当static_cast从派生类到基类时会发生什么？

Question

While reading the C++ standard, I read that static_cast is a kind of direct initialization (C++ standard 8.5/15).
I think this means that during a static_cast , the corresponding overloaded constructor is called.
For example, there is a type B and type D derived from B, and an object D d . Then the expression static_cast<B>(d) is a static_cast expression.

As the standard means, this static_cast expression is a direct initialization . Does it mean that this will call the constructor of type B and return a new constructed object of type B ?

---

EDIT
Another issue is how about B & b = d or B b = d ? Does these two statements involve constructor of B ?

Answer 1

What they mean in the standard is that you can cast for example a float to an integer. At this point conversion will happen. You can say that the resulting int is directly initialized at this point.

If class that participates in casting have corresponding overloaded conversion, then yes, it will be called. I personally would not recommend to actively use this feature. Your code will be difficult to read.

Answer 2

是的，对象类型的static_cast （即，不是对引用或指针类型的static_cast转换）将使用适当的构造函数来创建临时对象。

Answer 3

不。直接初始化意味着将从类D的对象复制B类对象中的每个字节，而不需要构造函数调用。