The changes in this PR update the following CI tests to use Ubuntu 22.04 instead of 20.04, and they all pass:

• p4c-lint
• test-p4c-debian / test-ubuntu20 (Unity OFF, GTest OFF) (pull_request)
  • Now has a new name: test-p4c-debian / test-ubuntu22 (Unity OFF, GTest OFF) (pull_request)
• test-p4c-debian / test-ubuntu20 (Unity ON, GTest ON) (pull_request)
  • Now has a new name: test-p4c-debian / test-ubuntu22 (Unity ON, GTest ON) (pull_request)
• static-build-test-p4c / Dynamic glibc (pull_request)
• static-build-test-p4c / Dynamic stdlib (pull_request)

Also several mentions of Ubuntu 20.04 in the top level README.md have been updated to 22.04.

See this comment for links to other draft PRs demonstrating that for some other CI tests, it is not as simple as replacing 20.04 with 22.04: #5155 (comment)

Nice! If (when) we drop Ubuntu 20, do we also want to shift the minimal GCC version required from 9.2 to something newer? Ubuntu 22.04 has GCC 11, which would be nice for C++20. Not sure if any downstream targets depend on GCC 9/Ubuntu 20.04 though (Altera does not; Tofino is now open-source so presumably that is one less to worry about).

Also remove the Ubuntu 20 sanitizer check?

Also remove the Ubuntu 20 sanitizer check?

I have done this with commit 10. Weirdly, if you look at commit 10 diffs on this PR, it shows that file as deleted. But for some strange reason when I look at the top-level list of files changed on this PR, it is not mentioned at all. I have never seen this before in a Github PR.

Also remove the Ubuntu 20 sanitizer check?

I have done this with commit 10. Weirdly, if you look at commit 10 diffs on this PR, it shows that file as deleted. But for some strange reason when I look at the top-level list of files changed on this PR, it is not mentioned at all. I have never seen this before in a Github PR.

The change indicates that the file was renamed, so should be ok. I actually do not know how Git figures this out.

Nice! If (when) we drop Ubuntu 20, do we also want to shift the minimal GCC version required from 9.2 to something newer? Ubuntu 22.04 has GCC 11, which would be nice for C++20. Not sure if any downstream targets depend on GCC 9/Ubuntu 20.04 though (Altera does not; Tofino is now open-source so presumably that is one less to worry about).

I am thinking one tiny step at a time right now, which is: avoid our CI tests failing randomly in March, and deterministically in April.

I don't know whether we have "officially" dropped support for Ubuntu 18.04 yet, since there is still an on-demand CI test that builds p4c and probably runs some tests on Ubuntu 18.04 in a Docker container.

I am happy to find out whether there are companies who want Ubuntu 20.04 support for a while longer. If they do, and if they want Ubuntu 20.04 CI tests on this public repo, I would recommend that someone from one of those companies should create a CI test that works after April 1, 2025 on Github.

The change indicates that the file was renamed, so should be ok. I actually do not know how Git figures this out.

heuristics :-(, git has sadly no real way of tracking renames

I am happy to find out whether there are companies who want Ubuntu 20.04 support for a while longer. If they do, and if they want Ubuntu 20.04 CI tests on this public repo, I would recommend that someone from one of those companies should create a CI test that works after April 1, 2025 on Github.

Sadly, I am afraid we have no good way of communicating downstream and many will not track the changes diligently :-(. A good starting point might be community notes on the various working groups and e-mails in them sufficiently before we drop the support. But I think ultimately we should be open to dropping the support for unsupported OSes, otherwise we will eventually freeze the code to the point we are a) having trouble with dependencies b) other downstreams will be annoyed at use being behind. C++17 is now 8 years old :-). But so far we are on the C++17 with the likes of LLVM, so we are not terribly behind :-D.

There are (relatively easy) ways of getting newer GCC on old Ubuntu, but if that is acceptable will depend a lot on the company policies so I am afraid we have no way of knowing unless someone tells us.

This has been updated to latest after #5011 was merged in.

Looks good to me. Please add e.g. an empty commit to trigger static & sanitizers suites (git commit --allow-empty ...).

Before this is merged, we will need to update the "Required" checks for PR passing in repo settings. Then all PRs would need to merge this before becoming green (curretly this PR is blocked as it is waiting for Ubuntu 20 test).

I have forced CI to run again, and the sanitizer and static tests run and pass, as they did earlier on this PR when I tried them out. I have verified in the CI logs that they are running on Ubuntu 22.04.

@fruffy I do not know whether the order of merging this vs. updating the list of required check names is critical. Let me know if you want me to try updating the names of the two required tests that now have 22 in their names instead of 20.

@fruffy I do not know whether the order of merging this vs. updating the list of required check names is critical. Let me know if you want me to try updating the names of the two required tests that now have 22 in their names instead of 20.

I'd guess there is someone who can override the check for this one. Either way we could get into situation where other PRs would need to update to have the right checks.

@fruffy I do not know whether the order of merging this vs. updating the list of required check names is critical. Let me know if you want me to try updating the names of the two required tests that now have 22 in their names instead of 20.

I'd guess there is someone who can override the check for this one. Either way we could get into situation where other PRs would need to update to have the right checks.

I can override it, but I'd rather wait until Fabian is back from vacation before making changes like this, in case there are unintended consequences that I need help with fixing. We still have 3 weeks before April 1, 2025, so merging this PR is not urgent for a while longer.