when resizing an array..

This is a discussion on when resizing an array.. within the C Programming forums, part of the General Programming Boards category; why is p[20] valid and can hold values when : Code: int *p; p = (int *)calloc(10, sizeof(int)); i mean ...

  1. #1
    former member Brain Cell's Avatar
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    Question when resizing an array..

    why is p[20] valid and can hold values when :
    Code:
    int *p;
    p = (int *)calloc(10, sizeof(int));
    i mean its out of the allocation range
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  2. #2
    Code Goddess Prelude's Avatar
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    It may be able to hold values, but it isn't valid. Accessing memory outside of your address space results in undefined behavior. That means that it could work like you expect, or it could fry your monitor. You just don't know.
    My best code is written with the delete key.

  3. #3
    and the hat of wrongness Salem's Avatar
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    However, the tendancy towards the latter varies according to
    - the larger the program becomes (larger programs die more frequently than small programs)
    - the longer the program takes to run (long running programs die more frequently than short lived programs)
    - the amount of time left before the deadline / release date (the closer the deadline, the more likely failure will occur)

    This means that simple one-line tests of out of bound accesses to malloc'ed memory almost always succeed, which is a pity really because newbies don't get to see the real mistake until much later, when they've learnt some bad habit.
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
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  4. #4
    Code Goddess Prelude's Avatar
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    >However, the tendancy towards the latter varies according to
    You forgot the most annoying one:

    - the time and place that the program is run (programs die more frequently during demos and reviews)
    My best code is written with the delete key.

  5. #5
    former member Brain Cell's Avatar
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    to get this straight , i should always use allocated spaces even if unallocated spaces work right?? (just to make sure)
    Last edited by Brain Cell; 03-23-2004 at 09:12 AM.
    My Tutorials :
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  6. #6
    Code Goddess Prelude's Avatar
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    >i should always use allocated spaces even if unallocated spaes work right??
    Yes.
    My best code is written with the delete key.

  7. #7
    former member Brain Cell's Avatar
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    Thanks for the quick help.

    Prelude : do you live on the board or something?? lol , you are everywhere..
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  8. #8
    Code Goddess Prelude's Avatar
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    >do you live on the board or something??
    Sadly, it seems that way.
    My best code is written with the delete key.

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