[#BloombergLP-bslma-AllocatorUtil_Traits-0f]
= xref:BloombergLP.adoc[BloombergLP]::xref:BloombergLP/bslma.adoc[bslma]::xref:BloombergLP/bslma/AllocatorUtil_Traits-02.adoc[AllocatorUtil_Traits]<t_MEMORY_RSRC*, t_TYPE>
:relfileprefix: ../../
:mrdocs:

This specialization is for allocators expressed as a pointer to class derived from `bsl::memory_resource`. The base class will be `bsl::allocator_traits<bsl::allocator<t_TYPE>>` if `t_MEMORY_RSRC` is derived from `bsl::Allocator`; otherwise the base class will be `bsl::allocator_traits<bsl::polymorphic_allocator<t_TYPE>>`.

== Synopsis

Declared in `<bslma_allocatorutil.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<
    class t_MEMORY_RSRC,
    class t_TYPE>
struct xref:BloombergLP/bslma/AllocatorUtil_Traits-02.adoc[AllocatorUtil_Traits]<t_MEMORY_RSRC*, t_TYPE>
    : xref:bsl/allocator_traits-0108.adoc[bsl::allocator_traits<bsl::conditional<bsl::is_convertible<t_MEMORY_RSRC *, bslma::Allocator *>::value, bsl::allocator<t_TYPE>, bsl::polymorphic_allocator<t_TYPE>>::type>]
----

== Base Classes

[cols="1,4"]
|===
| Name| Description
| `xref:bsl/allocator_traits-0108.adoc[bsl::allocator_traits<bsl::conditional<bsl::is_convertible<t_MEMORY_RSRC *, bslma::Allocator *>::value, bsl::allocator<t_TYPE>, bsl::polymorphic_allocator<t_TYPE>>::type>]`
| This class supports the complete interface of the C++11 `allocator_traits` class template, which provides a uniform mechanism for accessing nested types within, and operations on, any standard‐conforming allocator. A specialization of this class template for `bsl::allocator` provides support for Bloomberg's `bslma` allocator model (see the `bslma_bslallocator` component for more details). In C++11 compilation environments, the `construct` methods forward to the allocator's `construct` method if such a method matching the (variable number of) specified constructor arguments exists; otherwise, the `construct` method falls back to invoking the constructor of the element type directly. In C++03 compilation environments, there is no reliable way to detect if the type provide a method that matches a (variable number of) specified arguments; therefore, we require that standard allocator types define `construct` methods taking a variable number of arguments in those environments. This implementation is not fully‐standard‐conforming in that it does not support deduce data types that are not specified in the allocator.
|===

== Type Aliases

[cols="1,4"]
|===
| Name| Description
| xref:bsl/allocator_traits-0108/allocator_type.adoc[`allocator_type`] 
| This `typedef` is an alias to the (template parameter) `ALLOCATOR_TYPE`.
| xref:bsl/allocator_traits-0108/const_pointer.adoc[`const_pointer`] 
| This `typedef` is an alias to `AllocatorTraits_ConstPointerType<ALLOCATOR_TYPE>::type`.
| xref:bsl/allocator_traits-0108/const_void_pointer.adoc[`const_void_pointer`] 
| Const void pointer type for the allocator.
| xref:bsl/allocator_traits-0108/difference_type.adoc[`difference_type`] 
| This `typedef` is an alias to `AllocatorTraits_DifferenceType<ALLOCATOR_TYPE>::type`.
| xref:bsl/allocator_traits-0108/is_always_equal.adoc[`is_always_equal`] 
| Identical to, or derived from `true_type` if two allocators of parameterized `ALLOCATOR_TYPE` always compare equal; otherwise identical to or derived from `false_type`. This type is `ALLOCATOR_TYPE::is_always_equal` if such a type is defined, and `is_empty<ALLOCATOR_TYPE>` otherwise.
| xref:bsl/allocator_traits-0108/pointer.adoc[`pointer`] 
| This `typedef` is an alias to `AllocatorTraits_PointerType<ALLOCATOR_TYPE>::type`.
| xref:bsl/allocator_traits-0108/propagate_on_container_copy_assignment.adoc[`propagate_on_container_copy_assignment`] 
| Identical to, or derived from `true_type` if an allocator of parameterized `ALLOCATOR_TYPE` should be copied when a container using that `ALLOCATOR_TYPE` is copy‐assigned; otherwise identical to or derived from `false_type`. This type is `ALLOCATOR_TYPE::propagate_on_container_copy_assignment` if such a type is defined, and `false_type` otherwise.
| xref:bsl/allocator_traits-0108/propagate_on_container_move_assignment.adoc[`propagate_on_container_move_assignment`] 
| Identical to, or derived from `true_type` if an allocator of parameterized `ALLOCATOR_TYPE` should be moved when a container using that `ALLOCATOR_TYPE` is move‐assigned; otherwise identical to or derived from `false_type`. This type is `ALLOCATOR_TYPE::propagate_on_container_move_assignment` if such a type is defined, and `false_type` otherwise.
| xref:bsl/allocator_traits-0108/propagate_on_container_swap.adoc[`propagate_on_container_swap`] 
| Identical to, or derived from `true_type` if the allocators of parameterized `ALLOCATOR_TYPE` should be swapped when containers using that `ALLOCATOR_TYPE` are swapped; otherwise identical to or derived from `false_type`. This type is `ALLOCATOR_TYPE::propagate_on_container_swap` if such a type is defined, and `false_type` otherwise.
| xref:bsl/allocator_traits-0108/rebind_alloc.adoc[`rebind_alloc`] 
| Rebind this allocator to the specified `ELEMENT_TYPE`.
| xref:bsl/allocator_traits-0108/rebind_traits.adoc[`rebind_traits`] 
| Rebind this allocator traits type to the specified `ELEMENT_TYPE`.
| xref:bsl/allocator_traits-0108/size_type.adoc[`size_type`] 
| This `typedef` is an alias to `AllocatorTraits_SizeType<ALLOCATOR_TYPE>::type`.
| xref:bsl/allocator_traits-0108/value_type.adoc[`value_type`] 
| This `typedef` is an alias to `ALLOCATOR_TYPE::value_type`.
| xref:bsl/allocator_traits-0108/void_pointer.adoc[`void_pointer`] 
| This `typedef` is an alias to `AllocatorTraits_VoidPointerType<ALLOCATOR_TYPE>::type`.
|===


== Static Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:bsl/allocator_traits-0108/allocate-03.adoc[`allocate`] 
| `allocate` overloads
| xref:bsl/allocator_traits-0108/construct.adoc[`construct`] 
| Construct an object of (template parameter) type `ELEMENT_TYPE` at the specified `elementAddr`, either by 1) calling the `construct` method on `basicAllocator` with `elemAddr` and the specified (variable number of) `arguments` if the (template parameter) type `ALLOCATOR_TYPE` defines such a method, or 2) forwarding the specified (variable number of) `arguments` to the constructor of `ELEMENT_TYPE` directly (and ignoring `basicAllocator`) otherwise. The behavior is undefined unless `elementAddr` refers to valid, uninitialized storage.
| xref:bsl/allocator_traits-0108/deallocate.adoc[`deallocate`] 
| Invoke `basicAllocator.deallocate(elementAddr, n)`. The behavior is undefined unless the specified `elementAddr` was returned from a prior call to the `allocate` method of an allocator that compares equal to the specified `allocator`, and has not yet been passed to a `deallocate` call of such an allocator object.
| xref:bsl/allocator_traits-0108/destroy.adoc[`destroy`] 
| Destroy the object of (template parameter) type `ELEMENT_TYPE` at the specified `elementAddr`, either by 1) calling the `destroy` method on `basicAllocator` with `elemAddr` as the sole argument if the (template parameter) type `ALLOCATOR_TYPE` defines such a method, or 2) calling the destructor directly on `elementAddr` (and ignoring `basicAllocator`) otherwise. The behavior is undefined unless `elementAddr` refers to a valid, constructed object.
| xref:bsl/allocator_traits-0108/max_size.adoc[`max_size`] 
| Return the largest number of `value_type` objects that could reasonably be returned by a single invocation of `allocate` for the specified `allocator`, i.e., `allocator.max_size()`.
| xref:bsl/allocator_traits-0108/select_on_container_copy_construction.adoc[`select_on_container_copy_construction`] 
| Return a copy of the allocator that should be used to copy‐ construct one container from another container whose allocator is the specified `rhs`. If the parameterized `ALLOCATOR_TYPE` defines a method `select_on_container_copy_construction`, this function returns the result of calling that method on `rhs`; otherwise, this method enforces the default policy of propagating the allocator on copy construction, as is standard practice for standard allocators (i.e., returns `rhs`). Note that the specialization of this class template for `bsl::allocator` (in the `bslma_bslallocator` component) provides the alternate default behavior of _not_ propagating the allocator on copy construction (i.e., returning a default‐constructed allocator object).
|===



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