Clang Error Raised When Compiling Using AVR-GCC on Mac OS - clang

Question

I am trying to cross compile a program for an AVR using avr-gcc that I installed through macports. In the terminal:
avr-gcc -O1 -DF_CPU=1000000UL -DBAUD=9600 -I. -I/opt/local/avr/include/ -Wl,-Map,main.map -mmcu=atmega328p main.c -c
which results in the errors:
clang: error: unknown argument: '-mgcc-isr'
clang: error: unknown argument: '-mno-skip-bug'
The above cross compile used to work but after updating to Catalina and reinstalling avr-gcc something has gotten messed up. Searching google I have found that, with newer versions of Clang, if Clang doesn't recognize the command line argument then it raises an error. The suggestions said to use something like -Wno-error=gcc-isr. So my command becomes:
avr-gcc -O1 -Wno-error=gcc-isr -DF_CPU=1000000UL -DBAUD=9600 -I. -I/opt/local/avr/include/ -Wl,-Map,main.map -mmcu=atmega328p main.c -c
which results in:
cc1: error: ‘-Werror=gcc-isr’: no option -Wgcc-isr
It looks like something is getting messed up between Clang and avr-gcc. Although I'm not sure why Clang gets called when I am using avr-gcc. Does anyone have any idea what's going on here?

Answer 1

Ok, I'm not sure why clang gets called with avr-gcc but I did manage to get the code to compile by uninstalling: (1) avr-gcc and (2) avr-binutils through macports using:
sudo port uninstall avr-binutils
sudo port uninstall avr-libc (I uninstalled this because it depends on avr-gcc)
sudo port uninstall avr-gcc
then I reinstalled it using
sudo port install avr-gcc
which asked if I wanted install avr-binutils. I then reinstalled avr-libc. These are the direct steps. I made a mistake by hitting 'N' when it asked me if I wanted to install avr-binutils. So I had add:
sudo port clean avr-binutils
to clear that error. Once that was cleared I could follow the above steps. Again, this cleared the error by just reinstalling the cross compiling software but I still think there is some underlying misunderstanding of the original problem.

Answer 2

I ran into the same issue while I was trying to compile a keyboard firmware that runs on an atmega32 microcontroller and I had to rebuild avr-gcc locally to fix things.
While the accepted solution did not work for me - I got the same error again
clang: error: unknown argument: '-mgcc-isr'
clang: error: unknown argument: '-mno-skip-bug'
What did work for me was to first uninstall avr-binutils and avr-gcc like so
brew uninstall --ignore-dependencies avr-binutils
brew uninstall --ignore-dependencoes avr-gcc#9
and then reinstall avr-binutils
brew install avr-binutils
Instead of simply reinstalling avr-gcc, install from source like so
brew install --build-from-source avr-gcc#9