C++ 值，指针，引用的讨论

源自 stackoverflow 论坛，很有意义

第一个问题，引用传递和按值传递的场合

There are four main cases where you should use pass-by-reference over pass-by-value:

1. If you are calling a function that needs to modify its arguments, use pass-by-reference or pass-by-pointer. Otherwise, you’ll get a copy of the argument.
2. If you're calling a function that needs to take a large object as a parameter, pass it by const reference to avoid making an unnecessary copy of that object and taking a large efficiency hit.
3. If you're writing a copy or move constructor which by definition must take a reference, use pass by reference.
4. If you're writing a function that wants to operate on a polymorphic class, use pass by reference or pass by pointer to avoid slicing.

来源：Where should I prefer pass-by-reference or pass-by-value?

int v = 5;

cout << v << endl; // prints 5
cout << &v << endl; // prints address of v

int* p;
p = &v; // stores address of v into p (p is a pointer to int)

int& r = v;

cout << r << endl; // prints 5

r = 6;

cout << r << endl; // prints 6
cout << v << endl; // prints 6 too because r is a reference to v

template<typename T>    
void moronic_delete(T*& p)
{
    delete p;
    p = nullptr;
}

附 C++ 各个阶段学习的书籍推荐，来源论坛大牛的回答

• The Definitive C++ Book Guide and List

C++ 并发编程实战感觉包含挺多工作上需要的知识点，比如，线程库、原子库、C++ 内存模型、锁和互斥锁，以及设计和调试多线程应用程序的问题，可以看看