2008.12.18 04:56 "[Tiff] tiffvers.h - TIFFLIB_RELEASE macro addition", by Frank Warmerdam

Folks,

In ancient times, the only version information available to applications building against libtiff was:

Circa 2000 or so I added:

This define can be used in code that requires
compilation-related definitions specific to a
version or versions of the library. Runtime
version checking should be done based on the
string returned by TIFFGetVersion.

*/
#define TIFFLIB_VERSION 20081217

in tiffvers.h. This is the date of release.

However, as we split the 3.9 and 4.0 branches a "time stamp" no longer clearly defines the libtiff version well. So I propose to add:

This define contains the library version number encode as
two digits each for major, minor and point. So, for instance,
3.9.8 would be 030908. This define was only introduced in libtiff4.

*/
#define TIFFLIB_RELEASE 040000

This macro should make it easy to do checks on features from different versions of libtiff. An example (whether TIFFUnsetField() is available) is demonstrated here:

#if TIFFLIB_VERSION >= 20081217 \
     && defined(TIFFLIB_RELEASE) && TIFFLIB_RELEASE >= 040000
         TIFFUnsetField( poGDS->hTIFF, TIFFTAG_COLORMAP );
#else
         CPLDebug( "GTiff",
                   "TIFFUnsetField() not supported, colormap may not be
cleared." );
#endif

Does the addition of TIFFLIB_RELEASE seem ok to folks? Any suggestions or caveats? Hmm, I just discovered that tiffvers.h is autogenerated by "make release" in the main libtiff makefile. Does anyone know why such a mechanism is used? It seems like it might be rather involved to cause it to generate the TIFFLIB_VERSION macro. I'm inclined to revert this to a manual process described in HOWTO-RELEASE unless someone sees a reason for it to be as complicated as it is now.

Best regards,

--
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I set the clouds in motion - turn up | Frank Warmerdam, warmerdam@pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam

and watch the world go round - Rush | Geospatial Programmer for Rent