[Boost-bugs] [Boost C++ Libraries] #5381: get_deleter<D>(ptr) needs D to be exactly known

Subject: [Boost-bugs] [Boost C++ Libraries] #5381: get_deleter<D>(ptr) needs D to be exactly known
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2011-03-28 11:17:53

#5381: get_deleter<D>(ptr) needs D to be  exactly known
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 Reporter:  christian.kotz@…           |       Owner:  pdimov   
     Type:  Feature Requests           |      Status:  new      
Milestone:  To Be Determined           |   Component:  smart_ptr
  Version:  Boost 1.45.0               |    Severity:  Problem  
 Keywords:                             |  
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 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)

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/5381>
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