Help/policy/CMP0092.rst

CMP0092
-------

MSVC warning flags are not in :variable:`CMAKE_<LANG>_FLAGS` by default.

When using MSVC-like compilers in CMake 3.14 and below, warning flags
like ``/W3`` are added to :variable:`CMAKE_<LANG>_FLAGS` by default.
This is problematic for projects that want to choose a different warning
level programmatically.  In particular, it requires string editing of the
:variable:`CMAKE_<LANG>_FLAGS` variables with knowledge of the
CMake builtin defaults so they can be replaced.

CMake 3.15 and above prefer to leave out warning flags from the value of
:variable:`CMAKE_<LANG>_FLAGS` by default.

This policy provides compatibility with projects that have not been updated
to expect the lack of warning flags.  The policy setting takes effect as of
the first :command:`project` or :command:`enable_language` command that
initializes :variable:`CMAKE_<LANG>_FLAGS` for a given lanuage ``<LANG>``.

.. 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 MSVC warning flags in the
default :variable:`CMAKE_<LANG>_FLAGS` cache entries.  The ``NEW`` behavior
for this policy is to *not* place MSVC warning flags in the default cache
entries.

This policy was introduced in CMake version 3.15.  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