[MacPorts] #62426: libc++: using a newer libc++ to build software on older macos systems

[MacPorts]

#62426: libc++: using a newer libc++ to build software on older macos systems
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  Reporter:  kencu                   |      Owner:  kencu
      Type:  enhancement             |     Status:  closed
  Priority:  Normal                  |  Milestone:
 Component:  ports                   |    Version:
Resolution:  fixed                   |   Keywords:
      Port:  libcxx macports-libcxx  |
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Comment (by RJVB):

 Right, so putting `std::filesystem` in there would not be, erm,
 upstreamable ;)

 I checked the effect of setting the `current version` to something
 definitely newer than I have on my system (900.99.1 instead of 9.0.1). It
 seems dyld ignores this information for libc++; building an app against
 that self-proclaimed newer version and then activating an older
 port:libcxx version does not cripple the app. There is also no impact on
 the effect of using `DYLD_INSERT_LIBRARIES`. Really weird.

 Though I can imagine Apple did this on purpose. Otherwise it would
 probably be impossible to target earlier OS versions when building
 software (libc++ not being included in the platform SDK, AFAIK).

-- 
Ticket URL: <https://trac.macports.org/ticket/62426#comment:77>
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