[MacPorts] #55619: compatibility_version blues

[MacPorts]

#55619: compatibility_version blues
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 Reporter:  RJVB         |      Owner:
     Type:  enhancement  |     Status:  new
 Priority:  Normal       |  Milestone:
Component:  ports        |    Version:
 Keywords:               |       Port:  freetype
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 I noticed that FreeType's autoconf/libtool system sets the dylib
 compatibility_version to the current_version (and both o some meaningless
 value rather than the FT version). When you build with CMake, the
 compatibility_version is set to vMaj.vMin.0 and the current_version to
 vMaj.vMin.vPatch. This is what one could expect if patchlevel releases do
 not introduce ABI incompatibilities that would prevent apps built against
 say 2.8.2 to run with 2.8.0 or 2.8.1 .

 I'm getting these dylib versions:
 - libtool version for 2.7.1 : 20
 - libtool version for 2.8.0 : 21
 - libtool version for 2.8.1 : 22

 I would suggest that 2.8.x builds should set the compatibility version to
 at most 21 so that users can re-activate older Freetype installs after
 they built against the newer version. The easiest (and probably only) way
 to do this is to patch `builds/unix/ltmain.sh` and replace
 `-compatibility_version $minor_current` with `-compatibility_version 21`.

 (In practice it seems even possible to run binaries built against FreeType
 2.8.1 with FreeType 2.7.1 .)

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Ticket URL: <https://trac.macports.org/ticket/55619>
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