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Groups > comp.lang.c > #73121

Re: C struct syntax allowance by usage

From Bartc <bc@freeuk.com>
Newsgroups comp.lang.c
Subject Re: C struct syntax allowance by usage
Date 2015-10-17 01:41 +0100
Organization A noiseless patient Spider
Message-ID <mvs5cf$281$1@dont-email.me> (permalink)
References <40812880-9a99-48c6-9d67-6d6a98be00e1@googlegroups.com> <mvrp94$p8a$1@dont-email.me> <1054a0bd-b310-42d6-a746-bde063310246@googlegroups.com>

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On 16/10/2015 23:28, supercat@casperkitty.com wrote:
> On Friday, October 16, 2015 at 4:15:25 PM UTC-5, Bart wrote:
>> What's the purpose?
>
> A real-world example of a place where I'd like such a feature is when
> writing code for one of Atmel's ARM controllers.  A little snippet from
> the vendor-supplied header [comments on each line deleted to keep line
> length reasonable]
>
>    /* From one of Atmel's include files */
>
>    typedef union {
>      struct {
>        uint32_t PINMASK:16;
>        uint32_t PMUXEN:1;
>        uint32_t INEN:1;
>        uint32_t PULLEN:1;
>        uint32_t :3;
>        uint32_t DRVSTR:1;
>        uint32_t :1;
>        uint32_t PMUX:4;
>        uint32_t WRPMUX:1;
>        uint32_t :1;
>        uint32_t WRPINCFG:1;
>        uint32_t HWSEL:1;
>      } bit;
>      uint32_t reg;
>    } PORT_WRCONFIG_Type;
>
> Every single I/O register in the chip is defined similarly, which means that
> it's necessary to attach ".reg" to every single I/O access

I'm not sure how Rick's feature works with unions, but you don't need to 
get involved with types.

What I think you want here is a top-level anonymous union:

      union {
           PORT_BITS bit;
           uint32_t reg;
      };

Here, you have a variable called 'bit', and one called 'reg', which 
share the same memory location (and happen to be the same size):

   reg = 0x70028224;

So you still have to write 'reg' everywhere that you set all these 32 
bits at once. But the 'reg' doesn't have to be a field of something else.

BTW C doesn't allow this, in case you thought it did. I've used this 
feature elsewhere, so there is a precedent.

-- 
Bartc

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C struct syntax allowance by usage "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-10-16 13:29 -0700
  Re: C struct syntax allowance by usage Siri Cruz <chine.bleu@yahoo.com> - 2015-10-16 13:47 -0700
    Re: C struct syntax allowance by usage supercat@casperkitty.com - 2015-10-16 14:12 -0700
  Re: C struct syntax allowance by usage Bartc <bc@freeuk.com> - 2015-10-16 22:15 +0100
    Re: C struct syntax allowance by usage "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-10-16 14:38 -0700
      Re: C struct syntax allowance by usage Bartc <bc@freeuk.com> - 2015-10-17 10:32 +0100
        Re: C struct syntax allowance by usage "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-10-17 05:26 -0700
          Re: C struct syntax allowance by usage Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-17 14:17 +0100
            Re: C struct syntax allowance by usage "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-10-17 06:48 -0700
              Re: C struct syntax allowance by usage Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-17 19:01 +0100
                Re: C struct syntax allowance by usage "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-10-17 11:17 -0700
    Re: C struct syntax allowance by usage supercat@casperkitty.com - 2015-10-16 15:28 -0700
      Re: C struct syntax allowance by usage Bartc <bc@freeuk.com> - 2015-10-17 01:41 +0100
        Re: C struct syntax allowance by usage "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-10-16 18:23 -0700
      Re: C struct syntax allowance by usage David Brown <david.brown@hesbynett.no> - 2015-10-18 11:04 +0200
  Re: C struct syntax allowance by usage Ian Collins <ian-news@hotmail.com> - 2015-10-17 10:31 +1300
    Re: C struct syntax allowance by usage "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-10-16 14:38 -0700
      Re: C struct syntax allowance by usage Ian Collins <ian-news@hotmail.com> - 2015-10-17 11:14 +1300
        Re: C struct syntax allowance by usage "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-10-16 15:25 -0700
          Re: C struct syntax allowance by usage Ian Collins <ian-news@hotmail.com> - 2015-10-17 11:31 +1300
            Re: C struct syntax allowance by usage "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-10-16 15:38 -0700
              Re: C struct syntax allowance by usage Ian Collins <ian-news@hotmail.com> - 2015-10-17 12:32 +1300
                Re: C struct syntax allowance by usage David Brown <david.brown@hesbynett.no> - 2015-10-18 11:35 +0200
                Re: C struct syntax allowance by usage Bartc <bc@freeuk.com> - 2015-10-18 11:16 +0100
                Re: C struct syntax allowance by usage David Brown <david.brown@hesbynett.no> - 2015-10-18 13:40 +0200
                Re: C struct syntax allowance by usage Bartc <bc@freeuk.com> - 2015-10-18 17:35 +0100
                Re: C struct syntax allowance by usage supercat@casperkitty.com - 2015-10-18 10:52 -0700
                Re: C struct syntax allowance by usage "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-10-18 11:02 -0700
                Re: C struct syntax allowance by usage Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-18 19:59 +0100
                Re: C struct syntax allowance by usage "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-10-18 12:15 -0700
                Re: C struct syntax allowance by usage Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-18 21:41 +0100
                Likeliehood of RDC/SeaAlive implementation (Was: C struct syntax allowance by usage) gazelle@shell.xmission.com (Kenny McCormack) - 2015-10-19 08:23 +0000
                Re: C struct syntax allowance by usage Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2015-10-18 14:02 -0400
                Re: C struct syntax allowance by usage Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2015-10-18 14:19 -0400
                Re: C struct syntax allowance by usage Bartc <bc@freeuk.com> - 2015-10-18 21:13 +0100
                Re: C struct syntax allowance by usage David Brown <david.brown@hesbynett.no> - 2015-10-18 20:37 +0200
                Re: C struct syntax allowance by usage Bartc <bc@freeuk.com> - 2015-10-18 20:27 +0100
                Re: C struct syntax allowance by usage David Brown <david.brown@hesbynett.no> - 2015-10-18 23:14 +0200
                Re: C struct syntax allowance by usage asetofsymbols@gmail.com - 2015-10-18 15:09 -0700
                Re: C struct syntax allowance by usage supercat@casperkitty.com - 2015-10-18 16:11 -0700
                Re: C struct syntax allowance by usage Ian Collins <ian-news@hotmail.com> - 2015-10-19 07:57 +1300
                Re: C struct syntax allowance by usage Bartc <bc@freeuk.com> - 2015-10-18 20:11 +0100
                Re: C struct syntax allowance by usage Ian Collins <ian-news@hotmail.com> - 2015-10-19 09:19 +1300
          Re: C struct syntax allowance by usage David Brown <david.brown@hesbynett.no> - 2015-10-18 11:19 +0200
            Re: C struct syntax allowance by usage Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-10-18 03:08 -0700
              Re: C struct syntax allowance by usage David Brown <david.brown@hesbynett.no> - 2015-10-18 13:52 +0200
                Re: C struct syntax allowance by usage Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-10-18 05:39 -0700
                Re: C struct syntax allowance by usage David Brown <david.brown@hesbynett.no> - 2015-10-18 14:57 +0200
                Re: C struct syntax allowance by usage Ian Collins <ian-news@hotmail.com> - 2015-10-19 10:31 +1300
              Re: C struct syntax allowance by usage Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-18 15:49 +0100
                Re: C struct syntax allowance by usage Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-10-18 16:53 -0700
                Re: C struct syntax allowance by usage Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-19 01:50 +0100
                Re: C struct syntax allowance by usage Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-10-19 02:28 -0700
                Re: C struct syntax allowance by usage David Brown <david.brown@hesbynett.no> - 2015-10-19 12:38 +0200
                Re: C struct syntax allowance by usage Bartc <bc@freeuk.com> - 2015-10-19 12:09 +0100
                Re: C struct syntax allowance by usage David Brown <david.brown@hesbynett.no> - 2015-10-19 14:26 +0200
                Re: C struct syntax allowance by usage Bartc <bc@freeuk.com> - 2015-10-19 13:34 +0100
                Re: C struct syntax allowance by usage glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-20 02:36 +0000
                Re: C struct syntax allowance by usage Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-10-19 05:09 -0700
                Re: C struct syntax allowance by usage David Brown <david.brown@hesbynett.no> - 2015-10-19 14:41 +0200
                Re: C struct syntax allowance by usage Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-10-19 06:08 -0700
                Re: C struct syntax allowance by usage David Brown <david.brown@hesbynett.no> - 2015-10-19 15:20 +0200
                Re: C struct syntax allowance by usage Keith Thompson <kst-u@mib.org> - 2015-10-19 08:24 -0700
                Re: C struct syntax allowance by usage Ian Collins <ian-news@hotmail.com> - 2015-10-20 08:43 +1300
                Re: C struct syntax allowance by usage Keith Thompson <kst-u@mib.org> - 2015-10-19 13:00 -0700
                Re: C struct syntax allowance by usage Jorgen Grahn <grahn+nntp@snipabacken.se> - 2015-10-19 20:34 +0000
                Re: C struct syntax allowance by usage Ian Collins <ian-news@hotmail.com> - 2015-10-20 09:47 +1300
                Re: C struct syntax allowance by usage supercat@casperkitty.com - 2015-10-19 16:32 -0700
                Re: C struct syntax allowance by usage Jorgen Grahn <grahn+nntp@snipabacken.se> - 2015-10-20 10:37 +0000
                Re: C struct syntax allowance by usage glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-19 21:24 +0000
                Re: C struct syntax allowance by usage Jorgen Grahn <grahn+nntp@snipabacken.se> - 2015-10-20 13:49 +0000
                Re: C struct syntax allowance by usage Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-10-20 07:33 -0700
                Re: C struct syntax allowance by usage glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-20 15:53 +0000
                Re: C struct syntax allowance by usage Keith Thompson <kst-u@mib.org> - 2015-10-20 10:37 -0700
                Re: C struct syntax allowance by usage glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-21 05:05 +0000
                Re: C struct syntax allowance by usage Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-10-21 02:02 -0700
                Re: C struct syntax allowance by usage supercat@casperkitty.com - 2015-10-21 06:07 -0700
                Re: C struct syntax allowance by usage Bartc <bc@freeuk.com> - 2015-10-21 14:15 +0100
                Re: C struct syntax allowance by usage supercat@casperkitty.com - 2015-10-21 09:23 -0700
                Re: C struct syntax allowance by usage Bartc <bc@freeuk.com> - 2015-10-21 18:30 +0100
                Re: C struct syntax allowance by usage supercat@casperkitty.com - 2015-10-21 12:13 -0700
                Re: C struct syntax allowance by usage Bartc <bc@freeuk.com> - 2015-10-21 21:17 +0100
                Re: C struct syntax allowance by usage supercat@casperkitty.com - 2015-10-21 14:21 -0700
                Re: C struct syntax allowance by usage "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-10-21 14:55 -0700
                Re: C struct syntax allowance by usage supercat@casperkitty.com - 2015-10-21 15:45 -0700
                Re: C struct syntax allowance by usage David Brown <david.brown@hesbynett.no> - 2015-10-22 14:33 +0200
                Re: C struct syntax allowance by usage supercat@casperkitty.com - 2015-10-22 08:54 -0700
                Re: C struct syntax allowance by usage David Brown <david.brown@hesbynett.no> - 2015-10-23 15:59 +0200
                Re: C struct syntax allowance by usage supercat@casperkitty.com - 2015-10-23 15:03 -0700
                Re: C struct syntax allowance by usage Richard Damon <Richard@Damon-Family.org> - 2015-10-24 10:37 -0400
                Re: C struct syntax allowance by usage Bartc <bc@freeuk.com> - 2015-10-21 23:26 +0100
                Re: C struct syntax allowance by usage supercat@casperkitty.com - 2015-10-21 15:56 -0700
                Re: C struct syntax allowance by usage glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-22 05:19 +0000
                Re: C struct syntax allowance by usage Bartc <bc@freeuk.com> - 2015-10-22 11:08 +0100
                Re: C struct syntax allowance by usage David Brown <david.brown@hesbynett.no> - 2015-10-22 14:58 +0200
                Re: C struct syntax allowance by usage David Brown <david.brown@hesbynett.no> - 2015-10-22 14:06 +0200
                Re: C struct syntax allowance by usage supercat@casperkitty.com - 2015-10-22 07:41 -0700
                Re: C struct syntax allowance by usage Bartc <bc@freeuk.com> - 2015-10-22 14:00 +0100
                Re: C struct syntax allowance by usage Jorgen Grahn <grahn+nntp@snipabacken.se> - 2015-10-22 21:00 +0000
                Re: C struct syntax allowance by usage supercat@casperkitty.com - 2015-10-22 14:57 -0700
                Re: C struct syntax allowance by usage Jorgen Grahn <grahn+nntp@snipabacken.se> - 2015-10-21 14:41 +0000
                Re: C struct syntax allowance by usage Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-10-21 13:01 -0700
                Re: C struct syntax allowance by usage supercat@casperkitty.com - 2015-10-21 13:25 -0700
                Re: C struct syntax allowance by usage Jorgen Grahn <grahn+nntp@snipabacken.se> - 2015-10-22 07:44 +0000
                Re: C struct syntax allowance by usage Jorgen Grahn <grahn+nntp@snipabacken.se> - 2015-10-21 13:41 +0000
                Re: C struct syntax allowance by usage glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-22 05:22 +0000
                Re: C struct syntax allowance by usage Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-10-22 01:01 -0700
                Re: C struct syntax allowance by usage Les Cargill <lcargill99@comcast.com> - 2015-10-22 08:00 -0500
                Re: C struct syntax allowance by usage James Kuyper <jameskuyper@verizon.net> - 2015-10-21 09:49 -0400
                Re: C struct syntax allowance by usage Jorgen Grahn <grahn+nntp@snipabacken.se> - 2015-10-21 13:20 +0000
                Re: C struct syntax allowance by usage glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-20 15:40 +0000
                Re: C struct syntax allowance by usage James Kuyper <jameskuyper@verizon.net> - 2015-10-20 11:55 -0400
                Re: C struct syntax allowance by usage Keith Thompson <kst-u@mib.org> - 2015-10-20 10:34 -0700
                Re: C struct syntax allowance by usage glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-21 05:20 +0000
                Re: C struct syntax allowance by usage glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-21 05:11 +0000
                Re: C struct syntax allowance by usage James Kuyper <jameskuyper@verizon.net> - 2015-10-21 09:47 -0400
                Re: C struct syntax allowance by usage glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-22 05:32 +0000
                Re: C struct syntax allowance by usage James Kuyper <jameskuyper@verizon.net> - 2015-10-22 10:08 -0400
                Re: C struct syntax allowance by usage glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-22 21:45 +0000
                Re: C struct syntax allowance by usage James Kuyper <jameskuyper@verizon.net> - 2015-10-22 19:09 -0400
                Re: C struct syntax allowance by usage James Kuyper <jameskuyper@verizon.net> - 2015-10-22 19:22 -0400
                Re: C struct syntax allowance by usage supercat@casperkitty.com - 2015-10-22 17:49 -0700
                Re: C struct syntax allowance by usage Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2015-10-22 21:13 -0400
                Re: C struct syntax allowance by usage glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-23 11:36 +0000
                Re: C struct syntax allowance by usage Robert Wessel <robertwessel2@yahoo.com> - 2015-10-22 20:18 -0500
                Re: C struct syntax allowance by usage glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-23 11:55 +0000
                Re: C struct syntax allowance by usage glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-23 11:14 +0000
                Re: C struct syntax allowance by usage Keith Thompson <kst-u@mib.org> - 2015-10-23 09:09 -0700
                Re: C struct syntax allowance by usage glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-24 09:31 +0000
                Re: C struct syntax allowance by usage raltbos@xs4all.nl (Richard Bos) - 2015-11-10 15:17 +0000
                Re: C struct syntax allowance by usage supercat@casperkitty.com - 2015-11-10 10:39 -0800
                Re: C struct syntax allowance by usage "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-11-10 11:02 -0800
                Re: C struct syntax allowance by usage James Kuyper <jameskuyper@verizon.net> - 2015-10-23 15:54 -0400
                Re: C struct syntax allowance by usage Keith Thompson <kst-u@mib.org> - 2015-10-23 13:51 -0700
                Re: C struct syntax allowance by usage James Kuyper <jameskuyper@verizon.net> - 2015-10-23 17:41 -0400
                Re: C struct syntax allowance by usage raltbos@xs4all.nl (Richard Bos) - 2015-11-10 15:32 +0000
                Re: C struct syntax allowance by usage supercat@casperkitty.com - 2015-10-23 15:17 -0700
                Re: C struct syntax allowance by usage Keith Thompson <kst-u@mib.org> - 2015-10-23 16:34 -0700
                Re: C struct syntax allowance by usage glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-24 09:51 +0000
                Re: C struct syntax allowance by usage Richard Damon <Richard@Damon-Family.org> - 2015-10-24 10:01 -0400
                Re: C struct syntax allowance by usage James Kuyper <jameskuyper@verizon.net> - 2015-10-24 12:38 -0400
                Re: C struct syntax allowance by usage Robert Wessel <robertwessel2@yahoo.com> - 2015-10-24 13:56 -0500
                Re: C struct syntax allowance by usage James Kuyper <jameskuyper@verizon.net> - 2015-10-24 15:17 -0400
                Re: C struct syntax allowance by usage Robert Wessel <robertwessel2@yahoo.com> - 2015-10-25 13:47 -0500
                Re: C struct syntax allowance by usage glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-25 23:46 +0000
                Re: C struct syntax allowance by usage glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-25 07:05 +0000
                Re: C struct syntax allowance by usage James Kuyper <jameskuyper@verizon.net> - 2015-10-25 10:59 -0400
                Re: C struct syntax allowance by usage glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-26 02:24 +0000
                Re: C struct syntax allowance by usage supercat@casperkitty.com - 2015-10-25 11:13 -0700
                Re: C struct syntax allowance by usage glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-26 02:58 +0000
                Re: C struct syntax allowance by usage supercat@casperkitty.com - 2015-10-24 11:02 -0700
                Re: C struct syntax allowance by usage Sjouke Burry <burrynulnulfour@ppllaanneett.nnll> - 2015-10-24 20:13 +0200
                Re: C struct syntax allowance by usage Keith Thompson <kst-u@mib.org> - 2015-10-24 12:45 -0700
                Re: C struct syntax allowance by usage Ian Collins <ian-news@hotmail.com> - 2015-10-24 10:30 +1300
                Re: C struct syntax allowance by usage Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-19 12:05 +0100
  Re: C struct syntax allowance by usage "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-10-16 15:57 -0700
    Re: C struct syntax allowance by usage Bartc <bc@freeuk.com> - 2015-10-17 00:54 +0100
      Re: C struct syntax allowance by usage "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-10-16 17:19 -0700
      Re: C struct syntax allowance by usage Ian Collins <ian-news@hotmail.com> - 2015-10-17 15:33 +1300
        Re: C struct syntax allowance by usage "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-10-16 19:41 -0700
          Re: C struct syntax allowance by usage Ian Collins <ian-news@hotmail.com> - 2015-10-17 15:58 +1300
            Re: C struct syntax allowance by usage "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-10-16 20:10 -0700
              Re: C struct syntax allowance by usage Ian Collins <ian-news@hotmail.com> - 2015-10-17 16:49 +1300
                Re: C struct syntax allowance by usage "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-10-16 20:59 -0700
                Re: C struct syntax allowance by usage David Brown <david.brown@hesbynett.no> - 2015-10-18 11:32 +0200
          Re: C struct syntax allowance by usage Richard Damon <Richard@Damon-Family.org> - 2015-10-16 23:15 -0400
            Re: C struct syntax allowance by usage "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-10-16 20:34 -0700
              Re: C struct syntax allowance by usage "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-10-16 20:45 -0700

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