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CI: style check will fail once ubuntu-latest moves to Ubuntu 26.04 (CMake 4)

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@italopaesano is already working on this.

Since Oct 13, 2026.

  • #3169 by @italopaesano — open

Assessment

Difficulty
2/5
Estimated time
Under an hour
Newbie friendliness
72/100
Issue type
Bug
Clarity
Clearly specified
Activity status
Active
Tech stack
cpp, github-actions
Domain
build-system, ci-cd

Research direction

The failing step is the cmake ../ configure call in the test_code_style job of the CI workflow file (ci.yaml), which builds the bundled uncrustify fork. Start by reading that job, then compare the configure step on an ubuntu-24.04 run with a run on ubuntu-26.04 (CMake 4.x). Done means the job configures and builds uncrustify on both images, with the style check still running the same rules. The issue leaves open whether to add -DCMAKE_POLICY_VERSION_MINIMUM=3.5 in the workflow or bump cmake_minimum_required in the fork, so confirm the choice with maintainers first.

Written by the indexing model from the issue text.

Description

The test_code_style job builds the uncrustify fork with a plain cmake ../. That fork declares cmake_minimum_required(VERSION 3.2), and CMake 4.0 removed support for compatibility below 3.5, so the configure step fails.

This isn't visible yet, because ubuntu-latest still resolves to Ubuntu 24.04. It will become visible as the runner image migrates.

Measured

I replicated the job's own steps in three jobs, changing one thing at a time:

image cmake --version cmake invocation result
ubuntu-24.04 3.31.6 as in ci.yaml uncrustify builds
ubuntu-26.04 4.4.3 as in ci.yaml configure fails
ubuntu-26.04 4.4.3 + -DCMAKE_POLICY_VERSION_MINIMUM=3.5 uncrustify builds

Run: https://github.com/italopaesano/wayfire/actions/runs/38393914614

The last two jobs run on the same image with the same CMake 4.4.3 and differ only by that flag, so the fix is verified rather than assumed.

(ubuntu-26.04 is already usable as an explicit label, as noted in actions/runner-images#14748.)

Error from the failing job:

CMake Error at CMakeLists.txt:1 (cmake_minimum_required):
  Compatibility with CMake < 3.5 has been removed from CMake.

  Update the VERSION argument <min> value.  Or, use the <min>...<max> syntax
  to tell CMake that the project requires at least <min> but has been updated
  to work with policies introduced by <max> or earlier.

  Or, add -DCMAKE_POLICY_VERSION_MINIMUM=3.5 to try configuring anyway.
Timing

Per actions/runner-images#14748, the migration rolls out over several weeks beginning 19 October 2026, with completion targeted for 19 November.

Because it is gradual rather than a single switch, the job will likely fail intermittently during that period: the same PR may fail, pass on re-run, and fail again. That usually reads as CI flakiness rather than as a reproducible problem, which is why I'm reporting this before the window opens rather than during it.

Possible fixes

Two options, both a single line:

  1. Pass the flag in the workflow — cmake -DCMAKE_POLICY_VERSION_MINIMUM=3.5 ../. It is the flag CMake itself suggests in the error message, and it is inert on CMake 3.x, so it can be applied now and requires no coordination with the migration schedule. Happy to open a PR for this.

  2. Bump cmake_minimum_required in the uncrustify fork, which would also fix it for anyone else building that fork.

No preference from my side — (2) is the more complete fix, (1) is entirely within this repository.

Either way the style check itself is unaffected: uncrustify is built and run exactly as before, with the same configuration, so PRs keep being evaluated against the same rules.

Dominant language
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Merged PRs (30d)
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Getting set up

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