NAME

deductionguidesforstd::shared_ptr - deductionguidesforstd::shared_ptr

Synopsis

Defined in header <memory>
template <class T> (1) (since C++17)
shared_ptr(std::weak_ptr<T>) -> shared_ptr<T>;
template <class T, class D> (2) (since C++17)
shared_ptr(std::unique_ptr<T, D>) -> shared_ptr<T>;

These deduction guides are provided for std::shared_ptr to account for the edge
cases missed by the implicit deduction guides.

Note that there is no class template argument deduction from pointer types because
it is impossible to distinguish pointers obtained from array and non-array forms of
new.

Example

// Run this code

#include <memory>

int main()
{
auto p = std::make_shared<int>(42);
std::weak_ptr w{p}; // explicit deduction guide is used in this case
std::shared_ptr p2{w}; // explicit deduction guide is used in this case
}