Add deprecated shared_array documentation

This commit is contained in:
Glen Fernandes
2017-06-15 08:16:50 -04:00
parent 7f760526ab
commit 61de342adc
3 changed files with 258 additions and 9 deletions

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@ -133,16 +133,16 @@ of the object is initialized to the corresponding element from `v`.
shall be interpreted to mean that each array element of the object is
value-initialized.
* When a (sub)object of non-array type `U` is specified to be initialized to
a value `v`, or constructed from `args$$...$$`, `make_shared` shall perform
a value `v`, or constructed from `args\...`, `make_shared` shall perform
this initialization via the expression `::new(p) U(expr)` (where
`_expr_` is `v` or `std::forward<Args>(args)$$...$$)` respectively) and `p`
`_expr_` is `v` or `std::forward<Args>(args)\...)` respectively) and `p`
has type `void*` and points to storage suitable to hold an object of type
`U`.
* When a (sub)object of non-array type `U` is specified to be initialized to
a value `v`, or constructed from `args$$...$$`, `allocate_shared` shall
a value `v`, or constructed from `args\...`, `allocate_shared` shall
perform this initialization via the expression
`std::allocator_traits<A2>::construct(a2, p, expr)` (where
`_expr_` is `v` or `std::forward<Args>(args)$$...$$)` respectively), `p`
`_expr_` is `v` or `std::forward<Args>(args)\...)` respectively), `p`
points to storage suitable to hold an object of type `U`, and `a2` of
type `A2` is a rebound copy `a` such that its `value_type` is `U`.
* When a (sub)object of non-array type `U` is specified to be
@ -183,7 +183,7 @@ template<class T, class A, class... Args>
Remarks::: These overloads shall only participate in overload resolution when
`T` is not an array type.
Returns::: A `shared_ptr` to an object of type `T`, constructed from
`args$$...$$`.
`args\...`.
Examples:::
* `auto p = make_shared<int>();`
* `auto p = make_shared<std::vector<int> >(16, 1);`

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@ -21,16 +21,16 @@ create `std::unique_ptr` objects.
## Rationale
The C$$++$$11 standard introduced `std::unique_ptr` but did not provide any
The {cpp}11 standard introduced `std::unique_ptr` but did not provide any
`make_unique` utility like `std::make_shared` that provided the same
exception safety and facility to avoid writing `new` expressions. Before it
was implemented by some standard library vendors (and prior to the C$$++$$14
was implemented by some standard library vendors (and prior to the {cpp}14
standard introducing `std::make_unique`), this library provided it due to
requests from users.
This library also provides additional overloads of `make_unique` for
default-initialization, when users do not need or want to incur the expense
of value-initialization. The C$$++$$ standard does not yet provide this
of value-initialization. The {cpp} standard does not yet provide this
feature with `std::make_unique`.
## Synopsis
@ -71,7 +71,7 @@ template<class T, class... Args>
::
Remarks::: These overloads shall only participate in overload resolution when
`T` is not an array type.
Returns::: `std::unique_ptr<T>(new T(std::forward<Args>(args)$$...$$)`.
Returns::: `std::unique_ptr<T>(new T(std::forward<Args>(args)\...)`.
Example::: `auto p = make_unique<int>();`
```

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@ -14,3 +14,252 @@ http://www.boost.org/LICENSE_1_0.txt
:toc-title:
:idprefix: shared_array_
NOTE: This facility is deprecated because a `shared_ptr` to `T[]` or `T[N]`
is now available, and is superior in every regard.
## Description
The `shared_array` class template stores a pointer to a dynamically allocated
array. (Dynamically allocated array are allocated with the C++ `new[]`
expression.) The object pointed to is guaranteed to be deleted when the last
`shared_array` pointing to it is destroyed or reset.
Every `shared_array` meets the _CopyConstructible_ and _Assignable_
requirements of the {cpp} Standard Library, and so can be used in standard
library containers. Comparison operators are supplied so that shared_array
works with the standard library's associative containers.
Normally, a `shared_array` cannot correctly hold a pointer to an object that
has been allocated with the non-array form of `new`. See `shared_ptr` for that
usage.
Because the implementation uses reference counting, cycles of `shared_array`
instances will not be reclaimed. For example, if `main` holds a shared_array
to `A`, which directly or indirectly holds a shared_array back to `A`, the use
count of `A` will be 2. Destruction of the original `shared_array` will leave
`A` dangling with a use count of 1.
A `shared_ptr` to a `std::vector` is an alternative to a `shared_array` that
is a bit heavier duty but far more flexible.
The class template is parameterized on `T`, the type of the object pointed to.
`shared_array` and most of its member functions place no requirements on `T`;
it is allowed to be an incomplete type, or `void`. Member functions that do
place additional requirements (constructors, reset) are explicitly documented
below.
## Synopsis
```
namespace boost {
template<class T> class shared_array {
public:
typedef T element_type;
explicit shared_array(T* p = 0);
template<class D> shared_array(T* p, D d);
shared_array(const shared_array& v) noexcept;
~shared_array() noexcept;
shared_array& operator=(const shared_array& v) noexcept;
void reset(T* p = 0);
template<class D> void reset(T* p, D d);
T& operator[](std::ptrdiff_t n) const noexcept;
T* get() const noexcept;
bool unique() const noexcept;
long use_count() const noexcept;
explicit operator bool() const noexcept;
void swap(shared_array<T>& v) noexcept;
};
template<class T> bool
operator==(const shared_array<T>& a, const shared_array<T>& b) noexcept;
template<class T> bool
operator!=(const shared_array<T>& a, const shared_array<T>& b) noexcept;
template<class T> bool
operator<(const shared_array<T>& a, const shared_array<T>& b) noexcept;
template<class T>
void swap(shared_array<T>& a, shared_array<T>& b) noexcept;
}
```
## Members
### element_type
```
typedef T element_type;
```
Type:: Provides the type of the stored pointer.
### Constructors
```
explicit shared_array(T* p = 0);
```
::
Effects::: Constructs a `shared_array`, storing a copy of `p`, which must be a
pointer to an array that was allocated via a C++ `new[]` expression or be 0.
Afterwards, the use count is 1 (even if `p == 0`; see `~shared_array`).
Requires::: `T` is a complete type.
Throws::: `std::bad_alloc`. If an exception is thrown, `delete[] p` is called.
```
template<class D> shared_array(T* p, D d);
```
::
Effects::: Constructs a `shared_array`, storing a copy of `p` and of `d`.
Afterwards, the use count is 1. When the the time comes to delete the array
pointed to by `p`, the object `d` is used in the statement `d(p)`.
Requires:::
* `T` is a complete type.
* The copy constructor and destructor of `D` must not throw.
* Invoking the object `d` with parameter `p` must not throw.
Throws::: `std::bad_alloc`. If an exception is thrown, `d(p)` is called.
```
shared_array(const shared_array& v) noexcept;
```
::
Effects::: Constructs a `shared_array`, as if by storing a copy of the pointer
stored in `v`. Afterwards, the use count for all copies is 1 more than the
initial use count.
Requires::: `T` is a complete type.
### Destructor
```
~shared_array() noexcept;
```
::
Effects::: Decrements the use count. Then, if the use count is 0, deletes the
array pointed to by the stored pointer. Note that `delete[]` on a pointer with
a value of 0 is harmless.
### Assignment
```
shared_array& operator=(const shared_array& v) noexcept;
```
::
Effects::: Constructs a new `shared_array` as described above, then replaces
this `shared_array` with the new one, destroying the replaced object.
Requires::: `T` is a complete type.
Returns::: `*this`.
### reset
```
void reset(T* p = 0);
```
::
Effects::: Constructs a new `shared_array` as described above, then replaces
this `shared_array` with the new one, destroying the replaced object.
Requires::: `T` is a complete type.
Throws::: `std::bad_alloc`. If an exception is thrown, `delete[] p` is called.
```
template<class D> void reset(T* p, D d);
```
::
Effects::: Constructs a new `shared_array` as described above, then replaces
this `shared_array` with the new one, destroying the replaced object.
Requires:::
* `T` is a complete type.
* The copy constructor of `D` must not throw.
Throws::: `std::bad_alloc`. If an exception is thrown, `d(p)` is called.
### Indexing
```
T& operator[](std::ptrdiff_t n) const noexcept;
```
Returns::: A reference to element `n` of the array pointed to by the stored
pointer. Behavior is undefined and almost certainly undesirable if the stored
pointer is 0, or if `n` is less than 0 or is greater than or equal to the
number of elements in the array.
Requires::: `T` is a complete type.
### get
```
T* get() const noexcept;
```
::
Returns::: The stored pointer.
### unique
```
bool unique() const noexcept;
```
::
Returns::: `true` if no other `shared_array` is sharing ownership of the
stored pointer, `false` otherwise.
### use_count
```
long use_count() const noexcept;
```
::
Returns::: The number of `shared_array` objects sharing ownership of the
stored pointer.
### Conversions
```
explicit operator bool() const noexcept;
```
::
Returns::: `get() != 0`.
Requires::: `T` is a complete type.
### swap
```
void swap(shared_array<T>& b) noexcept;
```
::
Effects::: Exchanges the contents of the two smart pointers.
## Free Functions
### Comparison
```
template<class T> bool
operator==(const shared_array<T>& a, const shared_array<T>& b) noexcept;
template<class T> bool
operator!=(const shared_array<T>& a, const shared_array<T>& b) noexcept;
template<class T> bool
operator<(const shared_array<T>& a, const shared_array<T>& b) noexcept;
```
::
Returns::: The result of comparing the stored pointers of the two smart
pointers.
NOTE: The `operator<` overload is provided to define an ordering so that
`shared_array` objects can be used in associative containers such as
`std::map`. The implementation uses `std::less<T*>` to perform the comparison.
This ensures that the comparison is handled correctly, since the standard
mandates that relational operations on pointers are unspecified (5.9
[expr.rel] paragraph 2) but `std::less` on pointers is well-defined (20.3.3
[lib.comparisons] paragraph 8).
### swap
```
template<class T>
void swap(shared_array<T>& a, shared_array<T>& b) noexcept;
```
::
Returns::: `a.swap(b)`
Requires::: `T` is a complete type.