Question

In C++ I have a header file I.h defining an abstract class (interface) with an empty
virtual destructor:

class I
{
  public:

    virtual ~I() {}
};

• Question 1: Is the object code for the empty destructor going to be generated in the object file of each .cpp file that includes I.h?
• Question 2: If the answer to question 1 is yes, can this be a problem (same method in different object files)?

Answer 1

No it will not. Methods defined inside the class definition are automatically inline, so no need to worry about it.

Note that a method being marked inline and actually be inlined in the binary is different. inline is just a marker (a compiler hint at best). Especially with virtual functions. Polymorphism is guaranteed to work, regardless of whether the methods are marked inline or not.