update CMAKE min version

[mosfet80]

cmake 3.0 is deprecated.
You need to upgrade to 3.5 (minimum supported version in cmake 4.0)

[VolkerEnderlein]

Thank you for the PR. I was not aware about the upcoming deprecation in CMake version 4.0. According to CMake documentation a command cmake_minimum_required(VERSION 3.0...3.29) is the preferred way to work with both obsoleted and current versions. 3.29 is the last version I checked explicitly. If you'll change your PR to this line I happily accept it.

[mosfet80]

Thank you for the PR. I was not aware about the upcoming deprecation in CMake version 4.0. According to CMake documentation a command cmake_minimum_required(VERSION 3.0...3.29) is the preferred way to work with both obsoleted and current versions. 3.29 is the last version I checked explicitly. If you'll change your PR to this line I happily accept it.

https://cmake.org/cmake/help/latest/release/3.31.html

Deprecated and Removed Features
Compatibility with versions of CMake older than 3.10 is now deprecated and will be removed from a future version.

[VolkerEnderlein]

The CMake release notes link and the cmake_minimum_required documentation exactly propose the syntax I mentioned for supporting both newer and older CMake versions.

[mosfet80]

The link you cite states that cmake versions < 3.5 have been removed.
Boost version 1.83 also requires cmake 3.5.
https://github.com/boostorg/boost/blob/boost-1.83.0/CMakeLists.txt

In order to support old and new version of cmake I propose to update to version 3.5

Thank you for your availability to review

[VolkerEnderlein]

Thanks for your reply. It does not matter what minimum version your choose. Only the maximum version matters, as it says "I am aware of all the policies and settings up to this version". It determines the maximum supported version without needing changes to the CMakeLists.txt. So you could keep the minimum version as is to enable maximum portability. As of Boost 1.83 only supporting CMake version 3.5: Coin suppports Boost since 1.35 and only requires the header only part of Boost. So that's not a problem.

[mosfet80]

I would like to point out that when github compiling "C.I." on ubuntu, it fails because of the incompatibility with cmake 4.

CMake Error at CMakeLists.txt:1 (cmake_minimum_required):

Compatibility with CMake < 3.5 has been removed from CMake.

https://github.com/coin3d/coin/actions/runs/14204262087/job/39798140761

One of these decisions can be made to solve the problem:

• not to support cmake 4
• impose cmake3.5 as the minimum version.
• add into cmake -DCMAKE_POLICY_VERSION_MINIMUM=3.5

[VolkerEnderlein]

The failing calls to CMake tell three ways how to solve the issue.

  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.

And instead of raising the minimum required version I prefer the <min>...<max> syntax to keep backwards compatibility.