c - How can I delete a undeclared pointer?-CodePudding

If the new operator was written in a function argument or constructor argument like:

Foo* f = new Foo(new Baz(0, 0));
// how to delete "new Baz(0, 0)"?
delete f;

I know it can be written to:

Baz* b = new Baz(0, 0)
Foo* f = new Foo(b);
delete b;
delete f;

But it became complicated, is there any better way?

Should I do something like this:

Class Foo {
private:
    Baz* _b;
public:
    Foo(Baz* b) : _b(b) {}
    ~Foo() {
        delete _b;
    }
}
// so that when I delete foo will also delete baz;

CodePudding user response：

Following my own recommendation about the rule of zero and using std::unique_ptr, I would do something like this:

class Foo
{
public:
    Foo(int a, int b)
        baz_{ std::make_unique<Baz>(a, b) }
    {
    }

private:
    std::unique_ptr<Baz> baz_;
};

And

auto foo = std::make_unique<Foo>(0, 0);

With this the foo object own its own unique Baz object.

If you want Foo to by copyable then use std::shared_ptr and std::make_shared instead.

CodePudding user response：

More or less Yes, you should delete an allocated field in the destructor.

If the class has children, make the destructor virtual.

However you could have passed an existing pointer. And then the field is not owned.

You can use one of the ptr classes, i.e. std::unique_ptr for the Baz.

Or defer the deletion to the caller in some form:

Baz* _b; // Or Baz _b.
Foo(const Baz& b) : _b(new Baz(b)) {} // When feasible a copy.

From design point it would