std::pmr::polymorphic_allocator

 

C++

Language

Standard Library Headers

Freestanding and hosted implementations

Named requirements

Language support library

Concepts library (C++20)

Diagnostics library

Utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Numerics library

Input/output library

Localizations library

Regular expressions library (C++11)

Atomic operations library (C++11)

Thread support library (C++11)

Filesystem library (C++17)

Technical Specifications

 

Dynamic memory management

Smart pointers unique_ptr (C++11) shared_ptr (C++11) weak_ptr (C++11) auto_ptr (until C++17) owner_less (C++11) enable_shared_from_this (C++11) bad_weak_ptr (C++11) default_delete (C++11) Allocators allocator allocator_traits (C++11) allocator_arg_t (C++11) allocator_arg (C++11) uses_allocator (C++11) uses_allocator_construction_args (C++20) make_obj_using_allocator (C++20) uninitialized_construct_using_allocator (C++20) scoped_allocator_adaptor (C++11) pmr::polymorphic_allocator (C++17) Memory resources pmr::memory_resource (C++17) pmr::get_default_resource (C++17) pmr::set_default_resource (C++17) pmr::new_delete_resource (C++17) pmr::null_memory_resource (C++17) pmr::synchronized_pool_resource (C++17) pmr::unsynchronized_pool_resource (C++17) pmr::monotonic_buffer_resource (C++17) pmr::pool_options (C++17)

Uninitialized storage uninitialized_copy uninitialized_fill uninitialized_move (C++17) uninitialized_default_construct (C++17) uninitialized_value_construct (C++17) destroy (C++17) uninitialized_copy_n (C++11) uninitialized_fill_n uninitialized_move_n (C++17) uninitialized_default_construct_n (C++17) uninitialized_value_construct_n (C++17) destroy_n (C++17) destroy_at (C++17) raw_storage_iterator (until C++20) get_temporary_buffer (until C++20) return_temporary_buffer (until C++20) Garbage collection support declare_reachable (C++11) undeclare_reachable (C++11) declare_no_pointers (C++11) undeclare_no_pointers (C++11) pointer_safety (C++11) get_pointer_safety (C++11) Miscellaneous pointer_traits (C++11) to_address (C++20) addressof (C++11) align (C++11) assume_aligned (C++20) C Library malloc aligned_alloc (C++17) calloc realloc free Low level memory management

 

std::pmr::polymorphic_allocator

Member functions

polymorphic_allocator::polymorphic_allocator

polymorphic_allocator::allocate

polymorphic_allocator::deallocate

polymorphic_allocator::construct

polymorphic_allocator::destroy

polymorphic_allocator::allocate_bytes (C++20)

polymorphic_allocator::deallocate_bytes (C++20)

polymorphic_allocator::allocate_object (C++20)

polymorphic_allocator::deallocate_object (C++20)

polymorphic_allocator::new_object (C++20)

polymorphic_allocator::delete_object (C++20)

polymorphic_allocator::select_on_container_copy_construction

polymorphic_allocator::resource

Non-member functions

operator==operator!=

 

template< class T > class polymorphic_allocator;		(since C++17) (until C++20)
template< class T = std::byte > class polymorphic_allocator;		(since C++20)

The class template std::pmr::polymorphic_allocator is an Allocator whose allocation behavior depends on the memory resource it is constructed with. Thus, different instances of polymorphic_allocator can exhibit entirely different allocation behavior. This runtime polymorphism allows objects using polymorphic_allocator to behave as if they used different allocator types at run time despite the identical static allocator type.

All specializations of polymorphic_allocator meet the Allocator completeness requirements.

Member types

Member type	definition
value_type	T

Member functions

(constructor)	Constructs a polymorphic_allocator (public member function)
(destructor) (implicitly declared)	Implicitly declared destructor (public member function)
operator= [deleted]	Copy assignment operator is deleted (public member function)
Public member functions
allocate	Allocate memory (public member function)
deallocate	Deallocate memory (public member function)
construct	Constructs an object in allocated storage (public member function)
destroy	Destroys an object in allocated storage (public member function)
allocate_bytes (C++20)	Allocate raw aligned memory from the underlying resource (public member function)
deallocate_bytes (C++20)	Free raw memory obtained from allocate_bytes (public member function)
allocate_object (C++20)	Allocates raw memory suitable for an object or an array (public member function)
deallocate_object (C++20)	Frees raw memory obtained by allocate_object (public member function)
new_object (C++20)	Allocates and constructs an object (public member function)
delete_object (C++20)	Destroys and deallocates an object (public member function)
select_on_container_copy_construction	Create a new polymorphic_allocator for use by a container's copy constructor (public member function)
resource	Returns a pointer to the underlying memory resource (public member function)

Non-member functions

operator==operator!=

compare two polymorphic_allocators (function)

Notes

polymorphic_allocator does not propagate on container copy assignment, move assignment, or swap. As a result, move assignment of a polymorphic_allocator-using container can throw, and swapping two polymorphic_allocator-using containers whose allocators do not compare equal results in undefined behavior.

See also

memory_resource (C++17)

an abstract interface for classes that encapsulate memory resources (class)