NAME

std::unexpected - std::unexpected

Synopsis

Defined in header <exception>
void unexpected(); (until C++11)
(since C++11)
[[noreturn]] void unexpected(); (deprecated)
(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 (until C++11)
will be called. (note: it was ambiguous whether re-throwing applied
the new handlers)
If a destructor reset the unexpected handler during stack unwinding,
it is unspecified which handler is called if the unwinding later led (since C++11)
to unexpected being called.

Parameters

(none)

Return value

(none)

Exceptions

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

Defect reports

The following behavior-changing defect reports were applied retroactively to
previously published C++ standards.

DR Applied to Behavior as published Correct behavior
effect of calling set_unexpected during stack
LWG 2111 C++11 unwinding differs from C++98 and breaks some made unspecified
ABIs

See also

unexpected represented as an unexpected value in expected
(C++23) (class template)
unexpected_handler the type of the function called by std::unexpected
(removed in C++17) (typedef)