阐明我对复制初始化和直接初始化的见解

定义一个类如下:

class A {
public:
  A(): s("") {}                             //default constructor
  A(const char* pStr): s(pStr) {}           //constructor with parameter
  A(const A& a) : s(a.s) {}                 //copy constructor
  ~A() {}                                   //destructor
private:
  std::string s;
};

下面的代码将执行直接初始化:

A a1("Hello!");   //direct initialization by calling constructor with parameter
A a2(a1);          //direct initialization by calling copy constructor

以下内容将执行复制初始化:

A a3 = a1;  
A a4 = "Hello!";

据我所知, A a4 = "Hello" 相当于:

//create a temporary object first, then "copy" this temporary object into a4 by calling copy constructor    
A temp("Hello!");    
A a4(temp);

那么 A a3 = a1 和 A a2(a1) ? 似乎他们都叫复制构造函数我上面的评论是否正确(没有编译器优化)