I have seen this question. It seems that regardless of the cast, the temporary object(s) will "survive" until the fullexpression evaluated. But in the following scenario:

void foo(boost::tuple<const double&> n) {
    printf("%lf\n", n.get<0>());
}
int main() {
    foo(boost::tuple<const double&>(2));//#1
    foo(boost::make_tuple(2));//#2
    return 0;
}

1 run well, but 2 do not. And MSVC gave me a warning about 2: "reference member is initialized to a temporary that doesn't persist after the constructor exits"

Now I am wondering why they both make a temporary "double" object and pass it to boost::tuple<const double&> and only 2 failed.