Question regarding pointer typecasting and manipulation

Discussion in 'C Programming' started by Arun Prasath, Nov 24, 2003.

  1. Arun Prasath

    Arun Prasath Guest

    Hi all,

    I have the following question regd pointer typecasting. Is the
    following type of pointer typecasting valid?


    #define ALLOC(type,num) ((type *)malloc(sizeof(type)*num))

    /*begin code*/

    struct node{
    :
    } node;

    typedef node *nodeptr;
    node **nodeptrptr;

    nodeptrptr = (nodeptr *)ALLOC(node,NUM_OF_NODES)

    /*end code*/

    Is the above code valid? If so, can anyone explain how it works? How
    can a pointer to a memory chunk be typecast to a pointer to a pointer
    to a memchunk?

    Thanks,
    Arun
     
    Arun Prasath, Nov 24, 2003
    #1
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  2. Arun Prasath

    James Hu Guest

    This cast is unecessary. Remove it.
    Wasn't the #define above code?
    This won't compile.
    Even after fixing struct node above, this won't compile.
    Ditto here.
    Since the declaration of nodeptrptr didn't compile, it is undefined
    at this point.
    The above code is invalid. It can't possibly work.

    It seems you intended to create a typename called node.
    If you remove the cast in the ALLOC macro, you won't need the
    cast in the assignment to nodeptrptr. However, the assignment
    is likely wrong, depending on how you define struct node.

    -- James
     
    James Hu, Nov 24, 2003
    #2
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  3. Groovy hepcat Arun Prasath was jivin' on 23 Nov 2003 22:38:09 -0800 in
    comp.lang.c.
    Question regarding pointer typecasting and manipulation's a cool
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    Peter Shaggy Haywood, Nov 26, 2003
    #3
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