Difference between revisions of "cpp/memory/polymorphic allocator"
From cppreference.com
(added link to memory_resource into "see also" block) |
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{{dsc inc | cpp/memory/polymorphic_allocator/dsc operator eq}} | {{dsc inc | cpp/memory/polymorphic_allocator/dsc operator eq}} | ||
{{dsc end}} | {{dsc end}} | ||
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| + | === Notes === | ||
| + | {{tt|polymorphic_allocator}} does not propagate on container copy assignment, move assignment, or swap. As a result, move assignment of a {{tt|polymorphic_allocator}}-using container can throw, and swapping two {{tt|polymorphic_allocator}}-using containers whose allocators do not compare equal results in undefined behavior. | ||
===See also=== | ===See also=== | ||
Revision as of 14:30, 13 June 2016
| Defined in header <memory_resource>
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| template< class T > class polymorphic_allocator; |
(since C++17) | |
The class template std::pmr::polymorphic_allocator is an Template:concept 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) |
