RE: [boost] change to weak_ptr.hpp to compile under Builder C++ 5 , etc

From: Bjorn.Karlsson_at_[hidden]
Date: 2002-05-15 05:40:00

> From: Thomas Witt [mailto:witt_at_[hidden]]
> 
> Peter,
> 
> can you explain why make_shared adds safety. Currently I am 
> unable to see why.
> IIUC what happens is a NULL ptr is dereferenced with or 
> without make_shared. 
> On the first look it seems as if make_shared pretends to be 
> safe but isn't. 
> When make shared is used the object might be gone already.
> 
> Thanks
> 
> Thomas

make_shared returns a shared_ptr that may contain a null pointer (thus, the
resulting shared_ptr should be tested before use). However, if the returned
shared_ptr contains a valid resource, then that shared_ptr can be safely
used because the reference count has been increased. That's not true for
weak_ptr, and that's why make_shared (and the constructor for shared_ptr
taking a weak_ptr as an argument) adds safety.

Bjorn Karlsson