23 General utilities library [utilities]

23.12 Memory resources [mem.res]

23.12.3 Class template polymorphic_­allocator [mem.poly.allocator.class]

23.12.3.2 polymorphic_­allocator member functions [mem.poly.allocator.mem]

Tp* allocate(size_t n);
Returns: Equivalent to
return static_cast<Tp*>(memory_rsrc->allocate(n * sizeof(Tp), alignof(Tp)));
void deallocate(Tp* p, size_t n);
Requires: p was allocated from a memory resource x, equal to *memory_­rsrc, using x.allocate(n * sizeof(Tp), alignof(Tp)).
Effects: Equivalent to memory_­rsrc->deallocate(p, n * sizeof(Tp), alignof(Tp)).
Throws: Nothing.
template <class T, class... Args> void construct(T* p, Args&&... args);
Requires: Uses-allocator construction of T with allocator resource() (see [allocator.uses.construction]) and constructor arguments std​::​forward<Args>(args)... is well-formed.
[Note
:
Uses-allocator construction is always well-formed for types that do not use allocators.
end note
]
Effects: Construct a T object in the storage whose address is represented by p by uses-allocator construction with allocator resource() and constructor arguments std​::​forward<Args>(args)....
Throws: Nothing unless the constructor for T throws.
template <class T1, class T2, class... Args1, class... Args2> void construct(pair<T1,T2>* p, piecewise_construct_t, tuple<Args1...> x, tuple<Args2...> y);
[Note
:
This member function and the construct member functions that follow are overloads for piecewise construction of pairs ([pairs.pair]).
end note
]
Effects: Let xprime be a tuple constructed from x according to the appropriate rule from the following list.
[Note
:
The following description can be summarized as constructing a pair<T1, T2> object in the storage whose address is represented by p, as if by separate uses-allocator construction with allocator resource() ([allocator.uses.construction]) of p->first using the elements of x and p->second using the elements of y.
end note
]
  • If uses_­allocator_­v<T1,memory_­resource*> is false
    and is_­constructible_­v<T1,Args1...> is true,
    then xprime is x.
  • Otherwise, if uses_­allocator_­v<T1,memory_­resource*> is true
    and is_­constructible_­v<T1,allocator_­arg_­t,memory_­resource*,Args1...> is true,
    then xprime is tuple_­cat(make_­tuple(allocator_­arg, resource()), std​::​move(x)).
  • Otherwise, if uses_­allocator_­v<T1,memory_­resource*> is true
    and is_­constructible_­v<T1,Args1...,memory_­resource*> is true,
    then xprime is tuple_­cat(std​::​move(x), make_­tuple(resource())).
  • Otherwise the program is ill formed.
Let yprime be a tuple constructed from y according to the appropriate rule from the following list:
  • If uses_­allocator_­v<T2,memory_­resource*> is false
    and is_­constructible_­v<T2,Args2...> is true,
    then yprime is y.
  • Otherwise, if uses_­allocator_­v<T2,memory_­resource*> is true
    and is_­constructible_­v<T2,allocator_­arg_­t,memory_­resource*,Args2...> is true,
    then yprime is tuple_­cat(make_­tuple(allocator_­arg, resource()), std​::​move(y)).
  • Otherwise, if uses_­allocator_­v<T2,memory_­resource*> is true
    and is_­constructible_­v<T2,Args2...,memory_­resource*> is true,
    then yprime is tuple_­cat(std​::​move(y), make_­tuple(resource())).
  • Otherwise the program is ill formed.
Then, using piecewise_­construct, xprime, and yprime as the constructor arguments, this function constructs a pair<T1, T2> object in the storage whose address is represented by p.
template <class T1, class T2> void construct(pair<T1,T2>* p);
Effects: Equivalent to:
construct(p, piecewise_construct, tuple<>(), tuple<>());
template <class T1, class T2, class U, class V> void construct(pair<T1,T2>* p, U&& x, V&& y);
Effects: Equivalent to:
construct(p, piecewise_construct,
          forward_as_tuple(std::forward<U>(x)),
          forward_as_tuple(std::forward<V>(y)));
template <class T1, class T2, class U, class V> void construct(pair<T1,T2>* p, const pair<U, V>& pr);
Effects: Equivalent to:
construct(p, piecewise_construct,
          forward_as_tuple(pr.first),
          forward_as_tuple(pr.second));
template <class T1, class T2, class U, class V> void construct(pair<T1,T2>* p, pair<U, V>&& pr);
Effects: Equivalent to:
construct(p, piecewise_construct,
          forward_as_tuple(std::forward<U>(pr.first)),
          forward_as_tuple(std::forward<V>(pr.second)));
template <class T> void destroy(T* p);
Effects: As if by p->~T().
polymorphic_allocator select_on_container_copy_construction() const;
Returns: polymorphic_­allocator().
[Note
:
The memory resource is not propagated.
end note
]
memory_resource* resource() const;
Returns: memory_­rsrc.