使用const引用值返回的值

string foo(int i) {
  string a;
  ... Process i to build a ...
  return a;
}

void bar(int j) {
  const string& b = foo(j);
  cout << b;
}

void bar(int j) {
  string b = foo(j);
  cout << b;
}

string foo(int i) {
    string a;
    // ...
    return a;
}

void bar(const string& str) {
    // ...
}

void buzz() {
    // We can safely call bar() with the temporary string returned by foo():
    bar(foo(42));
}

void f()
{
   const string& a = foo(10);

   //some work with a

   {
     const string& b = foo(20);

     //some work with b

   } //<----- b gets destroyed here, so the temporary also gets destroyed!

   //some more work with a

} //<----- a gets destroyed here, so the temporary associated 
                                  //with it also gets destroyed!