[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  |
--------------------------+----------------------

Comment (by jeremyhu):

 Replying to [comment:20 RJVB]:
 > Replying to [comment:18 jeremyhu]:
 >
 > > 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.
 >
 > I was counting on the ports to be mostly similar, I also hope my changes
 can land at about the same time in both ports. Users interested in testing
 libc++ support should be able to do so with a release compiler.
 >
 > > How do you intend to handle conflicts between gcc7 and gcc8-provided
 libgcc in your variant scheme?
 >
 > There shouldn't be any more conflicts than there are currently.
 Certainly not between the gcc7-provided libgcc and the gcc8-provided
 libgcc-devel as those ports conflict.

 As I see it, there are more conflicts than before:

 libgcc-devel now conflicts with gcc7+with_libgcc for instance.
 gcc8+with_libgcc is conflicting with gcc+with_libgcc ... etc.

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Ticket URL: <https://trac.macports.org/ticket/54773#comment:21>
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