Re: Data alignment questin, structures

From	glen herrmannsfeldt <gah@ugcs.caltech.edu>
Newsgroups	comp.lang.c
Subject	Re: Data alignment questin, structures
Date	2013-01-21 20:53 +0000
Organization	Aioe.org NNTP Server
Message-ID	<kdk9re$fd4$1@speranza.aioe.org> (permalink)
References	(5 earlier) <kdhct5$bmb$1@dont-email.me> <kdhlfn$6fc$1@dont-email.me> <kdig35$1m1$1@dont-email.me> <kdik6p$hc5$1@dont-email.me> <87vcaqkfx9.fsf@temporary-address.org.uk>

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Dr Nick <nospam-4@temporary-address.org.uk> wrote:

(snip)

> Structures are one of the areas where I think C has ended up in a rather
> strange place.  They don't (as discussed here) work for mapping memory
> to abstract data types and they don't work quite as well as they could
> do for structuring program data.

> I'd love to see something where I could tell the compiler "I've got
> zillions of these things in my program, please order them in the most
> memory efficient way" or "this is master configuration data that will be
> used all over the place but there's only one copy, so optimise for rapid
> access".  

Fortran theoretically can do this by default for structures.
There is the SEQUENCE attribute when you don't want it to reorder
stucture members, though I don't know of any compilers that actually
do reorder them. Then there is the BIND(C) attribute when you want
it done exactly like C.

> But in both cases I could lay out the structure when defined
> in a way that made the code as self-documenting as possible.

> Forcing my ordering, but allowing for indeterminate padding leaves us
> somewhere between two stools.

Isn't that usual for any compromise?

-- glen

Thread

Data alignment questin, structures mathog <mathog@caltech.edu> - 2013-01-12 10:15 -0800
  Re: Data alignment questin, structures Ben Bacarisse <ben.usenet@bsb.me.uk> - 2013-01-12 18:54 +0000
    Re: Data alignment questin, structures Jorgen Grahn <grahn+nntp@snipabacken.se> - 2013-01-15 20:14 +0000
      Re: Data alignment questin, structures Eric Sosman <esosman@comcast-dot-net.invalid> - 2013-01-15 16:29 -0500
  Re: Data alignment questin, structures Eric Sosman <esosman@comcast-dot-net.invalid> - 2013-01-12 15:41 -0500
    Re: Data alignment questin, structures mathog <dmathog@gmail.com> - 2013-01-18 10:24 -0800
      Re: Data alignment questin, structures James Kuyper <jameskuyper@verizon.net> - 2013-01-18 14:05 -0500
      Re: Data alignment questin, structures Eric Sosman <esosman@comcast-dot-net.invalid> - 2013-01-18 14:46 -0500
      Re: Data alignment questin, structures glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2013-01-18 21:11 +0000
      Re: Data alignment questin, structures Shao Miller <sha0.miller@gmail.com> - 2013-01-18 17:14 -0500
        Re: Data alignment questin, structures glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2013-01-18 23:09 +0000
      Re: Data alignment questin, structures Keith Thompson <kst-u@mib.org> - 2013-01-18 16:23 -0800
      Re: Data alignment questin, structures mathog <mathog@caltech.edu> - 2013-01-19 21:02 -0800
        Re: Data alignment questin, structures Shao Miller <sha0.miller@gmail.com> - 2013-01-20 01:25 -0500
        Re: Data alignment questin, structures glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2013-01-20 07:53 +0000
        Re: Data alignment questin, structures Ben Bacarisse <ben.usenet@bsb.me.uk> - 2013-01-20 14:02 +0000
        Re: Data alignment questin, structures Keith Thompson <kst-u@mib.org> - 2013-01-20 07:35 -0800
          Re: Data alignment questin, structures 88888 Dihedral <dihedral88888@googlemail.com> - 2013-01-20 11:49 -0800
        Re: Data alignment questin, structures James Kuyper <jameskuyper@verizon.net> - 2013-01-20 12:30 -0500
          Re: Data alignment questin, structures mathog <mathog@caltech.edu> - 2013-01-20 10:26 -0800
            Re: Data alignment questin, structures Shao Miller <sha0.miller@gmail.com> - 2013-01-20 15:11 -0500
            Re: Data alignment questin, structures "BartC" <bc@freeuk.com> - 2013-01-20 20:34 +0000
            Re: Data alignment questin, structures James Kuyper <jameskuyper@verizon.net> - 2013-01-20 15:53 -0500
              Re: Data alignment questin, structures 88888 Dihedral <dihedral88888@googlemail.com> - 2013-01-20 13:16 -0800
              Re: Data alignment questin, structures mathog <mathog@caltech.edu> - 2013-01-20 20:27 -0800
                Re: Data alignment questin, structures Shao Miller <sha0.miller@gmail.com> - 2013-01-21 00:37 -0500
                Re: Data alignment questin, structures Dr Nick <nospam-4@temporary-address.org.uk> - 2013-01-21 10:07 +0000
                Re: Data alignment questin, structures mathog <mathog@caltech.edu> - 2013-01-21 10:21 -0800
                Re: Data alignment questin, structures Tim Rentsch <txr@alumni.caltech.edu> - 2013-01-21 10:34 -0800
                Re: Data alignment questin, structures Keith Thompson <kst-u@mib.org> - 2013-01-21 13:07 -0800
                Re: Data alignment questin, structures "BartC" <bc@freeuk.com> - 2013-01-21 22:24 +0000
                Re: Data alignment questin, structures mathog <dmathog@gmail.com> - 2013-01-22 10:18 -0800
                Re: Data alignment questin, structures glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2013-01-22 20:57 +0000
                Re: Data alignment questin, structures Keith Thompson <kst-u@mib.org> - 2013-01-22 14:51 -0800
                Re: Data alignment questin, structures Ian Collins <ian-news@hotmail.com> - 2013-01-22 11:12 +1300
                Re: Data alignment questin, structures glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2013-01-21 20:53 +0000
                Re: Data alignment questin, structures Keith Thompson <kst-u@mib.org> - 2013-01-20 22:06 -0800
                Re: Data alignment questin, structures Philip Lantz <prl@canterey.us> - 2013-01-22 00:27 -0800
                Re: Data alignment questin, structures James Kuyper <jameskuyper@verizon.net> - 2013-01-22 06:44 -0500
                Re: Data alignment questin, structures Bart van Ingen Schenau <bart@ingen.ddns.info.invalid> - 2013-01-21 10:19 +0000
            Re: Data alignment questin, structures glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2013-01-20 22:19 +0000
          Re: Data alignment questin, structures glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2013-01-20 22:14 +0000
          Re: Data alignment questin, structures "BartC" <bc@freeuk.com> - 2013-01-20 22:48 +0000
            Re: Data alignment questin, structures Les Cargill <lcargill99@comcast.com> - 2013-01-20 18:11 -0600
            Re: Data alignment questin, structures Ian Collins <ian-news@hotmail.com> - 2013-01-21 14:07 +1300
  Re: Data alignment questin, structures Shao Miller <sha0.miller@gmail.com> - 2013-01-12 17:45 -0500
    Re: Data alignment questin, structures mathog <mathog@caltech.edu> - 2013-01-13 10:17 -0800
      Re: Data alignment questin, structures Shao Miller <sha0.miller@gmail.com> - 2013-01-13 17:16 -0500

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