[#bsl-allocator-0df]
= xref:bsl.adoc[bsl]::allocator
:relfileprefix: ../
:mrdocs:

An STL‐compatible allocator that forwards to a `bslma::Allocator`.

== Synopsis

Declared in `<bslma_bslallocator.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<class TYPE = polymorphic_allocator<>::value_type>
class allocator
    : public xref:bsl/polymorphic_allocator.adoc[polymorphic_allocator<TYPE>]
----

== Description

An STL‐compatible allocator that forwards allocation calls to an underlying mechanism object of a type derived from `bslma::Allocator`. This class template adheres to the allocator requirements defined in section [allocator.requirements]and implements a superset of the `std::pmr::polymorphic_allocator` class template described in section [mem.poly.allocator.class]of the C++ standard and may be used to instantiate any [container]class template that follows the STL allocator protocol. The allocation mechanism is chosen at run‐time, giving the programmer run‐time control over how a container allocates and frees memory.

== Base Classes

[cols="1,4"]
|===
| Name| Description
| `xref:bsl/polymorphic_allocator.adoc[polymorphic_allocator<TYPE>]`
| Alias for `std::pmr::polymorphic_allocator` in the `bsl` namespace.
|===

== Types

[cols="1,4"]
|===
| Name| Description
| xref:bsl/allocator-0df/rebind.adoc[`rebind`] 
| Rebind this allocator to another type.
|===


== Type Aliases

[cols="1,4"]
|===
| Name| Description
| xref:bsl/allocator-0df/const_pointer.adoc[`const_pointer`] 
| This `typedef` is an alias to `BaseTraits::const_pointer`.
| xref:bsl/allocator-0df/const_reference.adoc[`const_reference`] 
| This `typedef` is an alias to a constant `value_type` reference.
| xref:bsl/allocator-0df/const_void_pointer.adoc[`const_void_pointer`] 
| This `typedef` is an alias to `BaseTraits::const_void_pointer`.
| xref:bsl/allocator-0df/difference_type.adoc[`difference_type`] 
| Difference type for allocations from this allocator.
| xref:bsl/allocator-0df/pointer.adoc[`pointer`] 
| This `typedef` is an alias to `BaseTraits::pointer`.
| xref:bsl/allocator-0df/reference.adoc[`reference`] 
| This `typedef` is an alias to a modifiable `value_type` reference.
| xref:bsl/allocator-0df/size_type.adoc[`size_type`] 
| Size type for allocations from this allocator.
| xref:bsl/allocator-0df/value_type.adoc[`value_type`] 
| This `typedef` is an alias to the (template parameter) `TYPE`.
| xref:bsl/allocator-0df/void_pointer.adoc[`void_pointer`] 
| This `typedef` is an alias to `BaseTraits::void_pointer`.
|===


== Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:bsl/allocator-0df/2constructor-0f.adoc[`allocator`]         [.small]#[constructor]#
| Create an allocator that uses the default allocator mechanism.
| xref:bsl/allocator-0df/2constructor-0c.adoc[`allocator`]         [.small]#[constructor]#
| Create an allocator that copies `original`.
| xref:bsl/allocator-0df/2constructor-0bc.adoc[`allocator`]         [.small]#[constructor]#
| Create an allocator sharing the mechanism of the specified `original`.
| xref:bsl/allocator-0df/2constructor-0b9.adoc[`allocator`]         [.small]#[constructor]#
| Convert a `bslma::Allocator` pointer to an `allocator` object.
| xref:bsl/allocator-0df/operator_assign.adoc[`operator=`] 
| Assign this allocator from the specified `rhs` if it is a no‐op assignment.
| xref:bsl/allocator-0df/address-08.adoc[`address`] 
| Return the address of the specified object `x`.
| xref:bsl/allocator-0df/address-04.adoc[`address`] 
| Return the address of the specified object `x`.
| xref:bsl/allocator-0df/allocate.adoc[`allocate`] 
| Return storage for `n` objects of `value_type`.
| xref:bsl/allocator-0df/construct-00.adoc[`construct`] 
| Default‐construct an `ELEMENT_TYPE` object at the specified `address`.
| xref:bsl/allocator-0df/construct-08.adoc[`construct`] 
| Construct an `ELEMENT_TYPE` at `address` from the arguments.
| xref:bsl/allocator-0df/construct-0e.adoc[`construct`] 
| Construct an `ELEMENT_TYPE` at `address` using perfect forwarding.
| xref:bsl/allocator-0df/deallocate.adoc[`deallocate`] 
| Deallocate the memory block at the specified `p` address.
| xref:bsl/allocator-0df/destroy.adoc[`destroy`] 
| Call the destructor for the object at the specified `address`.
| xref:bsl/allocator-0df/max_size.adoc[`max_size`] 
| Return the maximum number of elements allocatable by this allocator.
| xref:bsl/allocator-0df/mechanism.adoc[`mechanism`] 
| Return a pointer to the mechanism object to which this proxy forwards allocation and deallocation calls.
| xref:bsl/allocator-0df/select_on_container_copy_construction.adoc[`select_on_container_copy_construction`] 
| Return a default‐constructed allocator.
| xref:bsl/allocator-0df/2conversion-0e.adoc[`operator BloombergLP::bslmf::NestedTraitDeclaration<allocator, IsBitwiseCopyable>`] 
| Return a tag declaring that this allocator is bitwise copyable.
| xref:bsl/allocator-0df/2conversion-04.adoc[`operator BloombergLP::bslmf::NestedTraitDeclaration<allocator, IsBitwiseEqualityComparable>`] 
| Declare that `allocator` is bitwise equality comparable.
|===


== Specializations

[cols="1,4"]
|===
| Name| Description
| xref:bsl/allocator-0a.adoc[`allocator<void>`] 
| Specialization of `allocator` for `void`.
|===


== Non-Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:bsl/format-0cb.adoc[`format`]
| Format `args` according to `fmtStr` using `alloc` and locale `loc`.
| xref:bsl/format-0ce.adoc[`format`]
| Format `args` according to `fmtStr` using allocator `alloc`.
| xref:bsl/format-0d.adoc[`format`]
| Format `args` according to `fmtStr` using `alloc` and locale `loc`.
| xref:bsl/format-0e.adoc[`format`]
| Format `args` according to `fmtStr` using allocator `alloc`.
| xref:bsl/vformat-00b.adoc[`vformat`]
| Format `args` according to `fmtStr` using allocator and locale.
| xref:bsl/vformat-0c3.adoc[`vformat`]
| Format `args` according to `fmtStr` using the given allocator.
| xref:bsl/vformat-0eb.adoc[`vformat`]
| Format `args` according to `fmtStr` using the given allocator.
| xref:bsl/vformat-0ef.adoc[`vformat`]
| Format `args` according to `fmtStr` using allocator and locale.
| xref:BloombergLP/bslfmt/format-06.adoc[`::BloombergLP::bslfmt::format`]
| Format `args` according to `fmtStr` using allocator `alloc`.
| xref:BloombergLP/bslfmt/format-099.adoc[`::BloombergLP::bslfmt::format`]
| Format `args` according to `fmtStr` using allocator `alloc`.
| xref:BloombergLP/bslfmt/vformat-0c.adoc[`::BloombergLP::bslfmt::vformat`]
| Format `args` according to `fmtStr` using the given allocator.
| xref:BloombergLP/bslfmt/vformat-0f.adoc[`::BloombergLP::bslfmt::vformat`]
| Format `args` according to `fmtStr` using the given allocator.
|===

== Derived Classes

[cols="1,4"]
|===
| Name| Description
| xref:bsl/allocator-0a.adoc[`allocator<void>`] 
| Specialization of `allocator` for `void`.
|===


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