Freeing memory for non-pointer variables

This is a discussion on Freeing memory for non-pointer variables within the C++ Programming forums, part of the General Programming Boards category; I haven't done much with C++ as of yet, but I come to the language with a ton of LPC ...

  1. #1
    Registered User SuperGodAntMan's Avatar
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    Freeing memory for non-pointer variables

    I haven't done much with C++ as of yet, but I come to the language with a ton of LPC (C derivant used with MudOS) experience. To the end of learning some of the low-level stuff LPC doesn't handle (instead leaving the MudOS driver to handle it for you), I've done some reading around on memory deallocation. However, all of the deallocation operators seem to be specific to arrays.

    Code:
       RECT crc, wrc;
       GetClientRect(hwnd, &crc);
       GetWindowRect(hwnd, &wrc);
       // This resizes things so we get a client rect of 408x408 pixels.
       SetWindowPos(hwnd, HWND_NOTOPMOST, wrc.left, wrc.top, 816-crc.right, 816-crc.bottom, 0);
    
       ShowWindow(hwnd, nFunsterStil);
    
       // If I'm lucky, this wipes the no longer needed crc and wrc variables.
       // If I'm unlucky, this is a really really really bad thing to do.
       delete &crc;
       delete &wrc;
    This all happens in the winmain function before the message loop. I'm not going to be using crc and wrc beyond this part of the code, so in the interests of perfectionist optimization, I'm getting rid of them. My question is, can you use delete in this way on single (non-array) variable instances?

  2. #2
    Yes, my avatar is stolen anonytmouse's Avatar
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    Welcome to the forums!
    My question is, can you use delete in this way on single (non-array) variable instances?
    No. You can only call delete with values that have been returned by new. Same with malloc/realloc and free.
    I'm not going to be using crc and wrc beyond this part of the code, so in the interests of perfectionist optimization, I'm getting rid of them.
    Perfectionist optimization is probably a futile goal. However, if you are really worried you can put the variables in a seperate block (or even better, a seperate function):
    Code:
    { // start block
       RECT crc, wrc;
       GetClientRect(hwnd, &crc);
       GetWindowRect(hwnd, &wrc);
       // This resizes things so we get a client rect of 408x408 pixels.
       SetWindowPos(hwnd, HWND_NOTOPMOST, wrc.left, wrc.top, 816-crc.right, 816-crc.bottom, 0);
    
       ShowWindow(hwnd, nFunsterStil);
    } // end block

  3. #3
    pwns nooblars
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    What you will want to do is make functions, when a function is called, it allocates the memory for all the variables that it needs created (excluding variables that are passed by reference instead of value) then deletes them all when it is done.

  4. #4
    Registered User SuperGodAntMan's Avatar
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    Thanks for the speedy responses, guys

    I eventually went with turning crc and wrc into a new'd array of RECTs, a la
    Code:
    RECT* rc = new RECT[1];
    which should make it compatible with delete.

  5. #5
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    >I eventually went with turning crc and wrc into a new'd array of RECTs, a la
    >RECT* rc = new RECT[1];
    Great. There's just a little problem. Your array only holds one element.

  6. #6
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    Why would you want to make it compatible with delete? What does delete do that you want to have happen?

    As anonytmouse mentioned, in the case of RECT there really is no reason to try to save that memory, but if you want them destroyed earlier just add an extra scope. Making a dynamic array just so you can call delete doesn't make sense, and is probably an unnecessary pessimization.

  7. #7
    pwns nooblars
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    I am with Daved, let the computer do the memory managment when it can, instead of doind explicit calls to delete things. It is easier on you, and easier on anyone that wants/needs to debug your code. Besides adding functions and what not makes your program easier to read and trace through.

  8. #8
    Registered User Kurisu's Avatar
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    don't worry SuperGod I find myself doing the same thing.. paranoid optimization via managing all memory myself.. though the other guys have point that dynamic memory when not necessary makes things alot tougher to manage.

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