gcc<10 on M1 Mac

[VACCARI FRANCO]

I’ve a temporary access to a new MacBook Air with M1 processor, to test on that Mac all our home made programs, mainly fortran. All external packages needed by our workflow were successfully installed (gnuplot, ImageMagick, gmt4 and many others), and I installed gcc11. 

Such modern compiler complains about some features in our code that are no longer supported, and fails to produce the executable. Of course one day we should update that code, but for the time being, and having to give back that Mac, I wanted to try with an older compiler. I installed gcc10 but that didn’t help.

I know that gcc8 works with our codes, so I tried to install that but failed.

The problem is that gcc8 requires libcc9, and that is marked as incompatible.

% sudo port install gcc8
--->  Computing dependencies for gcc8
The following dependencies will be installed: 
 libgcc8
 libgcc9
Continue? [Y/n]: 
--->  Fetching archive for libgcc9
--->  Attempting to fetch libgcc9-9.4.0_0.darwin_20.arm64.tbz2 from https://fra.de.packages.macports.org/libgcc9
--->  Attempting to fetch libgcc9-9.4.0_0.darwin_20.arm64.tbz2 from http://fco.it.packages.macports.org/libgcc9
--->  Attempting to fetch libgcc9-9.4.0_0.darwin_20.arm64.tbz2 from https://packages.macports.org/libgcc9
--->  Fetching distfiles for libgcc9
Error: gcc9 9.4.0 is not supported on Darwin 20 arm
Error: Failed to fetch libgcc9: incompatible OS X version
Error: See /opt/local/var/macports/logs/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_lang_gcc9/libgcc9/main.log for details.
Error: Follow https://guide.macports.org/#project.tickets if you believe there
is a bug.
Error: Processing of port gcc8 failed
locadmin at eAir ~ %

Actually any version from 5 to 9 requires libcc9

sudo port install gcc5
--->  Computing dependencies for gcc5
The following dependencies will be installed: 
 isl18
 libgcc6
 libgcc7
 libgcc8
 libgcc9
Continue? [Y/n]:

and therefore fails to install. 

gcc49 is a different story, as it’s clearly declared unsupported for Xcode 9 or greater:

sudo port install gcc49
Password:
--->  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_macports_release_tarballs_ports_lang_gcc49/gcc49/main.log for details.
Error: Follow https://guide.macports.org/#project.tickets if you believe there
is a bug.
Error: Processing of port gcc49 failed

Is it really so that gcc9 and earlier will never be compatible with M1 Macs? And why libgcc9 is needed by gcc5?

Thanks

Franco