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

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C++
Memory management library
( exposition only* )
Allocators
Uninitialized memory algorithms
Constrained uninitialized memory algorithms
Memory resources
Uninitialized storage (until C++20)
( until C++20* )
( until C++20* )
( until C++20* )

Garbage collector support (until C++23)
(C++11) (until C++23)
(C++11) (until C++23)
(C++11) (until C++23)
(C++11) (until C++23)
(C++11) (until C++23)
(C++11) (until C++23)
std::polymorphic
constexpr polymorphic & operator = ( const polymorphic & other ) ;
(1) (since C++26)
constexpr polymorphic & operator = ( polymorphic && other )
noexcept ( /* see below */ ) ;
(2) (since C++26)

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:

Contents

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

This section is incomplete
Reason: no example