TriBITS: Upgrade minimum CMake version to 3.28 or newer?

[bartlettroscoe]

CC: @trilinos/framework, @sebrowne

Enhancement

It has been since Feb 2023 that Trilinos upgraded the min CMake version to 3.23 (see #11583).
CMake 3.23.0 was released in March 2022 (see https://github.com/Kitware/CMake/releases/tag/v3.23.0).

Given that CMake 3.28 was released in Dec 2023 (see https://github.com/Kitware/CMake/releases/tag/v3.28.0), it seems reasonable to upgrade the minimum CMake version of Trilinos and TriBITS to CMake 3.28 or newer.

[cwpearson]

I'm happy to defer to the framework team either way, however this might only be worth doing if 3.28 provides some fixes or quality-of-life improvements that are useful to the project.

[bartlettroscoe]

As per:

• https://bssw.io/items/cmake-tutorial-and-reference-resources

CMake (which includes the executable tools cmake, ctest and cpack with each CMake installation) continues to evolve and improve fairly rapidly from release to release.

We want to do yearly upgrades of CMake so that:

• We get to take advantage of better defaults
• Allow developers and users to take advantage of newer features and fixes

That helps to reduce technical debt in the build system incrementally.

And the CMake release notes don't always highlight how big/useful a new version of CMake can be.

@cwpearson, is there a good reason to not to regular yearly upgrades of CMake?

[jjellio]

I'm less worried about the new features, but more about CMake deprecating something. That said, on ATS-4, I regularly build from source (Via spack) and use whatever the latest cmake is from there. There are always some policy warnings.

Chasing the latest version can create a real pain point if you are trying to do things on older platforms.

[bartlettroscoe]

Chasing the latest version can create a real pain point if you are trying to do things on older platforms.

@jjellio, what are the pain points from using newer CMake versions on older platforms (other than having to build CMake from source in case the admins are not installing newer CMake versions for you)?

NOTE: AUE currently seems to be supporting CMake 3.29.4.

[jhux2]

Updating on a regular basis seems like a good idea, if nothing else to keep ahead of whatever minimum cmake version that downstream apps require.

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[cgcgcg]

@trilinos/framework Should we take the opportunity to advance the CMake requirement as part of Trilinos 17?

[sebrowne]

@cgcgcg I think that's a perfectly fine plan. We currently have 3.31.6, 3.31.8, and 3.31.9 installed in our container images, so we're good on that front (but should probably get an upgrade in there sooner than later for the next minimum advancement).

[cgcgcg]

Does anyone have feelings about which version we should require? Is 3.28 reasonable?

[bartlettroscoe]

@sebrowne and @cgcgcg,

NOTE: The version CMake 3.28 was selected when this issue was first opened over a year ago. In the past, we have targeted upgrading to a CMake version that have been out for about 12 months (to give users time to have that version installed locally). However, given this is a major Trilinos version update (allowing breaking changes), we might shoot for some version of CMake 4.x? The first release on that sequence was CMake v4.0.0, released back in 3/27/2025 which was 8 months ago. Otherwise, to go back 12 full months would take you to CMake v3.31.0. If we don't take this opportunity, we may have to wait several years for Trilinos 18.0 to get upgrade to CMake v4.0+.

NOTE: TriBITS was upgraded to CMake 4.0.0 months ago and there is an automated build for it (see here).

[cgcgcg]

I'd be more cautious about updating to a relatively recent version of CMake. Installing a newer CMake isn't difficult, but having to do it on every system that we are on would be annoying.