20 Memory management library [mem]

20.2 Memory [memory]

20.2.8 uses_allocator [allocator.uses] uses_allocator trait [allocator.uses.trait]

template<class T, class Alloc> struct uses_allocator;
Remarks: Automatically detects whether T has a nested allocator_type that is convertible from Alloc.
Meets the Cpp17BinaryTypeTrait requirements ([meta.rqmts]).
The implementation shall provide a definition that is derived from true_type if the qualified-id T​::​allocator_type is valid and denotes a type ([temp.deduct]) and is_convertible_v<Alloc, T​::​allocator_type> != false, otherwise it shall be derived from false_type.
A program may specialize this template to derive from true_type for a program-defined type T that does not have a nested allocator_type but nonetheless can be constructed with an allocator where either:
  • the first argument of a constructor has type allocator_arg_t and the second argument has type Alloc or
  • the last argument of a constructor has type Alloc.