Re: [boost] Re: scoped_ptr: trivial dtor?

From: David Abrahams (abrahams_at_[hidden])
Date: 2001-04-03 14:03:21

----- Original Message -----
From: "Beman Dawes" <bdawes_at_[hidden]>

>  >>
>  >> |> ----- Original Message -----
>  >> |> From: "Beman Dawes" <bdawes_at_[hidden]>
>  >> |>
>  >> |> > Although you have to be careful that the destructor is trivial,
it
>  >> |> > is highly desirable to be able to use scoped_ptr with
>  >> |> incomplete types.
>  >> |>
>  >> |> Why is that desirable?
>  >>
>  >> Support the pimpl idiom for forward declared types?
>  >
>  >// C.hpp
>  >class Cimpl;
>  >class C {
>  >public:
>  >  ~C();
>  >private:
>  >  boost::scoped_ptr<Cimpl> impl;
>  >};
>  >
>  >// C.cpp
>  >class Cimpl {
>  >};
>  >
>  >C::~C()
>  >{
>  >}
>  >
>  >Am I missing something, or are you talking about a different idiom?
>
> That is the idiom I was talking about.

With the code as written, the definition of Cimpl is only needed in C.cpp,
which nicely shields the Pimpl's users from implementation details. Since
scoped_ptr<CImpl>::~scoped_ptr() is only instantiated in c.cpp, there
shouldn't be any problem with mentioning sizeof(T) (i.e. sizeof(Cimpl))
there.

-Dave