Hello Even,
My apologies for the late reply.
I took the quick and not-so-dirty way : gdal is repackaged in the OTB
ppas, where I have applied the last strategy you mention : I let the
warning about libtiff version mismatch be emitted, but still register
the driver.
Everything is back to normal with this, and the patch is not very intrusive.
Hopefully this will be only temporary, waiting for this "versioned
symbols" solution from the Debian folks, and I will be able to throw
away our specific gdal package soon.
Thanks,
Julien
Le 11/05/2011 20:03, Even Rouault a écrit :
Le mercredi 11 mai 2011 18:51:07, Julien Malik a écrit :
Hello list,
I had a bad surprise today using the new gdal 1.8 package available in
ubuntugis-unstable :
When linked both to tiff v3 and gdal 1.8, the GTIFF driver is disabled
with a warning appearing like :
WARNING ! libtiff version mismatch : You're linking against libtiff
3.X but GDAL has been compiled against libtiff>= 4.0.0
I understand from frmts/gtiff/geotiff.cpp that this is voluntary (though
the warning does not say it actually disables the GTiff driver).
I'm a bit frustrated... I put this check to avoid bug reports actually ;-) Too
many people get hurt because of a version mismatch and have a hard tried
figuring what goes wrong.
In my case (building the Orfeo Toolbox library, which has a dependency
needing TIFF and GeoTiff, but not gdal), it has the undesirable
consequence of breaking TIFF support for our ubuntu packages based on
the ubuntugis-unstable ppa
(https://launchpad.net/~otb/+archive/orfeotoolbox-nightly and
https://launchpad.net/~otb/+archive/orfeotoolbox-stable-ubuntugis).
The issue has already been discussed on this list, but just to recall :
we had a solution providing usable executables with TIFF support, even
though they were linked to the system libtiff and libgeotiff (it
involved ensuring the proper link order between '-lgdal' and '-lgeotiff').
That's why I think disabling the driver completely is a little hard.
In my case it represents a major regression, and I don't have a lot of
ideas to work around it...
Is it possible to *not* disable the driver, and keep the warning ?
If your question is "without changing the code ?", the answer is no.
If Debian/Ubuntu goes into the way of using versionned symbols, they can just
apply a local trivial patch to disable this check. My rationale is that people
that want to mix both libtiff 3 and libtiff 4 are considered to be sufficient
advanced users to make patches to undo the sanity checks if they really know
what they are doing. IMHO, the default should be to stick to safe settings.
But perhaps I did go too far and I'm open to suggestions. Changing the
behaviour of this check is trivial. The difficult part is to figure out the
expected behaviour and I just don't know what would be the option that would
satisfy most/all people. One possibility would be to disable the driver unless
an environment variable GDAL_ACCEPT_MIXED_LIBTIFF_VERSIONS is defined ?? But
that seems to a bit too convoluted. Or just emit the warning and still enables
the driver, considering that the warning is enough and that if people get
crashes, they would know why. I'm interested by opinion from other people.
Best regards,
Even
Regards,
Julien
NB: I filed a ticket in our bug tracker
(http://bugs.orfeo-toolbox.org/view.php?id=296), feel free to leave
comments there.
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