[MacPorts] #55413: Uninstalling a selected port leaves broken symlinks (was: Gcc49 not available any longer: silent bug with select)

[MacPorts]

#55413: Uninstalling a selected port leaves broken symlinks
-----------------------+--------------------
  Reporter:  lucbouge  |      Owner:
      Type:  defect    |     Status:  new
  Priority:  Normal    |  Milestone:
 Component:  base      |    Version:  2.4.2
Resolution:            |   Keywords:  select
      Port:            |
-----------------------+--------------------
Changes (by ryandesign):

 * component:  ports => base
 * port:  gcc49 =>


Comment:

 `sudo port select gcc mp-gcc49` should still work fine. Not sure why it
 stopped working on your system.

 {{{
 $ sudo port select gcc mp-gcc49
 Selecting 'mp-gcc49' for 'gcc' succeeded. 'mp-gcc49' is now active.
 $ ls -l /opt/local/bin/g++
 lrwxr-xr-x  1 root  wheel  25 Nov 26 07:17 /opt/local/bin/g++ ->
 /opt/local/bin/g++-mp-4.9
 $ g++ --version
 g++ (MacPorts gcc49 4.9.4_2+universal) 4.9.4
 Copyright (C) 2015 Free Software Foundation, Inc.
 This is free software; see the source for copying conditions.  There is NO
 warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR
 PURPOSE.
 }}}

 But note that gcc49 is obsolete and is not supported on macOS High Sierra
 or later. Consider using a newer version, such as gcc5, gcc6, or the
 current stable version, gcc7.

 Or perhaps that was the problem: Perhaps you have already upgraded to High
 Sierra and were for that reason unable to reinstall gcc49 after upgrading
 the OS, leaving your /opt/local/bin/g++ etc. symlinks broken.

 I was surprised I couldn't find an existing ticket about that, though I've
 thought of the problem often. It would be great if MacPorts would either
 automatically "unselect" a port if you uninstall a port that is
 "selected", or else prevent the uninstallation of a port until the user
 manually "unselects" it, but currently neither of those occurs, and it is
 possible to uninstall a selected port, resulting in dangling symlinks.

--
Ticket URL: <https://trac.macports.org/ticket/55413#comment:1>
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