Re: [Boost-users] Thread Safety of shared_ptr

Subject: Re: [Boost-users] Thread Safety of shared_ptr
From: Peter Dimov (pdimov_at_[hidden])
Date: 2011-05-02 08:16:13

Kevin Frey wrote:
> Hello,
>
> I wish to clarify a point on the thread-safety of shared_ptr. [...]

>   //--- Example 4 ---
>   // thread A
>   p3 = p2; // reads p2, writes p3
>
>   // thread B
>   // p2 goes out of scope: undefined, the destructor is considered a 
> "write access"

This example just says that you can't make a copy of a destroyed shared_ptr, 
or one that is in the process of being destroyed. In principle, it has 
nothing to do with reference counts. Doing something with a destroyed object 
of any type is undefined behavior in C++.