[gdal-dev] WMS MINRESOLUTION can lead to overflow of raster dimensions

[Even Rouault]

Tim,

> Would it make sense to do something as follows?  (Note:  I haven't tried
> this yet, I'm just soliciting early feedback so please bare with me )
> 
> 
>      if (osMinResolution.size() != 0)
>      {
>          double dfMinResolution = CPLAtofM(osMinResolution);
> 
>          while (nOverviewCount > 20)
>          {
>              nOverviewCount --;
>              dfMinResolution *= 2;
>          }
> 
>          // *** Changes here ***
>          // Determine a suitable resolution that doesn't overflow max int.
>          double dXSize = ((dfMaxX - dfMinX) / dfMinResolution + 0.5);
>          double dYSize = ((dfMaxY - dfMinY) / dfMinResolution + 0.5);
> 
>          while (dXSize > INT_MAX || dYSize > INT_MAX)
>          {
>              nOverviewCount --;

I'm not sure we need to decrement the number of overviews in that loop.

>              dfMinResolution *= 2;
> 
>              dXSize = ((dfMaxX - dfMinX) / dfMinResolution + 0.5);
>              dYSize = ((dfMaxY - dfMinY) / dfMinResolution + 0.5);
>          }
> 
>          nXSize = (int) dXSize;
>          nYSize = (int) dYSize;
>      }
> 
> Any thoughts?

If that works, please open a ticket with the patch.

For extra bonus, I see that a few lines below a similar overflow could also 
occur :

"""
    else
    {
        double dfRatio = (dfMaxX - dfMinX) / (dfMaxY - dfMinY);
        if (dfRatio > 1)
        {
            nXSize = nTileSize;
            nYSize = (int) (nXSize / dfRatio);
        }
        else
        {
            nYSize = nTileSize;
            nXSize = (int) (nYSize * dfRatio);
        }

        if (nOverviewCount < 0 || nOverviewCount > 20)
            nOverviewCount = 20;

        nXSize = nXSize * (1 << nOverviewCount);
        nYSize = nYSize * (1 << nOverviewCount);
    }
"""

Even

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