Undefined reference to vtable

Question

When building my C++ program, I\'m getting the error message

undefined reference to \'vtable...

What is the cause of this probl

Answer 1

I just ran into another cause for this error that you can check for.

The base class defined a pure virtual function as:

virtual int foo(int x = 0);

And the subclass had

int foo(int x) override;

The problem was the typo that the "=0" was supposed to be outside of the parenthesis:

virtual int foo(int x) = 0;

So, in case you're scrolling this far down, you probably didn't find the answer - this is something else to check for.