[gdal-dev] Add capability to safely link against an external libtiff (3.X) and a GDAL build with internal libtiff (4.0) support

[Antonio Valentino]

Hi Even,

Il 03/07/2011 18:01, Even Rouault ha scritto:
> Folks,
> 
> Hopefully this is the solution to a long-standing problem. Below the inline 
> text of http://trac.osgeo.org/gdal/ticket/4144
> 
> """
> Currently it is not safe for an application to link libgdal built with 
> internal libtiff support with system libtiff (3.X), because of the difference of 
> ABI. The same issue could potentially happen with libgeotiff (in 1.9.0dev 
> trunk, it's at v1.3.0, whereas in the wild you mostly find it at v1.2.0).
> 
> The solution implemented consists in :
>     * compiling a libtiff.so/libgeotiff.so,
>     * extracting the symbols from the .so with objdump,
>     * and creating a header file that does #define original_symbol_name 
> gdal_original_symbol_name for each symbol. 
> 
> This process is automated by a dump_symbols.sh scripts in frmts/gtiff/libtiff 
> and frmts/gtiff/libgeotiff that must be run whenever internal libtiff/libgeotiff 
> is updated (and that the version includes new symbols). The generated files are 
> placed in svn to avoid running the script at each build, mainly because the 
> script might only work on Linux. Wouldn't work as it on MacOS. But the end-
> result should be portable.
> 
> Of course, one also must make sure this header file is included at the 
> appropriate places. This mainly consists in including it in the tif_config.h 
> and geo_config.h, but also in the INGR, NITF, JPEG drivers happen to use libtiff 
> symbols, and MrSID for libgeotiff.
> 
> The renaming of the symbols is enabled if --with-rename-internal-libtiff-
> symbols is defined. (--with-rename-internal-libgeotiff-symbols for geotiff).
> 
> This can be combined with the --with-hide-internal-symbols of course so that 
> those gdal_ prefixed symbols are not exported, but this is an orthogonal issue.
> 
> """

congratulations, this was a big headache in some situation.

> This solution is now implemented in trunk. Testing from others appreciated ! 
> Although I've tested various combinations internal/external libtiff/libgeotiff, 
> with/without the new flags, there might still be issues.
> 
> Best regards,
> 
> Even

Do you have some particular indication about how to test it?
Which test programs did you use?


It seems to me that people of the the OTB project had serious problems
with this issue in the past and they have a fantastic test framework.

Maybe we could also ask to them for a little help for testing.


ciao

-- 
Antonio Valentino