Thread: returning pointers

  1. #1
    Registered User
    Join Date
    Jun 2007

    returning pointers


    I've spent a long time on the web & reading books trying to find out how to do this for myself.
    No luck, there's a lot of stuff refering to using pointer to a function but very little on returning a pointer and it doesn't appear to do what I want it to
    So I'm hopping someone knows how to return a pointer

    I want to call a procedure and for that procedure to return a pointer.
    The procedure builds a linked list of a struct

    struct1 read()
    	// init stuff
    	struct1 *start_pointer;
    	loop till end
    	get data
    	create new record for list
    	insert into list
    	if this is the first recored, set a pointer to the start of the list
    	return start_pointer
    	//init stuff
    	struct1 *ptr;
    	ptr = read();  //I want ptr to point to the start of the linked list created in read
    	// other stuff

    It looks like I'm passing pointers to pointers, but I get an error -
    <cannot convert from 'struct netData *' to 'const struct netData'>

    Prefixing the return parameter with a * gives error on the calling line
    <binary '=' : no operator defined which takes a right-hand operand of type 'struct netData'>

    while prefixing with & gives -
    <cannot convert from 'struct netData ** ' to 'const struct netData'>

    I also get errors prefixing both ptr and the calling read
    - yes I am clutching at straws.

    I have tried using this, but also get errors here

    Gratefull for any help given

  2. #2
    Deathray Engineer MacGyver's Avatar
    Join Date
    Mar 2007
    int *read(void);
    int *read(void)
    	int *a = new int;
    	*a = 0;
    	return a;
    int main()
    	int *x = read();
    	delete x;
    	return 0;
    Works fine for me.

  3. #3
    Dr Dipshi++ mike_g's Avatar
    Join Date
    Oct 2006
    On me hyperplane
    For a start you are missing a semicolon:
    return start_pointer
    A simple function to return a pionter would be something like:
    struct1 *GetPointer()          
        return pointer; 

  4. #4
    and the hat of int overfl Salem's Avatar
    Join Date
    Aug 2001
    The edge of the known universe
    struct1 *read()
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.

  5. #5
    Registered User
    Join Date
    Nov 2006
    Quote Originally Posted by spudval View Post
    So I'm hopping someone knows how to return a pointer
    your function is a source function. that means it allocates memory and returns a handle to it to some sink function. returning a pointer possibly results in a memory leak. in projects more complex than a few lines of code the caller will forget to call delete some day. c++ has auto_ptr for source and sink functions.

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