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 02:19 +0000
Organization	A noiseless patient Spider
Message-ID	<87a6utro41.fsf@bsb.me.uk> (permalink)
References	<87czzszjhs.fsf@fedora.osfans.org> <goto-20201204151951@ram.dialup.fu-berlin.de> <pOAyH.58886$OP2.50627@fx18.iad> <goto-20201205020907@ram.dialup.fu-berlin.de> <sJByH.38188$vhX.5591@fx17.iad>

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Richard Damon <Richard@Damon-Family.org> writes:

> On 12/4/20 8:15 PM, Stefan Ram wrote:
>> Richard Damon <Richard@Damon-Family.org> writes:
>>> This only works if the target is at a point compatible with one of
>>> these, it isn't always,
>> 
>>   It worked for me so far (I'm not a professional programmer,
>>   however, but an amateur programmer and a freelance instructor
>>   for programming languages). 
>> 
>>   Maybe someone can show a compiling piece of code with
>>   "goto"s, and I might then try and convert it to my style
>>   (if I can find the time, maybe only in some weeks or so).
>> 
>>>                        or the use of ifs will create a lot of
>>> indentation when using the goto to move forward to near the end of the
>>> function to perform the needed cleanup of resources already allocated.
>> 
>>   When one has a lot of indentation, the function definition
>>   is too large. (I can show how to meaningfully extract sub-
>>   functions, which will reduce indentation if someone would
>>   care to submit a compiling piece of code - if I can find 
>>   the time, maybe only in some weeks or so).
>> 
>>   When would I use "goto"? When I have to translate a piece of
>>   code from some other language to C or have to integrate a
>>   piece of C code and do not have the time to carefully remove
>>   the "goto"s, I'd rather leave the "goto"s in the code than
>>   to introduce bugs by hastily trying to remove them.
>> 
>
> When using the goto to jump to the resource cleanup at the end of the
> function, changing those to ifs adds a level for each resource that
> needs to be gotten. If you have 4 resources, at an indent of 4, is 16
> characters, or 25% of the 'typical' 80 character line. If the 'meat' of
> the function uses a couple more, that can be excessive.

Not necessarily; that's an overly general claim:

  char *buffer = 0, *workspace = 0;
  FILE *fp = 0;

  // get what we need...
  if ((buffer    = malloc(2*SIZE))     &&
      (workspace = malloc(SIZE))       &&
      (fp        = fopen(fname, "r"))) {
        // meat of the function...
  }

  // cleanup...
  free(buffer);
  free(workspace);
  if (fp) fclose(fp);

Depending on the situation, one might even get away with

  char *buffer    = malloc(2*SIZE),
       *workspace = malloc(SIZE);
  FILE *fp        = fopen(fname, "r");

  if (buffer && workspace && fp) {
      // meat of the function...
  }

  // cleanup...
  free(buffer);
  free(workspace);
  if (fp) fclose(fp);

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.

-- 
Ben.

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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