:00 +0000 |
| Organization | A noiseless patient Spider |
| Message-ID | <87d1vwfwnr.fsf@bsb.me.uk> (permalink) |
| References | (4 earlier) <n08kk2$a6d$1@dont-email.me> <n0tfor$ek6$1@speranza.aioe.org> <9c00a627-ce2b-41bf-a970-c8672a25d914@googlegroups.com> <56329244.13725875@news.xs4all.nl> <n0uu22$d51$1@speranza.aioe.org> |
"Morten W. Petersen" <morphex@gmail.com> writes:
> On 29.10.2015 22:45, Richard Bos wrote:
<snip>
>> You could allocate an array of eight void *s, malloc() a single byte**
>> of memory for each, and compare to that. Each pointer is guaranteed to
>> be unique, different from all other valid objects; each pointer is
>> guaranteed not to be valid (but do remember to check for null returns
>> from malloc(), uproariously unlikely as they may be in this case); and
>> crucially, being void *s and returns from malloc(), each is guaranteed
>> to be maximally aligned.
>>
>> _Or_ you could be sensible and not abuse different pointer values as
>> error indicators.
>
> OK. But then it should be OK to allocate
>
> void *pointers[8] = {NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL};
>
> And do
>
> void *pointer = some_function();
> if (pointer >= &pointers && pointer <= &pointers+8) {
> Some code here
> }
>
> Right?
No, the types are wrong. There are various ways to do this but more
people are reluctant to put the effort in to writing it out as working
code because they don't think it's a good idea.
--
Ben.
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Pointers as error values "Morten W. Petersen" <morphex@gmail.com> - 2015-10-19 00:53 -0700
Re: Pointers as error values gazelle@shell.xmission.com (Kenny McCormack) - 2015-10-19 08:26 +0000
Re: Pointers as error values "Morten W. Petersen" <morphex@gmail.com> - 2015-10-19 02:27 -0700
Re: Pointers as error values Richard Damon <Richard@Damon-Family.org> - 2015-10-19 23:38 -0400
Re: Pointers as error values jacobnavia <jacob@jacob.remcomp.fr> - 2015-10-19 10:34 +0200
Re: Pointers as error values "Morten W. Petersen" <morphex@gmail.com> - 2015-10-19 02:29 -0700
Re: Pointers as error values mark.bluemel@gmail.com - 2015-10-19 05:53 -0700
Re: Pointers as error values glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-19 10:00 +0000
Re: Pointers as error values Jorgen Grahn <grahn+nntp@snipabacken.se> - 2015-10-19 14:00 +0000
Re: Pointers as error values gwowen <gwowen@gmail.com> - 2015-10-19 08:02 -0700
Re: Pointers as error values James Kuyper <jameskuyper@verizon.net> - 2015-10-19 11:53 -0400
Re: Pointers as error values Ken Brody <kenbrody@spamcop.net> - 2015-10-19 11:25 -0400
Re: Pointers as error values supercat@casperkitty.com - 2015-10-19 08:41 -0700
Re: Pointers as error values Keith Thompson <kst-u@mib.org> - 2015-10-19 08:59 -0700
Re: Pointers as error values "Morten W. Petersen" <morphex@gmail.com> - 2015-10-21 07:32 +0200
Re: Pointers as error values Ian Collins <ian-news@hotmail.com> - 2015-10-21 19:17 +1300
Re: Pointers as error values "Morten W. Petersen" <morphex@gmail.com> - 2015-10-21 08:31 +0200
Re: Pointers as error values Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-21 12:46 +0100
Re: Pointers as error values Robert Wessel <robertwessel2@yahoo.com> - 2015-10-21 09:35 -0500
Re: Pointers as error values Ken Brody <kenbrody@spamcop.net> - 2015-10-21 15:24 -0400
Re: Pointers as error values glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-22 05:44 +0000
Re: Pointers as error values Keith Thompson <kst-u@mib.org> - 2015-10-21 10:41 -0700
Re: Pointers as error values supercat@casperkitty.com - 2015-10-21 11:28 -0700
Re: Pointers as error values John Temples <usenet@xargs-spam.com> - 2015-10-21 17:45 +0000
Re: Pointers as error values James Kuyper <jameskuyper@verizon.net> - 2015-10-21 14:15 -0400
Re: Pointers as error values "Morten W. Petersen" <morphex@gmail.com> - 2015-10-29 16:59 +0100
Re: Pointers as error values supercat@casperkitty.com - 2015-10-29 12:35 -0700
Re: Pointers as error values raltbos@xs4all.nl (Richard Bos) - 2015-10-29 21:45 +0000
Re: Pointers as error values "Morten W. Petersen" <morphex@gmail.com> - 2015-10-30 06:09 +0100
Re: Pointers as error values Rosario19 <Ros@invalid.invalid> - 2015-10-30 08:59 +0100
Re: Pointers as error values Rosario19 <Ros@invalid.invalid> - 2015-10-30 09:07 +0100
Re: Pointers as error values Rosario19 <Ros@invalid.invalid> - 2015-10-30 09:38 +0100
Re: Pointers as error values Rosario19 <Ros@invalid.invalid> - 2015-10-30 09:40 +0100
Re: Pointers as error values Robert Wessel <robertwessel2@yahoo.com> - 2015-10-30 04:56 -0500
Re: Pointers as error values Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-30 11:00 +0000
Re: Pointers as error values Robert Wessel <robertwessel2@yahoo.com> - 2015-10-29 23:48 -0500
Re: Pointers as error values "Morten W. Petersen" <morphex@gmail.com> - 2015-10-30 11:05 +0100
Re: Pointers as error values Richard Damon <Richard@Damon-Family.org> - 2015-10-30 07:45 -0400
Re: Pointers as error values Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-10-30 05:04 -0700
Re: Pointers as error values "Morten W. Petersen" <morphex@gmail.com> - 2015-10-30 16:09 +0100
Re: Pointers as error values Keith Thompson <kst-u@mib.org> - 2015-10-30 11:16 -0700
Re: Pointers as error values glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-30 20:58 +0000
Re: Pointers as error values Eric Sosman <esosman@comcast-dot-net.invalid> - 2015-10-30 17:12 -0400
Re: Pointers as error values supercat@casperkitty.com - 2015-10-30 14:54 -0700
Re: Pointers as error values Robert Wessel <robertwessel2@yahoo.com> - 2015-10-30 18:48 -0500
Re: Pointers as error values glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-11-01 04:00 +0000
Re: Pointers as error values Robert Wessel <robertwessel2@yahoo.com> - 2015-11-01 01:24 -0500
Re: Pointers as error values "Morten W. Petersen" <morphex@gmail.com> - 2015-10-31 20:35 +0100
Re: Pointers as error values supercat@casperkitty.com - 2015-10-31 13:33 -0700
Re: Pointers as error values Richard Damon <Richard@Damon-Family.org> - 2015-10-30 22:19 -0400
Re: Pointers as error values supercat@casperkitty.com - 2015-10-30 08:22 -0700
Re: Pointers as error values Geoff <geoff@invalid.invalid> - 2015-10-30 13:11 -0700
Re: Pointers as error values Geoff <geoff@invalid.invalid> - 2015-10-30 13:23 -0700
Re: Pointers as error values Geoff <geoff@invalid.invalid> - 2015-10-21 11:13 -0700
Re: Pointers as error values Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-21 20:31 +0100
Re: Pointers as error values Geoff <geoff@invalid.invalid> - 2015-10-22 07:13 -0700
Re: Pointers as error values "Morten W. Petersen" <morphex@gmail.com> - 2015-10-26 07:16 +0100
Re: Pointers as error values Jorgen Grahn <grahn+nntp@snipabacken.se> - 2015-10-26 09:37 +0000
Re: Pointers as error values glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-22 05:38 +0000
Re: Pointers as error values Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-22 13:51 +0100
Re: Pointers as error values Keith Thompson <kst-u@mib.org> - 2015-10-22 08:29 -0700
Re: Pointers as error values supercat@casperkitty.com - 2015-10-22 09:21 -0700
Re: Pointers as error values Keith Thompson <kst-u@mib.org> - 2015-10-22 10:52 -0700
Re: Pointers as error values "Morten W. Petersen" <morphex@gmail.com> - 2015-10-26 07:20 +0100
Re: Pointers as error values Keith Thompson <kst-u@mib.org> - 2015-10-26 08:09 -0700
Re: Pointers as error values supercat@casperkitty.com - 2015-10-26 08:40 -0700
Re: Pointers as error values glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-26 20:02 +0000
Re: Pointers as error values supercat@casperkitty.com - 2015-10-26 13:56 -0700
Re: Pointers as error values glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-22 21:58 +0000
Re: Pointers as error values James Kuyper <jameskuyper@verizon.net> - 2015-10-22 19:12 -0400
Re: Pointers as error values asetofsymbols@gmail.com - 2015-10-22 18:36 -0700
Re: Pointers as error values asetofsymbols@gmail.com - 2015-10-29 12:47 -0700
Re: Pointers as error values Lőrinczy Zsigmond <nospam@for.me> - 2015-10-20 17:06 +0200
Re: Pointers as error values Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-20 19:45 +0100
Re: Pointers as error values supercat@casperkitty.com - 2015-10-20 14:19 -0700
Re: Pointers as error values glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-21 05:28 +0000
Re: Pointers as error values supercat@casperkitty.com - 2015-10-21 05:48 -0700
Re: Pointers as error values glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-22 05:52 +0000
Re: Pointers as error values Ken Brody <kenbrody@spamcop.net> - 2015-10-21 15:19 -0400
Re: Pointers as error values glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-22 06:06 +0000
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