Update cmake minimum version

Question

Update cmake minimum version

Closed this issue 9 months ago · 4 comments

The current minimum version is 3.3, but recent cmake (3.27) started to give this warning

CMake Deprecation Warning at /home/lbertag/workdir/scream/scream-src/master/externals/ekat/CMakeLists.txt:1 (cmake_minimum_required):
  Compatibility with CMake < 3.5 will be removed from a future version of
  CMake.

  Update the VERSION argument <min> value or use a ...<max> suffix to tell
  CMake that the project does not need compatibility with older versions.

Considering that most machines feature a relatively recent cmake, we could probably bump this up to something like 3.1X. Here you can find the release notes for 3.X. Some interesting ones that may be relevant for ekat:

3.11: adds FetchContent: a somewhat hybrid approach between add_subdirectory and ExternalProject_add.
3.12: find_package searches <PackageName>_ROOT cmake/env variables.
3.14: FetchContent_MakeAvailable is added
3.15: cmake_parse_arguments() adds a way to check if a keyword arg is missing values.
3.16: target_precompile_headers()

In general, each version also adds QoL improvements, (see the ZIP_LISTS option in foreach added in 3.17), so the more recent the version, the more robust/concise our CMake syntax can be. Of course, asking for 3.28 is too much (I don't have it on my laptop either), so we need to be a bit conservative. Nevertheless, 3.3 is a bit old...

@jgfouca @jeff-cohere @tcclevenger thoughts?

Answer 1 · 2024-02-09T00:16:00.000Z

I think we should use at least 3.12 to avoid violating the Principle of Least Astonishment for using find_package.

Answer 2 · 2024-02-09T00:22:44.000Z

Yes. The <PackageName>_ROOT is something quite useful, since it allows to avoid having to add all those HINTS/PATHS args to the find_package calls. In a way, it's a standardized way of specifying PATHS and HINTS.

Answer 3 · 2024-02-09T15:56:07.000Z

All the TPL work I did a few months ago depends on <PackageName>_ROOT being available, so at the very least 3.12 should be the minimum.

Answer 4 · 2024-02-12T17:38:38.000Z

And it's fair to assume at this point that 3.12 is available on all machines. CMake v3.12.0 was released in Nov 2018...