cmake: Bump min policy version

[arno-lunarg]

We are getting this error:

 CMake Error at external/Release/64/jsoncpp/build/install/lib/cmake/jsoncpp/jsoncppConfig.cmake:2 (cmake_policy):
  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.
Call Stack (most recent call first):
  CMakeLists.txt:32 (find_package)

Is bumping minimum to 3.5 ok?

[spencer-lunarg]

not a CMake guru here, but wanted to add context the issue is we pull this in as a dependency and Github Action runners started used cmake 4.0 from 3.31.6 and that is where this started occuring

[bcsgh]

I'd think the correct thing would be to bump up the max, not the min?

As long as things build under v3.0, there should be no reason to change the min. That should only happen if the config starts using something that isn't added until a later version.

[flichtenheld]

Yes, 1.9.6 should be fine with the addition of the max version. You should verify that you actually 1.9.6.

[impala454]

I see this was fixed in September with 1.9.6. Any idea how/when that makes it to the mainline debian respositories? My Ubuntu 22.04.5 install still pulls 1.9.5.

[flichtenheld]

This is maybe not the correct forum to discuss Debian/Ubuntu release procedures but in general, these distributions aim to provide a consistent experience where the jsoncpp in them compiles with the CMake in them. They do not generally provide updates. So Ubuntu 22.04 will be forever stuck with 1.9.5, but it also ships with a compatible CMake. (Ubuntu 25.04 will likely be the first to have 1.9.6) If you want to have the latest CMake you also need to make sure to get a consistent environment with that. So use a distro that always has the latest like Arch or the almost latest like Fedora. Or get your dependencies from a different source like vcpkg or similar.