How does boost::ptr_vector deep copy the underlying objects?

Question

ptr_vector is copy constructible and copy assignable. How can it deep copy the underlying objects when it doesn\'t know their concrete types?

Answer 1

The boost::ptr_vector container has an optional template parameter, CloneAllocator, that defines the cloning policy. The default allocator is the heap_clone_allocator, which simply invokes the copy constructor to clone an object.

The Clone Allocator is used as a way to add a layer of indirection around the cloning. For example, it allows you to provide a custom allocator that correctly handles cloning of a noncopyable type.

You can find more information in the Boost Pointer Containers Library documentation, which explains the Clonable and Clone Allocator concepts.