Re: [Boost-users] shared_ptr design question

Subject: Re: [Boost-users] shared_ptr design question
From: John M. Dlugosz (mpbecey7gu_at_[hidden])
Date: 2011-09-17 04:34:38

On 9/16/2011 1:24 PM, Emil Dotchevski wrote:
> On Fri, Sep 16, 2011 at 11:11 AM, John M. Dlugosz
> <mpbecey7gu_at_[hidden]>  wrote:
>> I'm wondering why there is not an efficient built-in way to check whether
>> two things (e.g. a shared_ptr and a weak_ptr, but any combination should
>> work) refer to the same object.
>
> It depends what you mean by "refer to the same object". You can use
> !(p1<p2)&&  !(p2<p1) with either shared_ptr or weak_ptr, which will
> tell you if they manage the lifetime of the same instance (or are both
> empty), but that doesn't necessarily mean that shared_ptr::get would
> return the same pointer for both.
>

I guess that is what I'm trying to figure out.
If two smart pointers manage the lifetime of the same entity, how can they not get() the 
same pointer?  I see that they might be different addresses if they refer to the object by 
different types, but that is true for regular pointers, and bringing them to a common base 
class would allow them to compare equal.