I have two threads referencing the same boost::shared_ptr:

boost::shared_ptr<Widget> shared;

On thread is spinning, waiting for the other thread to reset the boost::shared_ptr:

while(shared)
   boost::thread::yield();

And at some point the other thread will call:

shared.reset();

My question is whether or not I need to declare the shared pointer as volatile to prevent the compiler from optimizing the call to shared.operator bool() out of the loop and never detecting the change? I know that if I were simply looping on a variable, waiting for it to reach 0 I would need volatile, but I'm not sure if boost::shared_ptr is implemented in such a way that it is not necessary here.