Thread: Returning references (scope problems?)

  1. #1
    Registered User
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    Dec 2001
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    Returning references (scope problems?)

    In an old C++ book I have, the following example is given for overloading the [] operator:

    int &IntArray::operator[] (int index)
    {
    static int dummy=0;
    if((index=0) && (index < length))
    return array[index];
    else
    {
    cout << "Error: index out of range.\n";
    return dummy;
    }
    }

    where length and array[] are member variables of the class IntArray.

    My question is as follows. Suppose you have this code:

    int x;
    {
    IntArray somearray;
    x=somearray[0];
    }
    Dosomethingwith(x);

    Since somearray[0] returns a reference to data in somearray and somearray goes out of scope before x does, wont bad things happen when Dosomethingwith() tries to use x?

  2. #2
    of Zen Hall zen's Avatar
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    dummy is a static variable. When static variables go out of scope they still exist in memory (they're not allocated on the stack), so it is legal to return a reference to one.
    zen

  3. #3
    Registered User
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    Right, but I'm talking about

    return array[index];

    not

    return dummy;

  4. #4
    of Zen Hall zen's Avatar
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    Sorry, yes bad things will happen in your second example. The first is OK though as array is presumably a class member and not local to the operator[] function.
    zen

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