[MacPorts] #44125: cmake needs to support building against / with a deployment target set (prevents libc++ support on Snow Leopard for cmake projects)

[MacPorts]

#44125: cmake needs to support building against / with a deployment target set
(prevents libc++ support on Snow Leopard for cmake projects)
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  Reporter:  mojca@…       |      Owner:  macports-tickets@…
      Type:  defect        |     Status:  reopened
  Priority:  Normal        |  Milestone:
 Component:  ports         |    Version:
Resolution:                |   Keywords:
      Port:  cmake libcxx  |
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Comment (by mojca@…):

 Seeing how many times things have changed and given that every change
 affects a different scenario, I think these issues with CMake deserve a
 "serious" test suite to avoid constant problems when introducing further
 changes.

 See also #41783 which is related to this change. If that ticket gets
 implemented, we would really need to install libc++ to a different place.

 I cannot comment on the patch because I don't fully understand it, but I
 would prefer to see some discussion with the upstream CMake developers if
 possible, so that we don't start diverging from their code too much.

 CMake serves both for installing ports for MacPorts as well as a
 standalone utility that users can use for external projects. If we diverge
 from the original too much just for the sake of smoother installation of
 other MacPorts software, that might influence regular CMake users. So we
 should fix this with coordination with upstream.

 I agree that it's totally weird that CMake requires setting both SDK and
 target version at the same time. (On the other hand I understand that
 setting target to 10.6 on 10.7 without specifying the SDK might render the
 resulting binary useless on 10.6. So CMake tries to be over-protective to
 its users. But it's pointless to require setting the SDK when building for
 the same/default target. But then again CMake's search algorithm for
 libraries and headers in FindFoo.cmake is totally weird, non-configurable
 etc. And setting the SDK explicitly probably avoids a couple of problems
 related to CMake's bad design decisions.)

-- 
Ticket URL: <https://trac.macports.org/ticket/44125#comment:14>
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