std::scoped_allocator_adaptor<OuterAlloc,InnerAlloc...>::construct

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std::scoped_allocator_adaptor
Defined in header <scoped_allocator>
template < class T, class... Args >
void construct( T* p, Args&&... args ) ;
(1)
template < class T1, class T2, class... Args1, class... Args2 >

void construct( std::pair <T1, T2> * p, std::piecewise_construct_t,

std::tuple <Args1...> x, std::tuple <Args2...> y ) ;
(2) (until C++20)
template < class T1, class T2 >
void construct( std::pair <T1, T2> * p ) ;
(3) (until C++20)
template < class T1, class T2, class U, class V >
void construct( std::pair <T1, T2> * p, U&& x, V&& y ) ;
(4) (until C++20)
template < class T1, class T2, class U, class V >
void construct( std::pair <T1, T2> * p, const std::pair <U, V> & xy ) ;
(5) (until C++20)
template < class T1, class T2, class U, class V >
void construct( std::pair <T1, T2> * p, std::pair <U, V> && xy ) ;
(6) (until C++20)
Helper function templates
template < class T, class... Args >
std::tuple < /* see below */ > /*concat-args*/ ( std::tuple <Args...> && tup ) ;
(7) (exposition only*)
(until C++20)

Constructs an object in allocated, but not initialized storage pointed to by p using the outer allocator and the provided constructor arguments. If the object is of a type that itself uses allocators , or if it is std::pair (until C++20)

1) Constructs an object of type T by uses-allocator construction at the uninitialized memory location indicated by p using the outermost allocator.

Given std::uses_allocator <T, inner_allocator_type> :: value as uses_inner

This overload participates in overload resolution only if T is not a specialization of std::pair.

(until C++20)

Equivalent to std::apply
(
[p, this] ( auto &&... newargs )
{
outermost-construct
(p, std::forward <decltype(newargs) > (newargs)...) ;
},
std::uses_allocator_construction_args
(inner_allocator( ), std::forward <Args> (args)...)
);

(since C++20)
2-6) Constructs a std::pair object by uses-allocator construction at the uninitialized memory location indicated by p
2) Let xprime be concat-args  <T1> (std:: move (x) ) , yprime be concat-args  <T2> (std:: move (y) ) , calls outermost-construct  (p, std::piecewise_construct, std:: move (xprime), std:: move (yprime) )
3) Equivalent to construct(p, std::piecewise_construct, std::tuple <> ( ), std::tuple <> ( ) ) ;
4-6) Equivalent to construct(p, std::piecewise_construct,
std::forward_as_tuple (xarg), std::forward_as_tuple (yarg) ) ; , where xarg and yarg are defined as follows:
Overload  xarg yarg
(4) std::forward <U> (x) std::forward <V> (y)
(5) xy.first xy.second
(6) std::forward <U> (xy.first ) std::forward <V> (xy.second )
7) Merges the arguments contained in tup and additional arguments required by uses-allocator construction of an object of type T
Given std::uses_allocator <T, inner_allocator_type> :: value as uses_inner:

Parameters

p - pointer to allocated, but not initialized storage
args - the constructor arguments to pass to the constructor of T
x - the constructor arguments to pass to the constructor of T1
y - the constructor arguments to pass to the constructor of T2
xy - the pair whose two members are the constructor arguments for T1 and T2
tup - the arguments to be merged

Notes

This function is called (through std::allocator_traits) by any allocator-aware object, such as std::vector, that was given a std::scoped_allocator_adaptor as the allocator to use. Since inner_allocator_type is itself a specialization of std::scoped_allocator_adaptor

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR Applied to Behavior as published Correct behavior
LWG 2203 C++11 inner allocators were obtained by value-initializing
an inner_allocator_type object 		obtained by calling inner_allocator()
LWG 2511
(P0475R1) 		C++11 concat-args might copy elements of std::tuples eliminated all element copy operations
LWG 2586 C++11 only constructions from
inner_allocator_type rvalues were checked 		checks constructions from non-const
inner_allocator_type lvalues instead
LWG 2975 C++11 overload (1) was not constrained constrained to refuse std::pair

See also

[static]
 constructs an object in the allocated storage
(function template)
(until C++20)
 constructs an object in allocated storage
(public member function of std::allocator<T>)
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