C++右值参数

我写这个代码：

#include <iostream>
using namespace std;
class Foo
{

public:
    int a = 0;
    Foo()
    {
        cout << "ctor: " << this << endl;

    }
    ~Foo() {
       cout << "dtor: " << this << endl;
    }
};

Foo f()
{
    Foo foo;
    cout << "f " << &foo << endl;
    return foo;
}
void ff(Foo &&ffoo)
{
    cout << "ff " << &ffoo << endl;

}

int main()
{
    ff(f());
    std::cout << "Hello World!n";
}

输出看起来不错：

ctor: 0x7ffeda89bd7c
f 0x7ffeda89bd7c
ff 0x7ffeda89bd7c
dtor: 0x7ffeda89bd7c

ctor: 0x7ffeda89bd7c
f 0x7ffeda89bd7c
ff 0x7ffeda89bd7c
dtor: 0x7ffeda89bd7c

但是当我删除~Foo()这样的：

我得到了这个输出：

ctor: 0x7fffd5c8bf4c
f 0x7fffd5c8bf4c
ff 0x7fffd5c8bf6c
Hello World!

为什么与 的地址ffoo不同f？不应该是一样的吗？

编译cmd是：

g++ tmp.cpp 
g++ --version
g++ (Debian 8.3.0-6) 8.3.0
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