问auto与auto&用于函数返回值

EN

struct A {
    // A: Another programmer changed it from:
    // int getVal() { return mInteger; }

    // B
    int &getVal() { return mInteger; }

private:
    int mInteger;
};

int main() {
    A *a = new A;

    auto   integerCopy = a->getVal();

    // int& on case B, int&& on case A.
    auto&& integerRvalueRef  = a->getVal();

    delete a;

    // Ok, no matter what getVal returns.
    std::cout << integerCopy;
    // Dangling Reference dereference if getVal returns a reference. 
    std::cout << integerRvalueRef;
}