使用 {} 和 () 进行结构初始化

Question

When I have a struct

   struct Point
    {
    int x;
    int y;
    int z;
    }

Why it's possible to write

Point p = {10, 20, 30};
Point p0 {10, 20, 30};
auto p1 = Point{10, 20, 30};

Using {}. But I can't write with ()

Point p(10,10,10);
auto p1 = Point(10,10,10);

With error

Error   C2440   'initializing': cannot convert from 'initializer list' to 'Point '  

Answer 1

Since C++20 you can perform aggregate-initialization with parentheses initializer.

 T object (arg1, arg2, ...); (5) (since C++20)

Before C++20, Point p(10,10,10); is supposed to call a constructor of Point taking 3 int s, but Point doesn't have such constructor. As you've showed you have to use braced initializer to perform aggregate-initialization, or provide such a constructor for Point then you could use both parentheses and braced initializer.