C++: warning: C4930: prototyped function not called (was a variable definition intended?) [duplicate]

Question

I have a class that does not have a default constructor, I created a variable without giving parameters by mistake, but instead of a nice compiler error, I got a linker error, where I couldn't find the line of code that was causing it.

In the end, I managed to find the code that caused this, and only then I noticed that I was getting this warning:

C++: warning: C4930: prototyped function not called (was a variable definition intended?)

What's weird is when I changed the code from:

MyClass foo();

to

MyClass foo;

I did get a compiler error.

Can someone explain to me why the compiler suddenly started acting strange, is it a bug or something?

Answer 1

This

MyClass foo();

is a function declaration that has return type MyClass and does not accept arguments..

This

MyClass foo;

is an object definition. As your class MyClass has no the default constructor the compiler issues an error.