< cpp‎ | error
Diagnostics library
Exception handling
Exception handling failures
(until C++17*)
(until C++17*)
(C++11)(until C++17*)    
(until C++17*)
Error codes
Error codes
Defined in header <exception>
void unexpected();
(until C++11)
[[noreturn]] void unexpected();
(since C++11)
(removed in C++17)

std::unexpected() is called by the C++ runtime when a dynamic exception specification is violated: an exception is thrown from a function whose exception specification forbids exceptions of this type.

std::unexpected() may also be called directly from the program.

In either case, std::unexpected calls the currently installed std::unexpected_handler. The default std::unexpected_handler calls std::terminate.

If a destructor reset the unexpected handler during stack unwinding and the unwinding later led to unexpected being called, the handler that was installed at the end of the throw expression is the one that will be called (note: it was ambiguous whether re-throwing applied the new handlers).

(until C++11)

If a destructor reset the unexpected handler during stack unwinding, it is unspecified which handler is called if the unwinding later led to unexpected being called.

(since C++11)

[edit] Exceptions

Throw any exception thrown by the currently installed std::unexpected_handler.

[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 2111 C++11 effect of calling std::set_unexpected during stack
unwinding differs from C++98 and breaks some ABIs
made unspecified

[edit] See also

represented as an unexpected value
(class template) [edit]
(removed in C++17)
the type of the function called by std::unexpected
(typedef) [edit]