std::pmr::polymorphic_allocator

 

C++

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Feature test macros (C++20)

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Dynamic memory management

Uninitialized memory algorithms uninitialized_copy uninitialized_fill uninitialized_move (C++17) uninitialized_default_construct (C++17) uninitialized_value_construct (C++17) destroy (C++17) destroy_at (C++17) voidify (C++20) 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) construct_at (C++20) Constrained uninitialized memory algorithms ranges::uninitialized_copy (C++20) ranges::uninitialized_fill (C++20) ranges::uninitialized_move (C++20) ranges::construct_at (C++20) ranges::destroy (C++20) ranges::destroy_n (C++20) ranges::destroy_at (C++20) ranges::uninitialized_copy_n (C++20) ranges::uninitialized_fill_n (C++20) ranges::uninitialized_move_n (C++20) ranges::uninitialized_default_construct (C++20) ranges::uninitialized_value_construct (C++20) ranges::uninitialized_default_construct_n (C++20)   ranges::uninitialized_value_construct_n (C++20) Allocators allocator allocator_traits (C++11) allocation_result (C++23) 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) Garbage collection support declare_reachable (C++11)(until C++23) undeclare_reachable (C++11)(until C++23) declare_no_pointers (C++11)(until C++23) undeclare_no_pointers (C++11)(until C++23) pointer_safety (C++11)(until C++23) get_pointer_safety (C++11)(until C++23) Uninitialized storage raw_storage_iterator (until C++20*) get_temporary_buffer (until C++20*) return_temporary_buffer (until C++20*) Explicit lifetime management start_lifetime_asstart_lifetime_as_array (C++23)(C++23)

Smart pointers unique_ptr (C++11) shared_ptr (C++11) weak_ptr (C++11) auto_ptr (until C++17*) owner_less (C++11) owner_less<void> (C++17) owner_hash (C++26) owner_equal (C++26) enable_shared_from_this (C++11) bad_weak_ptr (C++11) default_delete (C++11) out_ptr_t (C++23) inout_ptr_t (C++23) Low level memory management operator new operator new[] operator delete operator delete[] get_new_handler (C++11) set_new_handler launder (C++17) bad_alloc bad_array_new_length (C++11) nothrow_t align_val_t (C++17) destroying_delete_t (C++20) new_handler nothrow Miscellaneous pointer_traits (C++11) to_address (C++20) addressof (C++11) align (C++11) assume_aligned (C++20) C Library malloc calloc realloc    aligned_alloc (C++17) free

 

std::pmr::polymorphic_allocator

Member functions

polymorphic_allocator::polymorphic_allocator

polymorphic_allocator::allocate

polymorphic_allocator::deallocate

polymorphic_allocator::construct

polymorphic_allocator::destroy (C++20/26*)

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!= (until C++20)

 

Defined in header <memory_resource>
template< class T > class polymorphic_allocator;		(since C++17)

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.

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 (deprecated in C++20)(undeprecated in C++26)	destroys an object in allocated storage (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!= (removed in C++20)

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)