Updated ubuntu image; added note for Apple Silicon users, xvfb dependency for GUI

[jasonhemann]

Dockerfile.base-image

• Switching to the 22.04 LTS base image
• adding xvfb for GUI programs

Makefile

• added a clean target

lib-grade.rkt

• caught a possible div-by-zero exception in tests.

[bennytheshap]

@jasonhemann apologies if this is the wrong place to ask, but not sure where would be better: Is there a specific docker or docker-like runtime that you recommend that people use when on ARM-based Macs?

Nothing to do with Racket, but I've been running into issues with xvfb, gradescope, and docker on my machine, and wondered if it could be because I'm using containerd instead of the official Docker Desktop product.

When I try to run code that needs to interact with X11 (xvfb), I get -- of all things -- LLVM errors (LLVM ERROR: 64-bit code requested on a subtarget that doesn't support it). Googling around suggests this is caused by quirks of some virtualization/containerization environments, so I wondered if there was a standard setup the Racket team uses that works well.

If so, you may want to mention that in your docs (apologies if I missed it), and I'd sure like to know what it is too.

Note: My container is already fully amd64, so it's not because I am mixing arm64 and amd64 in the same container or something like that.

[jasonhemann]

@bennytheshap Ooh, interesting and unfortunate. I've not run across that.

I'm using whatever version of docker I get w/ brew install --cask docker-desktop, IIRC.

I couldn't say WRT that error, but can you reproduce it running your container locally, w/something other than the gradescope base image? That'd be valuable info if you can exclude the architecture rosetta, gradescope, and their containerization environment, and containerd even from the problem description, on even a hello GUI world example.

[bennytheshap]

I'm using whatever version of docker I get w/ brew install --cask docker-desktop, IIRC.

This no longer exists. Could you be using orka-desktop?

[bennytheshap]

Just tried this with Docker Desktop (so annoying how they've changed their license terms and UI) and it now works correctly!