Making a container allocator-aware

Having covered memory resources (heaps) and allocators (handles to heaps), let's turn now to the third leg of the tripod: container classes. Inside each allocator-aware container, at least four things have to happen:

• The container instance must store an allocator instance as member data. (Therefore the container must take the type of the allocator as a template parameter; otherwise it can't know how much space to reserve for that member variable.)
• The container must provide constructors taking an allocator argument.
• The container must actually use its allocator to allocate and deallocate memory; every use of new or delete must be banished.
• The container's move constructor, move assignment operator, and swap function must all propagate the allocator according to its allocator_traits.

Here is a very simple allocator-aware container--a container of just one single object, allocated on the heap. This is something like an allocator-aware version of std::unique_ptr...