# CMP0149

New in version 3.27.

Visual Studio Generators select latest Windows SDK by default.

Visual Studio Generators select a Windows SDK version to put in the `WindowsTargetPlatformVersion` setting in `.vcxproj` files. CMake sets the `CMAKE_VS_WINDOWS_TARGET_PLATFORM_VERSION` variable to the selected SDK version.

Prior to CMake 3.27, the SDK version was always selected by the value of the `CMAKE_SYSTEM_VERSION` variable. Users or toolchain files could set that variable to one of the exact Windows SDK versions available on the host system. Since `CMAKE_SYSTEM_VERSION` defaults to `CMAKE_HOST_SYSTEM_VERSION`, and it is not guaranteed that a matching Windows SDK version is available, CMake had to fall back to using the latest Windows SDK version if no exact match was available. This approach was problematic:

- The latest Windows SDK might or might not be selected based on whether the host version of Windows happens to match an available SDK version.

- An old Windows SDK version might be selected that has not been updated for newer language standards such as C11.

CMake 3.27 and higher prefer to ignore the exact value of `CMAKE_SYSTEM_VERSION` and by default select the latest SDK version available. An exact SDK version may be specified explicitly using a `version=` field in the `CMAKE_GENERATOR_PLATFORM` variable. See Visual Studio Platform Selection.

This policy provides compatibility for projects, toolchain files, and build scripts that have not been ported away from using `CMAKE_SYSTEM_VERSION` to specify an exact SDK version.

The `OLD` behavior for this policy is to use the exact value of `CMAKE_SYSTEM_VERSION` if possible. The `NEW` behavior for this policy is to ignore it.

This policy was introduced in CMake version 3.27. Use the `cmake_policy()` command to set it to `OLD` or `NEW` explicitly. Unlike many policies, CMake version 3.28.0-rc5 does not warn when this policy is not set and simply uses `OLD` behavior.

Note

The `OLD` behavior of a policy is `deprecated by definition` and may be removed in a future version of CMake.