With CMake release 4.0.0, compatibility with CMake < 3.5 has been (soft-)removed. This causes builds to fail due to a compatibility problem in core/libcorrect/CMakeLists.txt.

Error Message

CMake Error at core/libcorrect/CMakeLists.txt:1 (cmake_minimum_required):
  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.

Steps To Reproduce
On a system with CMake 4.0, checkout git repository of SDR++ and run cmake:

$ git clone https://github.com/AlexandreRouma/SDRPlusPlus
$ cd SDRPlusPlus
$ cmake -B build -S .

Software

• CMake version 4.0.0
• Operating System: Manjaro Linux x86_64 (as of April 24, 2025)
• SDR++: Latest commit on main, 2dd8c6c

Workaround
Add argument -DCMAKE_POLICY_VERSION_MINIMUM=3.5 to cmake (only works until the compatibility is hard-removed).

Suggested solutions

Update the cmake_minimum_required version in core/libcorrect/CMakeLists.txt to 3.5 or higher.

Additional Notes
This problem has been reported by Arch Linux users building from AUR.