Help/policy/CMP0184.rst

CMP0184
-------

.. versionadded:: 4.0

MSVC runtime checks flags are selected by an abstraction.

Compilers targeting the MSVC ABI have flags to select the runtime checks.
Runtime checks selection typically varies with build
configuration.

In CMake 3.31 and below, runtime checks flags are added to
the default :variable:`CMAKE_<LANG>_FLAGS_<CONFIG>` cache entries by CMake
automatically.  This allows users to edit their cache entries to adjust the
flags.  However, the presence of such default flags is problematic for
projects that want to choose different runtime checks programmatically.
In particular, it requires string editing of the
:variable:`CMAKE_<LANG>_FLAGS_<CONFIG>` variables with knowledge of the
CMake builtin defaults so they can be replaced.

CMake 4.0 and above prefer to leave the runtime checks flags
out of the default :variable:`CMAKE_<LANG>_FLAGS_<CONFIG>` values and instead
offer a first-class abstraction.  The
:variable:`CMAKE_MSVC_RUNTIME_CHECKS` variable and
:prop_tgt:`MSVC_RUNTIME_CHECKS` target property may be set to
select the MSVC runtime checks.  If they are not set, CMake
enables runtime checks for the ``Debug`` configuration only using the default
value ``$<$<CONFIG:Debug>:StackFrameErrorCheck;UninitializedVariable>``, if
supported by the compiler, or an empty value otherwise.

This policy provides compatibility with projects that have not been updated
to be aware of the abstraction.  The policy setting takes effect as of the
first :command:`project` or :command:`enable_language` command that enables
a language whose compiler targets the MSVC ABI.

.. note::

  Once the policy has taken effect at the top of a project, that choice
  will be used throughout the tree.  In projects that have nested projects
  in subdirectories, be sure to confirm if everything is working with the
  selected policy behavior.

The ``OLD`` behavior for this policy is to place MSVC runtimes checks
flags in the default :variable:`CMAKE_<LANG>_FLAGS_<CONFIG>` cache
entries and ignore the :variable:`CMAKE_MSVC_RUNTIME_CHECKS`
abstraction.  The ``NEW`` behavior for this policy is to *not* place MSVC
runtime checks flags in the default cache entries and use
the abstraction instead.

.. |INTRODUCED_IN_CMAKE_VERSION| replace:: 4.0
.. |WARNS_OR_DOES_NOT_WARN| replace:: does *not* warn
.. include:: include/STANDARD_ADVICE.rst

.. include:: include/DEPRECATED.rst