bsl::allocator_traits

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.

Synopsis

Declared in <bslma_allocatortraits.h>

template<class ALLOCATOR_TYPE>
struct allocator_traits;

Type Aliases

Name	Description
`allocator_type`	This `typedef` is an alias to the (template parameter) `ALLOCATOR_TYPE`.
`const_pointer`	This `typedef` is an alias to `AllocatorTraits_ConstPointerType<ALLOCATOR_TYPE>::type`.
`const_void_pointer`	Const void pointer type for the allocator.
`difference_type`	This `typedef` is an alias to `AllocatorTraits_DifferenceType<ALLOCATOR_TYPE>::type`.
`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.
`pointer`	This `typedef` is an alias to `AllocatorTraits_PointerType<ALLOCATOR_TYPE>::type`.
`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.
`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.
`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.
`rebind_alloc`	Rebind this allocator to the specified `ELEMENT_TYPE`.
`rebind_traits`	Rebind this allocator traits type to the specified `ELEMENT_TYPE`.
`size_type`	This `typedef` is an alias to `AllocatorTraits_SizeType<ALLOCATOR_TYPE>::type`.
`value_type`	This `typedef` is an alias to `ALLOCATOR_TYPE::value_type`.
`void_pointer`	This `typedef` is an alias to `AllocatorTraits_VoidPointerType<ALLOCATOR_TYPE>::type`.

Static Member Functions

Name	Description
`allocate`	`allocate` overloads
`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.
`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.
`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.
`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()`.
`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).

Specializations

Name	Description
`allocator_traits<allocator<Attribute>>`	This `struct` template provides a specialization of the `allocator_traits` class template for `bsl::allocator`. This specialization is not strictly necessary, but its presence speeds up compliation by bypassing a significant amount of metaprogramming.
`allocator_traits<allocator<Json>>`	This `struct` template provides a specialization of the `allocator_traits` class template for `bsl::allocator`. This specialization is not strictly necessary, but its presence speeds up compliation by bypassing a significant amount of metaprogramming.
`allocator_traits<allocator<ManagedAttribute>>`	This `struct` template provides a specialization of the `allocator_traits` class template for `bsl::allocator`. This specialization is not strictly necessary, but its presence speeds up compliation by bypassing a significant amount of metaprogramming.
`allocator_traits<allocator<MetricSampleGroup>>`	This `struct` template provides a specialization of the `allocator_traits` class template for `bsl::allocator`. This specialization is not strictly necessary, but its presence speeds up compliation by bypassing a significant amount of metaprogramming.
`allocator_traits<allocator<UserFieldValue>>`	This `struct` template provides a specialization of the `allocator_traits` class template for `bsl::allocator`. This specialization is not strictly necessary, but its presence speeds up compliation by bypassing a significant amount of metaprogramming.
`allocator_traits<allocator<ZoneinfoTransition>>`	This `struct` template provides a specialization of the `allocator_traits` class template for `bsl::allocator`. This specialization is not strictly necessary, but its presence speeds up compliation by bypassing a significant amount of metaprogramming.
`allocator_traits<allocator<bool>>`	This `struct` template provides a specialization of the `allocator_traits` class template for `bsl::allocator`. This specialization is not strictly necessary, but its presence speeds up compliation by bypassing a significant amount of metaprogramming.
`allocator_traits<allocator<char>>`	This `struct` template provides a specialization of the `allocator_traits` class template for `bsl::allocator`. This specialization is not strictly necessary, but its presence speeds up compliation by bypassing a significant amount of metaprogramming.
`allocator_traits<allocator<char16_t>>`	This `struct` template provides a specialization of the `allocator_traits` class template for `bsl::allocator`. This specialization is not strictly necessary, but its presence speeds up compliation by bypassing a significant amount of metaprogramming.
`allocator_traits<allocator<char32_t>>`	This `struct` template provides a specialization of the `allocator_traits` class template for `bsl::allocator`. This specialization is not strictly necessary, but its presence speeds up compliation by bypassing a significant amount of metaprogramming.
`allocator_traits<allocator<char8_t>>`	This `struct` template provides a specialization of the `allocator_traits` class template for `bsl::allocator`. This specialization is not strictly necessary, but its presence speeds up compliation by bypassing a significant amount of metaprogramming.
`allocator_traits<allocator<double>>`	This `struct` template provides a specialization of the `allocator_traits` class template for `bsl::allocator`. This specialization is not strictly necessary, but its presence speeds up compliation by bypassing a significant amount of metaprogramming.
`allocator_traits<allocator<float>>`	This `struct` template provides a specialization of the `allocator_traits` class template for `bsl::allocator`. This specialization is not strictly necessary, but its presence speeds up compliation by bypassing a significant amount of metaprogramming.
`allocator_traits<allocator<int>>`	This `struct` template provides a specialization of the `allocator_traits` class template for `bsl::allocator`. This specialization is not strictly necessary, but its presence speeds up compliation by bypassing a significant amount of metaprogramming.
`allocator_traits<allocator<long>>`	This `struct` template provides a specialization of the `allocator_traits` class template for `bsl::allocator`. This specialization is not strictly necessary, but its presence speeds up compliation by bypassing a significant amount of metaprogramming.
`allocator_traits<allocator<long double>>`	This `struct` template provides a specialization of the `allocator_traits` class template for `bsl::allocator`. This specialization is not strictly necessary, but its presence speeds up compliation by bypassing a significant amount of metaprogramming.
`allocator_traits<allocator<long long>>`	This `struct` template provides a specialization of the `allocator_traits` class template for `bsl::allocator`. This specialization is not strictly necessary, but its presence speeds up compliation by bypassing a significant amount of metaprogramming.
`allocator_traits<allocator<short>>`	This `struct` template provides a specialization of the `allocator_traits` class template for `bsl::allocator`. This specialization is not strictly necessary, but its presence speeds up compliation by bypassing a significant amount of metaprogramming.
`allocator_traits<allocator<signed char>>`	This `struct` template provides a specialization of the `allocator_traits` class template for `bsl::allocator`. This specialization is not strictly necessary, but its presence speeds up compliation by bypassing a significant amount of metaprogramming.
`allocator_traits<allocator<unsigned char>>`	This `struct` template provides a specialization of the `allocator_traits` class template for `bsl::allocator`. This specialization is not strictly necessary, but its presence speeds up compliation by bypassing a significant amount of metaprogramming.
`allocator_traits<allocator<unsigned int>>`	This `struct` template provides a specialization of the `allocator_traits` class template for `bsl::allocator`. This specialization is not strictly necessary, but its presence speeds up compliation by bypassing a significant amount of metaprogramming.
`allocator_traits<allocator<unsigned long>>`	This `struct` template provides a specialization of the `allocator_traits` class template for `bsl::allocator`. This specialization is not strictly necessary, but its presence speeds up compliation by bypassing a significant amount of metaprogramming.
`allocator_traits<allocator<unsigned long long>>`	This `struct` template provides a specialization of the `allocator_traits` class template for `bsl::allocator`. This specialization is not strictly necessary, but its presence speeds up compliation by bypassing a significant amount of metaprogramming.
`allocator_traits<allocator<unsigned short>>`	This `struct` template provides a specialization of the `allocator_traits` class template for `bsl::allocator`. This specialization is not strictly necessary, but its presence speeds up compliation by bypassing a significant amount of metaprogramming.
`allocator_traits<allocator<wchar_t>>`	This `struct` template provides a specialization of the `allocator_traits` class template for `bsl::allocator`. This specialization is not strictly necessary, but its presence speeds up compliation by bypassing a significant amount of metaprogramming.
`allocator_traits<allocator<pair<Date, DayOfWeekSet>>>`	This `struct` template provides a specialization of the `allocator_traits` class template for `bsl::allocator`. This specialization is not strictly necessary, but its presence speeds up compliation by bypassing a significant amount of metaprogramming.
`allocator_traits<allocator<pair<TimeInterval const, Node*>>>`	This `struct` template provides a specialization of the `allocator_traits` class template for `bsl::allocator`. This specialization is not strictly necessary, but its presence speeds up compliation by bypassing a significant amount of metaprogramming.
`allocator_traits<allocator<pair<int const, pair<shared_ptr<Statistics>, shared_ptr<Collector<OsLinux>>>>>>`	This `struct` template provides a specialization of the `allocator_traits` class template for `bsl::allocator`. This specialization is not strictly necessary, but its presence speeds up compliation by bypassing a significant amount of metaprogramming.
`allocator_traits<allocator<pair<basic_string<char> const, Json>>>`	This `struct` template provides a specialization of the `allocator_traits` class template for `bsl::allocator`. This specialization is not strictly necessary, but its presence speeds up compliation by bypassing a significant amount of metaprogramming.
`allocator_traits<allocator<void*>>`	This `struct` template provides a specialization of the `allocator_traits` class template for `bsl::allocator`. This specialization is not strictly necessary, but its presence speeds up compliation by bypassing a significant amount of metaprogramming.
`allocator_traits<allocator<char const*>>`	This `struct` template provides a specialization of the `allocator_traits` class template for `bsl::allocator`. This specialization is not strictly necessary, but its presence speeds up compliation by bypassing a significant amount of metaprogramming.
`allocator_traits<polymorphic_allocator<Attribute>>`	This `struct` template provides a specialization of the `allocator_traits` class template for `bsl::polymorphic_allocator`. This specialization is not strictly necessary, but its presence speeds up compilation by bypassing a significant amount of metaprogramming.
`allocator_traits<polymorphic_allocator<BslAllocator_Voidish>>`	This `struct` template provides a specialization of the `allocator_traits` class template for `bsl::polymorphic_allocator`. This specialization is not strictly necessary, but its presence speeds up compilation by bypassing a significant amount of metaprogramming.
`allocator_traits<polymorphic_allocator<Json>>`	This `struct` template provides a specialization of the `allocator_traits` class template for `bsl::polymorphic_allocator`. This specialization is not strictly necessary, but its presence speeds up compilation by bypassing a significant amount of metaprogramming.
`allocator_traits<polymorphic_allocator<ManagedAttribute>>`	This `struct` template provides a specialization of the `allocator_traits` class template for `bsl::polymorphic_allocator`. This specialization is not strictly necessary, but its presence speeds up compilation by bypassing a significant amount of metaprogramming.
`allocator_traits<polymorphic_allocator<MetricSampleGroup>>`	This `struct` template provides a specialization of the `allocator_traits` class template for `bsl::polymorphic_allocator`. This specialization is not strictly necessary, but its presence speeds up compilation by bypassing a significant amount of metaprogramming.
`allocator_traits<polymorphic_allocator<UserFieldValue>>`	This `struct` template provides a specialization of the `allocator_traits` class template for `bsl::polymorphic_allocator`. This specialization is not strictly necessary, but its presence speeds up compilation by bypassing a significant amount of metaprogramming.
`allocator_traits<polymorphic_allocator<ZoneinfoTransition>>`	This `struct` template provides a specialization of the `allocator_traits` class template for `bsl::polymorphic_allocator`. This specialization is not strictly necessary, but its presence speeds up compilation by bypassing a significant amount of metaprogramming.
`allocator_traits<polymorphic_allocator<bool>>`	This `struct` template provides a specialization of the `allocator_traits` class template for `bsl::polymorphic_allocator`. This specialization is not strictly necessary, but its presence speeds up compilation by bypassing a significant amount of metaprogramming.
`allocator_traits<polymorphic_allocator<char>>`	This `struct` template provides a specialization of the `allocator_traits` class template for `bsl::polymorphic_allocator`. This specialization is not strictly necessary, but its presence speeds up compilation by bypassing a significant amount of metaprogramming.
`allocator_traits<polymorphic_allocator<char16_t>>`	This `struct` template provides a specialization of the `allocator_traits` class template for `bsl::polymorphic_allocator`. This specialization is not strictly necessary, but its presence speeds up compilation by bypassing a significant amount of metaprogramming.
`allocator_traits<polymorphic_allocator<char32_t>>`	This `struct` template provides a specialization of the `allocator_traits` class template for `bsl::polymorphic_allocator`. This specialization is not strictly necessary, but its presence speeds up compilation by bypassing a significant amount of metaprogramming.
`allocator_traits<polymorphic_allocator<char8_t>>`	This `struct` template provides a specialization of the `allocator_traits` class template for `bsl::polymorphic_allocator`. This specialization is not strictly necessary, but its presence speeds up compilation by bypassing a significant amount of metaprogramming.
`allocator_traits<polymorphic_allocator<double>>`	This `struct` template provides a specialization of the `allocator_traits` class template for `bsl::polymorphic_allocator`. This specialization is not strictly necessary, but its presence speeds up compilation by bypassing a significant amount of metaprogramming.
`allocator_traits<polymorphic_allocator<float>>`	This `struct` template provides a specialization of the `allocator_traits` class template for `bsl::polymorphic_allocator`. This specialization is not strictly necessary, but its presence speeds up compilation by bypassing a significant amount of metaprogramming.
`allocator_traits<polymorphic_allocator<int>>`	This `struct` template provides a specialization of the `allocator_traits` class template for `bsl::polymorphic_allocator`. This specialization is not strictly necessary, but its presence speeds up compilation by bypassing a significant amount of metaprogramming.
`allocator_traits<polymorphic_allocator<long>>`	This `struct` template provides a specialization of the `allocator_traits` class template for `bsl::polymorphic_allocator`. This specialization is not strictly necessary, but its presence speeds up compilation by bypassing a significant amount of metaprogramming.
`allocator_traits<polymorphic_allocator<long double>>`	This `struct` template provides a specialization of the `allocator_traits` class template for `bsl::polymorphic_allocator`. This specialization is not strictly necessary, but its presence speeds up compilation by bypassing a significant amount of metaprogramming.
`allocator_traits<polymorphic_allocator<long long>>`	This `struct` template provides a specialization of the `allocator_traits` class template for `bsl::polymorphic_allocator`. This specialization is not strictly necessary, but its presence speeds up compilation by bypassing a significant amount of metaprogramming.
`allocator_traits<polymorphic_allocator<short>>`	This `struct` template provides a specialization of the `allocator_traits` class template for `bsl::polymorphic_allocator`. This specialization is not strictly necessary, but its presence speeds up compilation by bypassing a significant amount of metaprogramming.
`allocator_traits<polymorphic_allocator<signed char>>`	This `struct` template provides a specialization of the `allocator_traits` class template for `bsl::polymorphic_allocator`. This specialization is not strictly necessary, but its presence speeds up compilation by bypassing a significant amount of metaprogramming.
`allocator_traits<polymorphic_allocator<unsigned char>>`	This `struct` template provides a specialization of the `allocator_traits` class template for `bsl::polymorphic_allocator`. This specialization is not strictly necessary, but its presence speeds up compilation by bypassing a significant amount of metaprogramming.
`allocator_traits<polymorphic_allocator<unsigned int>>`	This `struct` template provides a specialization of the `allocator_traits` class template for `bsl::polymorphic_allocator`. This specialization is not strictly necessary, but its presence speeds up compilation by bypassing a significant amount of metaprogramming.
`allocator_traits<polymorphic_allocator<unsigned long>>`	This `struct` template provides a specialization of the `allocator_traits` class template for `bsl::polymorphic_allocator`. This specialization is not strictly necessary, but its presence speeds up compilation by bypassing a significant amount of metaprogramming.
`allocator_traits<polymorphic_allocator<unsigned long long>>`	This `struct` template provides a specialization of the `allocator_traits` class template for `bsl::polymorphic_allocator`. This specialization is not strictly necessary, but its presence speeds up compilation by bypassing a significant amount of metaprogramming.
`allocator_traits<polymorphic_allocator<unsigned short>>`	This `struct` template provides a specialization of the `allocator_traits` class template for `bsl::polymorphic_allocator`. This specialization is not strictly necessary, but its presence speeds up compilation by bypassing a significant amount of metaprogramming.
`allocator_traits<polymorphic_allocator<wchar_t>>`	This `struct` template provides a specialization of the `allocator_traits` class template for `bsl::polymorphic_allocator`. This specialization is not strictly necessary, but its presence speeds up compilation by bypassing a significant amount of metaprogramming.
`allocator_traits<polymorphic_allocator<pair<Date, DayOfWeekSet>>>`	This `struct` template provides a specialization of the `allocator_traits` class template for `bsl::polymorphic_allocator`. This specialization is not strictly necessary, but its presence speeds up compilation by bypassing a significant amount of metaprogramming.
`allocator_traits<polymorphic_allocator<pair<TimeInterval const, Node*>>>`	This `struct` template provides a specialization of the `allocator_traits` class template for `bsl::polymorphic_allocator`. This specialization is not strictly necessary, but its presence speeds up compilation by bypassing a significant amount of metaprogramming.
`allocator_traits<polymorphic_allocator<pair<int const, pair<shared_ptr<Statistics>, shared_ptr<Collector<OsLinux>>>>>>`	This `struct` template provides a specialization of the `allocator_traits` class template for `bsl::polymorphic_allocator`. This specialization is not strictly necessary, but its presence speeds up compilation by bypassing a significant amount of metaprogramming.
`allocator_traits<polymorphic_allocator<pair<basic_string<char> const, Json>>>`	This `struct` template provides a specialization of the `allocator_traits` class template for `bsl::polymorphic_allocator`. This specialization is not strictly necessary, but its presence speeds up compilation by bypassing a significant amount of metaprogramming.
`allocator_traits<polymorphic_allocator<void*>>`	This `struct` template provides a specialization of the `allocator_traits` class template for `bsl::polymorphic_allocator`. This specialization is not strictly necessary, but its presence speeds up compilation by bypassing a significant amount of metaprogramming.
`allocator_traits<polymorphic_allocator<char const*>>`	This `struct` template provides a specialization of the `allocator_traits` class template for `bsl::polymorphic_allocator`. This specialization is not strictly necessary, but its presence speeds up compilation by bypassing a significant amount of metaprogramming.
`allocator_traits<allocator<TYPE>>`	This `struct` template provides a specialization of the `allocator_traits` class template for `bsl::allocator`. This specialization is not strictly necessary, but its presence speeds up compliation by bypassing a significant amount of metaprogramming.
`allocator_traits<std::allocator<ALLOCATOR_TYPE>>`
`allocator_traits<polymorphic_allocator<TYPE>>`	This `struct` template provides a specialization of the `allocator_traits` class template for `bsl::polymorphic_allocator`. This specialization is not strictly necessary, but its presence speeds up compilation by bypassing a significant amount of metaprogramming.
`allocator_traits<ALLOCATOR_TYPE*>`	TBD: improve comment This is an empty class specialization of `allocator_traits` for pointer types that (intentionally) does not define any of the traits typedefs. It's needed in order make unambiguous function overloads that take both a standard allocator by value and a `bslma::Allocator *`. By using the typedefs defined in `allocator_traits` in the signature of functions taking standard allocators, we can ensure that those overloads are not considered when using `bslma`-style allocators.

Derived Classes

Name	Description
`AllocatorUtil_Traits<t_MEMORY_RSRC*, t_TYPE>`	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>>`.