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Re: Struct and Union

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On 10/07/15 08:49, janus wrote:
> Hello All,
>
> I have 2 options but which one is idiomatic C?
>
> 1)
> typedef struct CStatement
> {
>      int stype;
>
>      union Statement
>      {
>          CPrintStatement* printstatement;
>          CInputStatement* inputstatement;
>          CAssignStatement* assignstatement;
>          CGotoStatement* gotostatement;
>          CIfThenStatement* ifthenstatement;
>          void* sstatement;
>
>      } statement;
> }CStatement;
>
>
> 2)
> typedef struct CStatement
> {
>      int stype;
>
>      void* sstatement;
>
> }CStatement;
>


To get your actual question out of the way, I would argue that the 
second is idiomatic C, whereas the first looks inelegant and crufty.

If it weren't for your catch-all void * in the first one, I'd say it was 
marginally safer, in that adding an extra type in one part of the code 
and forgetting to support it everywhere else is more likely to bite you 
at compile time rather than at runtime (which is a Good Thing), but the 
catch-all void * somewhat diminishes that advantage.

Which would I choose? The second one, without question. But I'd tread 
carefully.

-- 
Richard Heathfield
Email: rjh at cpax dot org dot uk
"Usenet is a strange place" - dmr 29 July 1999
Sig line 4 vacant - apply within

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Struct and Union janus <emekamicro@gmail.com> - 2015-07-10 00:49 -0700
  Re: Struct and Union Richard Heathfield <rjh@cpax.org.uk> - 2015-07-10 09:04 +0100
    Re: Struct and Union janus <emekamicro@gmail.com> - 2015-07-10 01:40 -0700
      Re: Struct and Union Richard Heathfield <rjh@cpax.org.uk> - 2015-07-10 09:50 +0100
        Re: Struct and Union Richard Heathfield <rjh@cpax.org.uk> - 2015-07-10 13:44 +0100
    Re: Struct and Union "Bill Davy" <Bill@SynectixLtd.com> - 2015-07-10 12:37 +0100
      Re: Struct and Union Keith Thompson <kst-u@mib.org> - 2015-07-10 08:24 -0700
        Re: Struct and Union Keith Thompson <kst-u@mib.org> - 2015-07-12 12:53 -0700
  Re: Struct and Union Ian Collins <ian-news@hotmail.com> - 2015-07-10 21:32 +1200
  Re: Struct and Union "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-07-10 05:12 -0700
    Re: Struct and Union Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-07-10 17:35 +0100
      Re: Struct and Union David Kleinecke <dkleinecke@gmail.com> - 2015-07-10 10:18 -0700
        Re: Struct and Union "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-07-10 10:23 -0700
        Re: Struct and Union James Kuyper <jameskuyper@verizon.net> - 2015-07-10 13:47 -0400
        Re: Struct and Union Keith Thompson <kst-u@mib.org> - 2015-07-10 12:38 -0700
      Re: Struct and Union "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-07-10 10:27 -0700
  Re: Struct and Union Bartc <bc@freeuk.com> - 2015-07-10 13:55 +0100
  Re: Struct and Union Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-07-10 21:48 +0100
    Re: Struct and Union "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-07-10 13:51 -0700
      Re: Struct and Union Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-07-10 23:45 +0100
        Re: Struct and Union "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-07-10 17:43 -0700
          Re: Struct and Union Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-07-11 13:04 +0100
            Re: Struct and Union "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-07-11 05:15 -0700
              Re: Struct and Union Bartc <bc@freeuk.com> - 2015-07-11 14:01 +0100
                Re: Struct and Union "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-07-11 06:05 -0700
                Re: Struct and Union "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-07-11 06:13 -0700
            Re: Struct and Union Keith Thompson <kst-u@mib.org> - 2015-07-11 13:51 -0700
              Re: Struct and Union Martin Shobe <martin.shobe@yahoo.com> - 2015-07-11 16:51 -0500
              Re: Struct and Union Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-07-11 23:13 +0100
                Re: Struct and Union Keith Thompson <kst-u@mib.org> - 2015-07-11 17:39 -0700
              Re: Struct and Union Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-07-11 16:56 -0700
  Re: Struct and Union Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-07-10 18:52 -0700
  Re: Struct and Union Tim Rentsch <txr@alumni.caltech.edu> - 2015-07-10 19:12 -0700

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