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Re: Effective uses of c `goto' statement

From kevin shell <kevin@fedora.osfans.org>
Newsgroups comp.lang.c
Subject Re: Effective uses of c `goto' statement
Date 2020-12-04 16:29 +0800
Organization A noiseless patient Spider
Message-ID <874kl22cub.fsf@fedora.osfans.org> (permalink)
References <87czzszjhs.fsf@fedora.osfans.org> <cc1a0392-9799-4e6d-8a8a-c2743c685a85n@googlegroups.com>

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"jfbod...@gmail.com" <jfbode1029@gmail.com> writes:

> On Wednesday, December 2, 2020 at 2:43:13 AM UTC-6, kevin shell wrote:
>> Hello C hackers/masters. :-) 
>> 
>> A lot of C textbooks say not to use `goto' statement, 
>> but the fact is I find lots of Unix/Linux 
>> C code often use `goto' statement. 
>
> There are times when it's not the wrong answer, usually when breaking out
> of a deeply nested loop.  
>   
>> My question is how to effectively use `goto' statement with C code, 
>> how to use `goto' to jump forward and jump back, 
>> how to avoid multiple `goto' statements with both jump forward and jump 
>> backward in the same function from messing up? 
>> 
>
> My personal rules:
>
> 1. Branch forward *only* - never branch backwards;

I think this advice is not practical,
I recently learned OpenBSD smtpd and
found quite lots of backward `goto'.

> 2. Limit the scope of the goto - that is, minimize the distance from the
>     goto statement to the label you're branching to;
> 3. Don't overlap scopes - that is, in the code between a goto and its
>     label, there should *not* be another goto that branches to a 
>     different label.
> 4. Never bypass the entry point of a control structure - that is, never
>     branch into the body of an if, switch, for, while, or do-while statement;
> 5. Never use goto in place of a control structure which accomplishes
>     the same thing.
>
Agreed. :-)

> About the only time I use a goto is to branch out of a deeply nested
> loop, and that's only if I can't think of a better way to deal with 
> the problem.  

This is only one often used case.

--
kevin

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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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