[MacPorts] #57576: llvm 8+ usability

[MacPorts]

#57576: llvm 8+ usability
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  Reporter:  RJVB         |      Owner:  (none)
      Type:  enhancement  |     Status:  new
  Priority:  Normal       |  Milestone:
 Component:  ports        |    Version:
Resolution:               |   Keywords:
      Port:  llvm-devel   |
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Comment (by RJVB):

 Well, that would depend on the older system, and how you use the port.
 Systems that came with libc++ would be concerned but only if you actually
 build against the libc++ 8 headers. I don't think even clang 8+ would do
 that (on Mac) unless instructed to do so explicitly. I think each clang
 version does use its own C++ headers on Linux, so I'll kick some tyres
 there to see what happens.

 On even older systems that didn't come with libc++ the system libraries
 were built against libstdc++, and we have to assume those will continue to
 work with userland libraries built against libc++ 8+. It's on these
 systems that problems may arise if you don't rebuild each and every port
 that depends on port:libcxx

 I have my own port:libcxx version which is already at 8.0.0, and I
 actually use DYLD_INSERT_LIBRARIES to load the new libc++ instead of the
 system runtime, and that works fine (but I built libc++ with clang 5 or
 clang 6).

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Ticket URL: <https://trac.macports.org/ticket/57576#comment:5>
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