[MacPorts] #58260: gcc{6, 7, 8, 9} : Build failures due to "Atomic" error with macOS 10.4.4 and Xcode 10.2

[MacPorts]

#58260: gcc{6,7,8,9} : Build failures due to "Atomic" error with macOS 10.4.4 and
Xcode 10.2
-------------------------------------+-------------------------------------
  Reporter:  physicsbeany            |      Owner:  Nullstelllensatz
                                     |  <50169837+Nullstelllensatz@…>
      Type:  defect                  |     Status:  closed
  Priority:  Normal                  |  Milestone:
 Component:  ports                   |    Version:  2.5.4
Resolution:  fixed                   |   Keywords:  mojave
      Port:  gcc9 gcc8 gcc7 gcc6     |
  libgcc-devel libgcc8 libgcc7       |
  libgcc6                            |
-------------------------------------+-------------------------------------

Comment (by jmon12):

 Replying to [comment:28 cjones051073]:
 > To be honest, I never considered the possibility to not have Xcode
 installed.
 >
 > Maybe it would work to just remove the version test. This would have to
 be tested though.
 >
 > Any reason you are installing from source, and not using the prebuilt
 binaries ? Do this, without Xcode installed, is probably not very well
 tested ground.

 I need to build gcc from source because of the issues in ticket #57937
 (see my comments).
 Summed up: the prebuilt gcc ports don't add `/` to the sysroot anymore
 (only xcode specific ones), which was forcing me to always run gcc with
 the `--sysroot=/ -Wl,-syslibroot,/` options.

 Removing the `xcodeversion` check, I could indeed build gcc5 with the
 (default) `/` sysroot, and it solved my problem.

 I think the check for the gcc ports should be done against a variable
 containing the SDK version, not the xcode version. It would solve my
 problem and is anyway more specific to the actual problem with the new
 headers if I'm not mistaking.

 From a debug configuration of the gcc5 port:

 {{{
 DEBUG: Xcode none
 DEBUG: SDK 10.14
 }}}

 As expected, Xcode variable is not populated, but the SDK one is.
 I will continue my exploration of the macports internals for finding the
 corresponding variable and provide a suggestion of a simple patch fixing
 the if-clause here.
 Do you have any obvious objection?

 PS: sorry for my late answer! I thought I would receive some kind of email
 notification and didn't see your comment.

-- 
Ticket URL: <https://trac.macports.org/ticket/58260#comment:29>
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