Difference between revisions of "cpp/memory/polymorphic allocator"
From cppreference.com
m (link to zh) |
m (Text replace - "{{concept" to "{{named req") |
||
| Line 6: | Line 6: | ||
}} | }} | ||
| − | The class template {{tt|std::pmr::polymorphic_allocator}} is an {{ | + | The class template {{tt|std::pmr::polymorphic_allocator}} is an {{named req|Allocator}} whose allocation behavior depends on the memory resource it is constructed with. Thus, different instances of {{tt|polymorphic_allocator}} can exhibit entirely different allocation behavior. This runtime polymorphism allows objects using {{tt|polymorphic_allocator}} to behave as if they used different allocator types at run time despite the identical static allocator type. |
=== Member types === | === Member types === | ||
Revision as of 14:49, 15 June 2018
| 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.
Contents |
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) | |
| (deprecated in C++20)(undeprecated in C++26) |
destroys an object in allocated storage (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
| (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
| (C++17) |
an abstract interface for classes that encapsulate memory resources (class) |
