Re: [boost] [shared_ptr] aliasing constructor mischief

From: Peter Dimov (pdimov_at_[hidden])
Date: 2008-04-29 10:06:06

Frank Mori Hess:
> On Tuesday 29 April 2008 09:26 am, Daniel Frey wrote:
>> On Tue, 2008-04-29 at 09:02 -0400, Frank Mori Hess wrote:
>> > I've noticed it is possible to construct a half-empty shared_ptr that 
>> > has
>> > an empty shared_count but a non-null pointer (brief example program
>> > attached). Perhaps the aliasing constructor, and similarly the
>> > shared_count constructor should do some argument checking?
>>
>> I think this is already a known problem/feature, see n2588
>> <http://www.open-std.org/JTC1/SC22/WG21/docs/papers/2008/n2588.pdf>,
>> 20.6.12.2.1/18. I don't know what it's good for, though.
>
> There's a note saying it is possible to create an empty shared_ptr with a
> non-null stored pointer, but it also states that get() is required to 
> return
> null for an empty shared_ptr, and operator* and operator-> require get() 
> !=
> 0.

http://www.open-std.org/JTC1/SC22/WG21/docs/lwg-active.html#711