using free on structures with pointers to data types inside

This is a discussion on using free on structures with pointers to data types inside within the C Programming forums, part of the General Programming Boards category; Code: struct hostent { char FAR * h_name; char FAR * FAR * h_aliases; short h_addrtype; short h_length; char FAR ...

  1. #1
    Climber spoon_'s Avatar
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    using free on structures with pointers to data types inside

    Code:
    struct hostent {
        char FAR *       h_name;
        char FAR * FAR * h_aliases;
        short            h_addrtype;
        short            h_length;
        char FAR * FAR * h_addr_list;
    };
    That is how the structure hostent is declared. Now, if I do this:

    Code:
    struct hostent *winfo = NULL;
    ....
    some code that puts info into winfo
    ....
    free(winfo)
    are the three pointers (h_name, h_aliases, h_addr_list) freed also?

    thanks,
    spoon_

  2. #2
    End Of Line Hammer's Avatar
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    6,231
    >>are the three pointers (h_name, h_aliases, h_addr_list) freed also?
    No. If you malloc() it, you must free() it.
    When all else fails, read the instructions.
    If you're posting code, use code tags: [code] /* insert code here */ [/code]

  3. #3
    ....
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    Your pointer winfo points to a piece of memory which contains an object of type struct hostent. The pointer-members of this struct each point to a piece of memory. If you release only the memory winfo points to, you only release the block of memory which contains the object of type struct hostent. But you don't release the blocks of memory where the pointer-members of that object pointed to.

    So before releasing the object, you should first release the memory the pointer-members are pointing to.

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