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std::bad_weak_ptr - cppreference.com

From cppreference.com

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.

cpp/error/exception

Inheritance diagram

Member functions

constructs a new bad_weak_ptr object
(public member function)
replaces the bad_weak_ptr object
(public member function)
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.

Return value

Pointer to an implementation-defined 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.

The returned string is encoded with the ordinary literal encoding during constant evaluation.

(since C++26)

Notes

Implementations are allowed but not required to override what().

Inherited from std::exception

Member functions

destroys the exception object
(virtual public member function of std::exception) [edit]
returns an explanatory string
(virtual public member function of std::exception) [edit]

Example

#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:

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 2376 C++11 calling what on a default-constructed bad_weak_ptr was required to return "bad_weak_ptr" the return value is implementation-defined

See also

smart pointer with shared object ownership semantics
(class template) [edit]
weak reference to an object managed by std::shared_ptr
(class template) [edit]