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std::make_shared, std::make_shared_for_overwrite cppreference.com
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std::make_shared, std::make_shared_for_overwrite

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no section name
( C++20*)
( C++20*)
( C++20*)
 
std::shared_ptr
 
<tbody> </tbody>
template< class T, class... Args > shared_ptr<T> make_shared( Args&&... args );
 (1) ( C++11)
(T )
template< class T > shared_ptr<T> make_shared( std::size_t N );
 (2) ( C++20)
(T U[])
template< class T > shared_ptr<T> make_shared();
 (3) ( C++20)
(T U[N])
template< class T > shared_ptr<T> make_shared( std::size_t N, const std::remove_extent_t<T>& u );
 (4) ( C++20)
(T U[])
template< class T > shared_ptr<T> make_shared( const std::remove_extent_t<T>& u );
 (5) ( C++20)
(T U[N])
template< class T > shared_ptr<T> make_shared_for_overwrite();
 (6) ( C++20)
(T U[])
template< class T > shared_ptr<T> make_shared_for_overwrite( std::size_t N );
 (7) ( C++20)
(T U[])
1) T std::shared_ptr, args T. ::new (pv) T(std::forward<Args>(args)...), pv void* , T. , sizeof(T), , T. std::shared_ptr, , shared_from_this T.

, T

( C++20)
2,3) , (1), , , , , , std::remove_all_extents_t<T> , new ::new(pv) std::remove_all_extents_t<T>(). (2) N . , , , .
4,5) , (2,3), u. U , new, (1); , (, ), , u new, (1). (4) N . , , , .
6) , (1), T , (3), T U[N], , .
7) , (2), , .

( , T ) ( C++20) p->~X(), p , X .

args , T.
N
u

std::shared_ptr T.

std::bad_alloc , T. , . , . ( C++20)

std::shared_ptr<T>(new T(args...)). :

  • std::shared_ptr<T>(new T(args...)) ( T ), std::make_shared<T> ( , ; )
  • - std::weak_ptr , std::make_shared , , T, , , , sizeof(T) .
  • std::shared_ptr<T>(new T(args...)) T, , , std::make_shared .
  • std::shared_ptr, std::make_shared .
  • std::make_shared ::new, , - operator new, std::shared_ptr<T>(new T(args...)).
( C++20)
  • , f(std::shared_ptr<int>(new int(42)), g()) , g new int(42) , f(std::make_shared<int>(42), g()) , .
 ( C++17)

shared_from_this ptr U* , , U ( C++17) , std::enable_shared_from_this, , : 

if (ptr != nullptr && ptr->weak_this.expired())
    ptr->weak_this = std::shared_ptr<std::remove_cv_t<U>>(
                         *this, const_cast<std::remove_cv_t<U>*>(ptr));

weak_this mutable std::weak_ptr std::enable_shared_from_this. weak_this . , shared_from_this() std::shared_ptr, .

ptr->weak_this.expired() , weak_this , . C++17.

__cpp_lib_shared_ptr_arrays 201707L (C++20) std::make_shared; (2-5)
__cpp_lib_smart_ptr_for_overwrite 202002L (C++20) (std::allocate_shared_for_overwrite, std::make_shared_for_overwrite, std::make_unique_for_overwrite); (6,7) 

#include <memory>
#include <vector>
#include <iostream>
#include <type_traits>

struct C
{
    //   ( C++20)
    C(int i) : i(i) {}
    C(int i, float f) : i(i), f(f) {}
    int i;
    float f{};
};

int main()
{
    //  `auto`   `sp1`
    auto sp1 = std::make_shared<C>(1); //  (1)
    static_assert(std::is_same_v<decltype(sp1), std::shared_ptr<C>>);
    std::cout << "sp1->{ i:" << sp1->i << ", f:" << sp1->f << " }\n";

    //     `sp2`
    std::shared_ptr<C> sp2 = std::make_shared<C>(2, 3.0f); //  (1)
    static_assert(std::is_same_v<decltype(sp2), std::shared_ptr<C>>);
    static_assert(std::is_same_v<decltype(sp1), decltype(sp2)>);
    std::cout << "sp2->{ i:" << sp2->i << ", f:" << sp2->f << " }\n";

    // shared_ptr    float[64];  (2):
    std::shared_ptr<float[]> sp3 = std::make_shared<float[]>(64);

    // shared_ptr    long[5][3][4];  (2):
    std::shared_ptr<long[][3][4]> sp4 = std::make_shared<long[][3][4]>(5);

    // shared_ptr    short[128];  (3):
    std::shared_ptr<short[128]> sp5 = std::make_shared<short[128]>();

    // shared_ptr    int[7][6][5];  (3):
    std::shared_ptr<int[7][6][5]> sp6 = std::make_shared<int[7][6][5]>();

    // shared_ptr  double[256],     2.0;  (4):
    std::shared_ptr<double[]> sp7 = std::make_shared<double[]>(256, 2.0);

    // shared_ptr  double[7][2],    double[2]
    //  {3.0, 4.0};  (4):
    std::shared_ptr<double[][2]> sp8 = std::make_shared<double[][2]>(7, {3.0, 4.0});

    // shared_ptr  vector<int>[4],   
    //   {5, 6};  (4):
    std::shared_ptr<std::vector<int>[]> sp9 =
        std::make_shared<std::vector<int>[]>(4, {5, 6});

    // shared_ptr  float[512],     1.0;  (5):
    std::shared_ptr<float[512]> spA = std::make_shared<float[512]>(1.0);

    // shared_ptr  double[6][2],   double[2] 
    //  {1.0, 2.0};  (5):
    std::shared_ptr<double[6][2]> spB = std::make_shared<double[6][2]>({1.0, 2.0});

    // shared_ptr  vector<int>[4],   
    //   {5, 6};  (5):
    std::shared_ptr<std::vector<int>[4]> spC =
        std::make_shared<std::vector<int>[4]>({5, 6});
}

: 

sp1->{ i:1, f:0 }
sp2->{ i:2, f:3 }

shared_ptr
(public -) []
(C++20)
 , ,
( ) []
(C++11)
 shared_ptr,
( ) []
(C++14)(C++20)
 ,
( ) []

() []
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