Re: Error codes vs. exceptions

From	Nobody <nobody@nowhere.com>
Subject	Re: Error codes vs. exceptions
Date	2012-05-31 05:04 +0100
Message-Id	<pan.2012.05.31.04.04.35.489000@nowhere.com>
Newsgroups	comp.programming, comp.lang.c++
References	<4f571f71-55ca-4922-b81b-31f954cac855@kw17g2000pbb.googlegroups.com> <4fc6db28$0$561$c3e8da3$4db35a27@news.astraweb.com>
Organization	Zen Internet

Cross-posted to 2 groups.

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On Wed, 30 May 2012 22:44:56 -0400, Pavel wrote:

> I know you have already received lots of advice; but I think they omit an
> important factor, namely whether you are writing a library. In my
> experience, I found it quite annoying when the API of a library I use can
> throw. Catching all possible exceptions after every call is even more
> disrupting than processing return codes and letting them through often
> creates a mess with multiple error processing policies coming from
> different libraries or from my application and library or libraries it
> uses.

That's a non-issue for exceptions which should never need to be thrown
in the first place, e.g. an invalid argument value. If you don't want to
have to catch such exceptions, don't cause them to be thrown.

Even where it is an issue, any API design involves trade-offs. Having
every function return a status indication may be more efficient for code
which always handles failures directly in the caller. OTOH, it imposes a
significant burden on code which would otherwise just allow an exception
to propagate up to a higher level.

It's impossible to provide a hard-and-fast definition of which conditions
are "exceptional", particularly for a library. OTOH, it's equally
impossible to provide a hard-and-fast rule regarding the side on which to
err.

Treating any condition which might conceivably be caught in the immediate
caller as non-exceptional is likely to result in a rather inconvenient API
for the majority of code. I mean, the STL *could* have a given every
container type a "bad bit" (in the same vein as iostream) to indicate
allocation failure, but I'm rather glad it didn't.

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Error codes vs. exceptions mike3 <mike4ty4@yahoo.com> - 2012-05-28 21:15 -0700
  Re: Error codes vs. exceptions BGB <cr88192@hotmail.com> - 2012-05-29 00:10 -0500
    Re: Error codes vs. exceptions mike3 <mike4ty4@yahoo.com> - 2012-05-28 22:41 -0700
      Re: Error codes vs. exceptions BGB <cr88192@hotmail.com> - 2012-05-29 01:34 -0500
    Re: Error codes vs. exceptions Adam Skutt <askutt@gmail.com> - 2012-05-29 07:16 -0700
      Re: Error codes vs. exceptions BGB <cr88192@hotmail.com> - 2012-05-29 09:45 -0500
  Re: Error codes vs. exceptions Marcel Müller <news.5.maazl@spamgourmet.com> - 2012-05-29 09:08 +0200
    Re: Error codes vs. exceptions mike3 <mike4ty4@yahoo.com> - 2012-05-31 13:52 -0700
      Re: Error codes vs. exceptions Ian Collins <ian-news@hotmail.com> - 2012-06-01 09:08 +1200
        Re: Error codes vs. exceptions mike3 <mike4ty4@yahoo.com> - 2012-05-31 22:32 -0700
  Re: Error codes vs. exceptions "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> - 2012-05-29 09:37 +0200
  Re: Error codes vs. exceptions "io_x" <a@b.c.invalid> - 2012-05-29 10:00 +0200
  Re: Error codes vs. exceptions Jorgen Grahn <grahn+nntp@snipabacken.se> - 2012-05-29 12:24 +0000
  Re: Error codes vs. exceptions Nobody <nobody@nowhere.com> - 2012-05-30 15:23 +0100
    Re: Error codes vs. exceptions BGB <cr88192@hotmail.com> - 2012-05-30 09:40 -0500
      Re: Error codes vs. exceptions Adam Skutt <askutt@gmail.com> - 2012-05-30 08:04 -0700
        Re: Error codes vs. exceptions BGB <cr88192@hotmail.com> - 2012-05-30 12:01 -0500
  Re: Error codes vs. exceptions Jeff Flinn <TriumphSprint2000@hotmail.com> - 2012-05-30 14:18 -0400
    Re: Error codes vs. exceptions Patricia Shanahan <pats@acm.org> - 2012-05-30 13:00 -0700
    Re: Error codes vs. exceptions Adam Skutt <askutt@gmail.com> - 2012-05-30 21:25 -0700
  Re: Error codes vs. exceptions Pavel <pauldontspamtolk@removeyourself.dontspam.yahoo> - 2012-05-30 22:44 -0400
    Re: Error codes vs. exceptions Nobody <nobody@nowhere.com> - 2012-05-31 05:04 +0100
    Re: Error codes vs. exceptions Pavel <pauldontspamtolk@removeyourself.dontspam.yahoo> - 2012-06-01 21:44 -0400
  Re: Error codes vs. exceptions "Alf P. Steinbach" <alf.p.steinbach+usenet@gmail.com> - 2012-06-02 08:39 +0200
    Re: Error codes vs. exceptions BGB <cr88192@hotmail.com> - 2012-06-02 16:31 -0500
    Re: Error codes vs. exceptions mike3 <mike4ty4@yahoo.com> - 2012-06-02 15:49 -0700
      Re: Error codes vs. exceptions Ian Collins <ian-news@hotmail.com> - 2012-06-03 11:17 +1200
      Re: Error codes vs. exceptions Rui Maciel <rui.maciel@gmail.com> - 2012-06-03 16:38 +0100
    Re: Error codes vs. exceptions Pavel <pauldontspamtolk@removeyourself.dontspam.yahoo> - 2012-06-03 20:26 -0400
  Re: Error codes vs. exceptions gremnebulin <peterdjones@yahoo.com> - 2012-06-20 12:05 -0700

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