20 Memory management library [mem]

20.3 Smart pointers [smartptr]

20.3.1 Unique-ownership pointers [unique.ptr]

20.3.1.2 Default deleters [unique.ptr.dltr]

20.3.1.2.1 In general [unique.ptr.dltr.general]

The class template default_­delete serves as the default deleter (destruction policy) for the class template unique_­ptr.
The template parameter T of default_­delete may be an incomplete type.