Re: [boost] [smart_ptr] enable_shared_from_this enhancement

From: Peter Dimov (pdimov_at_[hidden])
Date: 2008-03-17 12:38:51

Frank Mori Hess:

> The implementation I've got in mind (haven't actually tried it yet)
> would work as follows.  I'd add two shared_ptrs to
> enable_shared_from_this, call them "internal_shared" and
> "external_shared".  external_shared would be assigned the external
> shared_ptr which first takes ownership of *this. internal_shared would
> be initialized with the "this" pointer, and a custom deleter which would
> reset external_shared.  internal_shared would be reset right after
> external_shared is initialized (when an external shared_ptr takes
> ownership of *this).  Any calls to shared_from_this() that occur prior
> to an external shared_ptr taking ownership of *this (such as in the
> constructor) would get a copy of internal_shared.

Interesting idea. I'm not sure why do you need the two pointers though.

How would you cope with the following scenarios:

class X: enable_shared_from_this<X> {};

int main()
{
    { X x; }
    { std::auto_ptr<X> px( new X ); }
}

?