[MacPorts] #54766: Does port:clang*'s libstdcxx have to be default?

[MacPorts]

#54766: Does port:clang*'s libstdcxx have to be default?
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  Reporter:  RJVB                 |      Owner:  MarcusCalhoun-Lopez
      Type:  defect               |     Status:  assigned
  Priority:  Normal               |  Milestone:
 Component:  ports                |    Version:
Resolution:                       |   Keywords:
      Port:  clang-4.0 clang-5.0  |
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Comment (by MarcusCalhoun-Lopez):

 I am fine not forcing the installation of GCC with Clang unless absolutely
 necessary.[[BR]]
 There are a few things, however, that I need to look into before making
 the change.
 1. If GCC is **not** installed, does {{{-stdlib=macports-libstdc++}}}
 cause a compile-time error or silently do the wrong thing?
 1. To avoid multiple recompilations of clang, can {{{-stdlib=macports-
 libstdc++}}} now use gcc7 header files?
 1. To avoid multiple recompilations of clang, add
 [https://github.com/macports/macports-
 ports/commit/be6401d19706f7317979dfbd680592cee5f7cf9d xcrun].

 It might be a few days before I can look into these.

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Ticket URL: <https://trac.macports.org/ticket/54766#comment:18>
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