std::pmr::polymorphic_allocator
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
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 memory (public member function) |
|
| Deallocate memory (public member function) |
|
| Constructs an object in allocated storage (public member function) |
|
| Destroys an object in allocated storage (public member function) |
|
|
(C++20) | Allocate raw aligned memory from the underlying resource (public member function) |
|
(C++20) | Free raw memory obtained from allocate_bytes (public member function) |
|
(C++20) | Allocates raw memory suitable for an object or an array (public member function) |
|
(C++20) | Frees raw memory obtained by allocate_object (public member function) |
|
(C++20) | Allocates and constructs an object (public member function) |
|
(C++20) | Destroys and deallocates an object (public member function) |
Create a new polymorphic_allocator for use by a container's copy constructor (public member function) |
|
| Returns a pointer to the underlying memory resource (public member function) |
|
Non-member functions
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
|
(C++17) | an abstract interface for classes that encapsulate memory resources (class) |
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