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:

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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;
}

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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.

Quote:

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Originally Posted by JulesGlass

Can anyone explain what is wrong with this code?

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

Quote:

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

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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.

Quote:

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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)

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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.