[MacPorts] #55410: gcc7 @7.2.0 does not build on Mac OS X 10.6.8, Snow Leopard, because of "Undefined symbols for architecture x86_64"

[MacPorts]

#55410: gcc7 @7.2.0 does not build on Mac OS X 10.6.8, Snow Leopard, because of
"Undefined symbols for architecture x86_64"
------------------------+--------------------
  Reporter:  ballapete  |      Owner:  (none)
      Type:  defect     |     Status:  new
  Priority:  Normal     |  Milestone:
 Component:  ports      |    Version:  2.4.2
Resolution:             |   Keywords:
      Port:  gcc7       |
------------------------+--------------------

Comment (by kencu):

 I assume you also have 10.6.8 configured with `cxx_stdlib libc++` and the
 default compiler is set to `clang-3.9` in macports.conf.

 If all that is true, I would go into macports.conf, temporarily disable
 the default compiler being clang-3.9 by commenting out that line, build
 gcc7 (which should complete without too much trouble with the standard
 10.6.8 compilers if we are at all lucky) and once it is installed, then
 re-enable the default compiler as `clang-3.9` in macports.conf.

 (I don't see this error, but I have modified my version of clang-3.9 to
 behave as clang behaves on all the newer systems, adding `-stdlib=libc++`
 to the link lines if no standard lib is specified, and I believe that is
 why I don't see it.)

-- 
Ticket URL: <https://trac.macports.org/ticket/55410#comment:8>
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