Re: [Boost-users] [exception] exception_ptr missing virtual base parameters

Subject: Re: [Boost-users] [exception] exception_ptr missing virtual base parameters
From: Emil Dotchevski (emildotchevski_at_[hidden])
Date: 2013-07-12 21:38:34

I apologize for the late reply. It seems like Steven is right, there is no
way to make this work. I had two ideas that I tried:

1) I tried to use operator= to copy the virtual bases after the clone_impl
constructor has initialized them using their default constructors
(unfortunately). This makes the test case Michael posted work, however
operator= is not available for types that contain members of reference
types. I don't know how common this situation is, but in the
boost::exception tests I did have such exceptions (not on purpose) which
maybe means it isn't too unusual.

2) My other idea was instead of operator= to call ~T(), then the T copy
constructor with placement new over the T sub-object of clone_impl<T>. This
duly crashed the test program, which isn't all that surprising but it was
worth a try. :)

Emil

On Thu, Apr 11, 2013 at 8:27 AM, Steven Watanabe <watanabesj_at_[hidden]>wrote:

> AMDG
>
> On 04/11/2013 08:17 AM, Steven Watanabe wrote:
> > On 04/10/2013 11:04 PM, Michael Caisse wrote:
> >> The basic problem I'm experiencing is that getting an exception_ptr
> >> results inherited parameters getting lost when virtual inheritance is
> used.
> >>
> >> <snip>
> >>
> >
> > The only way to make it work is to
> > restructure clone_impl to use the compiler
> > generated copy constructor.
> >
>
> ...and the templated constructor is not
> a copy constructor.  It's impossible to
> make this work.
>
> In Christ,
> Steven Watanabe
>
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