bslma_bslallocator.h

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/// @file bslma_bslallocator.h
///
/// The content of this file has been pre-processed for Doxygen.
///
 
 
// bslma_bslallocator.h                                               -*-C++-*-
#ifndef INCLUDED_BSLMA_BSLALLOCATOR
#define INCLUDED_BSLMA_BSLALLOCATOR
 
#include <bsls_ident.h>
BSLS_IDENT("$Id: $")
 
/// @defgroup bslma_bslallocator bslma_bslallocator
/// @brief  Provide an STL-compatible proxy for `bslma::Allocator` objects.
/// @addtogroup bsl
/// @{
/// @addtogroup bslma
/// @{
/// @addtogroup bslma_bslallocator
/// @{
///
/// <h1> Outline </h1>
/// * <a href="#bslma_bslallocator-purpose"> Purpose</a>
/// * <a href="#bslma_bslallocator-classes"> Classes </a>
/// * <a href="#bslma_bslallocator-canonical-header"> Canonical Header </a>
/// * <a href="#bslma_bslallocator-description"> Description </a>
///   * <a href="#bslma_bslallocator-relationship-to-bsl-polymorphic_allocator"> Relationship to bsl::polymorphic_allocator </a>
///   * <a href="#bslma_bslallocator-c-03-restrictions-on-allocator-usage"> C++03 Restrictions on Allocator Usage </a>
///   * <a href="#bslma_bslallocator-thread-safety"> Thread Safety </a>
///   * <a href="#bslma_bslallocator-usage"> Usage </a>
///     * <a href="#bslma_bslallocator-example-1-a-fixed-size-array"> Example 1: A fixed size array </a>
///     * <a href="#bslma_bslallocator-example-2-propagation-of-the-allocator-to-elements"> Example 2: Propagation of the Allocator to Elements </a>
///
/// # Purpose {#bslma_bslallocator-purpose}
/// Provide an STL-compatible proxy for `bslma::Allocator` objects.
///
/// # Classes {#bslma_bslallocator-classes}
///
/// -  bsl::allocator: STL-compatible allocator template
/// -  bsl::allocator_traits<bsl::allocator>: specialization for `bsl::allocator`
///
/// # Canonical Header {#bslma_bslallocator-canonical-header}
/// bsl_memory.h
///
/// @see  bslma_allocator
///
/// # Description {#bslma_bslallocator-description}
/// This component provides an STL-compatible proxy for any
/// allocator class derived from `bslma::Allocator`.  The proxy class,
/// `bsl::allocator` is a template that adheres to the allocator requirements
/// defined in section 20.5.3.5 [allocator.requirements] of the C++17 standard.
/// `bsl::allocator` may be used to instantiate any class template that is
/// parameterized by a standard allocator.  The container is expected to
/// allocate memory for its own use through the allocator.  The `bsl::allocator`
/// object holds a pointer to an object (the allocation *mechanism*) of class
/// type derived from `bslma::Allocator`.  Different mechanism types allocate
/// memory in different ways or from different pools, so this approach gives the
/// programmer run time control over how the container obtains memory.
///
/// The `bsl::allocator` template is intended to solve a problem created by the
/// C++ standard allocator protocol.  In STL, the allocator type is specified at
/// compile time as a container template parameter, so the allocation mechanism
/// becomes an explicit part of the resulting container type.  Two containers
/// cannot have the same type unless they are instantiated with the same
/// allocator type.  The `bsl::allocator` template breaks the connection between
/// the *compile-time* allocator type and the *run-time* allocation mechanism.
/// The allocation mechanism is chosen at run-time by *initializing* (contrast
/// with *instantiating*) the `bsl::allocator` with a pointer to a *mechanism*
/// *object* derived from `bslma::Allocator`.  Each class derived from
/// `bslma::Allocator` implements a specific allocation mechanism and is thus
/// called a *mechanism* *class* within this component.  The `bsl::allocator`
/// object forwards calls made through the standard allocator interface to the
/// mechanism object with which it was initialized.  In this way, two containers
/// instantiated with `bsl::allocator` can use different allocation mechanisms
/// even though they have the same compile-time type.  The default mechanism
/// object, if none is supplied to the `bsl::allocator` constructor, is
/// `bslma::Default::defaultAllocator()`.
///
/// A container constructs its elements by calling the `construct` method on its
/// allocator.  Importantly, `bsl::allocator` is a *scoped* *allocator* -- when
/// its `construct` method is called, the allocator passes itself to the
/// constructor of the object being constructed (if that object is allocator
/// aware (AA) and uses a compatible allocator type).  Thus, a container
/// instantiated with a scoped allocator ensures that its elements use the same
/// allocator as the container itself.  The `bsl::allocator::construct` method
/// will propagate the allocator not only to element types that use
/// `bsl::allocator`, but also to any types that use `bslma::Allocator *` --
/// i.e., all type for which the `bslma::UsesBslmaAllocator` trait is true.
///
/// A container using `bsl::allocator` should not copy its allocator on
/// assignment and thus assignment of `bsl::allocator` objects is almost always
/// incorrect.  Its base class, `bsl::polymorphic_allocator`, is not assignable,
/// in fact but, for compatibility with some existing code, assignment of
/// `bsl::allocator` must compile, but it is a precondition violation if the
/// allocators being assigned are not already equal at run time (i.e., when
/// assignment is a a no-op).  The assignment operator is deprecated and might
/// be removed in the future, once all existing uses have been excised.
///
/// Instantiations of `bsl::allocator` have reference semantics.  A
/// `bsl::allocator` object does not "own" the `bslma::Allocator` with which it
/// is initialized; copying a `bsl::allocator` object does not copy its
/// mechanism object and destroying a `bsl::allocator` does not destroy its
/// mechanism object.  Two `bsl::allocator` objects compare equal if and only if
/// the mechanism objects they refer to compare equal.
///
/// ## Relationship to bsl::polymorphic_allocator {#bslma_bslallocator-relationship-to-bsl-polymorphic_allocator}
///
///
/// The `bsl::allocator` class template was the inspiration for the C++17
/// `std::pmr::polymorphic_allocator` class template (section 23.12.3,
/// [mem.poly.allocator.class] in the C++17 Standard) and `bslma::Allocator` was
/// the inspiration for the C++17 `std::pmr::memory_resource` (section 23.12.2,
/// mem.res.class] in the C++17 Standard).  For compatibility with the C++17
/// standard, `bsl::allocator` is derived from `bsl::polymorphic_allocator`
/// which, when using a C++17 library, is identical to
/// `std::pmr::polymorphic_allocator`.  Similarly, `bslma::Allocator` is derived
/// from `bsl::memory_resource`, which is identical to
/// `std::pmr::memory_resource`.  These inheritance relationships ensure that a
/// `bsl::allocator` instance can be passed to any type that is instantiated
/// with a `std::pmr::polymorphic_allocator`, including `pmr` containers from
/// the platform library.  Similarly, a pointer to `bslma::Allocator` is
/// implicitly convertible to both `std::pmr::memory_resource *` and
/// `std::pmr::polymorphic_allocator`.
///
/// ## C++03 Restrictions on Allocator Usage {#bslma_bslallocator-c-03-restrictions-on-allocator-usage}
///
///
/// The allocator requirements section of the C++03 standard (section 20.1.5
/// [lib.allocator.requirements]) permits containers to assume that two
/// allocators of the same type always compare equal, effectively limiting C++03
/// to stateless allocators.  This assumption is incorrect for instantiations of
/// `bsl::allocator`.  Therefore, for a container (or other facility) to use
/// `bsl::allocator`, it must operate correctly in the presence of non-equal
/// `bsl::allocator` objects.  In practice, this means that a container cannot
/// transfer ownership of allocated memory to another container unless the two
/// containers use equal allocators.  Older third-party templates that assume
/// stateless allocators might not work correctly when instantiated with
/// `bsl::allocator`.
///
/// ## Thread Safety {#bslma_bslallocator-thread-safety}
///
///
/// Because it is immutable, non-assignable, and has reference semantics, a
/// single `bsl::allocator` object is safe for concurrent access by multiple
/// threads if and only if the `bslma::Allocator` it references is safe for
/// concurrent access from multiple threads.  Separate objects of
/// `bsl::allocator` type may safely be used in separate threads if and only if
/// the `bslma::Allocator` objects they reference are, themselves, safe for
/// concurrent access.
///
/// ## Usage {#bslma_bslallocator-usage}
///
///
/// This section illustrates intended use of this component.
///
/// ### Example 1: A fixed size array {#bslma_bslallocator-example-1-a-fixed-size-array}
///
///
/// We first show how to define a container type parameterized with an STL-style
/// allocator template parameter.  To avoid issues concerning reallocation,
/// dynamic growth, etc., we choose an array whose size is fixed at
/// construction.  Our array will accept any STL-compatible allocator; we do not
/// assume as scoped allocator, which would dictate that we pass the allocator
/// through to the parameterized `T` contained type (see the @ref bslma_allocator 
/// component and @ref bslma_constructionutil  package).
///
/// We begin by defining member variables to hold the allocator, length, and
/// allocated array:
/// @code
/// /// This class provides an array of (the template parameter) `TYPE` of
/// /// fixed length as determined at construction time, using an instance
/// /// of (the template parameter) `ALLOC` type to supply memory.
/// template <class TYPE, class ALLOC>
/// class my_FixedSizeArray {
///
///     // DATA
///     ALLOC  d_allocator;
///     int    d_length;
///     TYPE  *d_array;
/// @endcode
/// Then, we define the public interface:
/// @code
///   public:
///     // TYPES
///     typedef ALLOC allocator_type;
///     typedef TYPE  value_type;
///
///     // CREATORS
///
///     /// Create a fixed-size array of the specified `length`, using the
///     /// optionally specified `allocator` to supply memory.  If
///     /// `allocator` is not specified, a default-constructed instance of
///     /// the parameterized `ALLOC` type is used.  All the elements in the
///     /// resulting array are default-constructed.
///     explicit my_FixedSizeArray(int          length,
///                                const ALLOC& allocator = ALLOC());
///
///     /// Create a copy of the specified `original` fixed-size array,
///     /// using the optionally specified `allocator` to supply memory.  If
///     /// `allocator` is not specified, a default-constructed instance of
///     /// the parameterized `ALLOC` type is used.
///     my_FixedSizeArray(const my_FixedSizeArray& original,
///                       const ALLOC&             allocator = ALLOC());
///
///     /// Destroy this fixed size array.
///     ~my_FixedSizeArray();
///
///     // MANIPULATORS
///
///     /// Assign to this array the value of the specified `original`
///     /// array.  Note that the length of this array might change.
///     my_FixedSizeArray& operator=(const my_FixedSizeArray& original);
///
///     /// Return a reference to the modifiable element at the specified
///     /// `index` position in this fixed size array.  The behavior is
///     /// undefined unless `index` is non-negative and less than
///     /// `length()`.
///     TYPE& operator[](int index) { return d_array[index]; }
///
///     // ACCESSORS
///
///     /// Return a reference to the non-modifiable element at the
///     /// specified `index` position in this fixed size array.  The
///     /// behavior is undefined unless `index` is non-negative and less
///     /// than `length()`.
///     const TYPE& operator[](int index) const { return d_array[index]; }
///
///     /// Return the allocator used by this fixed size array to supply
///     /// memory.
///     allocator_type get_allocator() const { return d_allocator; }
///
///     /// Return the length specified at construction of this fixed size
///     /// array.
///     int length() const { return d_length; }
/// };
///
/// // FREE OPERATORS
///
/// /// Return `true` if the specified `lhs` fixed-size array has the same
/// /// value as the specified `rhs` fixed-size array, and `false`
/// /// otherwise.  Two fixed-size arrays have the same value if they have
/// /// the same length and if the element at any index in `lhs` has the
/// /// same value as the corresponding element at the same index in `rhs`.
/// template<class TYPE, class ALLOC>
/// bool operator==(const my_FixedSizeArray<TYPE, ALLOC>& lhs,
///                 const my_FixedSizeArray<TYPE, ALLOC>& rhs);
///
/// /// Return `true` if the specified `lhs` fixed-size array does not have
/// /// the same value as the specified `rhs` fixed-size array, and `false`
/// /// otherwise.  Two fixed-size arrays have the same value if they have
/// /// the same length and if the element at any index in `lhs` has the
/// /// same value as the corresponding element at the same index in `rhs`.
/// template<class TYPE, class ALLOC>
/// bool operator!=(const my_FixedSizeArray<TYPE, ALLOC>& lhs,
///                 const my_FixedSizeArray<TYPE, ALLOC>& rhs);
/// @endcode
/// Next, we define the first constructor, which uses the allocator's `allocate`
/// memory to obtain memory, then uses its `construct` method to construct each
/// element.  To provide a uniform and future-proof interface, the standard way
/// to call `allocate` and `construct` is indrectly though
/// `bsl::allocator_traits`.  If `ALLOC` is a `bsl::allocator` object, then the
/// `construct` method will attempt to pass the allocator to the constructed
/// elements.  Note that exception safety has been sacrificed for simplicity of
/// presentation; a production version of `my_FixedSizeArray` would need to
/// unwind any constructed elements and the allocation if an exception were
/// thrown.
/// @code
/// #include <bslma_allocatortraits.h>
///
/// // CREATORS
/// template<class TYPE, class ALLOC>
/// my_FixedSizeArray<TYPE, ALLOC>::my_FixedSizeArray(int          length,
///                                                   const ALLOC& allocator)
///     : d_allocator(allocator), d_length(length)
/// {
///     typedef bsl::allocator_traits<ALLOC> Traits;
///
///     d_array = Traits::allocate(d_allocator, d_length);
///
///     // Default construct each element of the array:
///     for (int i = 0; i < d_length; ++i) {
///         Traits::construct(d_allocator, &d_array[i]);
///     }
/// }
/// @endcode
/// Next, we define the copy constructor, which initializes the allocator member
/// but defers the rest of the work to the assignment operator:
/// @code
/// template<class TYPE, class ALLOC>
/// my_FixedSizeArray<TYPE, ALLOC>::my_FixedSizeArray(
///                                         const my_FixedSizeArray& original,
///                                         const ALLOC&             allocator)
///     : d_allocator(allocator), d_length(0), d_array(0)
/// {
///     *this = original;
/// }
/// @endcode
/// Now we define the assignment operator, which allocates the array and copies
/// elements from the `rhs` array.  Note, again, that we simplified the code by
/// omitting exception-safety constructs.
/// @code
/// template<class TYPE, class ALLOC>
/// my_FixedSizeArray<TYPE, ALLOC>&
/// my_FixedSizeArray<TYPE, ALLOC>::operator=(const my_FixedSizeArray& rhs)
/// {
///     typedef bsl::allocator_traits<ALLOC> Traits;
///
///     if (this != &rhs) {
///         // Call destructor for each old element
///         for (int i = 0; i < d_length; ++i) {
///             Traits::destroy(d_allocator, &d_array[i]);
///         }
///
///         // Deallocate old storage
///         Traits::deallocate(d_allocator, d_array, d_length);
///
///         // Set length and allocate new array.  Do not assign the allocator!
///         d_length = rhs.d_length;
///         d_array  = Traits::allocate(d_allocator, d_length);
///
///         // Construct each element of the `lhs` array from the corresponding
///         // `rhs` element.
///         for (int i = 0; i < d_length; ++i) {
///             Traits::construct(d_allocator, &d_array[i], rhs.d_array[i]);
///         }
///     }
///
///     return *this;                                                 // RETURN
/// }
/// @endcode
/// Next, we define the destructor, which uses the allocator's `destroy` method
/// to destroy each element, then the allocator's `deallocate` method to return
/// memory to the allocator:
/// @code
/// template<class TYPE, class ALLOC>
/// my_FixedSizeArray<TYPE, ALLOC>::~my_FixedSizeArray()
/// {
///     typedef bsl::allocator_traits<ALLOC> Traits;
///
///     // Call destructor for each element
///     for (int i = 0; i < d_length; ++i) {
///         Traits::destroy(d_allocator, &d_array[i]);
///     }
///
///     // Return memory to allocator.
///     Traits::deallocate(d_allocator, d_array, d_length);
/// }
/// @endcode
/// The equality and inequality operators simply compare the lengths and element
/// values of the two arrays:
/// @code
/// // FREE OPERATORS
/// template<class TYPE, class ALLOC>
/// bool operator==(const my_FixedSizeArray<TYPE, ALLOC>& lhs,
///                 const my_FixedSizeArray<TYPE, ALLOC>& rhs)
/// {
///     if (lhs.length() != rhs.length()) {
///         return false;                                             // RETURN
///     }
///     for (int i = 0; i < lhs.length(); ++i) {
///         if (lhs[i] != rhs[i]) {
///             return false;                                         // RETURN
///         }
///     }
///     return true;
/// }
///
/// template<class TYPE, class ALLOC>
/// inline
/// bool operator!=(const my_FixedSizeArray<TYPE, ALLOC>& lhs,
///                 const my_FixedSizeArray<TYPE, ALLOC>& rhs) {
///     return ! (lhs == rhs);
/// }
/// @endcode
/// Now we can create array objects with different allocator mechanisms.  First
/// we create an array, `a1`, using the default allocator and fill it with the
/// values `1 .. 5`:
/// @code
/// #include <bslma_bslallocator.h>
/// #include <bslma_testallocator.h>
///
/// int main() {
///
///     my_FixedSizeArray<int, bsl::allocator<int> > a1(5);
///     assert(5                                  == a1.length());
///     assert(bslma::Default::defaultAllocator() == a1.get_allocator());
///
///     for (int i = 0; i < a1.length(); ++i) {
///         a1[i] = i + 1;
///     }
/// @endcode
/// Finally, we create a copy of `a1` using a test allocator.  The values of
/// `a1` and `a2` are equal, even though they have different allocation
/// mechanisms.  We verify that the test allocator was used to allocate the new
/// array elements:
/// @code
///     bslma::TestAllocator                         testAlloc;
///     my_FixedSizeArray<int, bsl::allocator<int> > a2(a1, &testAlloc);
///     assert(a1 == a2);
///     assert(a1.get_allocator() != a2.get_allocator());
///     assert(&testAlloc         == a2.get_allocator());
///     assert(1 == testAlloc.numBlocksInUse());
/// }
/// @endcode
///
/// ### Example 2: Propagation of the Allocator to Elements {#bslma_bslallocator-example-2-propagation-of-the-allocator-to-elements}
///
///
/// In this example, we use the `FixedSizeArray` template defined in Example 1
/// and demonstrate how `bsl::allocator` propagates itself to the elements it
/// constructs, such that the container and its elements all use the same
/// allocator.
///
/// First, we create a representative element class, `MyType`, that allocates
/// memory using the `bslma::Allocator` protocol:
/// @code
/// #include <bslma_allocator.h>
/// #include <bslma_default.h>
/// #include <bslma_usesbslmaallocator.h>
///
/// class MyType {
///
///     bslma::Allocator *d_allocator_p;
///     // etc.
///
///   public:
///     // TRAITS
///     BSLMF_NESTED_TRAIT_DECLARATION(MyType, bslma::UsesBslmaAllocator);
///
///     // CREATORS
///     explicit MyType(bslma::Allocator* basicAlloc = 0)
///       : d_allocator_p(bslma::Default::allocator(basicAlloc)) { /* ... */ }
///     MyType(const MyType&, bslma::Allocator* basicAlloc = 0)
///       : d_allocator_p(bslma::Default::allocator(basicAlloc)) { /* ... */ }
///     // etc.
///
///     // ACCESSORS
///     bslma::Allocator *allocator() const { return d_allocator_p; }
///
///     // etc.
/// };
/// @endcode
/// Now, we instantiate `my_FixedSizeArray` using `MyType` and verify that,
/// when we provide the address of an allocator to the constructor of the
/// container, the same address is passed to the constructor of the container's
/// elements:
/// @code
/// #include <bslmf_issame.h>
///
/// int main()
/// {
///     typedef my_FixedSizeArray<MyType, bsl::allocator<MyType> > ArrayType;
///
///     const int            arrayLen = 7;
///
///     bslma::TestAllocator testAlloc;
///     ArrayType            C1(arrayLen, &testAlloc);
///     assert((bsl::is_same<ArrayType::allocator_type,
///                          bsl::allocator<MyType> >::value));
///     assert(C1.get_allocator()    == bsl::allocator<MyType>(&testAlloc));
///     for (int i = 0; i < arrayLen; ++i) {
///         assert(C1[i].allocator() == &testAlloc);
///     }
/// @endcode
/// Next, we copy-construct the container and verify that the copy uses the
/// default allocator, not the allocator from the original; moreover, we verify
/// that the elements stored in the copy also use the default allocator.
/// @code
///     ArrayType C2(C1);
///     assert(C2.get_allocator() != C1.get_allocator());
///     assert(C2.get_allocator() == bsl::allocator<MyType>());
///     for (int i = 0; i < arrayLen; ++i) {
///         assert(C2[i].allocator() != &testAlloc);
///         assert(C2[i].allocator() == bslma::Default::defaultAllocator());
///     }
/// @endcode
/// Finally, we create a third array using the test allocator and use assignment
/// to give it the same value as the second array.  We then verify that the
/// assignment did not modify the allocator of the lhs array and that the
/// elements of the resulting copy use the same allocator as the lhs array:
/// @code
///     bslma::TestAllocator testAlloc2;
///     ArrayType            C3(1, &testAlloc2);
///     assert(1 == testAlloc2.numBlocksInUse());
///     assert(1 == C3.length());
///     assert(C3.get_allocator() == bsl::allocator<MyType>(&testAlloc2));
///     assert(C3[0].allocator() == &testAlloc2);
///
///     C3 = C2;  // Assignment
///     assert(1        == testAlloc2.numBlocksInUse());
///     assert(arrayLen == C3.length());
///     assert(C3.get_allocator() == bsl::allocator<MyType>(&testAlloc2));
///     for (int i = 0; i < arrayLen; ++i) {
///         assert(C3[i].allocator() == &testAlloc2);
///     }
/// }
/// @endcode
/// @}
/** @} */
/** @} */
 
/** @addtogroup bsl
 * @{
 */
/** @addtogroup bslma
 * @{
 */
/** @addtogroup bslma_bslallocator
 * @{
 */
 
 
#include <bslscm_version.h>
 
#include <bslma_allocator.h>
#include <bslma_allocatortraits.h>
#include <bslma_constructionutil.h>
#include <bslma_default.h>
#include <bslma_destructionutil.h>
#include <bslma_isstdallocator.h>
#include <bslma_polymorphicallocator.h>
#include <bslma_usesbslmaallocator.h>
 
#include <bslmf_isbitwisecopyable.h>
#include <bslmf_isbitwiseequalitycomparable.h>
#include <bslmf_nestedtraitdeclaration.h>
#include <bslmf_util.h>    // 'forward(V)' for C++03
 
#include <bsls_annotation.h>
#include <bsls_assert.h>
#include <bsls_compilerfeatures.h>
#include <bsls_deprecatefeature.h>
#include <bsls_keyword.h>
#include <bsls_platform.h>
#include <bsls_review.h>
#include <bsls_util.h>     // `addressof`
 
#include <cstddef>
 
#if BSLS_COMPILERFEATURES_SIMULATE_CPP11_FEATURES
// clang-format off
// Include version that can be compiled with C++03
// Generated on Mon Jan 13 08:31:27 2025
// Command line: sim_cpp11_features.pl bslma_bslallocator.h
 
# define COMPILING_BSLMA_BSLALLOCATOR_H
# include <bslma_bslallocator_cpp03.h>
# undef COMPILING_BSLMA_BSLALLOCATOR_H
 
// clang-format on
#else
 
#define BSLMA_BSLALLOCATOR_DEPRECATE_ASSIGN \
    BSLS_DEPRECATE_FEATURE("bsl", "bsl_allocator_assign", \
                           "Do not assign allocators.")
 
 
namespace bslma {
 
// FORWARD DECLARATIONS
 
/// Object type that will be placeholder for 'void'
struct BslAllocator_Voidish;
 
}  // close package namespace
 
 
namespace bsl {
 
                              // ===============
                              // class allocator
                              // ===============
 
/// 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.
///
/// See @ref bslma_bslallocator 
template <class TYPE = polymorphic_allocator<>::value_type>
class allocator : public polymorphic_allocator<TYPE> {
 
    // PRIVATE TYPES
    typedef polymorphic_allocator<TYPE> Base;
    typedef allocator_traits<Base>      BaseTraits;
 
  public:
    // TRAITS
    // Note that `allocator` is not trivially copyable because its assignment
    // operator is not trivial.
    BSLMF_NESTED_TRAIT_DECLARATION(allocator,
                                   BloombergLP::bslmf::IsBitwiseCopyable);
    BSLMF_NESTED_TRAIT_DECLARATION(allocator,
                              BloombergLP::bslmf::IsBitwiseEqualityComparable);
 
    // PUBLIC TYPES
    typedef TYPE                                    value_type;
    typedef value_type&                             reference;
    typedef value_type const&                       const_reference;
    typedef typename BaseTraits::size_type          size_type;
    typedef typename BaseTraits::difference_type    difference_type;
    typedef typename BaseTraits::pointer            pointer;
    typedef typename BaseTraits::const_pointer      const_pointer;
    typedef typename BaseTraits::void_pointer       void_pointer;
    typedef typename BaseTraits::const_void_pointer const_void_pointer;
 
    /// This nested `struct` template, parameterized by `ANY_TYPE`, provides
    /// a namespace for an `other` type alias, which is this template instantiated with `ANY_TYPE` instead of `TYPE`.  
    /// 
    /// \note Note that   this
    /// allocator type is convertible to and from `other` for any type,
    /// including `void`.
    ///
    /// See @ref bslma_bslallocator 
    template <class ANY_TYPE>
    struct rebind {
 
        typedef allocator<ANY_TYPE> other;
    };
 
    // CREATORS
 
    /// Create an allocator that will forward allocation calls to the
    /// object pointed to by `bslma::Default::defaultAllocator()`.
    /// Postcondition:
    /// @code
    /// this->mechanism() == bslma::Default::defaultAllocator()
    /// @endcode
    allocator();
 
    /// Convert a `bslma::Allocator` pointer to an `allocator` object that
    /// forwards allocation calls to the object pointed to by the specified
    /// `mechanism`.  If `mechanism` is 0, then the currently installed
    /// default allocator is used instead.  Postcondition:
    /// @code
    /// this->mechanism() == bslma::Default::allocator(mechanism)
    /// @endcode
    allocator(BloombergLP::bslma::Allocator *mechanism);            // IMPLICIT
 
#ifdef BSLS_COMPILERFEATURES_SUPPORT_DEFAULTED_FUNCTIONS
    allocator(const allocator& original) BSLS_KEYWORD_NOEXCEPT = default;
#else
    allocator(const allocator& original) BSLS_KEYWORD_NOEXCEPT;
#endif
    /// Create an allocator sharing the same mechanism object as the
    /// specified `original`.  The newly constructed allocator will compare
    /// equal to `original`, even though they may be instantiated on
    /// different types.  Postconditions:
    /// @code
    /// *this == original
    /// this->mechanism() == original.mechanism()
    /// @endcode
    template <class ANY_TYPE>
    allocator(const allocator<ANY_TYPE>& original) BSLS_KEYWORD_NOEXCEPT;
 
    /// Destroy this object.  
    /// \note Note that  this destructor does not delete the
    /// object pointed to by `mechanism()`.
     ~allocator() = default;
 
    // MANIPULATORS
    BSLMA_BSLALLOCATOR_DEPRECATE_ASSIGN
    /// Modify this allocator to use the same mechanism as the specified `rhs`
    /// allocator and return a modifiable reference to this object.  
    /// 
    /// \note Note that   `bsl::allocator` objects should never be assigned at runtime, but, in
    /// the absence of `if constexpr`, such assignments can sometimes be found
    /// legitimately in dead branches (branches that are never taken at
    /// runtime) within function templates; ideally, such code would be
    /// replaced by more sophisticated metaprogramming that avoided calls to
    /// this operator entirely.  Invoking this assignment will result in a
    /// review error unless `rhs == *this`, i.e., when the assignment would be
    /// a no-op.  In the future, the review error may be replaced with an a
    /// hard assertion failure.
    ///
    /// @deprecated `bsl::allocator` should not be assigned.
    allocator& operator=(const allocator& rhs);
 
    /// Return a block of memory having sufficient size and alignment to
    /// hold the specified `n` objects of `value_type`, allocated from the
    /// memory resource held by this allocator.  Optionally specify a
    /// `hint`, which is ignored by this allocator type but theoretically
    /// used by other allocators as an aid for optimizing locality.
    BSLS_ANNOTATION_NODISCARD
    pointer allocate(size_type n, const void *hint = 0);
 
    /// Deallocate a block of memory at the specified `p` address by
    /// returning it to the memory resource held by this allocator.
    /// Optionally specify the number of objects, `n`, to deallocate.  
    /// 
    /// \pre The behavior is undefined   unless `p` is the address of a block
    /// previously allocated by a call to `allocate` with the same `n` from
    /// a copy of this allocator having the same `value_type` and not yet
    /// deallocated.
    void deallocate(TYPE *p, std::size_t n = 1);
 
    /// Create a default-constructed object of (template parameter)
    /// `ELEMENT_TYPE` at the specified `address`.  If `ELEMENT_TYPE`
    /// supports `bslma`-style allocation, this allocator passes itself to
    /// the extended default constructor.  If the constructor throws, the
    /// memory at `address` is left in an unspecified state.  
    /// 
    /// \pre The behavior is undefined   unless `address` refers to a block of sufficient size
    /// and properly aligned for objects of `ELEMENT_TYPE`.
    template <class ELEMENT_TYPE>
    void construct(ELEMENT_TYPE *address);
 
#if !BSLS_COMPILERFEATURES_SIMULATE_CPP11_FEATURES // $var-args=14
 
    /// Create an object of (template parameter) `ELEMENT_TYPE` at the
    /// specified `address`, constructed by forwarding the specified
    /// `argument1` and the (variable number of) additional specified
    /// `arguments` to the corresponding constructor of `ELEMENT_TYPE`.  If
    /// `ELEMENT_TYPE` supports `bslma`-style allocation, this allocator
    /// passes itself to the constructor.  If
    /// the constructor throws, the memory at `address` is left in an unspecified state.  
    /// 
    /// \note Note that,   in C++03, perfect forwarding is
    /// limited such that any lvalue reference in the `arguments` parameter
    /// pack is const-qualified when forwarded to the `ELEMENT_TYPE`
    /// constructor; only `argument1` can be forwarded as an unqualified lvalue.  
    /// 
    /// \pre The behavior is undefined   unless `address` refers to a
    /// block of sufficient size and properly aligned for objects of
    /// `ELEMENT_TYPE`.
    template <class ELEMENT_TYPE, class ARG1, class... ARGS>
    void construct(ELEMENT_TYPE            *address,
                   ARG1&                    argument1,
                   ARGS&&...                arguments);
    template <class ELEMENT_TYPE, class ARG1, class... ARGS>
    void construct(ELEMENT_TYPE                            *address,
                   BSLS_COMPILERFEATURES_FORWARD_REF(ARG1)  argument1,
                   ARGS&&...                                arguments);
#endif
 
    /// Call the `TYPE` destructor for the object pointed to by the
    /// specified `address`.  Do not directly deallocate any memory.
    template <class ELEMENT_TYPE>
    void destroy(ELEMENT_TYPE *address);
 
    // ACCESSORS
 
    /// Return the address of the object referred to by the specified `x`
    /// reference, even if the (template parameter) `TYPE` overloads the
    /// unary `operator&`.
    pointer       address(reference x) const;
    const_pointer address(const_reference x) const;
 
    /// Return the maximum number of elements of (template parameter) `TYPE` that can be allocated using this allocator.  
    /// 
    /// \note Note that   there is no
    /// guarantee that attempts at allocating fewer elements than the value
    /// returned by @ref max_size  will not throw.
    BSLS_KEYWORD_CONSTEXPR
    size_type max_size() const;
 
    /// Return a pointer to the mechanism object to which this proxy
    /// forwards allocation and deallocation calls.
    BloombergLP::bslma::Allocator *mechanism() const;
 
    /// Return a default-constructed allocator.
    allocator select_on_container_copy_construction() const;
};
 
                           // =====================
                           // class allocator<void>
                           // =====================
 
/// Specialization of `allocator<T>` where `T` is `void`.  Does not contain members that are unrepresentable for `void`.  
/// 
/// \note Note that   this
/// specialization may be removed in the future.  Use `allocator<>` or
/// `allocator<char>` instead.
template <>
class allocator<void>
    : public allocator<BloombergLP::bslma::BslAllocator_Voidish>
{
 
    // PRIVATE TYPES
    typedef allocator<BloombergLP::bslma::BslAllocator_Voidish> Base;
 
    // NOT DEFINED
    void allocate();     // Hide name inherited from base class
    void deallocate();   // Hide name inherited from base class
    void construct();    // Hide name inherited from base class
    void destroy();      // Hide name inherited from base class
    void max_size(int);  // Hide name inherited from base class
 
  public:
    // TRAITS
    // Note that `allocator` is not trivially copyable because its assignment
    // operator is not trivial.
    BSLMF_NESTED_TRAIT_DECLARATION(allocator,
                                   BloombergLP::bslmf::IsBitwiseCopyable);
    BSLMF_NESTED_TRAIT_DECLARATION(allocator,
                              BloombergLP::bslmf::IsBitwiseEqualityComparable);
 
    // PUBLIC TYPES
    typedef void           *pointer;
    typedef const void     *const_pointer;
    typedef void           *void_pointer;
    typedef const void     *const_void_pointer;
    typedef void            value_type;
 
    // CREATORS
 
    /// Create a proxy object that will forward allocation calls to the
    /// object pointed to by `bslma::Default::defaultAllocator()`.
    /// Postcondition:
    /// @code
    /// this->mechanism() == bslma::Default::defaultAllocator();
    /// @endcode
    allocator();
 
    /// Convert a `bslma::Allocator` pointer to an `allocator` object that
    /// forwards allocation calls to the object pointed to by the specified
    /// `mechanism`.  If `mechanism` is 0, then the currently installed
    /// default allocator is used instead.  Postcondition:
    /// @code
    /// this->mechanism() == bslma::Default::allocator(mechanism);
    /// @endcode
    allocator(BloombergLP::bslma::Allocator *mechanism);            // IMPLICIT
 
    /// Create a proxy object sharing the same mechanism object as the
    /// specified `original`.  The newly constructed allocator will compare
    /// equal to `original`, even though they may be instantiated on
    /// different types.  Postcondition:
    /// @code
    /// this->mechanism() == original.mechanism();
    /// @endcode
#ifdef BSLS_COMPILERFEATURES_SUPPORT_DEFAULTED_FUNCTIONS
    allocator(const allocator& original) BSLS_KEYWORD_NOEXCEPT = default;
#else
    allocator(const allocator& original) BSLS_KEYWORD_NOEXCEPT;
#endif
    template <class ANY_TYPE>
    allocator(const allocator<ANY_TYPE>& original) BSLS_KEYWORD_NOEXCEPT;
 
    /// Destroy this object.  
    /// \note Note that  this does not delete the object
    /// pointed to by `mechanism()`.  Also note that this method's
    /// definition is compiler generated.
     ~allocator();
 
    // MANIPULATORS
 
    /// Compiler-generated assign operator.
     allocator& operator=(const allocator& rhs) = default;
 
    // ACCESSORS
 
    /// Return a default-constructed allocator.
    allocator select_on_container_copy_construction() const;
};
 
                  // ========================================
                  // class 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.
template <class TYPE>
struct allocator_traits<allocator<TYPE> > {
 
    // PUBLIC TYPES
    typedef allocator<TYPE>                             allocator_type;
    typedef TYPE                                        value_type;
 
    typedef typename allocator_type::pointer            pointer;
    typedef typename allocator_type::const_pointer      const_pointer;
    typedef typename allocator_type::void_pointer       void_pointer;
    typedef typename allocator_type::const_void_pointer const_void_pointer;
    typedef typename allocator_type::difference_type    difference_type;
    typedef typename allocator_type::size_type          size_type;
 
#ifdef BSLS_COMPILERFEATURES_SUPPORT_ALIAS_TEMPLATES
    template <class ELEMENT_TYPE>
    using rebind_alloc = allocator<ELEMENT_TYPE>;
 
    template <class ELEMENT_TYPE>
    using rebind_traits = allocator_traits<allocator<ELEMENT_TYPE> >;
#else
    template <class ELEMENT_TYPE>
    struct rebind_alloc : allocator<ELEMENT_TYPE> {
        rebind_alloc()
        : allocator<ELEMENT_TYPE>()
        {
        }
 
        // Convert from anything that can be used to cosntruct the base type.
        // This might be better if SFINAE-ed out using `is_convertible`, but
        // stressing older compilers more seems unwise.
        template <typename ARG>
        rebind_alloc(const ARG& allocatorArg)
        : allocator<ELEMENT_TYPE>(allocatorArg)
        {
        }
    };
 
    template <class ELEMENT_TYPE>
    struct rebind_traits : allocator_traits<allocator<ELEMENT_TYPE> > {
    };
#endif
 
    static pointer allocate(allocator_type& m, size_type n)
    {
        return m.allocate(n);
    }
 
    static pointer allocate(allocator_type&    m,
                            size_type          n,
                            const_void_pointer /* hint */)
    {
        return m.allocate(n);
    }
 
    static void deallocate(allocator_type& m, pointer p, size_type n)
    {
        m.deallocate(p, n);
    }
 
    template <class TYPE2>
    static void construct(allocator_type&  m,
                          TYPE2           *p)
    {
        m.construct(p);
    }
 
#if !BSLS_COMPILERFEATURES_SIMULATE_CPP11_FEATURES // $var-args=14
    template <class TYPE2, class ARG1, class... ARGS>
    static void construct(allocator_type&  m,
                          TYPE2           *p,
                          ARG1&            argument1,
                          ARGS&&...        arguments)
    {
        m.construct(p,
                    argument1,
                    BSLS_COMPILERFEATURES_FORWARD(ARGS, arguments)...);
    }
 
    template <class TYPE2, class ARG1, class... ARGS>
    static void construct(allocator_type&                          m,
                          TYPE2                                   *p,
                          BSLS_COMPILERFEATURES_FORWARD_REF(ARG1)  argument1,
                          ARGS&&...                                arguments)
    {
        m.construct(p,
                    BSLS_COMPILERFEATURES_FORWARD(ARG1, argument1),
                    BSLS_COMPILERFEATURES_FORWARD(ARGS, arguments)...);
    }
#endif
 
    template <class ELEMENT_TYPE>
    static void destroy(allocator_type& m, ELEMENT_TYPE *p)
    {
        m.destroy(p);
    }
 
    BSLS_KEYWORD_CONSTEXPR
    static size_type max_size(const allocator_type& m)
    {
        return m.max_size();
    }
 
    // Allocator propagation traits
    static
    allocator_type select_on_container_copy_construction(const allocator_type&)
    {
        return allocator_type();
    }
 
    typedef false_type is_always_equal;
 
    typedef false_type propagate_on_container_copy_assignment;
 
    typedef false_type propagate_on_container_move_assignment;
 
    typedef false_type propagate_on_container_swap;
};
 
 
// ============================================================================
//                      INLINE FUNCTION DEFINITIONS
// ============================================================================
 
                              // ---------------
                              // class allocator
                              // ---------------
 
// CREATORS
template <class TYPE>
inline
allocator<TYPE>::allocator()
: Base(BloombergLP::bslma::Default::defaultAllocator())
{
}
 
template <class TYPE>
inline
allocator<TYPE>::allocator(BloombergLP::bslma::Allocator *mechanism)
: Base(BloombergLP::bslma::Default::allocator(mechanism))
{
}
 
#ifndef BSLS_COMPILERFEATURES_SUPPORT_DEFAULTED_FUNCTIONS
// In C++11 and later, this copy constructor is defaulted.
template <class TYPE>
inline
allocator<TYPE>::allocator(const allocator& original) BSLS_KEYWORD_NOEXCEPT
: Base(original)
{
}
#endif
 
template <class TYPE>
template <class ANY_TYPE>
inline
allocator<TYPE>::allocator(const allocator<ANY_TYPE>& original)
                                                          BSLS_KEYWORD_NOEXCEPT
: Base(original)
{
}
 
// MANIPULATORS
template <class TYPE>
inline
allocator<TYPE>&
allocator<TYPE>::operator=(const allocator& rhs)
{
    BSLS_REVIEW_OPT(rhs == *this &&
                    "'bsl::allocator' objects cannot be assigned");
 
    if (this != &rhs) {
        // As the base class does not support assignment, the only way to
        // change the mechanism is to destroy and re-create this object
        this->~allocator();
        return *::new(this) allocator(rhs);
    }
 
    return *this;
}
 
template <class TYPE>
inline
typename allocator<TYPE>::pointer
allocator<TYPE>::allocate(size_type n, const void * /* hint */)
{
    return Base::allocate(n);
}
 
template <class TYPE>
inline
void allocator<TYPE>::deallocate(TYPE *p, std::size_t n)
{
    Base::deallocate(p, n);
}
 
template <class TYPE>
template <class ELEMENT_TYPE>
inline
void allocator<TYPE>::construct(ELEMENT_TYPE *address)
{
    BloombergLP::bslma::ConstructionUtil::construct(address, *this);
}
 
#if !BSLS_COMPILERFEATURES_SIMULATE_CPP11_FEATURES
template <class TYPE>
template <class ELEMENT_TYPE, class ARG1, class... ARGS>
inline
void allocator<TYPE>::construct(ELEMENT_TYPE *address,
                                ARG1&         argument1,
                                ARGS&&...     arguments)
{
    BloombergLP::bslma::ConstructionUtil::construct(
        address,
        *this,
        argument1,
        BSLS_COMPILERFEATURES_FORWARD(ARGS, arguments)...);
}
 
template <class TYPE>
template <class ELEMENT_TYPE, class ARG1, class... ARGS>
inline
void allocator<TYPE>::construct(
                            ELEMENT_TYPE                            *address,
                            BSLS_COMPILERFEATURES_FORWARD_REF(ARG1)  argument1,
                            ARGS&&...                                arguments)
{
    BloombergLP::bslma::ConstructionUtil::construct(
        address,
        *this,
        BSLS_COMPILERFEATURES_FORWARD(ARG1, argument1),
        BSLS_COMPILERFEATURES_FORWARD(ARGS, arguments)...);
}
#endif
 
template <class TYPE>
template <class ELEMENT_TYPE>
inline
void allocator<TYPE>::destroy(ELEMENT_TYPE *address)
{
    BloombergLP::bslma::DestructionUtil::destroy(address);
}
 
 
// ACCESSORS
template <class TYPE>
inline
typename allocator<TYPE>::pointer
allocator<TYPE>::address(reference x) const
{
    return BloombergLP::bsls::Util::addressOf(x);
}
 
template <class TYPE>
inline
typename allocator<TYPE>::const_pointer
allocator<TYPE>::address(const_reference x) const
{
    return BloombergLP::bsls::Util::addressOf(x);
}
 
template <class TYPE>
BSLS_KEYWORD_CONSTEXPR inline
typename allocator<TYPE>::size_type allocator<TYPE>::max_size() const
{
    // Return the largest value, `v`, such that `v * sizeof(T)` fits in a
    // `size_type`.  Note that `~size_type(0)` is the maximum value for
    // `size_type`, the largest possible sequence of bytes to store `TYPE`
    // objects in.
 
    return ~size_type(0) / sizeof(TYPE);
}
 
template <class TYPE>
inline
BloombergLP::bslma::Allocator *allocator<TYPE>::mechanism() const
{
    return static_cast<BloombergLP::bslma::Allocator *>(this->resource());
}
 
template <class TYPE>
inline
allocator<TYPE> allocator<TYPE>::select_on_container_copy_construction() const
{
    return allocator();
}
 
                           // ---------------------
                           // class allocator<void>
                           // ---------------------
 
// CREATORS
inline
allocator<void>::allocator()
{
}
 
inline
allocator<void>::allocator(BloombergLP::bslma::Allocator *mechanism)
: Base(mechanism)
{
}
 
#ifndef BSLS_COMPILERFEATURES_SUPPORT_DEFAULTED_FUNCTIONS
// In C++11 and later, this copy constructor is defaulted.
inline
allocator<void>::allocator(const allocator& original) BSLS_KEYWORD_NOEXCEPT
: Base(original)
{
}
#endif
 
template <class ANY_TYPE>
inline
allocator<void>::allocator(const allocator<ANY_TYPE>& original)
                                                          BSLS_KEYWORD_NOEXCEPT
: Base(original)
{
}
 
inline
allocator<void> allocator<void>::select_on_container_copy_construction() const
{
    return allocator<void>();
}
 
}  // close namespace bsl
 
#if BSLS_PLATFORM_CMP_MSVC
// As of MSVC 19.30.30709 (2022), the following workaround is still needed.
// When a fix is released, the above `#if` condition should be updated to apply
// only to versions before the fixed one.
 
// These equality and inequality operators should be unnecessary because they
// automatically fall back on @ref polymoprhic_allocator .  However an odd bug in
// MSVC causes it, in the presence of `<bslma_convertibleallocator.h>` to
// include the `bslma::ConvertibleAllocator` "hidden friend" equality operators
// in the the lookup set even if neither argument is `ConvertibleAllocator`,
// thus making `operator==` ambiguous when comparing `bsl::allocator` to
// `bslma::Allocator *`.  Strangely `using namespace bslma` suppresses this
// bug, but it is not practical to require clients to do that.  The operators
// below quash this ambiguity.  Although harmless for other platforms, they are
// compiled only for affected versions of MSVC and are considered an
// implementation detail (not part of the interface for `bsl::allocator`).
 
template <class TYPE>
inline
bool operator==(const bsl::allocator<TYPE>&    a,
                BloombergLP::bslma::Allocator *b)
{
    return a.resource() == b || a.resource()->is_equal(*b);
}
 
template <class TYPE>
inline
bool operator==(BloombergLP::bslma::Allocator *a,
                const bsl::allocator<TYPE>&    b)
{
    return a == b.resource() || a->is_equal(*b.resource());
}
 
template <class TYPE>
inline
bool operator!=(const bsl::allocator<TYPE>&    a,
                BloombergLP::bslma::Allocator *b)
{
    return ! (a.resource() == b || a.resource()->is_equal(*b));
}
 
template <class TYPE>
inline
bool operator!=(BloombergLP::bslma::Allocator *a,
                const bsl::allocator<TYPE>&    b)
{
    return ! (a == b.resource() || a->is_equal(*b.resource()));
}
#endif
 
// ============================================================================
//                                TYPE TRAITS
// ============================================================================
 
 
namespace bslma {
 
/// An allocator is not *itself* an allocator-aware type, even though it is
/// convertible from `bsl::Allocator *`.
template <class TYPE>
struct UsesBslmaAllocator< ::bsl::allocator<TYPE> > : bsl::false_type {
};
 
/// A `bsl::allocator` inherits its `allocate` method from a base class,
/// which causes `IsStdAllocator` to fail the auto-detected it.
template <class TYPE>
struct IsStdAllocator<bsl::allocator<TYPE> > : bsl::true_type {
};
 
/// `bsl::allocator<void>` is not an allocator type, even though all other
/// instantiations are allocator types.
template <>
struct IsStdAllocator<bsl::allocator<void> > : bsl::false_type {
};
 
}  // close namespace bslma
 
 
#endif // End C++11 code
 
#endif
 
// ----------------------------------------------------------------------------
// Copyright 2013 Bloomberg Finance L.P.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// ----------------------------- END-OF-FILE ----------------------------------
 
/** @} */
/** @} */
/** @} */