Plus the difference between the parentheses without parentheses when you define an object

https://www.cnblogs.com/traeyee/p/4892410.html

https://blog.csdn.net/Windgs_YF/article/details/80927058

https://www.cnblogs.com/Braveliu/p/4263145.html

Note: Define custom object on the heap and stack objects without parentheses and brackets plus there is a difference.