Alright, thansk for the explanation.
I managed to solve this error. My problem was
I had a function declaration in a .hpp in a class
Then, in my .cpp where i include my header file and also my implementation of myfunc(), I had the below (which is wrong)
void myfunc() //this line is WRONG, I should use void aclass::myfunc() instead
//do something here
And all is well now.