C++ concepts: AllocatorAwareContainer
An AllocatorAwareContainer is a Container that holds an instance of an Allocator and uses that instance in all its member functions to allocate and deallocate memory and to construct and destroy objects in that memory (such objects may be container elements, nodes, or, for unordered containers, bucket arrays).
The following rules apply to container construction
-  Copy constructors of AllocatorAwareContainers obtain their instances of the allocator by calling std::allocator_traits<allocator_type>::select_on_container_copy_construction on the allocator of the container being copied.
- Move constructors obtain their instances of allocators by move-constructing from the allocator belonging to the old container.
- All other constructors take an allocator parameter.
The only way to replace an allocator is copy-assignment, move-assignment, and swap:
- Copy-assignment will replace the allocator only if std::allocator_traits<allocator_type>::propagate_on_container_copy_assignment::value is true
- Move-assignment will replace the allocator only if std::allocator_traits<allocator_type>::propagate_on_container_move_assignment::value is true
-  Swap will replace the allocator only if std::allocator_traits<allocator_type>::propagate_on_container_swap::value is true. Specifically, it will exchange the allocator instances through an unqualified call to the non-member function swap, see Swappable.
Note: swapping two containers with unequal allocators if propagate_on_container_swap is false is undefined behavior.
-  The accessor get_allocator()obtains a copy of the allocator that was used to construct the container or installed by the most recent allocator replacement operation.
| Contents | 
[edit] Requirements
| Legend | |
| X | Container type | 
| T | Element type | 
| A | Allocator for T | 
| a,b | Objects of type X(non-const lvalue) | 
| t | Object of type X(lvalue or const rvalue) | 
| rv | Object of type X(non-const rvalue) | 
| m | Object of type A | 
| Q | Allocator type | 
| expression | return type | pre/requirements | post/effects | complexity | 
|---|---|---|---|---|
| allocator_type | A | allocator_type::value_type must be the same as X::value_type | compile-time | |
| get_allocator() | A | constant | ||
| X u; | AisDefaultConstructible | u.empty() == true && u.get_allocator() == A() | constant | |
| X u(m); | u.empty() == true && u.get_allocator() == m | constant | ||
| X u(t,m); | TisCopyInsertableintoX | u == t && u.get_allocator() == m | linear | |
| X u(rv); | Move constructor of Amust not throw exceptions | uhas the same elements and an equal allocator asrvhad before the construction | constant | |
| X u(rv,m); | TisMoveInsertableintoX | The elements of uare the same or copies of those ofrvand u.get_allocator() == m | constant if m == rv.get_allocator(), otherwise linear | |
| a = t | X& | TisCopyInsertableintoXandCopyAssignable | a == t | linear | 
| a = rv | X& | If the allocator will not be replaced by move-assignment (see above), then TisMoveInsertableintoXandMoveAssignable | All existing elements of aare either move assigned to or destroyed;ais equal to the value thatrvhad before the assignment | linear | 
| a.swap(b) | void | Exchanges the contents of aandb | constant | 
[edit] Concept requirements
- A
- T
- X
[edit] Notes
Allocator-aware containers always call std::allocator_traits<A>::construct(m, p, args) to construct an object of type A at p using args, with m == get_allocator(). The default construct in std::allocator calls ::new((void*)p) T(args), but specialized allocators may choose a different definition
[edit] Standard library
All standard library containers except std::array are AllocatorAwareContainers:


