std::bad_weak_ptr(3)

NAME
std::bad_weak_ptr - std::bad_weak_ptr

Synopsis
   Defined in header <memory>
   class bad_weak_ptr; (since C++11)
   std::bad_weak_ptr is the type of the object thrown as exceptions by the constructors
   of std::shared_ptr that take std::weak_ptr as the argument, when the std::weak_ptr
   refers to an already deleted object.
   std-bad weak ptr-inheritance.svg
                        Inheritance diagram

Member functions
   constructor constructs a new bad_weak_ptr object
                 (public member function)
   operator= replaces the bad_weak_ptr object
                 (public member function)
   what returns the explanatory string
                 (public member function) std::bad_weak_ptr::bad_weak_ptr
   bad_weak_ptr() noexcept; (1) (since C++11)
   bad_weak_ptr( const bad_weak_ptr& other ) noexcept; (2) (since C++11)
   Constructs a new bad_weak_ptr object with an implementation-defined null-terminated
   byte string which is accessible through what().
   1) Default constructor.
   2) Copy constructor. If *this and other both have dynamic type std::bad_weak_ptr
   then std::strcmp(what(), other.what()) == 0.

Parameters
   other - another exception object to copy std::bad_weak_ptr::operator=
   bad_weak_ptr& operator=( const bad_weak_ptr& other ) noexcept; (since C++11)
   Assigns the contents with those of other. If *this and other both have dynamic type
   std::bad_weak_ptr then std::strcmp(what(), other.what()) == 0 after assignment.

Parameters
   other - another exception object to assign with

Return value
   *this std::bad_weak_ptr::what
   virtual const char* what() const noexcept; (since C++11)
   Returns the explanatory string.

Parameters
   (none)

Return value
   Pointer to a null-terminated string with explanatory information. The string is
   suitable for conversion and display as a std::wstring. The pointer is guaranteed to
   be valid at least until the exception object from which it is obtained is destroyed,
   or until a non-const member function (e.g. copy assignment operator) on the
   exception object is called.

Notes
   Implementations are allowed but not required to override what(). Inherited from std::exception

Member functions
   destructor destroys the exception object
   [virtual] (virtual public member function of std::exception)
   what returns an explanatory string
   [virtual] (virtual public member function of std::exception)

Example
// Run this code
 #include <iostream>
 #include <memory>
 int main()
 {
     std::shared_ptr<int> p1(new int(42));
     std::weak_ptr<int> wp(p1);
     p1.reset();
     try
     {
         std::shared_ptr<int> p2(wp);
     }
     catch (const std::bad_weak_ptr& e)
     {
         std::cout << e.what() << '\n';
     }
 }

Possible output:
 std::bad_weak_ptr
   Defect reports
   The following behavior-changing defect reports were applied retroactively to
   previously published C++ standards.
      DR Applied to Behavior as published Correct behavior
                       calling what on a default-constructed the return value is
   LWG 2376 C++11 bad_weak_ptr was required to return implementation-defined
                       "bad_weak_ptr"

See also
   shared_ptr smart pointer with shared object ownership semantics
   (C++11) (class template)
   weak_ptr weak reference to an object managed by std::shared_ptr
   (C++11) (class template)