c++ - What is the reason for "declaration does not declare anything" error? -

if have class called 'rock', , :-

int main() {     rock; } 

why "declaration not declare anything" error ?

shouldn't call default constructor , create object @ moment?

ofcourse won't able use object , destroyed when go out of scope of function, why not creating @ all?

in other programming languages java, variables not compulsory. can new rock() , fine.

i know isn't of use want clear confusion.

rock name of class. there no variable name declared. call constructor/create object, need declare name of variable: rock r;

this creates object on stack destroyed when goes out of scope