[MacPorts] #44125: cmake: default values of CMAKE_OSX_SYSROOT/DEPLOYMENT_TARGET (prevent linking against libc++)

[MacPorts]

#44125: cmake: default values of CMAKE_OSX_SYSROOT/DEPLOYMENT_TARGET (prevent
linking against libc++)
---------------------------+--------------------------------
  Reporter:  mojca@…       |      Owner:  macports-tickets@…
      Type:  defect        |     Status:  new
  Priority:  Normal        |  Milestone:
 Component:  ports         |    Version:
Resolution:                |   Keywords:
      Port:  cmake libcxx  |
---------------------------+--------------------------------

Comment (by ionic@…):

 `libc++` should be pretty much the only software affected, for one reason:
 it's not shipped or supported by Apple, but has to be prominently
 installed into `/usr/lib`. It's a really rare occasion, as most software
 is bundled within `${prefix}` by MacPorts.

 The other thing is that `/Developer/SDKs/...` is and should remain Apple-
 land only. Installing `libc++` to that place is "dirtying" the SDKs, which
 sounds like a bad idea to me.

 I'd even let the `cmake PortGroup` as-is, with one little change: on 10.6
 (and maybe 10.7? I have never used 10.7, so no idea whether MacPorts
 installed `libc++` into /usr/lib on 10.7 as well or Apple ships it
 themselves, which would alleviate the problem altogether), and if `libc++`
 is explicitly requested/set (the default is libstdc++ anyway), set

 {{{
 -DCMAKE_OSX_SYSROOT="/" \
 -DCMAKE_OSX_DEPLOYMENT_TARGET=""
 }}}

 else keep the current behavior.

-- 
Ticket URL: <https://trac.macports.org/ticket/44125#comment:5>
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