Re: [Boost-users] shared_ptr race condition

From: David Abrahams (dave_at_[hidden])
Date: 2008-08-16 16:42:39

on Sat Aug 16 2008, Mika Heiskanen <mika.heiskanen-AT-fmi.fi> wrote:

> David Abrahams wrote:
>> on Sat Aug 16 2008, "Eduardo Panisset" <eduardo.panisset-AT-gmail.com> wrote:
>>
>>>         if( new_use_count == 0 )
>>>         {
>>>             dispose();
>>>             weak_release();
>>>         }
>>>  How Can I ensure that the release member function wouldn't dispose
>>> a pointee
>>> more than one time ? (release executing concurrently from different
>>> shared_ptr instances) 
>>
>> Because the reference count was 1, there can be only one shared_ptr
>> instance that owns the pointee.  No other threads can be referencing it.
>
> But since the mutex is released, a copy could be created before the
> new_use_count test is reached? Or is it impossible to create a copy if
> use_count_ is zero?

What thread can create a copy?  We know exactly what the only thread
that has a reference to the owned object is doing (it's executing the
very code we're concerned with).

-- 
Dave Abrahams
BoostPro Computing
http://www.boostpro.com