Pointer to array as member data...

Can anyone explain what is wrong with this code? This is a simplification of a problem I isolated in another class. I am using Microsoft Visual C++ in Visual Studio .NET 2003 but using unmanaged code here.

Code:

class c
{
public:
        c () {pa = new int [2];}

        int f ()
        {
                pa [0] = 1;
                pa [1] = 1;

                return 0; // breakpoint here
        }

private:
        int* pa;
};

int main ()
{
        c* pc = new c;
        pc -> f();

        return 0;
}

Querying the contents of pa at the breakpoint gives pa[0] == 1 but pa[1] == 0. Using numbers other than 1 yields the right result for pa[0] only, and if pa is extended beyond 2 parts it again only works for pa[0]. Help!!!

I just tested the code in Dev-c++, and it works fine there. Both pa[0] and pa[1] is 1

I also tested in Visual Studio 2005 and it works fine too. I don't see why it wouldn't work as expected.

Originally Posted by JulesGlass

Can anyone explain what is wrong with this code?

For starters, no destructor, assignment operator, or copy constructor.

For starters, no destructor, assignment operator, or copy constructor.

I think the compiler makes them for you? (which I guess I can argue is a good idea or not when using pointers)

Yes, it does. I can see that this is a "starting out" class, so you don't need them just yet.
However, since you are allocating memory, it's generally recommended that you overload a copy constructor and assignment operator since otherwise you will get unexpected results if you makes copies of the class.

Originally Posted by h3ro

I think the compiler makes them for you? (which I guess I can argue is a good idea or not when using pointers)

Yes, unless the desired behavior is a shallow copy of the pointer, this code is broken. At the very least one should forbid copying and assignment.

The lack of a destructor will result in a memory leak.