C++ Primer, Fifth Edition

12.2.2. The allocator Class

An aspect of new that limits its flexibility is that new combines allocating memory with constructing object(s) in that memory. Similarly, delete combines destruction with deallocation. Combining initialization with allocation is usually what we want when we allocate a single object. In that case, we almost certainly know the value the object should have.

When we allocate a block of memory, we often plan to construct objects in that memory as needed. In this case, we’d like to decouple memory allocation from object construction. Decoupling construction from allocation means that we can allocate memory in large chunks ...