id	summary	reporter	owner	description	type	status	milestone	component	version	severity	resolution	keywords	cc
5381	get_deleter<D>(ptr) needs D to be  exactly known	christian.kotz@…	Peter Dimov	"get_deleter<Base_of_D>(ptr) returns 0.

This makes efficient polymorphous COW pointer implementations internally based on shared_pointer inefficient, because it is not possible to have reference count (deleter) and pointee allocated in one memory block, as is done in boost:::make_shared. Note, COW pointer need access to the deleter for the clone function at a time later than the constructor.

Suggestion:
either supply:

template <typename T, D>
void const * get_deleter_raw(shared_ptr<T> const & ptr);

or implement 

Base_of_D const * get_deleter<Base_of_D>(shared_ptr<T> const & ptr) 

returning pointer to ptrs deleter of type D (using dynamic_cast?) if B is a virtual class, (maybe using trait has_virtual_destructor) 

"	Feature Requests	closed	To Be Determined	smart_ptr	Boost 1.45.0	Problem	wontfix