[MacPorts] #56326: rev-upgrade considers gcc as broken due to libstdc++

[MacPorts]

#56326: rev-upgrade considers gcc as broken due to libstdc++
---------------------+--------------------
  Reporter:  raimue  |      Owner:  (none)
      Type:  defect  |     Status:  new
  Priority:  Normal  |  Milestone:
 Component:  base    |    Version:  2.4.99
Resolution:          |   Keywords:
      Port:          |
---------------------+--------------------

Comment (by neverpanic):

 pgAdmin3 is considered broken because of
 {{{
 Could not open /opt/local/lib/libreadline.6.dylib: Error opening or
 reading file (referenced from
 /Applications/MacPorts/pgAdmin3.app/Contents/SharedSupport/psql)
 }}}
 It seems it should have been revbumped for the readline update.

 gcc6 and gcc7 seem to be considered broken because the discovered value
 for the c++ stdlib used by the port does not match your global
 configuration (which defaults to libc++). Of course that's a false
 positive for these ports. There is an override to deal with this, but the
 override requires information from the Portfile to be set. This only works
 when installing the port freshly, but does not work when rev-upgrade
 initially determines the c++ stdlib usage of a port, which is why this
 code path assumes a false value for cxx_stdlib_overridden, which then
 causes this problem.

 This should not occur when compiling GCC from source, and it should also
 not occur when installing from a prebuilt package, but only if the
 prebuilt package was compiled with a version of MacPorts that supports
 setting this flag (which of course our buildbots are currently not running
 yet).

 This is not ideal. Maybe jmr has an idea how to solve this?

-- 
Ticket URL: <https://trac.macports.org/ticket/56326#comment:1>
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