[MacPorts] #53201: cmake, "compile features" and macports-clang

[MacPorts]

#53201: cmake, "compile features" and macports-clang
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  Reporter:  RJVB    |      Owner:
      Type:  defect  |     Status:  new
  Priority:  Normal  |  Milestone:
 Component:  ports   |    Version:
Resolution:          |   Keywords:
      Port:  cmake   |
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Comment (by RJVB):

 Hah, that's you and Qt's Thiago who agree that CMake should be doing
 something about this, and as I expected the consensus among the CMake devs
 (in the form of a single person) is that there is no bug, projects just
 have to do the right thing, know all the little details on all platforms
 where they might be deployed, etc.

 Evidently I would have made either the minimum version configurable, or
 else the whole init.cache thing optional. But that point is moot: it seems
 one cannot select a minimum version that way.

 So I'll stick to setting `-DCMAKE_POLICY_DEFAULT_CMP0025=NEW` in
 `configure.pre_args`. That is something that can be undone with the usual
 methods, but a priori it only has the effect that cmake will accept any
 clang compiler on Mac, not just one identifying as AppleClang. That seems
 a behaviour we want anyway.

 If we agree on that we can also just remove the policy 25 checks in
 Clang-C.cmake and Clang-CXX.cmake. The effect of that will be that OS X is
 not treated any different than standard Unix (rather, anything not Win32)
 in that no more difference will be made between Apple clang, macports-
 clang or any other home brewn clang ;)

 >  If you've done that already, please provide a link to the bug report.

 I can't: bugs are reported on their mailing list, and I'm not yet seeing
 an archived version. The discussion thread subject is `COMPILE_FEATURES,
 Mac and non-Apple clang versions`.

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Ticket URL: <https://trac.macports.org/ticket/53201#comment:6>
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