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Groups > comp.lang.c > #156965

Re: Effective uses of c `goto' statement

From Ben Bacarisse <ben.usenet@bsb.me.uk>
Newsgroups comp.lang.c
Subject Re: Effective uses of c `goto' statement
Date 2020-12-05 22:42 +0000
Organization A noiseless patient Spider
Message-ID <87tuszri2s.fsf@bsb.me.uk> (permalink)
References (2 earlier) <pOAyH.58886$OP2.50627@fx18.iad> <goto-20201205020907@ram.dialup.fu-berlin.de> <sJByH.38188$vhX.5591@fx17.iad> <87a6utro41.fsf@bsb.me.uk> <YlLyH.89633$J736.63364@fx42.ams4>

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Bart <bc@freeuk.com> writes:

> On 05/12/2020 02:19, Ben Bacarisse wrote:
>
>> There's been a lot of talk about code looking "clean", but I like code
>> to be easy to reason about, and goto can seriously mess that up.
>>
>
> Not using goto can mess it up too, if it means lots more code, more
> identation and more logic.

Maybe.  I'm always looking for good examples.

> Take this switch-case:
>
>     switch (a) {
>     case 10:
>         puts("ten");
>         break;
>     case 20:
>         puts("twenty");
>         break;
>     default:
>         puts("other");
>     }
>
> This a pattern of code I use a lot, but frequently, I want to execute
> the body of case 10 followed by that of 20. Or sometimes part of case
> 20, followed by part of case 10.

But this is not real code with a real purpose.  It's possible that these
requirements stem from some earlier design decisions that may not have
been optimal.  This is what I was saying before -- the simplest solution
/from here/ is not necessarily the best overall.  Good code rarely
results from many locally optimal changes.

> These will be simple bits of code that are not worth putting into
> separate functions.

What is your criterion for that?  I've written functions as simple as

  double square(double x) { return x * x; }

I like functions.  A lot.

> The following is a more specific pattern that for me occurs over and
> over again (the switch-cases and if-else chains or nested switch-case
> are usually much longer):
>
>     switch (a) {
>     case 10:
>         if (a)
>         else if (b)
>         else
>             <error handling code>
>         break;
>     case 20
>         if (c)
>            if (x) <error handling code>
>         else if (d)
>         else
>             <error handling code>
>         break;
>     default:
>         <error handling code>
>     }

There are too many unknowns here to be sure what the best design is.

> The error code is the same in each case (and can use locals so is not
> practical to off-load to a function) This statement is not the last
> thing in a function, so it is not cleanup code at the end of a
> function like the other examples in the thread.
>
> What is the simplest solution in C?

There's no way to know.  Do you have a real function with a well-defined
purpose that I could look at?

-- 
Ben.

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Thread

Effective uses of c `goto' statement kevin shell <kevin@fedora.osfans.org> - 2020-12-02 16:42 +0800
  Re: Effective uses of c `goto' statement Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-12-02 01:07 -0800
  Re: Effective uses of c `goto' statement Anton Shepelev <anton.txt@gmail.com> - 2020-12-02 20:18 +0300
    Re: Effective uses of c `goto' statement Anton Shepelev <anton.txt@gmail.com> - 2020-12-02 20:56 +0300
    Re: Effective uses of c `goto' statement David Brown <david.brown@hesbynett.no> - 2020-12-02 19:30 +0100
      Re: Effective uses of c `goto' statement Kaz Kylheku <563-365-8930@kylheku.com> - 2020-12-02 19:35 +0000
        Re: Effective uses of c `goto' statement David Brown <david.brown@hesbynett.no> - 2020-12-02 21:05 +0100
  Re: Effective uses of c `goto' statement Vir Campestris <vir.campestris@invalid.invalid> - 2020-12-02 18:07 +0000
    Re: Effective uses of c `goto' statement David Brown <david.brown@hesbynett.no> - 2020-12-02 19:33 +0100
  Re: Effective uses of c `goto' statement Siri Cruise <chine.bleu@yahoo.com> - 2020-12-02 10:22 -0800
    Re: Effective uses of c `goto' statement Kaz Kylheku <563-365-8930@kylheku.com> - 2020-12-02 20:18 +0000
      Re: Effective uses of c `goto' statement David Brown <david.brown@hesbynett.no> - 2020-12-02 23:16 +0100
        Re: Effective uses of c `goto' statement Kaz Kylheku <563-365-8930@kylheku.com> - 2020-12-03 01:31 +0000
          Re: Effective uses of c `goto' statement David Brown <david.brown@hesbynett.no> - 2020-12-03 08:39 +0100
            Re: Effective uses of c `goto' statement Siri Cruise <chine.bleu@yahoo.com> - 2020-12-02 23:48 -0800
            Re: Effective uses of c `goto' statement Kaz Kylheku <563-365-8930@kylheku.com> - 2020-12-03 17:49 +0000
          Re: Effective uses of c `goto' statement Bonita Montero <Bonita.Montero@gmail.com> - 2020-12-03 17:09 +0100
      Re: Effective uses of c `goto' statement Tim Rentsch <tr.17687@z991.linuxsc.com> - 2020-12-05 08:28 -0800
        Re: Effective uses of c `goto' statement Richard Damon <Richard@Damon-Family.org> - 2020-12-05 12:41 -0500
          Re: Effective uses of c `goto' statement Tim Rentsch <tr.17687@z991.linuxsc.com> - 2020-12-06 05:03 -0800
            Re: Effective uses of c `goto' statement Richard Damon <Richard@Damon-Family.org> - 2020-12-06 08:51 -0500
              Re: Effective uses of c `goto' statement Richard Damon <Richard@Damon-Family.org> - 2020-12-06 08:56 -0500
              Re: Effective uses of c `goto' statement Tim Rentsch <tr.17687@z991.linuxsc.com> - 2020-12-06 18:43 -0800
            Re: Effective uses of c `goto' statement Öö Tiib <ootiib@hot.ee> - 2020-12-06 05:58 -0800
              Re: Effective uses of c `goto' statement Tim Rentsch <tr.17687@z991.linuxsc.com> - 2020-12-06 16:54 -0800
        Re: Effective uses of c `goto' statement Siri Cruise <chine.bleu@yahoo.com> - 2020-12-05 10:01 -0800
          Re: Effective uses of c `goto' statement Tim Rentsch <tr.17687@z991.linuxsc.com> - 2020-12-06 04:55 -0800
    Re: Effective uses of c `goto' statement Tim Rentsch <tr.17687@z991.linuxsc.com> - 2020-12-03 21:20 -0800
      Re: Effective uses of c `goto' statement Siri Cruise <chine.bleu@yahoo.com> - 2020-12-03 21:50 -0800
        Re: Effective uses of c `goto' statement Tim Rentsch <tr.17687@z991.linuxsc.com> - 2020-12-03 23:06 -0800
          Re: Effective uses of c `goto' statement Siri Cruise <chine.bleu@yahoo.com> - 2020-12-04 00:27 -0800
  Re: Effective uses of c `goto' statement foo <opaquefoo@gmail.com> - 2020-12-02 11:03 -0800
    Re: Effective uses of c `goto' statement David Brown <david.brown@hesbynett.no> - 2020-12-02 21:02 +0100
      Re: Effective uses of c `goto' statement Öö Tiib <ootiib@hot.ee> - 2020-12-05 03:04 -0800
        Re: Effective uses of c `goto' statement Öö Tiib <ootiib@hot.ee> - 2020-12-05 03:36 -0800
          Good thing this isn't a Python group (Was: Effective uses of c `goto' statement) gazelle@shell.xmission.com (Kenny McCormack) - 2020-12-05 11:45 +0000
            Re: Good thing this isn't a Python group (Was: Effective uses of c `goto' statement) David Brown <david.brown@hesbynett.no> - 2020-12-05 14:38 +0100
              Re: Good thing this isn't a Python group (Was: Effective uses of c `goto' statement) Jorgen Grahn <grahn+nntp@snipabacken.se> - 2020-12-06 11:00 +0000
                Re: Good thing this isn't a Python group (Was: Effective uses of c `goto' statement) gazelle@shell.xmission.com (Kenny McCormack) - 2020-12-06 12:33 +0000
                Re: Good thing this isn't a Python group Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-12-06 14:09 -0800
                Re: Good thing this isn't a Python group Jorgen Grahn <grahn+nntp@snipabacken.se> - 2020-12-08 21:01 +0000
          Re: Effective uses of c `goto' statement David Brown <david.brown@hesbynett.no> - 2020-12-05 14:37 +0100
  Re: Effective uses of c `goto' statement Kaz Kylheku <563-365-8930@kylheku.com> - 2020-12-02 20:07 +0000
  Re: Effective uses of c `goto' statement Bonita Montero <Bonita.Montero@gmail.com> - 2020-12-03 17:10 +0100
  Re: Effective uses of c `goto' statement "jfbod...@gmail.com" <jfbode1029@gmail.com> - 2020-12-03 15:40 -0800
    Re: Effective uses of c `goto' statement Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2020-12-03 16:14 -0800
    Re: Effective uses of c `goto' statement kevin shell <kevin@fedora.osfans.org> - 2020-12-04 16:29 +0800
      Re: Effective uses of c `goto' statement "jfbod...@gmail.com" <jfbode1029@gmail.com> - 2020-12-04 07:09 -0800
      Re: Effective uses of c `goto' statement "james...@alumni.caltech.edu" <jameskuyper@alumni.caltech.edu> - 2020-12-04 10:14 -0800
    Re: Effective uses of c `goto' statement Bart <bc@freeuk.com> - 2020-12-04 11:19 +0000
      Re: Effective uses of c `goto' statement Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2020-12-04 04:35 -0800
        Re: Effective uses of c `goto' statement Bart <bc@freeuk.com> - 2020-12-04 13:50 +0000
          Re: Effective uses of c `goto' statement Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-12-04 10:49 -0800
      Re: Effective uses of c `goto' statement Ben Bacarisse <ben.usenet@bsb.me.uk> - 2020-12-04 13:09 +0000
        Re: Effective uses of c `goto' statement Bart <bc@freeuk.com> - 2020-12-04 14:03 +0000
  Re: Effective uses of c `goto' statement Tim Rentsch <tr.17687@z991.linuxsc.com> - 2020-12-03 23:02 -0800
    Re: Effective uses of c `goto' statement Bonita Montero <Bonita.Montero@gmail.com> - 2020-12-04 19:38 +0100
      Re: Effective uses of c `goto' statement Tim Rentsch <tr.17687@z991.linuxsc.com> - 2020-12-05 01:29 -0800
    Re: Effective uses of c `goto' statement kegs@provalid.com (Kent Dickey) - 2020-12-09 00:23 -0600
      Re: Effective uses of c `goto' statement Bart <bc@freeuk.com> - 2020-12-09 12:39 +0000
      Re: Effective uses of c `goto' statement Tim Rentsch <tr.17687@z991.linuxsc.com> - 2020-12-10 10:45 -0800
  Re: Effective uses of c `goto' statement Bonita Montero <Bonita.Montero@gmail.com> - 2020-12-04 19:35 +0100
  Re: Effective uses of c `goto' statement Richard Damon <Richard@Damon-Family.org> - 2020-12-04 19:49 -0500
    Re: Effective uses of c `goto' statement Richard Damon <Richard@Damon-Family.org> - 2020-12-04 20:52 -0500
      Re: Effective uses of c `goto' statement Ben Bacarisse <ben.usenet@bsb.me.uk> - 2020-12-05 02:19 +0000
        Re: Effective uses of c `goto' statement Tim Rentsch <tr.17687@z991.linuxsc.com> - 2020-12-05 01:43 -0800
        Re: Effective uses of c `goto' statement "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2020-12-05 02:00 -0800
          Re: Effective uses of c `goto' statement "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2020-12-05 02:01 -0800
          Re: Effective uses of c `goto' statement Ben Bacarisse <ben.usenet@bsb.me.uk> - 2020-12-05 22:45 +0000
            Re: Effective uses of c `goto' statement "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2020-12-11 19:33 -0800
              Re: Effective uses of c `goto' statement Ben Bacarisse <ben.usenet@bsb.me.uk> - 2020-12-12 21:12 +0000
        Re: Effective uses of c `goto' statement Bart <bc@freeuk.com> - 2020-12-05 12:49 +0000
          Re: Effective uses of c `goto' statement Ben Bacarisse <ben.usenet@bsb.me.uk> - 2020-12-05 22:42 +0000
            Re: Effective uses of c `goto' statement Tim Rentsch <tr.17687@z991.linuxsc.com> - 2020-12-06 05:46 -0800
            Re: Effective uses of c `goto' statement Bart <bc@freeuk.com> - 2020-12-06 14:16 +0000
              Re: Effective uses of c `goto' statement Öö Tiib <ootiib@hot.ee> - 2020-12-06 06:54 -0800
                Re: Effective uses of c `goto' statement Bart <bc@freeuk.com> - 2020-12-06 16:19 +0000
                Re: Effective uses of c `goto' statement Öö Tiib <ootiib@hot.ee> - 2020-12-06 15:34 -0800
                Re: Effective uses of c `goto' statement Bart <bc@freeuk.com> - 2020-12-06 23:56 +0000
                Re: Effective uses of c `goto' statement David Brown <david.brown@hesbynett.no> - 2020-12-07 11:11 +0100
                Re: Effective uses of c `goto' statement Bart <bc@freeuk.com> - 2020-12-07 11:41 +0000
                Re: Effective uses of c `goto' statement David Brown <david.brown@hesbynett.no> - 2020-12-07 15:35 +0100
                Re: Effective uses of c `goto' statement Bart <bc@freeuk.com> - 2020-12-07 15:48 +0000
                Re: Effective uses of c `goto' statement Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-12-07 11:46 -0800
                Re: Effective uses of c `goto' statement Bart <bc@freeuk.com> - 2020-12-07 20:01 +0000
                Re: Effective uses of c `goto' statement Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-12-07 13:03 -0800
                Re: Effective uses of c `goto' statement David Brown <david.brown@hesbynett.no> - 2020-12-07 11:01 +0100
                Re: Effective uses of c `goto' statement Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2020-12-07 03:35 -0800
                Re: Effective uses of c `goto' statement Richard Damon <Richard@Damon-Family.org> - 2020-12-07 07:33 -0500
                Re: Effective uses of c `goto' statement gazelle@shell.xmission.com (Kenny McCormack) - 2020-12-07 13:11 +0000
                Re: Effective uses of c `goto' statement Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2020-12-07 05:24 -0800
                Re: Effective uses of c `goto' statement Richard Damon <Richard@Damon-Family.org> - 2020-12-07 08:58 -0500
                Re: Effective uses of c `goto' statement David Brown <david.brown@hesbynett.no> - 2020-12-07 15:48 +0100
                Re: Effective uses of c `goto' statement David Brown <david.brown@hesbynett.no> - 2020-12-07 15:45 +0100
                Re: Effective uses of c `goto' statement Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2020-12-07 07:29 -0800
                Re: Effective uses of c `goto' statement Ben Bacarisse <ben.usenet@bsb.me.uk> - 2020-12-07 22:34 +0000
                Re: Effective uses of c `goto' statement David Brown <david.brown@hesbynett.no> - 2020-12-07 15:38 +0100
          Re: Effective uses of c `goto' statement kegs@provalid.com (Kent Dickey) - 2020-12-10 15:45 -0600
        Re: Effective uses of c `goto' statement Vir Campestris <vir.campestris@invalid.invalid> - 2020-12-07 21:43 +0000
          Re: Effective uses of c `goto' statement Ben Bacarisse <ben.usenet@bsb.me.uk> - 2020-12-07 23:02 +0000
            Re: Effective uses of c `goto' statement Vir Campestris <vir.campestris@invalid.invalid> - 2020-12-10 21:15 +0000
              Re: Effective uses of c `goto' statement Ben Bacarisse <ben.usenet@bsb.me.uk> - 2020-12-10 22:48 +0000
                Re: Effective uses of c `goto' statement Vir Campestris <vir.campestris@invalid.invalid> - 2020-12-11 20:59 +0000
                Re: Effective uses of c `goto' statement Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-12-11 14:07 -0800
      Re: Effective uses of c `goto' statement Bonita Montero <Bonita.Montero@gmail.com> - 2020-12-05 08:55 +0100
      Re: Effective uses of c `goto' statement Tim Rentsch <tr.17687@z991.linuxsc.com> - 2020-12-05 02:04 -0800
      Re: Effective uses of c `goto' statement Vir Campestris <vir.campestris@invalid.invalid> - 2020-12-07 21:37 +0000
        Re: Effective uses of c `goto' statement James Kuyper <jameskuyper@alumni.caltech.edu> - 2020-12-07 17:03 -0500
          Re: Effective uses of c `goto' statement David Brown <david.brown@hesbynett.no> - 2020-12-07 23:17 +0100
        Re: Effective uses of c `goto' statement Kaz Kylheku <563-365-8930@kylheku.com> - 2020-12-07 22:19 +0000
          Re: Effective uses of c `goto' statement Vir Campestris <vir.campestris@invalid.invalid> - 2020-12-10 21:13 +0000
      Re: Effective uses of c `goto' statement kegs@provalid.com (Kent Dickey) - 2020-12-10 15:30 -0600
  Re: Effective uses of c `goto' statement "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2020-12-05 13:01 -0500
  Re: Effective uses of c `goto' statement luser droog <luser.droog@gmail.com> - 2020-12-11 19:27 -0800

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