TIFF Reading Problems / libpdf / multiple copies of libtiff.

[Frank Warmerdam]

Folks,

A few days ago the First Base Solutions guys mentioned some problems
serving WMS layers from GeoTIFF via MapServer.  Since they are just 10 minutes
drive away, I went over and figured out what was going wrong.  It turns out
the problem was that libpdf.a include a whole copy of a slightly outdated
copy of libtiff.

The result was that some TIFF functions ended up coming from the GDAL TIFF
code, and others came from the libpdf.a.  But, since they used different
versions of the TIFF structures things ended up crashing.

So the lesson is, be very wary of getting multiple versions of sub-libraries
(like libtiff, libpng, libgif, libz) linked into your Mapserver application.
I was quite surprised to discover that libpdf included a copy of libtiff
code!  And these sorts of problems are just devilishly hard to debug.

Best regards,
--
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | Geospatial Programmer for Rent