deductionguidesforstd::shared_ptr (3) - Linux Manuals

deductionguidesforstd::shared_ptr: deductionguidesforstd::shared_ptr

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
  }