Re: [boost] any_function (callback) library

From: David Abrahams (abrahams_at_[hidden])
Date: 2001-04-11 07:35:49

I tend to agree with Jesse here. If somebody wants the throwing behavior
(s)he can always add it atop the other one. If not, there is no recourse.

-Dave

----- Original Message -----
From: "Jesse Jones" <jesjones_at_[hidden]>
To: "Peter Dimov" <pdimov_at_[hidden]>; <boost_at_[hidden]>
Sent: Tuesday, April 10, 2001 7:55 PM
Subject: Re: [boost] any_function (callback) library

> At 8:34 PM +0300 4/10/01, Peter Dimov wrote:
> >From: "Jesse Jones" <jesjones_at_[hidden]>
> >
> >>  >if(f) f();
> >>
> >>  1) It parallels what you would do with an ordinary function pointer.
> >>  2) Why call a function if it's empty?
> >
> >Yes, this makes sense. But introducing undefined behavior still feels
> >somewhat wrong to me. Undefined behavior is usually introduced when
validity
> >checks (a) will have severe performance impact, or (b) are impossible.
> >Neither of these applies.
>
> The problem is that as a library author you can't determine if
> checking preconditions in release is going to have a "severe
> performance impact". You have no idea how sensitive the app is to
> small performance hits and no idea how often clients are actually
> calling your function. Throwing an exception, asserting, crashing,
> no-op are all policy decisions that belong to the user. But, by and
> large, they're global policies. By using an assert we provide a hook
> under which we can implement these policies at a later date.
>
> >  > Exceptions should be used for
> >>  errors. This smells too much like using exceptions to control program
> >>  flow.
> >
> >:-)
> >
> >Exceptions _are_ a control flow mechanism, no more, no less.
>
> Well, there's a reason people disparage using exceptions to control
> flow: they obfuscate the program flow and they're much more expensive
> than the normal mechanisms. I've used exceptions to control flow, but
> only very rarely.
>
>    -- Jesse
>
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