operator+ loses pointer in member object

I have a C++ class with this data member:

Code:

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                char ** data;

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The memory for this variable is properly allocated and the variable is usable throughout the entire program, but after using the overloaded plus operator (implemented as a friend function) my program gets an Invalid Allocation Size error.

Here is an example of a line that errors. s1, sa3, and sa4 are all properly created stringArray objects:

Code:

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                s1 = sa3 + sa4;

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Here is the operator+ function:

Code:

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                stringArray& operator+(const stringArray& arr1, const stringArray& arr2)
                {
                        stringArray temp(arr1.count + arr2.count);

                        for(size_t i = 0; i < arr1.count; i++)
                        {
                                if(arr1.data[i] != NULL)
                                {
                                        temp.addString(arr1.data[i]);
                                }
                        }

                        for(size_t i = 0; i < arr2.count; i++)
                        {
                                if(arr1.data[i] != NULL)
                                        temp.addString(arr2.data[i]);
                        }

                        return temp;
                }

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temp gets correctly created and has all of the strings created, but once the function returns, the data variable is an undefined pointer.

I think the issue is that temp is created on the stack. I do not know what convention C++ uses to return object, but I assume that they put the memory location of the object in the return register. If this is the case, I understand that when the stack was decremented, that the memory location is lost.

I am hoping someone can explain to me how other people create the operator+ function when they have a pointer in their class, it seems like the only thing to do would be to return a point (created in heap) and take the memory leak.

Thank you.

Return by value, not reference. Make sure you copy constructor works correctly.

Also, implement + in terms of +=. I've never come across a regular (as in, didn't do weird things) + operator that didn't look or shouldn't have looked like this:

Code:

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Whatever operator +(const Whatever& lhs, const Whatever& rhs) {
  Whatever t(lhs);
  t += rhs;
  return t;
}

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