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std::uses_allocator(3) C++ Standard Libary std::uses_allocator(3)


std::uses_allocator - std::uses_allocator


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

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.


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 true
[static] (public static member constant)

Member functions

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

Member types

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

See also

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