[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:  assigned
  Priority:  Normal                  |  Milestone:
 Component:  ports                   |    Version:
Resolution:                          |   Keywords:
      Port:  libcxx macports-libcxx  |
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Comment (by kencu):

 Two-level namespace won't differentiate between the libc++ dylibs.

 If we run into trouble with this issue (not clear that we will, but we
 might) the only thing I know of that could work is to force everything to
 use one libc++.dylib (the new one) by setting DYLD_LIBRARY_PATH to the new
 libc++.dylib.

 The legacysupport 1.1 PG does that now by generating a wrapper for
 software linked against libstdc++.dylib that shows this problem. Check out
 the cmake wrappers used on Leopard or Tiger for an example.

 If we run into this issue  then we could do a wrapper like that for the
 new libc++.dylib too. To a large extent, though, it has to be low-
 maintenance or no-maintenace, and as transparent as possible to current
 devs with the current systems, otherwise it will collapse as unsustainable
 for the main MacPorts repo.

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Ticket URL: <https://trac.macports.org/ticket/62426#comment:22>
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