[MacPorts] #55135: gcc5 @5.5.0 fails to build on Snow Leopard, Mac OS X 10.6.8, because linker command failed with undefined symbols for architecture x86_64

[MacPorts]

#55135: gcc5 @5.5.0 fails to build on Snow Leopard, Mac OS X 10.6.8, because linker
command failed with undefined symbols for architecture x86_64
------------------------+-------------------------
  Reporter:  ballapete  |      Owner:
      Type:  defect     |     Status:  new
  Priority:  Normal     |  Milestone:
 Component:  ports      |    Version:  2.4.2
Resolution:             |   Keywords:  snowleopard
      Port:  gcc5       |
------------------------+-------------------------

Comment (by ballapete):

 Replying to [comment:1 kencu]:
 > Peter, these are the exact errors you see when there is an ABI mismatch
 between standard libs.
 >
 > You recently had an issue on your system where many things were rebuilt
 by gcc. How did that wind up getting resolved?

 I uninstalled all packages built with GCC 6 and re-activated the old
 outdated versions. Then I built `py27-cython` with GCC 5 and installed it.
 This allowed `port` to upgrade or re-install nghttp2 and curl which
 depends on it. On this basis `port` could build `clang-3.9` and
 `llvm-3.9`. Afterwards `port` could upgrade some 40 packages. `Gcc5` is
 the last outdated package. This is the sequence in which the packages were
 built:

 {{{
 2017-10-20 20:36:57
 /opt/local/var/macports/software/py27-cython/py27-cython-0.27.1_0.darwin_10.x86_64.tbz2
 2017-10-20 20:43:55
 /opt/local/var/macports/software/nghttp2/nghttp2-1.24.0_0+python27.darwin_10.x86_64.tbz2
 2017-10-20 21:10:29
 /opt/local/var/macports/software/llvm-3.9/llvm-3.9-3.9.1_5.darwin_10.x86_64.tbz2
 2017-10-20 21:56:43
 /opt/local/var/macports/software/clang-3.9/clang-3.9-3.9.1_7+analyzer+libstdcxx.darwin_10.x86_64.tbz2
 2017-10-20 23:14:26
 /opt/local/var/macports/software/libgcc/libgcc-7.2.0_1.darwin_10.x86_64.tbz2
 2017-10-21 00:15:33
 /opt/local/var/macports/software/llvm-4.0/llvm-4.0-4.0.1_2.darwin_10.x86_64.tbz2
 2017-10-21 01:10:16
 /opt/local/var/macports/software/clang-4.0/clang-4.0-4.0.1_3+analyzer+libstdcxx.darwin_10.x86_64.tbz2
 2017-10-21 01:15:39
 /opt/local/var/macports/software/python36/python36-3.6.3_0.darwin_10.x86_64.tbz2
 }}}

--
Ticket URL: <https://trac.macports.org/ticket/55135#comment:2>
MacPorts <https://www.macports.org/>
Ports system for macOS