Dynamic Memory and assignment operator overloading of objects

Question

If I'm using an assignment operator overload with dynamic memory should I check to see if there's something inside the pointer already?

for example if object A has a dynamic memory allocation in the constructor for an array called "name".

stored in object A is the name "John" with the memory allocated in the constructor through

name = new char[strlen(userinput)+1];

If I wanted to copy object B into object A through an assignment operator overload would I have to write

if(name != null){delete [] name;}
name = new char[strlen(src.name)+1];

To first clear the array out or do I not have to delete name before reallocating memory?

If you are juggling with dynamically allocated memory, there's probably more to fix than what you're asking for. I'd seriously recommend using a std::vector<char> instead of struggling new/delete yourself. — πάντα ῥεῖ
– πάντα ῥεῖ, Commented Apr 18, 2015 at 23:51
@user3551329 you don't actually have to test if(name != nullptr), since deleting a nullptr is a no-op. Just delete[] name; should do. — vsoftco
– vsoftco, Commented Apr 19, 2015 at 0:21

Community · Accepted Answer · 2017-05-23 11:51:05Z

2

"To first clear the array out or do I not have to delete name before reallocating memory?"

This way, you have to take care about memory management and de-/allocation all the time. You have to obey for copy constructions, assignments also (see What is the Rule of Three?).

if(name != nullptr){delete [] name;}
        // ^^^^^^^ The correct term is nullptr

You have to manage the nullptr value yourself. delete/delete [] don't assign a nullptr value automatically, but leave you with a dangling pointer.

The better solution instead of managing dynamically allocated memory yourself, is to use an appropriate container class like std::vector<char> or std::string:

class A {
    std::string name;
};

edited May 23, 2017 at 11:51

CommunityBot

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answered Apr 19, 2015 at 0:02

πάντα ῥεῖ

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