[MacPorts] #54773: port:libgcc/port:gcc7: proposed modifications, efficiency + libc++ support

[MacPorts]

#54773: port:libgcc/port:gcc7: proposed modifications, efficiency + libc++ support
--------------------------+----------------------
  Reporter:  RJVB         |      Owner:
      Type:  enhancement  |     Status:  new
  Priority:  Normal       |  Milestone:
 Component:  ports        |    Version:
Resolution:               |   Keywords:  haspatch
      Port:  gcc7 libgcc  |
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Comment (by jeremyhu):

 Replying to [comment:17 RJVB]:
 > Is it still possible to target 10.5 or 10.4 from, say, 10.9?

 Yes, quite possible.

 > I presume you'd need the corresponding SDKs, can you just copy them
 over?

 No, you can use the current SDK to target older OS versions.  The SDKs
 contain availability annotation such that functionality that is newer than
 the deployment target is weakly linked instead of strongly linked.

 > I'm going to prepare updated patches. They'll look even more complex
 because I've been moving more things around in an effort to improve
 maintainability and upgrading.
 >
 > I'll start giving port:gcc8 the same makeover but I can't promise I'll
 be doing a lot of testing with a beta compiler. I have no idea what new
 amazing features gcc8 introduces but unless there's something we never
 knew we wanted in there I would expect the gcc7 audience to be larger and
 just as entitled to improvements as those living on the bleeding edge.

 gcc7 should really only get changes after they've landed in gcc8.  Just do
 your testing against the gcc7 port and then apply the diff to gcc8.
 They're basically identical.

 How do you intend to handle conflicts between gcc7 and gcc8-provided
 libgcc in your variant scheme?

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Ticket URL: <https://trac.macports.org/ticket/54773#comment:18>
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