Difference between revisions of "cpp/memory/bad weak ptr"
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{{cpp/title|bad_weak_ptr}} | {{cpp/title|bad_weak_ptr}} | ||
| − | {{cpp/memory | + | {{cpp/memory/navbar}} |
{{dcl begin}} | {{dcl begin}} | ||
| − | {{dcl header | memory}} | + | {{dcl header|memory}} |
| − | {{dcl | | + | {{dcl|since=c++11|1= |
class bad_weak_ptr; | class bad_weak_ptr; | ||
}} | }} | ||
| Line 13: | Line 13: | ||
===Member functions=== | ===Member functions=== | ||
| − | {{ | + | {{cpp/error/exception/member of derived|bad_weak_ptr|std=c++11}} |
| − | + | ||
| − | + | ||
{{cpp/error/exception/inherit}} | {{cpp/error/exception/inherit}} | ||
| Line 21: | Line 19: | ||
===Example=== | ===Example=== | ||
{{example | {{example | ||
| − | + | |code= | |
| − | + | ||
| − | + | ||
#include <iostream> | #include <iostream> | ||
| + | #include <memory> | ||
| + | |||
int main() | int main() | ||
{ | { | ||
| Line 30: | Line 28: | ||
std::weak_ptr<int> wp(p1); | std::weak_ptr<int> wp(p1); | ||
p1.reset(); | p1.reset(); | ||
| − | try { | + | try |
| + | { | ||
std::shared_ptr<int> p2(wp); | std::shared_ptr<int> p2(wp); | ||
| − | } catch(const std::bad_weak_ptr& e) { | + | } |
| + | catch (const std::bad_weak_ptr& e) | ||
| + | { | ||
std::cout << e.what() << '\n'; | std::cout << e.what() << '\n'; | ||
} | } | ||
} | } | ||
| − | + | |p=true | |
| + | |output= | ||
std::bad_weak_ptr | std::bad_weak_ptr | ||
}} | }} | ||
| + | |||
| + | ===Defect reports=== | ||
| + | {{dr list begin}} | ||
| + | {{dr list item|wg=lwg|dr=2376|std=C++11|before=calling {{tt|what}} on a default-constructed {{tt|bad_weak_ptr}} was required to return {{c|"bad_weak_ptr"}}|after=the return value is implementation-defined}} | ||
| + | {{dr list end}} | ||
===See also=== | ===See also=== | ||
{{dsc begin}} | {{dsc begin}} | ||
| − | {{dsc inc | cpp/memory/dsc shared_ptr}} | + | {{dsc inc|cpp/memory/dsc shared_ptr}} |
| − | {{dsc inc | cpp/memory/dsc weak_ptr}} | + | {{dsc inc|cpp/memory/dsc weak_ptr}} |
{{dsc end}} | {{dsc end}} | ||
| − | + | {{langlinks|de|es|fr|it|ja|pt|ru|zh}} | |
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Latest revision as of 10:55, 12 June 2023
| 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.
Inheritance diagram
Contents |
[edit] 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().
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
| [virtual] |
destroys the exception object (virtual public member function of std::exception)
|
| [virtual] |
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:
std::bad_weak_ptr
[edit] 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 |
[edit] See also
| (C++11) |
smart pointer with shared object ownership semantics (class template) |
| (C++11) |
weak reference to an object managed by std::shared_ptr (class template) |
