Through the years, we have not actually bumped the minimum CMake version we support, and that has sometimes meant having to implement things in a more difficult way or turning down contributions altogether since it would not be possible to support. (Publicly we have bumped the minimum, but in fact we haven't bumped the actual version checks, see below).

Backwards compatibility with CMake version 3.5 is also no longer supported by newer CMake releases, and 3.10 has been deprecated. This does not impact us negatively currently, but it might at some point.

Changed in version 4.0: Compatibility with versions of CMake older than 3.5 is removed. Calls to cmake_minimum_required(VERSION) or cmake_policy(VERSION) that do not specify at least 3.5 as their policy version (optionally via ...) will produce an error in CMake 4.0 and above.

Changed in version 3.31: Compatibility with versions of CMake older than 3.10 is deprecated. Calls to cmake_minimum_required(VERSION) or cmake_policy(VERSION) that do not specify at least 3.10 as their policy version (optionally via ...) will produce a deprecation warning in CMake 3.31 and above.

For the upcoming 2.3.x release series, I'd like to bump the minimum CMake version we support, and I'd like to suggest 3.12.

I chose to suggest 3.12 based on what features we already depend on for Google Benchmark and what I could find that various Linux distros are shipping, it seems like a good middle ground between keeping up with new features and keeping backwards compatibility. We could also choose 3.14, but I haven't found any new feature that would require that, in fact I didn't see anything interesting until 3.18, and even that was not really that interesting.

We currently specify 3.14 as the minimum CMake version we pledge to support for 2.1.x/2.2.x on the Wiki. I guess we could edit that to say 3.12 now that those releases won't have any new features that would require updating the version. Should we say 3.12 for 2.3.x as well if we land on that for the actual CMake requirement?
Ref: https://github.com/zlib-ng/zlib-ng/wiki

For reference:
3.5 released 2016
3.12 released 2018
3.14 release 2019

In addition to a plethora of general improvements, such as improved understanding of compilers, platforms, libraries, etc, these CMake features improvements stood out to me while reading through the release notes as things we might want to utilize:

3.6:

• A CMAKE_TRY_COMPILE_PLATFORM_VARIABLES variable was added for use by toolchain files to specify platform-specific variables that must be propagated by the try_compile() command into test projects.
• A CMAKE_TRY_COMPILE_TARGET_TYPE variable was added to optionally tell the try_compile() command to build a static library instead of an executable. This is useful for cross-compiling toolchains that cannot link binaries without custom flags or scripts.

3.7:

• The if() command gained new boolean comparison operations LESS_EQUAL, GREATER_EQUAL, STRLESS_EQUAL, STRGREATER_EQUAL, VERSION_LESS_EQUAL, and VERSION_GREATER_EQUAL.

3.9:

• GoogleTest module added
  https://cmake.org/cmake/help/latest/module/GoogleTest.html

3.10:

• gtest_discover_tests Automatically add tests with CTest by querying the compiled test executable
  https://cmake.org/cmake/help/latest/module/GoogleTest.html#command:gtest_discover_tests

3.12:

• The cmake_minimum_required() and cmake_policy(VERSION) commands now accept a version range using the form [...]. This allows projects to specify a range of versions for which they have been updated and avoid explicit policy settings.

Summary by CodeRabbit

• New Requirements
  • Raised minimum CMake version to 3.12 (now supports 3.12–3.29).
• Chores
  • Configure step now shows the detected CMake version.
• Tests
  • Simplified benchmark build logic; benchmarks are no longer auto-disabled based on CMake version (note: overall project now requires CMake 3.12+).