Re: [Boost-users] shared_ptr and thread safety 2

From: Peter Dimov (pdimov_at_[hidden])
Date: 2007-08-06 11:11:12

gast128 wrote:

> The atomic increment and decrement ref counting then only work for a
> shared const shared pointer:

No, the presence or absence of 'const' do not affect the thread safety of a 
piece of code.

> void g(boost::shared_ptr<const B> ptr)
> {
>   //...
> }
>
> void f()
> {
>  boost::shared_ptr<const B> ptr(new B);
>
>  //give ptr to threads
>  boost::thread thrd1(boost::bind(&g, ptr));
>  boost::thread thrd2(boost::bind(&g, ptr));
>
>  //fire and forget
>  ptr.reset();
> }

This example is OK. You have three distinct shared_ptr variables, all named 
'ptr' (one per thread). Despite them having the same name, they are still 
different objects, not shared among threads, so you can assign/reset/destroy 
them at will.