[boost] Re: Virtual inheritance in exception hierarchies

From: David Abrahams (dave_at_[hidden])
Date: 2003-09-02 13:32:21

"Iain K. Hanson" <iain.hanson_at_[hidden]> writes:

>> But is this a good design?  It certainly isn't the only possible one.
>> (Making all the code depend upon the definitions of both Network_err and
>> File_system_err - which no doubt drags other stuff into the translation unit
>> - isn't a design choice I'd make lightly.)
>
> In certain places it may be the most natural design choice. Whether it
> is a good idea to pay for virtual inheritance in every exception derived
> from class exception is a separate issue. Exception handling incurs a
> significant cost once an exception is thrown. Adding to that cost could
> drive more users away from exception handling.

Do you think dynamic downcasting through a layer of virtual
inheritance is significantly more expensive than downcasting through a
layer of regular inheritance?

> Also, I'm not sure that this use case is sufficiently common to burden
> all exceptions with.

What's the burden?

I'm just askin', is all.

-- 
Dave Abrahams
Boost Consulting
www.boost-consulting.com