Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]
| From | glen herrmannsfeldt <gah@ugcs.caltech.edu> |
|---|---|
| Newsgroups | comp.lang.c |
| Subject | Re: Pointer to structure |
| Date | 2014-12-22 06:23 +0000 |
| Organization | Aioe.org NNTP Server |
| Message-ID | <m78dd2$dvn$1@speranza.aioe.org> (permalink) |
| References | (3 earlier) <Iuzlw.227520$p95.10761@fx38.am4> <chine.bleu-CBB10B.05052221122014@news.eternal-september.org> <lHzlw.145625$c73.56007@fx27.am4> <m77prn$d50$1@speranza.aioe.org> <nkKlw.823906$DX.466140@fx06.iad> |
Richard Damon <Richard@damon-family.org> wrote:
(snip, I wrote)
>> There is a common C trick, likely UB in the standard, but usually
>> works, to declare an array, usually [1] at the end of the struct,
>> and then allocate it an apprropriate amount of memory.
>> struct ps {
>> char length;
>> char data[1];
>> }
>> int n=80;
>> struct ps *x=malloc(sizeof(*x)-1+n);
(snip)
> Actually, C99 codified something almost like this.
Last time I used it was before 1999.
Some years ago, I was using the Metagraphics package, which had
many structs that worked this way.
> struct ps {
> unsigned char length;
> char data[]; // Note, empty brackets
> };
> struct ps *x = malloc(sizeof(*x) + n);
> *x->length = n;
And it nicely avoids the -1 that is needed the other way.
-- glen
Back to comp.lang.c | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread
Pointer to structure Dexterr <dejangru@gmail.com> - 2014-12-21 03:16 -0800
Re: Pointer to structure BartC <bc@freeuk.com> - 2014-12-21 12:09 +0000
Re: Pointer to structure Siri Crews <chine.bleu@yahoo.com> - 2014-12-21 04:39 -0800
Re: Pointer to structure BartC <bc@freeuk.com> - 2014-12-21 12:59 +0000
Re: Pointer to structure Siri Crews <chine.bleu@yahoo.com> - 2014-12-21 05:05 -0800
Re: Pointer to structure BartC <bc@freeuk.com> - 2014-12-21 13:12 +0000
Re: Pointer to structure Siri Crews <chine.bleu@yahoo.com> - 2014-12-21 05:55 -0800
Re: Pointer to structure BartC <bc@freeuk.com> - 2014-12-21 14:31 +0000
Re: Pointer to structure Siri Crews <chine.bleu@yahoo.com> - 2014-12-21 06:47 -0800
Re: Pointer to structure BartC <bc@freeuk.com> - 2014-12-21 20:10 +0000
Re: Pointer to structure Geoff <geoff@invalid.invalid> - 2014-12-21 10:00 -0800
Re: Pointer to structure Ben Bacarisse <ben.usenet@bsb.me.uk> - 2014-12-21 22:44 +0000
Re: Pointer to structure raltbos@xs4all.nl (Richard Bos) - 2014-12-21 18:01 +0000
Re: Pointer to structure BartC <bc@freeuk.com> - 2014-12-21 21:21 +0000
Re: Pointer to structure raltbos@xs4all.nl (Richard Bos) - 2014-12-22 12:11 +0000
Re: Pointer to structure Ben Bacarisse <ben.usenet@bsb.me.uk> - 2014-12-21 22:36 +0000
Re: Pointer to structure Stephen Sprunk <stephen@sprunk.org> - 2014-12-27 17:56 -0600
Re: Pointer to structure Siri Crews <chine.bleu@yahoo.com> - 2014-12-27 16:33 -0800
Re: Pointer to structure Stephen Sprunk <stephen@sprunk.org> - 2015-01-15 12:29 -0600
Re: Pointer to structure glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2014-12-22 00:50 +0000
Re: Pointer to structure Richard Damon <Richard@Damon-Family.org> - 2014-12-21 20:19 -0500
Re: Pointer to structure glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2014-12-22 06:23 +0000
Re: Pointer to structure gazelle@shell.xmission.com (Kenny McCormack) - 2014-12-22 12:03 +0000
Re: Pointer to structure gazelle@shell.xmission.com (Kenny McCormack) - 2014-12-21 13:20 +0000
Re: Pointer to structure Siri Crews <chine.bleu@yahoo.com> - 2014-12-21 05:40 -0800
Re: Pointer to structure Ben Bacarisse <ben.usenet@bsb.me.uk> - 2014-12-21 13:16 +0000
Re: Pointer to structure Barry Schwarz <schwarzb@dqel.com> - 2014-12-21 10:02 -0800
Re: Pointer to structure Keith Thompson <kst-u@mib.org> - 2014-12-21 12:25 -0800
Re: Pointer to structure Dexterr <dejangru@gmail.com> - 2014-12-21 15:07 -0800
csiph-web