[MacPorts] #57578: __has_feature(cxx_exceptions) returns true but fails to compile std::uncaught_exceptions()

[MacPorts]

#57578: __has_feature(cxx_exceptions) returns true but fails to compile
std::uncaught_exceptions()
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  Reporter:  noloader   |      Owner:  jeremyhu
      Type:  defect     |     Status:  assigned
  Priority:  Normal     |  Milestone:
 Component:  ports      |    Version:
Resolution:             |   Keywords:
      Port:  clang-6.0  |
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Comment (by jmroot):

 You're asking whether the car has brakes and expecting an answer of yes to
 mean it has ABS. IOW, this feature test macro does not test for the
 feature you think it does.

 I don't see any mention of `__has_feature` on the page you linked, but
 according to it, it looks like `__cpp_lib_uncaught_exceptions` is what you
 should be checking.

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Ticket URL: <https://trac.macports.org/ticket/57578#comment:8>
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