Allocating memory for a structure member

This is a discussion on Allocating memory for a structure member within the C++ Programming forums, part of the General Programming Boards category; Hi I am new to C++ and obviously I have a few questions. Code: // If I declare a node ...

  1. #1
    Registered User dalek's Avatar
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    Allocating memory for a structure member

    Hi

    I am new to C++ and obviously I have a few questions.

    Code:
    // If I declare a node like this
    typedef struct NODE
    {
    	int *data;
    	NODE *next;
    }Node;
    
    // And I have created a variable of this
    // type and allocated memory for it like this
    Node *rootp = new Node;
    
    // I understand I have to allocate 
    // Memory for the variable *data 
    // to use it..
    rootp->data = new int;
    rootp->data = 10;
    Now, I know there is a mistake above, but I am not sure why - my understanding of pointers is limited, I'm good if it is a single variable, but I get confused when I am face with structures or function arguments...

  2. #2
    Registered User dalek's Avatar
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    May 2003
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    Oh god - thanks.

    It's funny - I had that originally but under the debugger it was failing on that line every time..
    Code:
    rootp = NULL;
    rootp->data = new int;
    *rootp->data = 10;
    I guess it was failing because rather than pointing the rootp->next member to NULL I was pointing rootp to NULL, which would mean I was writing data nowhere?? Is that correct?

    Thanks for the help Salem.

  3. #3
    Registered User dalek's Avatar
    Join Date
    May 2003
    Posts
    135
    Cheers - I think I am learning!

    Thanks Salem.

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