From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Roman V. Shaposhnick" <vugluskr@unicorn.math.spbu.ru>
To: 9fans@cse.psu.edu
Subject: Re: [9fans] how to avoid a memset() optimization
Message-ID: <20021119103808.B13548@unicorn.math.spbu.ru>
References: <38aa463bafe23035decff6b0364f7553@plan9.bell-labs.com>
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In-Reply-To: <38aa463bafe23035decff6b0364f7553@plan9.bell-labs.com>
Date: Tue, 19 Nov 2002 10:38:08 +0300
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On Thu, Nov 14, 2002 at 11:47:11AM -0500, presotto@plan9.bell-labs.com wrote:
> Our waserror()/nexterror() stuff completely
> blew away optimizing compilers since they are essentially longjumps.
........
> My three main conclusions from this were:
> 1) waserror/nexterror is definitely evil unless understood by the
>  compiler and perhaps even then.  It's a step outside the language
>  definition and therefore a dangerous step to take.  We were
>  comfortable with it in Plan 9 because we controlled the compilers
>  but it became tortuous when someone else controlled them.

  That's a very interesting remark, since I've always wondered why don't
  you use waserror()/nexterror() in the rest of the Plan9 source tree
  as a regular error handling mechanism.

  Personally I'm still struggling with developing an error handling
  policy that I'd feel comfortable with. Of course, good old:

       if ((a = do_it()) == BadThingHappened)
            return TellEmAboutIt;

  works, but costs a little bit too much when clarity is needed. Especially
  when a "transaction" like pattern is needed ( e.g. I need to
  to have o1 = f1(); o2 = f2(); o3 = f3(); but if any of f* fails,
  I have to destroy what I've got so far ).

  C++ style exceptions are nice, but easily abused, and I haven't seen
  any way of emulating then in pure C.

  So, what your experience has been with error handling ( granted, you
  must've had plenty ;-) ) and what would you consider the most
  comfortable one ?

Thanks,
Roman.