[no bug]heapsort invalid pointer

[henko]

Using: Irrlicht branch 1.7, revision 3926

I'm chasing a bug for hours now. My program started to crash when i'm calling

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driver->addTexture(name, image);

The debugger shows that access violation happens when irrlicht tries to sort my textures after adding the new one.

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//! adds a surface, not loaded or created by the Irrlicht Engine
void CNullDriver::addTexture(video::ITexture* texture)
{
        if (texture)
        {
                SSurface s;
                s.Surface = texture;
                texture->grab();
 
                Textures.push_back(s);
 
                // the new texture is now at the end of the texture list. when searching for
                // the next new texture, the texture array will be sorted and the index of this texture
                // will be changed. to let the order be more consistent to the user, sort
                // the textures now already although this isn't necessary:
 
                Textures.sort();
        }
}

The sort is done by heapsort which is like this:

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//! Sorts an array with size 'size' using heapsort.
template<class T>
inline void heapsort(T* array_, s32 size)
{
        // for heapsink we pretent this is not c++, where
        // arrays start with index 0. So we decrease the array pointer,
        // the maximum always +2 and the element always +1
 
        T* virtualArray = array_ - 1;
        s32 virtualSize = size + 2;
        s32 i;
 
        // build heap
 
        for (i=((size-1)/2); i>=0; --i)
                heapsink(virtualArray, i+1, virtualSize-1);
 
        // sort array, leave out the last element (0)
        for (i=size-1; i>0; --i)
        {
                T t = array_[0];
                array_[0] = array_[i];
                array_[i] = t;
                heapsink(virtualArray, 1, i + 1);
        }
}

It says that virtualArray is an invalid pointer which seems true considering that the original array pointer is decreased by one. Which means that it will point before the array to an invalid memory. I don't know what is the reason for this, but it seems wrong to me.



Any thoughts? Where else could this bug come from? It seems that the < operator fails to compare the names in irrString.h, because one name has an invalid pointer inside.

[CuteAlien]

Did you maybe release one of the textures you added before?
I'm sorry, but that is not enough information, you have to give us something which we can reproduce to find such problems.

[henko]

After hours of debugging I have found the problem. It's not a bug in irrlicht, so you can remove the topic if you want.

The problem was the following:

I have created a render target by:

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ITexture* target = driver->addRenderTargetTexture(...)

And I though I can drop it when i'm done, so i called:

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target->drop()

But now I know that I have to call:

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driver->removeTexture(target)

instead of dropping it. :)

Sorry for the false bug report. :)

[hybrid]

Yeah, the add* in the method name hints for this behavior