[MacPorts] #57415: gcc9 fails to install on High Sierra Xcode10

[MacPorts]

#57415: gcc9 fails to install on High Sierra Xcode10
---------------------+--------------------
 Reporter:  SebKeen  |      Owner:  (none)
     Type:  defect   |     Status:  new
 Priority:  Normal   |  Milestone:
Component:  ports    |    Version:  2.5.4
 Keywords:  hdf5     |       Port:  gcc9
---------------------+--------------------
 Hi,

 I just tried to install a new port, and had to update mac port to version
 2.5.4, and also Xcode to version 10. The port fails to update because of
 dependencies related to gcc49 and message that the compiler is not
 supported for Xcode 9.0 and higher. Thus, I tried to port install gcc9,
 and this again fails because of a dependency on hdf5-18
 @1.8.17+cxx+gcc49+hl.

 Here is the log:

 bash-3.2$ sudo port install gcc9
 --->  Computing dependencies for gcc9
 --->  Cleaning gcc9
 --->  Scanning binaries for linking errors
 --->  Found 9 broken files, matching files to ports
 --->  Found 5 broken ports, determining rebuild order
 You can always run 'port rev-upgrade' again to fix errors.
 The following ports will be rebuilt:
  hdf5-18 @1.8.17+cxx+gcc49+hl
  cdo @1.7.2+szip
  ncview @2.1.1
  wgrib2 @2.0.5
  grads @2.0.2
 Continue? [Y/n]: y
 --->  hdf5-18 is replaced by hdf5
 --->  Fetching distfiles for gcc49
 Error: building gcc49 is not supported with Xcode 9 or greater
 Error: Failed to fetch gcc49: unsupported platform
 Error: See
 /opt/local/var/macports/logs/_opt_local_var_macports_sources_rsync.macports.org_release_tarballs_ports_lang_gcc49/gcc49/main.log
 for details.
 Error: Problem while installing gcc49
 Error: rev-upgrade failed: Error rebuilding hdf5-18
 Error: Follow https://guide.macports.org/#project.tickets to report a bug.

 I hope someone can point in the right direction.

 Noel

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Ticket URL: <https://trac.macports.org/ticket/57415>
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