Thread: Using delete to clear a STL vector

  1. #1
    Registered User starkhorn's Avatar
    Join Date
    Sep 2003

    Using delete to clear a STL vector


    I've created 2 classes, called TEST1 and TEST2. In TEST1, I've declared a STL vector of the TEST2 class. Each time my program is run, there is a random number generated which specifies the number of instances of TEST2 that should be contained within the vector. That obviously required a initialisation function which I've written below

    vector<TEST2> test2_list;
    for (int i = 0; i < random_num; i++)
    		TEST2 *temp = new TEST2(param1, param2, param3);
    This works great. It initialises the vector exactly as I need it.

    My question is now on how do I delete the memory that I used with the new command once the program has stopped running.

    Do I put in the deconstructor of TEST1 a command to clear the vector. Will that delete the memory ?

    Or do I need to put something in the deconstructor of TEST2 like

    delete this;
    Unsure on how to delete this memory again once this program is complete. Obviously at the moment, I've got some memory leak so it's certainly a problem.

    Any help, would be much appreciated.


  2. #2
    Registered User
    Join Date
    Aug 2003
    do you mean that you wanna delete the memory when the vector is destructed?
    if so, don't care about this, the vector will destruct the elements object and delete the memory automatically.
    Nana C++ Library is a GUI framework that designed to be C++ style, cross-platform and easy-to-use.

  3. #3
    Cat without Hat CornedBee's Avatar
    Join Date
    Apr 2003
    for (int i = 0; i < random_num; i++)
    	TEST2 *temp = new TEST2(param1, param2, param3);
    You're apparently not aware of what this code does. You allocate memory for a TEST2 object and initialize it. Then, you put a copy of that object into the vector. The vector automatically allocates memory to hold it. Then you start the next iteration, thus losing the pointer to the memory you just allocated and creating an irrecoverable memory leak.

    Since the way you have it now is "working", you probably want this:
    test2_list.reserve(random_num); // This line makes the loop faster.
    for (int i = 0; i < random_num; i++)
    	test2_list.push_back(TEST2(param1, param2, param3));
    In that case, you don't need to worry about the memory anymore. When the vector is destructed, the associated memory gets freed.
    All the buzzt!

    "There is not now, nor has there ever been, nor will there ever be, any programming language in which it is the least bit difficult to write bad code."
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