What is an rvalue reference to function type?

Question

I have recently wrapped my mind around the C++0x\'s concepts of glvalues, xvalues and prvalues, as well as the rvalue references. However, there\'s one thing which still elu

Answer 1

In the old c++ standard the following is forbidden:

int foo();
void bar(int& value);

int main()
{
    bar(foo());
}

because the return type of foo() is an rvalue and is passed by reference to bar().

This was allowed though with Microsoft extensions enabled in visual c++ since (i think) 2005.

Possible workarounds without c++0x (or msvc) would be declaring

void bar(const int& value); 

or using a temp-variable, storing the return-value of foo() and passing the variable (as reference) to bar():

int main()
{
    int temp = foo();
    bar(temp);
}