Class object memory usage?

This is a discussion on Class object memory usage? within the C++ Programming forums, part of the General Programming Boards category; Say a class has 30 bytes of data storage (char of 30 bytes, say) and 5 methods for manipulating the ...

  1. #1
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    Class object memory usage?

    Say a class has 30 bytes of data storage (char of 30 bytes, say) and 5 methods for manipulating the data. How much memory would be used if 1000 of these objects were created ? Would it be (1000 * 30) + method code size, or 1000 * (30 + method code size) ?

    (That is, is the code in the method duplicated for each created instance of it, or just once and pointers used for the rest ?)

  2. #2
    Toaster Zach L.'s Avatar
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    The program can use only one set of code per class because, in addition to the normal arguments you would call for any methods in the structure, a pointer to the calling structure is also passed (the 'this' pointer).
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    Crazy Fool Perspective's Avatar
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    Originally posted by Salem
    > Would it be (1000 * 30) + method code size
    This one.
    in addition. you would have + 4 bytes if one or more of those functions are virtual.

  4. #4
    I lurk
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    Originally posted by Perspective
    in addition. you would have + 4 bytes if one or more of those functions are virtual.
    Blah blah blah, plus any padding done by the compiler.
    There's many factors...

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    Thanks, makes the coding a little easier. I can just use an iterator on the vector of my class now then and just tell each instance of the class to save itself to an opened file rather than worrying about how to save each type of class. Suppose it makes it more generic now too.

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