[MacPorts] #44129: cmake: fix build against libc++ on Lion

[MacPorts]

#44129: cmake: fix build against libc++ on Lion
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  Reporter:  mojca@…  |      Owner:  michaelld@…
      Type:  defect   |     Status:  new
  Priority:  Normal   |  Milestone:
 Component:  ports    |    Version:
Resolution:           |   Keywords:  lion
      Port:  cmake    |
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Comment (by michaelld@…):

 Does this summary make sense to folks?

 Reading through the Portfile for libcxx (and libcxxabi), I see that it
 builds without forcing (via +replacemnt_libcxx) on 10.5 and 10.6 only; one
 has to force it on 10.7+; this means that on 10.7+ by default, we get
 whatever libc++ is provided by Xcode. I just tested Mojca's C++ stream
 code on 10.8 (Xcode 5.1.1, Clang 503.0.40), and it is OK -- which fits
 with the "blacklist" above too (do not use clang < 500). So, if folks are
 up to date on 10.8, then they should be OK. I don't know what Xcode is
 provided on 10.7, but it sounds like even the most recent not be recent
 enough to provide a usable libc++. But, if clang/llvm (per libcxx[abi])
 uses the built-in libc++ as provided by Xcode, then it seems like we have
 an issue: even blacklisting (clang < 500) && (mp-clang < 3.3) won't do the
 trick because the libc++ is broken to begin with. What they need is an
 updated libc++, via the "libcxx +replacemnt_lbcxx" port / variant.

 I really can't test out this hypothesis, since I don't have access to a
 10.7- box (I have 10.8 and 10.10 boxes).

-- 
Ticket URL: <https://trac.macports.org/ticket/44129#comment:18>
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