c++11 - C++ 11的range for里面定义的引用，为什么能被修改？

Question

以下代码节选自 C++ Primer 5th Ed.

string s("Hello World");
for (auto &c: s)
    c = toupper(c);
cout << s << endl;

这里面有一个引用类型的变量c。
在for循环遍历字符串的过程中，这个引用岂不是指向了不同的位置？
不是说引用的指向不能改变吗？

Answer 1

The c here is an alias of a variable (iterator). What you are changing is that the content pointed to by c is not a reference

Answer 2

Just think that every time you loop, you will newly define a reference whose scope is limited to one loop:-)