std:: unexpected_handler

std::unexpected_handler is the function pointer type (pointer to function that takes no arguments and returns void), which is installed and queried by the functions std::set_unexpected and std::get_unexpected and called by std::unexpected .

The C++ implementation provides a default std::unexpected_handler function, which calls std::terminate() . If the null pointer value is installed (by means of std::set_unexpected ), the implementation may restore the default handler instead.

A user-defined std::unexpected_handler is expected to either terminate the program or throw an exception. If it throws an exception, one of the following three situations may be encountered:

1) the exception thrown by std::unexpected_handler satisfies the dynamic exception specification that was violated earlier. The new exception is allowed to escape the function and stack unwinding continues.

2) the exception thrown by std::unexpected_handler still violates the exception specification:

2a) however, the exception specification allows std::bad_exception : the thrown exception object is destroyed, and std::bad_exception is constructed by the C++ runtime and thrown instead.

2b) the exception specification does not allow std::bad_exception : std::terminate() is called.

See also