# CMP0203

Added in version 4.2.

`_WINDLL` is defined for shared libraries targeting the MSVC ABI.

In CMake 4.1 and below, Visual Studio Generators compile sources in shared libraries with `_WINDLL` defined due to behavior of Visual Studio itself. The preprocessor definition is not modeled by CMake and is therefore not added by other generators, such as `Ninja`.

CMake 4.2 and above, when targeting the MSVC ABI, prefer to compile sources in shared libraries with `_WINDLL` defined by all generators. This policy provides compatibility with projects that have not been updated to be aware of the definition. Its setting is recorded by each target as it is created, and affects compilation of sources in that target.

The `OLD` behavior for this policy does not model the `_WINDLL` preprocessor definition in CMake itself. The `NEW` behavior for this policy adds the `_WINDLL` preprocessor definition to sources in shared libraries when targeting the MSVC ABI.

This policy was introduced in CMake version 4.2. It may be set by `cmake_policy()` or `cmake_minimum_required()`. If it is not set, CMake does not warn, and uses `OLD` behavior.

Note

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