CODEWITHSUNDEEP
c++heap-memoryheap-corruption
Jimmy Constant
Jimmy Constant

Reputation: 43

C++ Heap Corruption: Local heap variable causing issues

I am working on some simple terrain with DirectX9 by manually assembling the verts for the ground.

On the part of my code where I set up the indices I get an error though:

Windows has triggered a breakpoint in test.exe.

This may be due to a corruption of the heap, which indicates a bug in test.exe or any of the DLLs it has loaded.

Here is the part of my code that is giving me problems, and I'm almost 100% sure that it is linked to my indices pointer, but I delete it when I'm finished... so I'm not sure what the problem is.

int total = widthQuads * heightQuads * 6;
DWORD *indices = new DWORD[totalIdx];
for (int y = 0; y < heightQuads; y++)
{
    for (int x = 0; x < widthQuads; x++)
    { //Width of nine:
        int lowerLeft = x + y * 9;
        int lowerRight = (x + 1) + y * 9;
        int topLeft = x + (y + 1) * 9;
        int topRight = (x + 1) + (y + 1) * 9;
        //First triangle:
        indices[counter++] = topLeft;
        indices[counter++] = lowerRight;
        indices[counter++] = lowerLeft;
        //Second triangle:
        indices[counter++] = topLeft;
        indices[counter++] = topRight;
        indices[counter++] = lowerRight;
    }
}

d3dDevice->CreateIndexBuffer(sizeof(DWORD)* total, 0, D3DFMT_INDEX16, 
    D3DPOOL_MANAGED, &groundindex, 0);
void* mem = 0;
groundindex->Lock(0, 0, &mem, 0);
memcpy(mem, indices, total * sizeof (DWORD));
groundindex->Unlock();

delete[] indices;

When I remove this block my program runs OK.

Upvotes: 2

Views: 608

Answers (2)

mjfgates
mjfgates

Reputation: 3431

int total = widthQuads * heightQuads * 6;
DWORD *indices = new DWORD[totalIdx];

Shouldn't you be doing "new DWORD[total];" here?

Upvotes: 0

vhallac
vhallac

Reputation: 13937

The code you've given looks OK - with one caveat: the initial value of counter is not in the code itself. So either you don't start at counter = 0, or some other piece of code is stomping on your indices buffer.

That's the beauty of heap corruptions. There is no guarantee that the bug is in the removed portion on the code. It may simply hide the bug that exists somewhere else in your code.

Upvotes: 2

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