[MacPorts] #58930: gcc 8.3.0_4 with _XOPEN_SOURCE=500 breaks with #include <complex>

[MacPorts]

#58930: gcc 8.3.0_4 with _XOPEN_SOURCE=500 breaks with #include <complex>
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  Reporter:  bernstei  |      Owner:  (none)
      Type:  defect    |     Status:  new
  Priority:  Normal    |  Milestone:
 Component:  ports     |    Version:
Resolution:            |   Keywords:
      Port:  gcc8      |
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Comment (by jmroot):

 It's correct that `ENOTRECOVERABLE` and `EOWNERDEAD` are not defined with
 `_XOPEN_SOURCE=500`. The issue is that error_constants.h is still
 referencing them in that case. It wraps the references in checks like
 `#ifdef _GLIBCXX_HAVE_EOWNERDEAD` but I guess those may be determined
 statically at build time or at least not change based on the current
 `__DARWIN_C_LEVEL` like the system headers do.

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Ticket URL: <https://trac.macports.org/ticket/58930#comment:3>
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