Calling delete upon a conditional call to new

Question

Suppose I have the following class:

foo{
    ~foo();

    private:
        char *bar;
};

Under certain conditions bar will create a new char array so what would be the correct way to handle the deletion of it? Would a simple bool do or would that be considered bad practice?

Answer 1

deleteing a null pointer is safe. That's why you should always set your pointer to NULL or nullptr when not in use:

struct foo{
    foo() : bar(NULL) {}
        //  ^ Initialize bar to NULL

    ~foo() {
       delete bar;
    }

    void some_method() {
        bar = new char;
        ...
        delete bar;
        bar = NULL;  // Immediately set bar back to NULL
    }

    private:
        char *bar;
};

Please note that when you set a pointer to the one returned by new, you must match it with delete, while if you set it using the pointer returned by new[], be sure to use delete[] on it.

Anyway, if you have access to C++11 smart pointers std::shared_ptr or std::unique_ptr, then they are your best bet.