# CMP0117

New in version 3.20.

MSVC RTTI flag `/GR` is not added to `CMAKE_CXX_FLAGS` by default.

When using MSVC-like compilers in CMake 3.19 and below, the RTTI flag `/GR` is added to `CMAKE_CXX_FLAGS` by default. This behavior is left from support for MSVC versions from Visual Studio 2003 and below that did not enable RTTI by default. It is no longer necessary. Furthermore, it is problematic for projects that want to change to `/GR-` programmatically. In particular, it requires string editing of the `CMAKE_CXX_FLAGS` variable with knowledge of the CMake builtin default so it can be replaced.

CMake 3.20 and above prefer to leave out `/GR` from the value of `CMAKE_CXX_FLAGS` by default.

This policy provides compatibility with projects that have not been updated to expect the lack of the `/GR` flag. The policy setting takes effect as of the first `project()` or `enable_language()` command that initializes `CMAKE_CXX_FLAGS`.

Note

Once the policy has taken effect at the top of a project for a given language, that choice must be used throughout the tree for that language. In projects that have nested projects in subdirectories, be sure to convert everything together.

The `OLD` behavior for this policy is to place the MSVC `/GR` flag in the default `CMAKE_CXX_FLAGS` cache entry. The `NEW` behavior for this policy is to not place the MSVC `/GR` flag in the default cache entry.

This policy was introduced in CMake version 3.20. Use the `cmake_policy()` command to set it to `OLD` or `NEW` explicitly. Unlike many policies, CMake version 3.27.6 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.