Re: [Boost-users] Thread Safety of shared_ptr

Subject: Re: [Boost-users] Thread Safety of shared_ptr
From: Kevin Frey (kfrey_at_[hidden])
Date: 2011-05-03 17:45:09

Peter,

can you please give an example how that can happen, given the
shared_counter is atomic. I thought the counter is first incremented
than the rest of the machinery deals with pointer copying etc. and in
case of underlying object destruction, the counter is first decremented
and than the object is destroyed. How is that possible, that
shared_counter reaches 0, destructor is called and afterwards the
underlying pointer will be assigned to the new shared instance?

 

With Kind Regards,

Ovanes

---
 
The main point that comes to mind is because the example I give is
specifically constructed to point out that the destruction of the object
in the second thread is a refcount decrement only, and does not result
in destruction of the shared object itself, only the shared_ptr
instance.
 
Hence the potential race condition does not apply to my example. The
actual destruction of the shared object occurs in a situation where I
know there will not be a simultaneous "copy".
 
Of course, Peter will provide his own answer.