# std::uses_allocator<std::function>

From cppreference.com
< cpp‎ | utility‎ | functional‎ | function

Defined in header `<functional>` |  |
template< class R, class... ArgTypes, class Alloc > struct uses_allocator<std::function<R(ArgTypes...)>, Alloc> : std::true_type { }; |  | (since C++11) (until C++17)

This specialization of std::uses_allocator informs other library components that all objects of type std::function support uses-allocator construction, even though they do not have a nested `allocator_type`.

### Notes

`std::function`'s allocator support was poorly specified and inconsistently implemented. Some implementations do not support uses-allocator construction at all, some provide the needed constructor overloads but ignore the supplied allocator argument, and some provide the overloads and use the supplied allocator for construction but not when the `std::function` is reassigned. As a result, allocator support was removed in C++17.

## Inherited from std::integral_constant

### Member constants

value [static] | true (public static member constant)

### Member functions

operator bool | converts the object to bool, returns value (public member function)
operator() (C++14) | returns value (public member function)

### Member types

Type | Definition
`value_type` | bool
`type` | std::integral_constant<bool, value>

### See also

uses_allocator (C++11) | checks if the specified type supports uses-allocator construction (class template)

Retrieved from "https://en.cppreference.com/mwiki/index.php?title=cpp/utility/functional/function/uses_allocator&oldid=139125"