Can't use std::unique_ptr with T being a forward declaration

Question

Now first, I am aware of the general issues with unique_ptr<> and forward declarations as in Forward declaration with unique_ptr? .

Consider these three files:

Answer 1

You also need to put A's constructor in C.cpp:

A.h

#include 
#include 

class B;

class A {
public:
     A();
    ~A();

private:
    std::unique_ptr m_tilesets;
};

C.cpp

#include "A.h"

class B {

};

A::~A() {

}

A::A() {

}

See this answer. The constructor needs access to the complete type as well. This is so that it can call the deleter if an exception is thrown during construction.