update

[James]

I believe 'if it aint broke, don't fix it'. 
After installing QT6, which works, I was nagged to selfupdate which failed. Can anyone hep me to understand, thanks.

...
checking for xcode-select... /usr/bin/xcode-select
checking macOS version... 12.4
checking Xcode location... /Applications/Xcode.app/Contents/Developer
checking Xcode version... 13.4.1
checking whether the C compiler works... no
configure: error: in `/opt/local/var/macports/sources/rsync.macports.org/macports/release/tarballs/base':
configure: error: C compiler cannot create executables
See `config.log' for more details
Command failed: CC=/usr/bin/cc SDKROOT=/Library/Developer/CommandLineTools/SDKs/MacOSX12.0.sdk ./configure --prefix=/opt/local --with-install-user=root --with-install-group=wheel --with-directory-mode=0755 --enable-readline && SDKROOT=/Library/Developer/CommandLineTools/SDKs/MacOSX12.0.sdk make SELFUPDATING=1 && make install SELFUPDATING=1
Exit code: 77
Error: Error installing new MacPorts base: command execution failed
...

I can also compile an arbituary program which does work!
[plasma] /Users/jam [511]% /usr/bin/cc fiforead.c
[plasma] /Users/jam [512]%

James