[PROJ] PROJ 9.0.0RC1 & PROJ-data 1.9RC1

[Sebastiaan Couwenberg]

On 2/16/22 09:35, Kristian Evers via PROJ wrote:
> Bas, I'm not sure how to understand this.
> 
>> So you go from (8.2.1):
>>
>>    /usr/lib/x86_64-linux-gnu/libproj.so -> libproj.so.22.2.1
>>    /usr/lib/x86_64-linux-gnu/libproj.so.22 -> libproj.so.22.2.1
>>    /usr/lib/x86_64-linux-gnu/libproj.so.22.2.1
>>
>> To (9.0.0):
>>
>>    /usr/lib/x86_64-linux-gnu/libproj.so -> libproj.so.9.0.0
>>    /usr/lib/x86_64-linux-gnu/libproj.so.25 -> libproj.so.9.0.0
>>    /usr/lib/x86_64-linux-gnu/libproj.so.9.0.0
>>
> 
> Are you suggesting that we ONLY use the major, minor and patch version
> numbers for the so-files and forget about the SOVERSION from now on?

No, SOVERSION is essential as it is part of the SONAME:

  <NAME>.so.<SOVERSION>

Where <NAME> = libproj, and <SOVERSION> = 25

> If that is the case, personally I'm all for it since I've always found the
> current/revision/age difficult (as is evident in several release candidates
> in the past) but is that a common practice among project that base their
> packages on CMake?

autotools determines the versions (both 22 and 22.2.1 in the above 
examples for 8.2.1 with version-info 24:1:2) based on the version-info.

SOVERSION (the 22 in libproj.so.22) is determined by CURRENT minus AGE, 
the filename version (22.2.1 in libproj.so.22.2.1) is determined by 
(CURRENT-AGE).AGE.REVISION or some other magic.

The SOVERSION cannot be decremented and must be incremented every 
release that breaks the ABI. This was 22 in 8.2.1, is currently 25 in 
9.0.0-rc1, and could also be 23 in 9.0.0-rc2.

You configure this in CMake with:

   set_target_properties(proj
     PROPERTIES
     VERSION <X>.<Y>.<Z>
     SOVERSION <N>
   )

This creates the files:

  libproj.so             (symlink to libproj.so.<X>.<Y>.<Z>)
  libproj.so.<N>         (symlink to libproj.so.<X>.<Y>.<Z>)
  libproj.so.<X>.<Y>.<Z>

Now that autotools and libtool are no longer used, you don't have to use 
the complicated logic to determine the VERSION value (<X>.<Y>.<Z>).

For projects that start with CMake and only support that it's common to 
use the project major version for the SOVERSION value and full project 
version for VERSION value.

That cannot be used for PROJ as it is migrating away from autotools and 
cannot decrement the SOVERSION to 9.

This situation is similar to what MapServer did some time ago, that 
currently uses:

   set_target_properties(mapserver
     PROPERTIES
     VERSION ${MapServer_VERSION_STRING}
     SOVERSION 2
   )

This is what I also suggest for PROJ to make library versioning easier 
now that the libtool complications are gone.

Since code speaks louder than words, see the attached patch for an 
example of what I mean.

Kind Regards,

Bas

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