参考:https://en.cppreference.com/w/cpp/language/copy_initialization
用一个对象初始化另一个对象,叫做拷贝初始化,不一定是拷贝构造,也可能是构造。
T object = other; (1)
T object = {
other}; (2) (until C++11)
f(other) (3)
return other; (4)
throw object;
catch (T object) (5)
T array[N] = {
other-sequence}; (6)