Binding temporary to a lvalue reference

Question

I have the following code

string three()
{
    return "three";
}

void mutate(string& ref)
{
}

int main()
{
    mutate(three()); 
    return 0;
}

You can see I am passing three() to mutate method. This code compiles well. My understanding is, temporaries can't be assigned to non-const references. If yes, how this program is compiling?

Any thoughts?

Edit:

Compilers tried : VS 2008 and VS2010 Beta

Answer 1

It used to compile in VC6 compiler, so I guess to maintain backward comptibility VS2008 is supporting this non-standard extension. Try with /Za (disable language extension) flag, you should get an error then.

Answer 2

It is VC++'s evil extension. If You oompile with /W4 then the compiler will warn you. I guess you are reading the Rvalue References: C++0x Features in VC10, Part 2. This article had also mentioned that issue.