std::polymorphic<T, Allocator>::operator=

 

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voidify (exposition only*) Allocators allocator allocator_traits (C++11) allocation_result (C++23) scoped_allocator_adaptor (C++11) pmr::polymorphic_allocator (C++17) 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) Uninitialized memory algorithms uninitialized_copy uninitialized_fill uninitialized_move (C++17) uninitialized_copy_n (C++11) uninitialized_fill_n uninitialized_move_n (C++17) construct_at (C++20) uninitialized_default_construct (C++17) uninitialized_value_construct (C++17) destroy (C++17) uninitialized_default_construct_n (C++17) uninitialized_value_construct_n (C++17) destroy_n (C++17) destroy_at (C++17) Constrained uninitialized memory algorithms ranges::uninitialized_copy (C++20) ranges::uninitialized_fill (C++20) ranges::uninitialized_move (C++20) ranges::uninitialized_copy_n (C++20)  ranges::uninitialized_fill_n (C++20) ranges::uninitialized_move_n (C++20) ranges::construct_at (C++20) ranges::uninitialized_default_construct (C++20) ranges::uninitialized_value_construct (C++20) ranges::destroy (C++20) ranges::uninitialized_default_construct_n (C++20)  ranges::uninitialized_value_construct_n (C++20) ranges::destroy_n (C++20) ranges::destroy_at (C++20) 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::pool_options (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) Explicit lifetime management start_lifetime_as (C++23) start_lifetime_as_array (C++23) Types for composite class design indirect (C++26) polymorphic (C++26) Uninitialized storage (until C++20) raw_storage_iterator (until C++20*) get_temporary_buffer (until C++20*) return_temporary_buffer (until C++20*) Garbage collector support (until C++23) declare_reachable (C++11)(until C++23) declare_no_pointers (C++11)(until C++23) pointer_safety (C++11)(until C++23) undeclare_reachable (C++11)(until C++23) undeclare_no_pointers (C++11)(until C++23) get_pointer_safety (C++11)(until C++23)

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std::polymorphic

Member functions

polymorphic::polymorphic

polymorphic::~polymorphic

polymorphic::operator=

Observers

polymorphic::operator->polymorphic::operator*

polymorphic::valueless_after_move

polymorphic::get_allocator

Modifiers

polymorphic::swap

Non-member functions

swap(std::polymorphic)

 

constexpr polymorphic& operator=( const polymorphic& other );	(1)	(since C++26)
constexpr polymorphic& operator=( polymorphic&& other ) noexcept(/* see below */);	(2)	(since C++26)

See More

Replaces contents of *this with the contents of other.

Let traits be std::allocator_traits<Allocator>:

1) If std::addressof(other) == this is true, does nothing. Otherwise, let need_update be traits::propagate_on_container_copy_assignment::value:

1. If other is valueless, proceeds to the next step. Otherwise, constructs a new owned object in *this using traits::construct with *other as the argument, using the allocator update_alloc ? other.alloc : alloc.
2. The previously owned object in *this (if any) is destroyed using traits::destroy and then the storage is deallocated.

After updating the object owned by *this, if need_update is true, alloc is replaced with a copy of other.alloc.

If T is an incomplete type, the program is ill-formed.

2) If std::addressof(other) == this is true, does nothing. Otherwise, let need_update be traits::propagate_on_container_move_assignment::value:

• If alloc == other.alloc is true, swaps the owned objects in *this and other; the owned object in other (if any) is then destroyed using traits::destroy and then the storage is deallocated.
• Otherwise:

1. If other is valueless, proceeds to the next step. Otherwise, constructs a new owned object in *this using traits::construct with std::move(*other) as the argument, using the allocator update_alloc ? other.alloc : alloc.
2. The previously owned object in *this (if any) is destroyed using traits::destroy and then the storage is deallocated.

After updating the objects owned by *this and other, if need_update is true, alloc is replaced with a copy of other.alloc.

If all following conditions are satisfied, the program is ill-formed:

• std::allocator_traits<Allocator>::is_always_equal::value is false.
• T is an incomplete type.

Parameters

other

-

another polymorphic object whose owned value (if exists) is used for assignment

Return value

*this

Exceptions

1) If any exception is thrown, there are no effects on *this.

2) If any exception is thrown, there are no effects on *this or other.

noexcept specification:  

noexcept(std::allocator_traits<Allocator>:: propagate_on_container_move_assignment::value || std::allocator_traits<Allocator>::is_always_equal::value)

Example