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Error returns and repeated code, GOTOs, etc.

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  Error returns and repeated code, GOTOs, etc. mike3 <mike4ty4@yahoo.com> - 2012-05-29 22:44 -0700
    Re: Error returns and repeated code, GOTOs, etc. Ike Naar <ike@sverige.freeshell.org> - 2012-05-30 06:38 +0000
    Re: Error returns and repeated code, GOTOs, etc. Nils M Holm <news2009@t3x.org> - 2012-05-30 06:57 +0000
    Re: Error returns and repeated code, GOTOs, etc. Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-05-30 00:52 -0700
      Re: Error returns and repeated code, GOTOs, etc. mike3 <mike4ty4@yahoo.com> - 2012-05-30 01:50 -0700
    Re: Error returns and repeated code, GOTOs, etc. MarkBluemel <mark_bluemel@pobox.com> - 2012-05-30 09:55 +0100
      Re: Error returns and repeated code, GOTOs, etc. Willem <willem@toad.stack.nl> - 2012-05-30 09:18 +0000
        Re: Error returns and repeated code, GOTOs, etc. tom st denis <tom@iahu.ca> - 2012-05-30 05:16 -0700
          Re: Error returns and repeated code, GOTOs, etc. Willem <willem@toad.stack.nl> - 2012-05-30 16:26 +0000
            Re: Error returns and repeated code, GOTOs, etc. tom st denis <tom@iahu.ca> - 2012-06-01 08:05 -0700
              Re: Error returns and repeated code, GOTOs, etc. Willem <willem@toad.stack.nl> - 2012-06-03 11:24 +0000
            Re: Error returns and repeated code, GOTOs, etc. jgk@panix.com (Joe keane) - 2012-06-02 13:54 +0000
              Re: Error returns and repeated code, GOTOs, etc. Jean-Christophe <5.d@free.fr> - 2012-06-02 07:24 -0700
                Re: Error returns and repeated code, GOTOs, etc. jgk@panix.com (Joe keane) - 2012-06-02 16:37 +0000
                  Re: Error returns and repeated code, GOTOs, etc. Jean-Christophe <5.d@free.fr> - 2012-06-02 12:46 -0700
              Re: Error returns and repeated code, GOTOs, etc. Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-06-02 15:42 +0100
                Re: Error returns and repeated code, GOTOs, etc. jgk@panix.com (Joe keane) - 2012-06-02 19:35 +0000
                  Re: Error returns and repeated code, GOTOs, etc. Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-06-03 03:53 +0100
                    Re: Error returns and repeated code, GOTOs, etc. Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2012-06-11 18:10 +0300
                      Re: Error returns and repeated code, GOTOs, etc. Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-06-11 16:19 +0100
              Re: Error returns and repeated code, GOTOs, etc. Martin Shobe <martin.shobe@yahoo.com> - 2012-06-02 19:27 +0000
                Re: Error returns and repeated code, GOTOs, etc. jgk@panix.com (Joe keane) - 2012-06-03 23:48 +0000
                  Re: Error returns and repeated code, GOTOs, etc. Ian Collins <ian-news@hotmail.com> - 2012-06-04 11:53 +1200
                  Re: Error returns and repeated code, GOTOs, etc. Martin Shobe <martin.shobe@yahoo.com> - 2012-06-04 03:32 +0000
      Re: Error returns and repeated code, GOTOs, etc. nick_keighley_nospam@hotmail.com - 2012-05-30 07:25 -0700
      Re: Error returns and repeated code, GOTOs, etc. falk@rahul.net (Edward A. Falk) - 2012-06-05 07:20 +0000
    Re: Error returns and repeated code, GOTOs, etc. Ian Collins <ian-news@hotmail.com> - 2012-05-30 21:50 +1200
      Re: Error returns and repeated code, GOTOs, etc. Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-05-30 03:34 -0700
        Re: Error returns and repeated code, GOTOs, etc. Ian Collins <ian-news@hotmail.com> - 2012-05-30 22:57 +1200
        Re: Error returns and repeated code, GOTOs, etc. Willem <willem@toad.stack.nl> - 2012-05-30 11:04 +0000
        Re: Error returns and repeated code, GOTOs, etc. nick_keighley_nospam@hotmail.com - 2012-05-30 04:53 -0700
    Re: Error returns and repeated code, GOTOs, etc. "BartC" <bc@freeuk.com> - 2012-05-30 13:28 +0100
      Re: Error returns and repeated code, GOTOs, etc. mike3 <mike4ty4@yahoo.com> - 2012-05-30 13:57 -0700
    Re: Error returns and repeated code, GOTOs, etc. "io_x" <a@b.c.invalid> - 2012-05-30 15:19 +0200
      Re: Error returns and repeated code, GOTOs, etc. Mark Bluemel <mark.bluemel@googlemail.com> - 2012-05-31 01:10 -0700
      Re: Error returns and repeated code, GOTOs, etc. "io_x" <a@b.c.invalid> - 2012-06-02 17:34 +0200
        Re: Error returns and repeated code, GOTOs, etc. "io_x" <a@b.c.invalid> - 2012-06-03 10:33 +0200
    Re: Error returns and repeated code, GOTOs, etc. Ike Naar <ike@iceland.freeshell.org> - 2012-05-30 13:56 +0000
      Re: Error returns and repeated code, GOTOs, etc. Kulin <remailer@reece.net.au> - 2012-05-30 17:29 +0000
    Re: Error returns and repeated code, GOTOs, etc. ImpalerCore <jadill33@gmail.com> - 2012-05-30 07:13 -0700
      Re: Error returns and repeated code, GOTOs, etc. Thad Smith <ThadSmith@acm.org> - 2012-06-02 07:20 -0600
    Re: Error returns and repeated code, GOTOs, etc. Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-05-30 16:37 +0100
    Re: Error returns and repeated code, GOTOs, etc. Johann Klammer <klammerj@NOSPAM.a1.net> - 2012-05-30 19:05 +0200
    Re: Error returns and repeated code, GOTOs, etc. Tim Rentsch <txr@alumni.caltech.edu> - 2012-05-31 13:19 -0700
      Re: Error returns and repeated code, GOTOs, etc. mike3 <mike4ty4@yahoo.com> - 2012-05-31 13:49 -0700
        Re: Error returns and repeated code, GOTOs, etc. "BartC" <bc@freeuk.com> - 2012-05-31 22:08 +0100
          Re: Error returns and repeated code, GOTOs, etc. mike3 <mike4ty4@yahoo.com> - 2012-05-31 16:08 -0700
        Re: Error returns and repeated code, GOTOs, etc. Tim Rentsch <txr@alumni.caltech.edu> - 2012-05-31 17:34 -0700
        Re: Error returns and repeated code, GOTOs, etc. Willem <willem@toad.stack.nl> - 2012-06-01 07:40 +0000
    GOTOs discovered in "real world" program! (was Re: Error returns and repeated code, GOTOs, etc.) mike3 <mike4ty4@yahoo.com> - 2012-05-31 16:39 -0700
      Re: GOTOs discovered in "real world" program! Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-06-01 03:21 +0100
        Re: GOTOs discovered in "real world" program! mike3 <mike4ty4@yahoo.com> - 2012-06-01 03:49 -0700
          Re: GOTOs discovered in "real world" program! Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-06-02 02:15 +0100
            Re: GOTOs discovered in "real world" program! mike3 <mike4ty4@yahoo.com> - 2012-06-01 19:45 -0700
              Re: GOTOs discovered in "real world" program! Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-06-02 15:00 +0100
                Re: GOTOs discovered in "real world" program! mike3 <mike4ty4@yahoo.com> - 2012-06-02 16:44 -0700
                  Re: GOTOs discovered in "real world" program! Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-06-03 03:51 +0100
        Re: GOTOs discovered in "real world" program! "Aaron W.  Hsu" <arcfide@sacrideo.us> - 2012-06-01 12:06 -0400
          Re: GOTOs discovered in "real world" program! Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-06-02 02:01 +0100
            Re: GOTOs discovered in "real world" program! mike3 <mike4ty4@yahoo.com> - 2012-06-01 19:46 -0700
              Re: GOTOs discovered in "real world" program! mike3 <mike4ty4@yahoo.com> - 2012-06-01 21:19 -0700
                Re: GOTOs discovered in "real world" program! blmblm@myrealbox.com <blmblm.myrealbox@gmail.com> - 2012-06-02 16:35 +0000
              Re: GOTOs discovered in "real world" program! Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-06-02 14:50 +0100
              Re: GOTOs discovered in "real world" program! Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-06-02 07:04 -0700
            Re: GOTOs discovered in "real world" program! "Aaron W. Hsu" <arcfide@sacrideo.us> - 2012-06-02 04:37 -0500
              Re: GOTOs discovered in "real world" program! mike3 <mike4ty4@yahoo.com> - 2012-06-02 03:40 -0700
                Re: GOTOs discovered in "real world" program! Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-06-02 14:46 +0100
                  Re: GOTOs discovered in "real world" program! "BartC" <bc@freeuk.com> - 2012-06-02 17:10 +0100
                  Re: GOTOs discovered in "real world" program! Robert Wessel <robertwessel2@yahoo.com> - 2012-06-02 11:35 -0500
      Re: GOTOs discovered in "real world" program! (was Re: Error returns and repeated code, GOTOs, etc.) "BartC" <bc@freeuk.com> - 2012-06-02 09:46 +0100
        Re: GOTOs discovered in "real world" program! (was Re: Error returns and repeated code, GOTOs, etc.) "io_x" <a@b.c.invalid> - 2012-06-03 10:43 +0200
          Re: GOTOs discovered in "real world" program! (was Re: Error returns and repeated code, GOTOs, etc.) "BartC" <bc@freeuk.com> - 2012-06-03 10:58 +0100
            Re: GOTOs discovered in "real world" program! (was Re: Error returns and repeated code, GOTOs, etc.) "io_x" <a@b.c.invalid> - 2012-06-03 17:18 +0200
            Re: GOTOs discovered in "real world" program! (was Re: Error returns and repeated code, GOTOs, etc.) jgk@panix.com (Joe keane) - 2012-06-04 20:40 +0000
              Re: GOTOs discovered in "real world" program! (was Re: Error returns and repeated code, GOTOs, etc.) jgk@panix.com (Joe keane) - 2012-06-05 01:03 +0000
                Re: GOTOs discovered in "real world" program! Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2012-06-04 21:36 -0600
                  Re: GOTOs discovered in "real world" program! jgk@panix.com (Joe keane) - 2012-06-05 15:13 +0000
                Re: GOTOs discovered in "real world" program! (was Re: Error returns and repeated code, GOTOs, etc.) Ike Naar <ike@sverige.freeshell.org> - 2012-06-05 08:12 +0000
                  Re: GOTOs discovered in "real world" program! (was Re: Error returns and repeated code, GOTOs, etc.) James Kuyper <jameskuyper@verizon.net> - 2012-06-05 06:00 -0400
              Re: GOTOs discovered in "real world" program! (was Re: Error returns and repeated code, GOTOs, etc.) jgk@panix.com (Joe keane) - 2012-06-05 02:05 +0000
                Re: GOTOs discovered in "real world" program! (was Re: Error returns and repeated code, GOTOs, etc.) Martin Shobe <martin.shobe@yahoo.com> - 2012-06-05 03:16 +0000
          Re: GOTOs discovered in "real world" program! (was Re: Error returns and repeated code, GOTOs, etc.) "io_x" <a@b.c.invalid> - 2012-06-03 17:30 +0200
            Re: GOTOs discovered in "real world" program! (was Re: Error returns and repeated code, GOTOs, etc.) Jean-Christophe <5.d@free.fr> - 2012-06-03 09:02 -0700
              Re: GOTOs discovered in "real world" program! (was Re: Error returns and repeated code, GOTOs, etc.) Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-06-03 22:37 +0100
                Re: GOTOs discovered in "real world" program! (was Re: Error returns and repeated code, GOTOs, etc.) Ike Naar <ike@iceland.freeshell.org> - 2012-06-04 07:28 +0000
                Re: GOTOs discovered in "real world" program! (was Re: Error returns and repeated code, GOTOs, etc.) Tim Rentsch <txr@alumni.caltech.edu> - 2012-06-08 01:28 -0700
      Why was there a GOTO? (was Re: GOTOs discovered in "real world" program!) mike3 <mike4ty4@yahoo.com> - 2012-06-06 02:54 -0700
        Re: Why was there a GOTO? (was Re: GOTOs discovered in "real world" program!) Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-06-06 13:14 +0100
          Re: Why was there a GOTO? (was Re: GOTOs discovered in "real world" program!) pete <pfiland@mindspring.com> - 2012-06-06 09:22 -0400
            Re: Why was there a GOTO? (was Re: GOTOs discovered in "real world" program!) Willem <willem@toad.stack.nl> - 2012-06-06 13:49 +0000
              Re: Why was there a GOTO? (was Re: GOTOs discovered in "real world" program!) Rui Maciel <rui.maciel@gmail.com> - 2012-06-06 14:56 +0100
              Re: Why was there a GOTO? (was Re: GOTOs discovered in "real world" program!) James Kuyper <jameskuyper@verizon.net> - 2012-06-06 10:17 -0400
        Re: Why was there a GOTO? (was Re: GOTOs discovered in "real world" program!) Angel <angel+news@spamcop.net> - 2012-06-06 13:06 +0000
          Re: Why was there a GOTO? (was Re: GOTOs discovered in "real world" program!) mike3 <mike4ty4@yahoo.com> - 2012-06-07 16:26 -0700
            Re: Why was there a GOTO? (was Re: GOTOs discovered in "real world" program!) Angel <angel+news@spamcop.net> - 2012-06-08 14:26 +0000
              Re: Why was there a GOTO? (was Re: GOTOs discovered in "real world" program!) mike3 <mike4ty4@yahoo.com> - 2012-06-08 15:19 -0700
                Re: Why was there a GOTO? (was Re: GOTOs discovered in "real world" program!) Angel <angel+news@spamcop.net> - 2012-06-08 23:32 +0000
                Re: Why was there a GOTO? (was Re: GOTOs discovered in "real world" program!) "BartC" <bc@freeuk.com> - 2012-06-09 01:14 +0100
                  Re: Why was there a GOTO? (was Re: GOTOs discovered in "real world" program!) Jean-Christophe <5.d@free.fr> - 2012-06-09 04:36 -0700
                  Re: Why was there a GOTO? (was Re: GOTOs discovered in "real world" program!) Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-06-09 05:54 -0700
                    Re: Why was there a GOTO? (was Re: GOTOs discovered in "real world" program!) "BartC" <bc@freeuk.com> - 2012-06-09 16:12 +0100
                      Re: Why was there a GOTO? (was Re: GOTOs discovered in "real world" program!) Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-06-09 08:44 -0700
                        Re: Why was there a GOTO? (was Re: GOTOs discovered in "real world" program!) "io_x" <a@b.c.invalid> - 2012-06-10 18:23 +0200
                          Re: Why was there a GOTO? (was Re: GOTOs discovered in "real world" program!) "io_x" <a@b.c.invalid> - 2012-06-10 19:42 +0200
                            Re: Why was there a GOTO? (was Re: GOTOs discovered in "real world" program!) "io_x" <a@b.c.invalid> - 2012-06-14 18:00 +0200
                          Re: Why was there a GOTO? (was Re: GOTOs discovered in "real world" program!) nick_keighley_nospam@hotmail.com - 2012-06-11 01:14 -0700
                            Re: Why was there a GOTO? (was Re: GOTOs discovered in "real world" program!) "io_x" <a@b.c.invalid> - 2012-06-12 08:01 +0200
                              Re: Why was there a GOTO? (was Re: GOTOs discovered in "real world" program!) nick_keighley_nospam@hotmail.com - 2012-06-12 05:27 -0700
                            Re: Why was there a GOTO? (was Re: GOTOs discovered in "real world" program!) "io_x" <a@b.c.invalid> - 2012-06-12 08:44 +0200
                    Re: Why was there a GOTO? (was Re: GOTOs discovered in "real world" program!) jgk@panix.com (Joe keane) - 2012-06-11 17:24 +0000
                      Re: Why was there a GOTO? (was Re: GOTOs discovered in "real world" program!) "BartC" <bc@freeuk.com> - 2012-06-11 19:02 +0100
                        Re: Why was there a GOTO? (was Re: GOTOs discovered in "real world" program!) jgk@panix.com (Joe keane) - 2012-06-12 20:03 +0000
                          Re: Why was there a GOTO? (was Re: GOTOs discovered in "real world" program!) nick_keighley_nospam@hotmail.com - 2012-06-13 00:58 -0700
                            Re: Why was there a GOTO? (was Re: GOTOs discovered in "real world" program!) James Kuyper <jameskuyper@verizon.net> - 2012-06-13 06:37 -0400
                              Evil in Programming   Was: Why was there a GOTO? (was Re: GOTOs discovered in "real world" program!) nick_keighley_nospam@hotmail.com - 2012-06-13 04:50 -0700
                            Re: Why was there a GOTO? (was Re: GOTOs discovered in "real world" program!) gwowen <gwowen@gmail.com> - 2012-06-13 07:02 -0700
                            Re: Why was there a GOTO? (was Re: GOTOs discovered in "real world" program!) Les Cargill <lcargill99@comcast.com> - 2012-06-13 12:47 -0500
                              Re: Why was there a GOTO? (was Re: GOTOs discovered in "real world" program!) James Kuyper <jameskuyper@verizon.net> - 2012-06-13 14:17 -0400
                                Re: Why was there a GOTO? (was Re: GOTOs discovered in "real world" program!) Willem <willem@toad.stack.nl> - 2012-06-13 19:44 +0000
                                  Re: Why was there a GOTO? (was Re: GOTOs discovered in "real world" program!) James Kuyper <jameskuyper@verizon.net> - 2012-06-13 15:52 -0400
                                Re: Why was there a GOTO? (was Re: GOTOs discovered in "real world" program!) Les Cargill <lcargill99@comcast.com> - 2012-06-13 17:45 -0500
                                  Re: Why was there a GOTO? (was Re: GOTOs discovered in "real world" program!) James Kuyper <jameskuyper@verizon.net> - 2012-06-13 19:07 -0400
                                Re: Why was there a GOTO? (was Re: GOTOs discovered in "real world" program!) jgk@panix.com (Joe keane) - 2012-06-14 23:03 +0000
                                Re: Why was there a GOTO? (was Re: GOTOs discovered in "real world" program!) Kaz Kylheku <kaz@kylheku.com> - 2012-06-14 23:25 +0000
                                  Re: Why was there a GOTO? (was Re: GOTOs discovered in "real world" program!) Les Cargill <lcargill99@comcast.com> - 2012-06-14 19:25 -0500
                                    Re: Why was there a GOTO? (was Re: GOTOs discovered in "real world" program!) 88888 Dihedral <dihedral88888@googlemail.com> - 2012-06-17 20:32 -0700
                                      Re: Why was there a GOTO? (was Re: GOTOs discovered in "real world" program!) nick_keighley_nospam@hotmail.com - 2012-06-18 01:30 -0700
                                        Re: Why was there a GOTO? (was Re: GOTOs discovered in "real world" program!) Les Cargill <lcargill99@comcast.com> - 2012-06-18 07:06 -0500
                            Re: Why was there a GOTO? Gareth Owen <gwowen@gmail.com> - 2012-06-13 19:57 +0100
                  Re: Why was there a GOTO? (was Re: GOTOs discovered in "real world" program!) jgk@panix.com (Joe keane) - 2012-06-10 16:56 +0000
    Another problem (was Re: Error returns and repeated code, GOTOs, etc.) mike3 <mike4ty4@yahoo.com> - 2012-05-31 16:46 -0700
      Re: Another problem (was Re: Error returns and repeated code, GOTOs, etc.) Ian Collins <ian-news@hotmail.com> - 2012-06-01 15:55 +1200
    Re: Error returns and repeated code, GOTOs, etc. gwowen <gwowen@gmail.com> - 2012-06-06 08:12 -0700

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#21522 — Error returns and repeated code, GOTOs, etc.

Hi.

I've got some stuff that looks like this:

---
ErrorCode MyFunc()
{
          BigNum a, b, c, d;
          ErrorCode rv;

          rv = BigNum_Initialize(&a);
          if(rv != ERROR_SUCCESS)
            return(rv);

          rv = BigNum_Initialize(&b);
          if(rv != ERROR_SUCCESS)
          {
            BigNum_Free(&a); /* and what if THIS fails??? :) */
            return(rv);
          }

          rv = BigNum_Initialize(&c);
          if(rv != ERROR_SUCCESS)
          {
            BigNum_Free(&b);
            BigNum_Free(&a);
            return(rv);
          }

          rv = BigNum_Initialize(&d);
          if(rv != ERROR_SUCCESS)
          {
            BigNum_Free(&c);
            BigNum_Free(&b);
            BigNum_Free(&a);
            return(rv);
          }

          /* do some math */
          rv = BigNum_Set(&b, 3);
          if(rv != ERROR_SUCCESS)
          {
            BigNum_Free(&d);
            BigNum_Free(&c);
            BigNum_Free(&b);
            BigNum_Free(&a);
            return(rv);
          }

          ...

          /* free buffers */
          rv = BigNum_Free(&d);
          if(rv != ERROR_SUCCESS)
          {
            BigNum_Free(&c);
            BigNum_Free(&b);
            BigNum_Free(&a);
            return(rv);
          }

          rv = BigNum_Free(&c);
          if(rv != ERROR_SUCCESS)
          {
            BigNum_Free(&b);
            BigNum_Free(&a);
            return(rv);
          }

          rv = BigNum_Free(&b);
          if(rv != ERROR_SUCCESS)
          {
            BigNum_Free(&a);
            return(rv);
          }

          rv = BigNum_Free(&a);
          if(rv != ERROR_SUCCESS)
            return(rv);

          return(ERROR_SUCCESS);
}
---

But this is nasty, with all those duplicated "free" blocks. What can
be done to relieve this code duplication? It's ugly, it hurts my
freaking eyes and my nose is screaming for relief. And it hurts
maintainability to no end -- what if we decide to add more capability
to MyFunc() that requires additional bignums? Oy... We'd have to
update _all those blocks_.

I was thinking about using a "goto", but Gotos are Bad, aren't they? I
can't believe I may have to use a goto! What about Djikstra's famous
letter? Is it possible that perhaps a goto may be GOOD here? Because
with a goto this would all seem much simpler. If we violate Djikstra,
we get:

---

ErrorCode MyFunc()
{
          BigNum a, b, c, d;
          ErrorCode rv;

          rv = BigNum_Initialize(&a); if(rv != ERROR_SUCCESS) goto
fail0;
          rv = BigNum_Initialize(&b); if(rv != ERROR_SUCCESS) goto
fail1;
          rv = BigNum_Initialize(&c); if(rv != ERROR_SUCCESS) goto
fail2;
          rv = BigNum_Initialize(&d); if(rv != ERROR_SUCCESS) goto
fail3;

          /* do some math */
          rv = BigNum_Set(&b, 3); if(rv != ERROR_SUCCESS) goto fail4;

          ...

          /* free buffers */
          rv = BigNum_Free(&d); if(rv != ERROR_SUCCESS) goto fail3;
          rv = BigNum_Free(&c); if(rv != ERROR_SUCCESS) goto fail2;
          rv = BigNum_Free(&b); if(rv != ERROR_SUCCESS) goto fail1;
          rv = BigNum_Free(&a); if(rv != ERROR_SUCCESS) goto fail0;

          return(ERROR_SUCCESS);

fail4:    BigNum_Free(&d);
fail3:    BigNum_Free(&c);
fail2:    BigNum_Free(&b);
fail1:    BigNum_Free(&a);
fail0:    return(rv);
}
---

But we've violated Djikstra and we've used a "bad" goto. How would
_you_ write MyFunc() above?

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#21523

On 2012-05-30, mike3 <mike4ty4@yahoo.com> wrote:
> Hi.
>
> I've got some stuff that looks like this:
>
> [stuff snipped]
>
> But this is nasty, with all those duplicated "free" blocks. What can
> be done to relieve this code duplication? It's ugly, it hurts my
> freaking eyes and my nose is screaming for relief. And it hurts
> maintainability to no end -- what if we decide to add more capability
> to MyFunc() that requires additional bignums? Oy... We'd have to
> update _all those blocks_.

ErrorCode MyFunc(void)
{
  BigNum a;
  ErrorCode rv = BigNum_Initialize(&a);
  if (rv == ERROR_SUCCESS)
  {
    BigNum b;
    rv = BigNum_Initialize(&b);
    if (rv == ERROR_SUCCESS)
    {
      BigNum c;
      rv = BigNum_Initialize(&c);
      if (rv == ERROR_SUCCESS)
      {
        BigNum d;
        rv = BigNum_Initialize(&d);
        if (rv == ERROR_SUCCESS)
        {
          /* do some math */
          rv = BigNum_Set(&b, 3);
          if (rv == ERROR_SUCCESS)
          {
            /* ... */
          }
          BigNum_Free(&d);
        }
        BigNum_Free(&c);
      }
      BigNum_Free(&b);
    }
    BigNum_Free(&a);
  }
  return rv;
}

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#21524

mike3 <mike4ty4@yahoo.com> wrote:
> But this is nasty, with all those duplicated "free" blocks. What can
> be done to relieve this code duplication? [...]

Add a garbage collector for BigNums.

-- 
Nils M Holm  < n m h @ t 3 x . o r g >  www.t3x.org

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#21525

בתאריך יום רביעי, 30 במאי 2012 06:44:06 UTC+1, מאת mike3:
> 
> But we've violated Djikstra and we've used a "bad" goto. How would
> _you_ write MyFunc() above?
>
I use gotos for handling memory allocation failures, but almost never for any other purpose.
-- 
Basic Algorithms - ANSI C source for fundamental programming operations.
http://www.malcolmmclean.site11.com/www
  

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#21527

On May 30, 1:52 am, Malcolm McLean <malcolm.mcle...@btinternet.com>
wrote:
> בתאריך יום רביעי, 30 במאי 2012 06:44:06 UTC+1, מאת mike3:
>
> > But we've violated Djikstra and we've used a "bad" goto. How would
> > _you_ write MyFunc() above?
>
> I use gotos for handling memory allocation failures, but almost never for any other purpose.

So what would you do in the above circumstance?

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#21528

On 05/30/2012 06:44 AM, mike3 wrote:

> But we've violated Djikstra and we've used a "bad" goto. How would
> _you_ write MyFunc() above?

I personally don't like the infinitely indented if approach...

In C, I think it's probably OK to use goto for "exception handling".

If you have some way of indicating that a BigNum is uninitialised (e.g. 
a BIGNUM_NULL macro) and you make BigNum_Free() set the BigNum to this 
value, you could use something like this - goto-rich but less repetitive:-

ErrorCode MyFunc()
{
           BigNum a = BIGNUM_NULL;
           BigNum b = BIGNUM_NULL;
           BigNum c = BIGNUM_NULL;
           BigNum d = BIGNUM_NULL;
           ErrorCode rv;

           rv = BigNum_Initialize(&a);
           if(rv != ERROR_SUCCESS)
            goto failed;

           rv = BigNum_Initialize(&b);
           if(rv != ERROR_SUCCESS)
            goto failed;

           rv = BigNum_Initialize(&c);
           if(rv != ERROR_SUCCESS)
            goto failed;

           rv = BigNum_Initialize(&d);
           if(rv != ERROR_SUCCESS)
            goto failed;

           /* do some math */
           rv = BigNum_Set(&b, 3);
           if(rv != ERROR_SUCCESS)
            goto failed;

           ...
          /* free buffers */
           rv = BigNum_Free(&d);
           if(rv != ERROR_SUCCESS)
            goto failed;

           rv = BigNum_Free(&c);
           if(rv != ERROR_SUCCESS)
            goto failed;

           rv = BigNum_Free(&b);
           if(rv != ERROR_SUCCESS)
            goto failed;

           rv = BigNum_Free(&a);
           if(rv != ERROR_SUCCESS)
            goto failed;

           return(ERROR_SUCCESS);

failed: /* we'll try and clean up, but won't care too much if it fails */
         if (d != BIGNUM_NULL)
           BigNum_Free(&d);
         if (c != BIGNUM_NULL)
           BigNum_Free(&c);
         if (b != BIGNUM_NULL)
           BigNum_Free(&b);
         if (a != BIGNUM_NULL)
           BigNum_Free(&a);

         return(rv);
}

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#21529

MarkBluemel wrote:
) On 05/30/2012 06:44 AM, mike3 wrote:
)
)> But we've violated Djikstra and we've used a "bad" goto. How would
)> _you_ write MyFunc() above?
)
) I personally don't like the infinitely indented if approach...
)
) In C, I think it's probably OK to use goto for "exception handling".
)
) If you have some way of indicating that a BigNum is uninitialised (e.g. 
) a BIGNUM_NULL macro) and you make BigNum_Free() set the BigNum to this 
) value, you could use something like this - goto-rich but less repetitive:-

Rewritten to get rid of the gotos:

ErrorCode DoMath(BigNum a, BigNum b. BigNum c, BigNum d)
{
        ErrorCode rv;
        /* do some math */
        rv = BigNum_Set(&b, 3);
        if (rv != ERROR_SUCCESS) return rv;

        ...

        return ERROR_SUCCESS;
}
ErrorCode MyFunc()
{
        BigNum a = BIGNUM_NULL;
        BigNum b = BIGNUM_NULL;
        BigNum c = BIGNUM_NULL;
        BigNum d = BIGNUM_NULL;
        ErrorCode rv = ERROR_SUCCESS;

        if (rv == ERROR_SUCCESS) rv = BigNum_Initialize(&a);
        if (rv == ERROR_SUCCESS) rv = BigNum_Initialize(&b);
        if (rv == ERROR_SUCCESS) rv = BigNum_Initialize(&c);
        if (rv == ERROR_SUCCESS) rv = BigNum_Initialize(&d);

        if (rv == ERROR_SUCCESS) rv = DoMath(a, b, c, d);

        /* BigNum_Free should check for BIGNUM_NULL itself */
        BigNum_Free(&d);
        BigNum_Free(&c); 
        BigNum_Free(&b);
        BigNum_Free(&a);

        return rv;
}

If you want to be more concise, you can make ERROR_SUCCESS equal 0,
and then you can simply do:

    rv = BigNum_Initialize(&a) || ... || BigNum_Set(&b, 3) || BigNum_AddTo(&a, &b) || ... ;

Which will short-circuit at the first failure.

SaSW, Willem
-- 
Disclaimer: I am in no way responsible for any of the statements
            made in the above text. For all I know I might be
            drugged or something..
            No I'm not paranoid. You all think I'm paranoid, don't you !
#EOT

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#21537

On May 30, 5:18 am, Willem <wil...@toad.stack.nl> wrote:
> If you want to be more concise, you can make ERROR_SUCCESS equal 0,
> and then you can simply do:
>
>     rv = BigNum_Initialize(&a) || ... || BigNum_Set(&b, 3) || BigNum_AddTo(&a, &b) || ... ;
>
> Which will short-circuit at the first failure.

Which in a sufficiently complicated function like an ECC point add/
double would result in spaghetti code and your termination.  :-)

The "if (err == OK) ..." method is cool but frankly I just like the
goto's when I'm writing out something the long way.

Tom

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#21548

tom st denis wrote:
) On May 30, 5:18?am, Willem <wil...@toad.stack.nl> wrote:
)> If you want to be more concise, you can make ERROR_SUCCESS equal 0,
)> and then you can simply do:
)>
)> ? ? rv = BigNum_Initialize(&a) || ... || BigNum_Set(&b, 3) || BigNum_AddTo(&a, &b) || ... ;
)>
)> Which will short-circuit at the first failure.
)
) Which in a sufficiently complicated function like an ECC point add/
) double would result in spaghetti code and your termination.  :-)

How can it be spaghetti when it's a single line of calls, one after
the other?  Spaghetti code is meant to be tangled, isn't it?

) The "if (err == OK) ..." method is cool but frankly I just like the
) goto's when I'm writing out something the long way.

I've seen the (err == OK) method used too much in code that didn't require
cleanup at end of function.  Apparently somebody at our company believes in
'one-function-one-return' religiously.  I agree gotos are better.


Another method is to have all 'bignum' functions check for 'error' inputs
and generate 'error' outputs when they encounter them (or whenever they
 encounter an error), and then you only have to check for an 'error'
result at the very end.

Something like:

int DoCalc()
{
  int rv;
  BigNum a;
  BigNum b;
  BigNum c;
  BigNum d;

  BigNum_Init(&a);
  BigNum_Init(&b);
  BigNum_Init(&c);
  BigNum_Init(&d);

  BigNum_Set(&a, 3);
  BigNum_Set(&b, 5);
  ...
  BigNum_Multiply(&c, &d);
  ...
  if ((rv = BigNum_GetError(&d)) != ERROR_SUCCESS) return rv;

  BigNum_Print("The result is: %bn", &d);
  BigNum_Free(&a);
  BigNum_Free(&b);
  BigNum_Free(&c);
  BigNum_Free(&d);

  return ERROR_SUCCESS;
}

The only weirdside to this is when a value is not used in the final result,
then that value will not be checked for errors.


SaSW, Willem
-- 
Disclaimer: I am in no way responsible for any of the statements
            made in the above text. For all I know I might be
            drugged or something..
            No I'm not paranoid. You all think I'm paranoid, don't you !
#EOT

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#21628

On May 30, 12:26 pm, Willem <wil...@toad.stack.nl> wrote:
> tom st denis wrote:
>
> ) On May 30, 5:18?am, Willem <wil...@toad.stack.nl> wrote:
> )> If you want to be more concise, you can make ERROR_SUCCESS equal 0,
> )> and then you can simply do:
> )>
> )> ? ? rv = BigNum_Initialize(&a) || ... || BigNum_Set(&b, 3) || BigNum_AddTo(&a, &b) || ... ;
> )>
> )> Which will short-circuit at the first failure.
> )
> ) Which in a sufficiently complicated function like an ECC point add/
> ) double would result in spaghetti code and your termination.  :-)
>
> How can it be spaghetti when it's a single line of calls, one after
> the other?  Spaghetti code is meant to be tangled, isn't it?
>
> ) The "if (err == OK) ..." method is cool but frankly I just like the
> ) goto's when I'm writing out something the long way.
>
> I've seen the (err == OK) method used too much in code that didn't require
> cleanup at end of function.  Apparently somebody at our company believes in
> 'one-function-one-return' religiously.  I agree gotos are better.
>
> Another method is to have all 'bignum' functions check for 'error' inputs
> and generate 'error' outputs when they encounter them (or whenever they
>  encounter an error), and then you only have to check for an 'error'
> result at the very end.
>
> Something like:
>
> int DoCalc()
> {
>   int rv;
>   BigNum a;
>   BigNum b;
>   BigNum c;
>   BigNum d;
>
>   BigNum_Init(&a);
>   BigNum_Init(&b);
>   BigNum_Init(&c);
>   BigNum_Init(&d);
>
>   BigNum_Set(&a, 3);
>   BigNum_Set(&b, 5);
>   ...
>   BigNum_Multiply(&c, &d);
>   ...
>   if ((rv = BigNum_GetError(&d)) != ERROR_SUCCESS) return rv;
>
>   BigNum_Print("The result is: %bn", &d);
>   BigNum_Free(&a);
>   BigNum_Free(&b);
>   BigNum_Free(&c);
>   BigNum_Free(&d);
>
>   return ERROR_SUCCESS;
>
> }
>
> The only weirdside to this is when a value is not used in the final result,
> then that value will not be checked for errors.

That only works if you capture the error codes in your bignum
structure otherwise it's not thread safe.

Tom

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#21746

tom st denis wrote:
) On May 30, 12:26?pm, Willem <wil...@toad.stack.nl> wrote:
)> Another method is to have all 'bignum' functions check for 'error' inputs
)> and generate 'error' outputs when they encounter them (or whenever they
)> ?encounter an error), and then you only have to check for an 'error'
)> result at the very end.
)>
)> Something like:

<snip>

)> The only weirdside to this is when a value is not used in the final result,
)> then that value will not be checked for errors.
)
) That only works if you capture the error codes in your bignum
) structure otherwise it's not thread safe.

I don't see any way to implement what I described other than storing
the error codes in the bignum structures.


SaSW, Willem
-- 
Disclaimer: I am in no way responsible for any of the statements
            made in the above text. For all I know I might be
            drugged or something..
            No I'm not paranoid. You all think I'm paranoid, don't you !
#EOT

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#21677

In article <slrnjscii7.2aju.willem@toad.stack.nl>,
Willem  <willem@toad.stack.nl> wrote:
>I agree gotos are better.

I agree gotos are better.

int func(int x)
{
    int err;
    struct bar *a;
    struct bar *b;
    struct bar *c;
    int err2;

    err = allocate_bar(&a);
    if (err != X_OK)
	goto done;

    err = allocate_bar(&b);
    if (err != X_OK)
	goto free_a;

    err = allocate_bar(&c);
    if (err != X_OK)
	goto free_b;

    ...

    /* normal exit */

    err = free_bar(c);

    err2 = free_bar(b);
    err = err != X_OK ? err : err2;

    err2 = free_bar(a);
    err = err != X_OK ? err : err2;
    return err;

    /* error exit */

    err2 = free_bar(c);
    (void) err2;

  free_b:
    err2 = free_bar(b);
    (void) err2;

  free_a:
    err2 = free_bar(a);
    (void) err2;

  done:
    return err;
}

do that in C++!

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#21685

On Jun 2, 3:54 pm, j...@panix.com (Joe keane) wrote:

> I agree gotos are better.

#define SIZE 3
int func(int x)
{
int i, err;
struct bar *s[SIZE];

// init
 for( err=X_OK, i=0; (err==X_OK) && (i<SIZE); i++ )
  err = allocate_bar( &s[i] );

// check success
 if( err == X_OK )
 { // process ...
 }

// free only allocated bar(s)
 while( --i >= 0 ) free_bar( s[i] );

// done
return err; // zero = success
}


> int func(int x)
> {
>     int err;
>     struct bar *a;
>     struct bar *b;
>     struct bar *c;
>     int err2;
>
>     err = allocate_bar(&a);
>     if (err != X_OK)
>         goto done;
>
>     err = allocate_bar(&b);
>     if (err != X_OK)
>         goto free_a;
>
>     err = allocate_bar(&c);
>     if (err != X_OK)
>         goto free_b;
>
>     ...
>
>     /* normal exit */
>
>     err = free_bar(c);
>
>     err2 = free_bar(b);
>     err = err != X_OK ? err : err2;
>
>     err2 = free_bar(a);
>     err = err != X_OK ? err : err2;
>     return err;
>
>     /* error exit */
>
>     err2 = free_bar(c);
>     (void) err2;
>
>   free_b:
>     err2 = free_bar(b);
>     (void) err2;
>
>   free_a:
>     err2 = free_bar(a);
>     (void) err2;
>
>   done:
>     return err;
> }

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#21695

In article <a77db563-a307-4c82-a32d-18fbc238afec@cu1g2000vbb.googlegroups.com>,
Jean-Christophe  <5.d@free.fr> wrote:
>#define SIZE 3
>int func(int x)
>{
>int i, err;
>struct bar *s[SIZE];
>
>// init
> for( err=X_OK, i=0; (err==X_OK) && (i<SIZE); i++ )
>  err = allocate_bar( &s[i] );
>
>// check success
> if( err == X_OK )
> { // process ...
> }
>
>// free only allocated bar(s)
> while( --i >= 0 ) free_bar( s[i] );
>
>// done
>return err; // zero = success
>}

I used 'struct bar',
for all of them,
for sake of example.

It's very likely that in real world code
they are all different types,
with different functions to allocate them and unallocate them,
and so some code to iterate over them is likely to be
some more confusing than helpful.

If they are the same type,
such that you can put them in an array,
then of course what you say is better.

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#21708

On 2 juin, 18:37, j...@panix.com (Joe keane) :

> I used 'struct bar',
> for all of them, for sake of example.
> It's very likely that in real world code
> they are all different types,
> with different functions to allocate them and unallocate them,
> and so some code to iterate over them is likely to be
> some more confusing than helpful.

I'd rather encapsulate functions pointers
( allocate, init, ... etc ... )
into the structure itself, to allow the
use of identical syntax all down the code.
It makes it more readable, and shorter.
And still, this is not C++, juste pure C.

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#21688

jgk@panix.com (Joe keane) writes:

> In article <slrnjscii7.2aju.willem@toad.stack.nl>,
> Willem  <willem@toad.stack.nl> wrote:
>>I agree gotos are better.
>
> I agree gotos are better.
>
> int func(int x)
> {
>     int err;
>     struct bar *a;
>     struct bar *b;
>     struct bar *c;
>     int err2;
>
>     err = allocate_bar(&a);
>     if (err != X_OK)
> 	goto done;
>
>     err = allocate_bar(&b);
>     if (err != X_OK)
> 	goto free_a;
>
>     err = allocate_bar(&c);
>     if (err != X_OK)
> 	goto free_b;
>
>     ...
>
>     /* normal exit */
>
>     err = free_bar(c);
>
>     err2 = free_bar(b);
>     err = err != X_OK ? err : err2;
>
>     err2 = free_bar(a);
>     err = err != X_OK ? err : err2;
>     return err;
>
>     /* error exit */
>
>     err2 = free_bar(c);
>     (void) err2;

This code is unreachable but I think it's not needed by any path so it's
probably just there due to an editing error.

>   free_b:
>     err2 = free_bar(b);
>     (void) err2;
>
>   free_a:
>     err2 = free_bar(a);
>     (void) err2;
>
>   done:
>     return err;
> }
>
> do that in C++!

Why do you think this is not already C++?

BTW, to my mind this API is broken.  I like allocation functions that
return NULL on failure.  If you need more data, an error-collecting
parameter can be passed.  Having NULL pointers make it possible to write
clean-up code that does not depend on the order of allocation.

However, using the same API, I'd write:

  int func(int x)
  {
      int err_a, err_b, err_c;
      struct bar *a, *b, *c;
 
      err_a = allocate_bar(&a);
      err_b = allocate_bar(&b);
      err_c = allocate_bar(&c);

      if (err_a == X_OK && err_b == X_OK && err_c == X_OK) {
         /* normal code */
      }
 
      if (err_a == X_OK) err_a = free_bar(a);
      if (err_b == X_OK) err_b = free_bar(b);
      if (err_c == X_OK) err_c = free_bar(c);
 
      return err_a == X_OK && err_b == X_OK && err_c == X_OK;
  }

This does not return the same value, as your code but that's not hard to
change.  I found your code's preference for one possible error over
another to be a little odd, so I changed it to appear more uniform.

-- 
Ben.

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#21705

In article <0.ad98122c5f4b9fe6aef5.20120602154227BST.87aa0lepws.fsf@bsb.me.uk>,
Ben Bacarisse  <ben.usenet@bsb.me.uk> wrote:
>I like allocation functions that return NULL on failure.

I like allocation functions that set the carry bit on failure.

My own convention is that if a function returns less than zero, it has
reset your state to the most extent possible, and none of the 'output'
parameters are changed (but be liberal in what you receive).

IMHE the stupid mistakes occur when you mix together conventions [it
-should- be easy to do this, but we are just monkeys].

When you prevent stupid mistakes, you force people to make the more
complicated mistakes.

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#21734

jgk@panix.com (Joe keane) writes:

> In article <0.ad98122c5f4b9fe6aef5.20120602154227BST.87aa0lepws.fsf@bsb.me.uk>,
> Ben Bacarisse  <ben.usenet@bsb.me.uk> wrote:
>>I like allocation functions that return NULL on failure.
>
> I like allocation functions that set the carry bit on failure.

I wish you and the carry bit all the best.

<snip>
-- 
Ben.

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#22115

Ben Bacarisse <ben.usenet@bsb.me.uk> writes:
> jgk@panix.com (Joe keane) writes:
> 
> > In article <0.ad98122c5f4b9fe6aef5.20120602154227BST.87aa0lepws.fsf@bsb.me.uk>,
> > Ben Bacarisse  <ben.usenet@bsb.me.uk> wrote:
> >>I like allocation functions that return NULL on failure.
> >
> > I like allocation functions that set the carry bit on failure.
> 
> I wish you and the carry bit all the best.

What carry bit? I've searched high and low on my poor old Alpha, 
and can't find one.

Phil
-- 
> I'd argue that there is much evidence for the existence of a God.
Pics or it didn't happen.
-- Tom (/. uid 822)

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#22116

Phil Carmody <thefatphil_demunged@yahoo.co.uk> writes:

> Ben Bacarisse <ben.usenet@bsb.me.uk> writes:
>> jgk@panix.com (Joe keane) writes:
>> 
>> > In article <0.ad98122c5f4b9fe6aef5.20120602154227BST.87aa0lepws.fsf@bsb.me.uk>,
>> > Ben Bacarisse  <ben.usenet@bsb.me.uk> wrote:
>> >>I like allocation functions that return NULL on failure.
>> >
>> > I like allocation functions that set the carry bit on failure.
>> 
>> I wish you and the carry bit all the best.
>
> What carry bit? I've searched high and low on my poor old Alpha, 
> and can't find one.

Why are you asking me?

-- 
Ben.

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