Re: Mechanism to generate annotated "error codes"

From	Don Y <this@isnotme.com>
Newsgroups	comp.lang.c
Subject	Re: Mechanism to generate annotated "error codes"
Date	2012-03-03 12:32 -0700
Organization	Aioe.org NNTP Server
Message-ID	<jitrk3$6mi$1@speranza.aioe.org> (permalink)
References	<jiojq3$3cm$1@speranza.aioe.org> <ea871b51-f766-4da3-ab1a-169434004f0d@p7g2000yqk.googlegroups.com> <jisie1$1qf$1@speranza.aioe.org> <71e9ea6e-f120-48e3-b139-ac68447963db@f2g2000yqh.googlegroups.com>

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Hi Malcolm,

On 3/3/2012 4:45 AM, Malcolm McLean wrote:
> On Mar 3, 7:49 am, Don Y<t...@isnotme.com>  wrote:
>>
>>> Centralised error systems mean that code will break if you try to move
>>> it to a different project.
>>
>> And, when our images are merged, we magically end up with the
>> union of error messages and "codes" that we have individually
>> used.
>
> You've described the problem.
>
> Fred scatters his code with
>
> log_error(ERR_TOOMANYFILESOPEN);
>
> Bert does the same with
>
> fprintf_error(EC_FILECOUNTEXCEEDED, "Too many files open (%d)\n",
> Nfiles);
>
> Now when we merge Fred's code with Bert's, what's going to happen?

If the same "underling" is signaling that count of files has been
exceeded, then that underling would have reported (to fred and
bert) in the manner that the underling has been documented.

E.g., (pseudocode)
    error_t error;

    if (!OpenFile(name_of_file, &error))
That line of code (or variant thereof) in bert and fred's code
would yield the same error code (and corresponding report) in
each case.  I.e., "Too many files open.  [The system can only
open 20 files for each user.  Close some file(s).]".

(the bracketed portion being "extra clarification")

Bert and fred can embellish/replace this as appropriate to their
contexts/roles.  E.g., bert might want to add "Too many photos
open.  [A maximum of 9 photos can be examined at any given time.]"

The user sees the "too many photos open" and, if that is
sufficient for him to understand the nature of the problem,
fine.  If he asks for more clarification, the "maximum of 9"
is offered up.  If this still does not resolve the issue
("I'm only viewing 7 photos!"), more, lower level details
are exposed by revealing the details of the error reported
by OpenFile -- "20 files for each user".  This suggests
that files are open elsewhere that aren't accounted for in
the "9 photos" context -- but that *are* known to lower
level OpenFile routine.  Either a bug *or* the error is
being reported too low in the application -- perhaps this
layer should have been embelished by the layer *above*...
the one that called OpenPhoto()!

Meanwhile, fred might have opted to *replace* the error with
a unilateral proclamation:  "Out of resources" with no further
reporting.

Note that this doesn't protect against fred writing his own
oPEN_fILE() routine and implementing whatever errors he wants
in it.  So, *his* oPEN_fILE might return reports like:
"Golly, gee... I just can't keep track of all these files
you keep wanting to open!"  :>

There is no way around this.  Just like you can write your own
strtod() to parse a string for a numeric value instead of
relying on the one provided by the library.  Fred can report
KB in units of 1,000 bytes while Bert can use 1,024.

But, if both fred and bert are aware of the ConvertToKB()
function's existence, then their notions of KB will be
consistent.

If they are both aware of the OpenFile() routine's existence,
then their error messages (from *that* layer) will be
consistent.

And, when BOTH fred and bert stop using OpenFile(), the
"Too many files open" error message will magically be excised
from the application -- along with the ERR_TOOMANYFILESOPEN
identifier.

I can't FORCE fred and bert to use OpenFile.  I can't *force*
them to write good error messages.  But, if I provide a
mechanism that makes presenting these messages to the user
easy and noticeably improves the quality of that experience,
they can exploit that mechanism easier than inventing an
ad hoc mechanism that they have to maintain for themselves

Corporate policy and peer pressure are the only real
policemen.  All I can do is make a mechanism that *wants*
to be used, makes it easy to be used and that reduces the
chance of error creeping into that aspect of the code.
Alice joins the team and encounters:
     MakeErrorCode(...)
and it doesn't take long for her to see how she can
exploit it to "explain" her code.

In regulated environments, this can go a long way to complying
with requirements for testing (has every error code been "touched"
during the execution of the test suite?  just instrument the
routine that resolves error codes and tally each unique code
that is presented to it!), elimination of dead code, etc.

Thread

Mechanism to generate annotated "error codes" Don Y <this@isnotme.com> - 2012-03-01 12:48 -0700
  Re: Mechanism to generate annotated "error codes" Willem <willem@toad.stack.nl> - 2012-03-01 21:29 +0000
    Re: Mechanism to generate annotated "error codes" Don Y <this@isnotme.com> - 2012-03-01 16:53 -0700
  Re: Mechanism to generate annotated "error codes" William Ahern <william@wilbur.25thandClement.com> - 2012-03-01 14:13 -0800
    Re: Mechanism to generate annotated "error codes" Don Y <this@isnotme.com> - 2012-03-01 22:07 -0700
  Re: Mechanism to generate annotated "error codes" Shao Miller <sha0.miller@gmail.com> - 2012-03-01 17:53 -0500
    Re: Mechanism to generate annotated "error codes" Don Y <this@isnotme.com> - 2012-03-01 23:05 -0700
      Re: Mechanism to generate annotated "error codes" Shao Miller <sha0.miller@gmail.com> - 2012-03-02 01:50 -0500
        Re: Mechanism to generate annotated "error codes" Don Y <this@isnotme.com> - 2012-03-02 00:43 -0700
          Re: Mechanism to generate annotated "error codes" Shao Miller <sha0.miller@gmail.com> - 2012-03-03 17:58 -0500
            Re: Mechanism to generate annotated "error codes" Shao Miller <sha0.miller@gmail.com> - 2012-03-04 03:16 -0500
              Re: Mechanism to generate annotated "error codes" Don Y <this@isnotme.com> - 2012-03-04 13:47 -0700
            Re: Mechanism to generate annotated "error codes" Don Y <this@isnotme.com> - 2012-03-04 13:45 -0700
              Re: Mechanism to generate annotated "error codes" Shao Miller <sha0.miller@gmail.com> - 2012-03-04 18:37 -0500
                Re: Mechanism to generate annotated "error codes" Don Y <this@isnotme.com> - 2012-03-04 22:12 -0700
                Re: Mechanism to generate annotated "error codes" Shao Miller <sha0.miller@gmail.com> - 2012-03-08 01:41 -0500
                Re: Mechanism to generate annotated "error codes" Don Y <this@isnotme.com> - 2012-03-09 14:34 -0700
  Re: Mechanism to generate annotated "error codes" Don Y <this@isnotme.com> - 2012-03-02 00:30 -0700
    Re: Mechanism to generate annotated "error codes" Keith Thompson <kst-u@mib.org> - 2012-03-02 02:05 -0800
      Re: Mechanism to generate annotated "error codes" Kaz Kylheku <kaz@kylheku.com> - 2012-03-02 10:47 +0000
      Re: Mechanism to generate annotated "error codes" gazelle@shell.xmission.com (Kenny McCormack) - 2012-03-02 14:18 +0000
      Re: Mechanism to generate annotated "error codes" Don Y <this@isnotme.com> - 2012-03-02 10:46 -0700
        Re: Mechanism to generate annotated "error codes" James Kuyper <jameskuyper@verizon.net> - 2012-03-02 14:08 -0500
          Re: Mechanism to generate annotated "error codes" Don Y <this@isnotme.com> - 2012-03-02 12:38 -0700
        Re: Mechanism to generate annotated "error codes" Kaz Kylheku <kaz@kylheku.com> - 2012-03-02 22:57 +0000
          Re: Mechanism to generate annotated "error codes" Don Y <this@isnotme.com> - 2012-03-02 17:14 -0700
            Re: Mechanism to generate annotated "error codes" Kaz Kylheku <kaz@kylheku.com> - 2012-03-03 02:25 +0000
            Re: Mechanism to generate annotated "error codes" James Kuyper <jameskuyper@verizon.net> - 2012-03-03 06:10 -0500
              Re: Mechanism to generate annotated "error codes" Shao Miller <sha0.miller@gmail.com> - 2012-03-03 16:12 -0500
        Re: Mechanism to generate annotated "error codes" Keith Thompson <kst-u@mib.org> - 2012-03-03 04:04 -0800
          Re: Mechanism to generate annotated "error codes" Kaz Kylheku <kaz@kylheku.com> - 2012-03-03 15:05 +0000
            Re: Mechanism to generate annotated "error codes" Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-03-03 16:25 +0000
          Re: Mechanism to generate annotated "error codes" Shao Miller <sha0.miller@gmail.com> - 2012-03-03 16:26 -0500
            Re: Mechanism to generate annotated "error codes" Keith Thompson <kst-u@mib.org> - 2012-03-03 13:40 -0800
      Re: Mechanism to generate annotated "error codes" Ian Collins <ian-news@hotmail.com> - 2012-03-03 12:03 +1300
        Re: Mechanism to generate annotated "error codes" Keith Thompson <kst-u@mib.org> - 2012-03-02 15:45 -0800
        Re: Mechanism to generate annotated "error codes" Don Y <this@isnotme.com> - 2012-03-02 17:18 -0700
      Re: Mechanism to generate annotated "error codes" blp@cs.stanford.edu (Ben Pfaff) - 2012-03-02 15:08 -0800
      Re: Mechanism to generate annotated "error codes" "BartC" <bc@freeuk.com> - 2012-03-03 10:30 +0000
        Re: Mechanism to generate annotated "error codes" James Kuyper <jameskuyper@verizon.net> - 2012-03-03 06:19 -0500
        Re: Mechanism to generate annotated "error codes" Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2012-03-03 15:15 +0200
        Re: Mechanism to generate annotated "error codes" Kaz Kylheku <kaz@kylheku.com> - 2012-03-03 14:52 +0000
          Re: Mechanism to generate annotated "error codes" Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-03-03 07:39 -0800
            Re: Mechanism to generate annotated "error codes" Jonathan Leffler <jleffler@earthlink.net> - 2012-03-03 23:56 -0800
              Re: Mechanism to generate annotated "error codes" Ian Collins <ian-news@hotmail.com> - 2012-03-05 09:20 +1300
                Re: Mechanism to generate annotated "error codes" Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-03-04 13:28 -0800
                Re: Mechanism to generate annotated "error codes" Ian Collins <ian-news@hotmail.com> - 2012-03-05 10:56 +1300
          Re: Mechanism to generate annotated "error codes" "BartC" <bc@freeuk.com> - 2012-03-03 17:02 +0000
        Re: Mechanism to generate annotated "error codes" Keith Thompson <kst-u@mib.org> - 2012-03-03 12:30 -0800
    Re: Mechanism to generate annotated "error codes" Don Y <this@isnotme.com> - 2012-03-03 19:15 -0700
      Re: Mechanism to generate annotated "error codes" Kaz Kylheku <kaz@kylheku.com> - 2012-03-04 03:20 +0000
        Re: Mechanism to generate annotated "error codes" Don Y <this@isnotme.com> - 2012-03-04 11:03 -0700
      Re: Mechanism to generate annotated "error codes" Don Y <this@isnotme.com> - 2012-03-04 16:31 -0700
        Re: Mechanism to generate annotated "error codes" Don Y <this@isnotme.com> - 2012-03-04 23:04 -0700
  Re: Mechanism to generate annotated "error codes" Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-03-02 22:13 -0800
    Re: Mechanism to generate annotated "error codes" Don Y <this@isnotme.com> - 2012-03-03 00:49 -0700
      Re: Mechanism to generate annotated "error codes" Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-03-03 03:32 -0800
        Re: Mechanism to generate annotated "error codes" Don Y <this@isnotme.com> - 2012-03-03 12:04 -0700
          Re: Mechanism to generate annotated "error codes" Lowell Gilbert <lgusenet@be-well.ilk.org> - 2012-03-03 15:06 -0500
            Re: Mechanism to generate annotated "error codes" Don Y <this@isnotme.com> - 2012-03-03 14:38 -0700
          Re: Mechanism to generate annotated "error codes" Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-03-03 12:15 -0800
            Re: Mechanism to generate annotated "error codes" Don Y <this@isnotme.com> - 2012-03-03 16:51 -0700
              Re: Mechanism to generate annotated "error codes" Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-03-04 14:08 -0800
                Re: Mechanism to generate annotated "error codes" Don Y <this@isnotme.com> - 2012-03-04 15:56 -0700
      Re: Mechanism to generate annotated "error codes" Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-03-03 03:45 -0800
        Re: Mechanism to generate annotated "error codes" Lowell Gilbert <lgusenet@be-well.ilk.org> - 2012-03-03 14:11 -0500
          Re: Mechanism to generate annotated "error codes" Don Y <this@isnotme.com> - 2012-03-03 13:03 -0700
        Re: Mechanism to generate annotated "error codes" Don Y <this@isnotme.com> - 2012-03-03 12:32 -0700
      Re: Mechanism to generate annotated "error codes" Don Y <this@isnotme.com> - 2012-03-03 15:04 -0700
        Re: Mechanism to generate annotated "error codes" Ian Collins <ian-news@hotmail.com> - 2012-03-04 11:09 +1300
          Re: Mechanism to generate annotated "error codes" Don Y <this@isnotme.com> - 2012-03-03 16:55 -0700
            Re: Mechanism to generate annotated "error codes" Ian Collins <ian-news@hotmail.com> - 2012-03-04 13:04 +1300
              Re: Mechanism to generate annotated "error codes" Don Y <this@isnotme.com> - 2012-03-03 18:24 -0700
        Re: Mechanism to generate annotated "error codes" Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-03-03 14:30 -0800
          Re: Mechanism to generate annotated "error codes" Don Y <this@isnotme.com> - 2012-03-03 17:06 -0700
  Re: Mechanism to generate annotated "error codes" Ian Collins <ian-news@hotmail.com> - 2012-03-05 10:09 +1300
    Re: Mechanism to generate annotated "error codes" Don Y <this@isnotme.com> - 2012-03-04 16:03 -0700
      Re: Mechanism to generate annotated "error codes" Ian Collins <ian-news@hotmail.com> - 2012-03-05 13:26 +1300
        Re: Mechanism to generate annotated "error codes" Don Y <this@isnotme.com> - 2012-03-04 22:21 -0700
          Re: Mechanism to generate annotated "error codes" Ian Collins <ian-news@hotmail.com> - 2012-03-05 20:46 +1300
            Re: Mechanism to generate annotated "error codes" Don Y <this@isnotme.com> - 2012-03-05 10:54 -0700
              Re: Mechanism to generate annotated "error codes" Ian Collins <ian-news@hotmail.com> - 2012-03-06 10:02 +1300
                Re: Mechanism to generate annotated "error codes" Don Y <this@isnotme.com> - 2012-03-05 16:09 -0700
            Re: Mechanism to generate annotated "error codes" "BartC" <bc@freeuk.com> - 2012-03-06 10:54 +0000
              Re: Mechanism to generate annotated "error codes" Ian Collins <ian-news@hotmail.com> - 2012-03-07 07:22 +1300
  Re: Mechanism to generate annotated "error codes" gordonb.8sa24@burditt.org (Gordon Burditt) - 2012-03-06 08:51 -0600
    Re: Mechanism to generate annotated "error codes" Don Y <this@isnotme.com> - 2012-03-06 11:21 -0700

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