c++的set_unexpected不起作用

// set_unexpected example
#include <iostream>       // std::cerr
#include <exception>      // std::set_unexpected

void myunexpected() {
        std::cerr << "unexpected called\n";
        throw 0;     // throws int (in exception-specification)
}

void myfunction() throw (int) {
        throw ‘x‘;   // throws char (not in exception-specification)
}

int main(void) {
        std::set_unexpected(myunexpected);
        try {
                myfunction();
        }
        catch (int) { std::cerr << "caught int\n"; }
        catch (...) { std::cerr << "caught some other exception type\n"; }
        return 0;
}