[gdal-dev] error reading AIG blocks

[Even Rouault]

On jeudi 11 mai 2017 23:29:15 CEST Gregory, Matthew wrote:
> Hi all,
> 
> I think this is a bug, but wanted to make sure I wasn't doing something
> stupid before I posted it as such.
> 
> At r32878 (git 1eb605a), Even added new logic for dealing with raw 32-bit
> AIG blocks.  I've got an AIG raster that has a few blocks where valid data
> is getting set to the min Int32 value (-2147483648) when doing a
> gdal_translate to GeoTiff.
> 
>   gdal_translate -of GTiff ai_bug ai_bug.tif
> 
> Note the "old" way of getting these values was providing the correct values
> in this case:
> 
>   panData[i] = pabyCur[0] * 256 * 256 * 256
>       + pabyCur[1] * 256 * 256
>       + pabyCur[2] * 256
>       + pabyCur[3] + nMin;
> 
> Note that this is only affecting selected blocks within the raster.  Other
> blocks seem to be just fine.
> 
> Test raster posted here:
> 
>   ftp://ftp.fsl.orst.edu/pub/gregorym/gdal/ai_bug.7z (1MB)
> 
> From my testing, <= 2.0 is OK, >= 2.1 is affected.  Tested on Windows 10
> 64-bit.

Matt

Thanks for the report. I've fixed the issue per 
https://trac.osgeo.org/gdal/ticket/6886

AIG relies on rollover on addition of big negative values, which is undefined behaviour in C. 
Interesting...

Can the test dataset be integrated in the GDAL test suite ? (probably in http://
download.osgeo.org/gdal/data/aig/ )

Even


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