Example

class MyClass
{
public:
friend int getA(MyClass& mc);
   
private:
int a;
};

int getA(
MyClass& mc){
return mc.a;
}

Solution
Extend the class interface instead of using friend functions.

class MyClass
{
public:
int getA();
   
private:
int a;
};

int MyClass::getA(){
return 
MyClass::a;
}