tmp/tmpvgrua9lb/{from.md → to.md}
RENAMED
|
@@ -1,19 +1,23 @@
|
|
| 1 |
### Class template `polymorphic_allocator` <a id="mem.poly.allocator.class">[[mem.poly.allocator.class]]</a>
|
| 2 |
|
|
|
|
|
|
|
| 3 |
A specialization of class template `pmr::polymorphic_allocator` meets
|
| 4 |
-
the *Cpp17Allocator* requirements
|
| 5 |
-
|
|
|
|
| 6 |
specialization of `pmr::polymorphic_allocator` can exhibit entirely
|
| 7 |
different allocation behavior. This runtime polymorphism allows objects
|
| 8 |
that use `polymorphic_allocator` to behave as if they used different
|
| 9 |
allocator types at run time even though they use the same static
|
| 10 |
allocator type.
|
| 11 |
|
| 12 |
-
|
| 13 |
the allocator completeness requirements
|
| 14 |
-
[[allocator.requirements.completeness]]
|
|
|
|
| 15 |
|
| 16 |
``` cpp
|
| 17 |
namespace std::pmr {
|
| 18 |
template<class Tp = byte> class polymorphic_allocator {
|
| 19 |
memory_resource* memory_rsrc; // exposition only
|
|
@@ -44,16 +48,19 @@ namespace std::pmr {
|
|
| 44 |
template<class T> void delete_object(T* p);
|
| 45 |
|
| 46 |
template<class T, class... Args>
|
| 47 |
void construct(T* p, Args&&... args);
|
| 48 |
|
| 49 |
-
template<class T>
|
| 50 |
-
void destroy(T* p);
|
| 51 |
-
|
| 52 |
polymorphic_allocator select_on_container_copy_construction() const;
|
| 53 |
|
| 54 |
memory_resource* resource() const;
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| 55 |
};
|
| 56 |
}
|
| 57 |
```
|
| 58 |
|
| 59 |
#### Constructors <a id="mem.poly.allocator.ctor">[[mem.poly.allocator.ctor]]</a>
|
|
@@ -151,11 +158,11 @@ template<class T>
|
|
| 151 |
```
|
| 152 |
|
| 153 |
*Effects:* Equivalent to `deallocate_bytes(p, n*sizeof(T), alignof(T))`.
|
| 154 |
|
| 155 |
``` cpp
|
| 156 |
-
template<class T, class
|
| 157 |
[[nodiscard]] T* new_object(CtorArgs&&... ctor_args);
|
| 158 |
```
|
| 159 |
|
| 160 |
*Effects:* Allocates and constructs an object of type `T`, as follows.
|
| 161 |
Equivalent to:
|
|
@@ -180,11 +187,11 @@ template<class T>
|
|
| 180 |
```
|
| 181 |
|
| 182 |
*Effects:* Equivalent to:
|
| 183 |
|
| 184 |
``` cpp
|
| 185 |
-
destroy(p);
|
| 186 |
deallocate_object(p);
|
| 187 |
```
|
| 188 |
|
| 189 |
``` cpp
|
| 190 |
template<class T, class... Args>
|
|
@@ -199,17 +206,10 @@ template<class T, class... Args>
|
|
| 199 |
represented by `p` by uses-allocator construction with allocator `*this`
|
| 200 |
and constructor arguments `std::forward<Args>(args)...`.
|
| 201 |
|
| 202 |
*Throws:* Nothing unless the constructor for `T` throws.
|
| 203 |
|
| 204 |
-
``` cpp
|
| 205 |
-
template<class T>
|
| 206 |
-
void destroy(T* p);
|
| 207 |
-
```
|
| 208 |
-
|
| 209 |
-
*Effects:* As if by `p->T̃()`.
|
| 210 |
-
|
| 211 |
``` cpp
|
| 212 |
polymorphic_allocator select_on_container_copy_construction() const;
|
| 213 |
```
|
| 214 |
|
| 215 |
*Returns:* `polymorphic_allocator()`.
|
|
|
|
| 1 |
### Class template `polymorphic_allocator` <a id="mem.poly.allocator.class">[[mem.poly.allocator.class]]</a>
|
| 2 |
|
| 3 |
+
#### General <a id="mem.poly.allocator.class.general">[[mem.poly.allocator.class.general]]</a>
|
| 4 |
+
|
| 5 |
A specialization of class template `pmr::polymorphic_allocator` meets
|
| 6 |
+
the *Cpp17Allocator* requirements [[allocator.requirements.general]] if
|
| 7 |
+
its template argument is a cv-unqualified object type. Constructed with
|
| 8 |
+
different memory resources, different instances of the same
|
| 9 |
specialization of `pmr::polymorphic_allocator` can exhibit entirely
|
| 10 |
different allocation behavior. This runtime polymorphism allows objects
|
| 11 |
that use `polymorphic_allocator` to behave as if they used different
|
| 12 |
allocator types at run time even though they use the same static
|
| 13 |
allocator type.
|
| 14 |
|
| 15 |
+
A specialization of class template `pmr::polymorphic_allocator` meets
|
| 16 |
the allocator completeness requirements
|
| 17 |
+
[[allocator.requirements.completeness]] if its template argument is a
|
| 18 |
+
cv-unqualified object type.
|
| 19 |
|
| 20 |
``` cpp
|
| 21 |
namespace std::pmr {
|
| 22 |
template<class Tp = byte> class polymorphic_allocator {
|
| 23 |
memory_resource* memory_rsrc; // exposition only
|
|
|
|
| 48 |
template<class T> void delete_object(T* p);
|
| 49 |
|
| 50 |
template<class T, class... Args>
|
| 51 |
void construct(T* p, Args&&... args);
|
| 52 |
|
|
|
|
|
|
|
|
|
|
| 53 |
polymorphic_allocator select_on_container_copy_construction() const;
|
| 54 |
|
| 55 |
memory_resource* resource() const;
|
| 56 |
+
|
| 57 |
+
// friends
|
| 58 |
+
friend bool operator==(const polymorphic_allocator& a,
|
| 59 |
+
const polymorphic_allocator& b) noexcept {
|
| 60 |
+
return *a.resource() == *b.resource();
|
| 61 |
+
}
|
| 62 |
};
|
| 63 |
}
|
| 64 |
```
|
| 65 |
|
| 66 |
#### Constructors <a id="mem.poly.allocator.ctor">[[mem.poly.allocator.ctor]]</a>
|
|
|
|
| 158 |
```
|
| 159 |
|
| 160 |
*Effects:* Equivalent to `deallocate_bytes(p, n*sizeof(T), alignof(T))`.
|
| 161 |
|
| 162 |
``` cpp
|
| 163 |
+
template<class T, class... CtorArgs>
|
| 164 |
[[nodiscard]] T* new_object(CtorArgs&&... ctor_args);
|
| 165 |
```
|
| 166 |
|
| 167 |
*Effects:* Allocates and constructs an object of type `T`, as follows.
|
| 168 |
Equivalent to:
|
|
|
|
| 187 |
```
|
| 188 |
|
| 189 |
*Effects:* Equivalent to:
|
| 190 |
|
| 191 |
``` cpp
|
| 192 |
+
allocator_traits<polymorphic_allocator>::destroy(*this, p);
|
| 193 |
deallocate_object(p);
|
| 194 |
```
|
| 195 |
|
| 196 |
``` cpp
|
| 197 |
template<class T, class... Args>
|
|
|
|
| 206 |
represented by `p` by uses-allocator construction with allocator `*this`
|
| 207 |
and constructor arguments `std::forward<Args>(args)...`.
|
| 208 |
|
| 209 |
*Throws:* Nothing unless the constructor for `T` throws.
|
| 210 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| 211 |
``` cpp
|
| 212 |
polymorphic_allocator select_on_container_copy_construction() const;
|
| 213 |
```
|
| 214 |
|
| 215 |
*Returns:* `polymorphic_allocator()`.
|