False negative: Missing virtual destructor (pointer alias)

[Daniel Marjamäki]

We have (had) some check for missing virtual destructors. Not sure why it does not warn below:

#include <memory>
#include <string>
#include <iostream>

class Fred {
public:
    Fred() { std::cout << "Fred\n"; }
    ~Fred() { std::cout << "~Fred\n"; }
};

class Base {
public:
    Base() { }
};

class Derived : public Base {
public:
    Derived() : Base(), x(std::make_shared<Fred>()) {}
private:
    std::shared_ptr<Fred> x;
};

int main() {
    Derived *derived = new Derived;
    Base *base = derived;
    delete base;
    return 0;
}

The message "~Fred" is not written so there seems to be a memory leak.

[chrchr]

We warn for

	Base *base = new Derived;
	delete base;

but not for

	Derived *derived = new Derived;
	Base *base = derived;
	delete base;

We should probably just warn based on the class definition instead of trying to detect all possible use cases:

	std::vector<std::unique_ptr<Base>> v(1);
	v[0].reset(new Derived);

[Daniel Marjamäki]

We should probably just warn based on the class definition instead of trying to detect all possible use cases:

The current checker writes a error message so it needs to be explicit. But yes I think we could add a warning or style checker that just enforce that base classes overall provide virtual destructors. I suggest that separate IDs would be used.

Imho, it's a really good idea to always provide virtual destructors in base classes. Maybe except if it can be seen that the derived destructor does nothing.