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diff --git a/Help/policy/CMP0117.rst b/Help/policy/CMP0117.rst new file mode 100644 index 0000000..0c4dd30 --- /dev/null +++ b/Help/policy/CMP0117.rst @@ -0,0 +1,43 @@ +CMP0117 +------- + +.. versionadded:: 3.20 + +MSVC RTTI flag ``/GR`` is not added to +:variable:`CMAKE_CXX_FLAGS <CMAKE_<LANG>_FLAGS>` by default. + +When using MSVC-like compilers in CMake 3.19 and below, the RTTI flag +``/GR`` is added to :variable:`CMAKE_CXX_FLAGS <CMAKE_<LANG>_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 :variable:`CMAKE_CXX_FLAGS <CMAKE_<LANG>_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 +:variable:`CMAKE_CXX_FLAGS <CMAKE_<LANG>_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 :command:`project` or :command:`enable_language` command that +initializes :variable:`CMAKE_CXX_FLAGS <CMAKE_<LANG>_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 :variable:`CMAKE_CXX_FLAGS <CMAKE_<LANG>_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 +:command:`cmake_policy` command to set it to ``OLD`` or ``NEW`` explicitly. +Unlike many policies, CMake version |release| does *not* warn +when this policy is not set and simply uses ``OLD`` behavior. + +.. include:: DEPRECATED.txt |