Question

Is the assignment and check for null explicitly required in the below snippet to achieve the same result. Also, is there anything wrong or can be improved here.

class Sample
{

private:
    char *bits;

public:

    Sample() 
    {
       bits = NULL; //should this be explicit?
    }


    ~Sample() 
    {
        if (bits != NULL) 
        {
           delete [] bits; //should this be explicit?
        }
        bits = NULL; //should this be explicit?
    }

};

Answer 1

In the first case, where you do this in the constructor:

Sample()
{
    bits = NULL;
}

Whether or not you need this assignment depends on your code – if bits may not have any memory allocated to it at all, then the NULL assignment should be there because of the delete in the destructor. And really as a safety issue, you would probably want the NULL unless you document some contract the user has to obey, but here since you are initializing the pointer to NULL, I will assume that means bits could realistically be NULL or actually have new-allocated memory at some point.

If you did not initialize the pointer, and it is never subsequently made ‘valid’ by being assigned something, and the object is destroyed, then bad stuff happens.

Also, as a habit, prefer to use initialization lists when possible in constructors:

Sample() 
    : bits(NULL)
{

}

For the destructor, you do not need to check if a pointer is not NULL before deleting it. delete on a NULL pointer is completely safe. You also don’t need to reassign the bits pointer back to NULL, the object is going away.

~Sample()
{
    delete [] bits;
}

Of course, if you delete an invalid pointer, then bad stuff will happen regardless.