[boost] Re: Constructing shared_ptr from weak_ptr

From: Matthew Chaplain (boost_fwd_at_[hidden])
Date: 2003-12-18 11:22:45

Rani Sharoni wrote:
> Hi,
> 
> Why is it important that the shared_ptr(weak_ptr<Y> const & r) constructor
> throws an exception?
> I can't avoid thinking that it can easily affect the exception safety of
> code that uses it and this exception indicates about a bug in many cases.

Hi.  This is my first attempt (other than a test posting elsewhere) to 
Boost via gmane, so I hope it comes out well.

I also came across this problem recently.  It was solved by two things:

a) The realisation that the whole purpose of weak_ptr<> is that you 
accept that an object may or may not exist the next time you come to 
access it.  If it still exists, all is well and you may create a 
shared_ptr<> from it.  If it does not exist, then you are informed and 
can handle it gracefully.

b) The discovery of the weak_ptr<>::lock member function.

Matt Chaplain.