CMP0091 | |
------- | |
.. versionadded:: 3.15 | |
MSVC runtime library flags are selected by an abstraction. | |
Compilers targeting the MSVC ABI have flags to select the MSVC runtime library. | |
Runtime library selection typically varies with build configuration because | |
there is a separate runtime library for Debug builds. | |
In CMake 3.14 and below, MSVC runtime library selection 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 a different runtime library 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 3.15 and above prefer to leave the MSVC runtime library selection flags | |
out of the default :variable:`CMAKE_<LANG>_FLAGS_<CONFIG>` values and instead | |
offer a first-class abstraction. The :variable:`CMAKE_MSVC_RUNTIME_LIBRARY` | |
variable and :prop_tgt:`MSVC_RUNTIME_LIBRARY` target property may be set to | |
select the MSVC runtime library. If they are not set then CMake uses the | |
default value ``MultiThreaded$<$<CONFIG:Debug>:Debug>DLL`` which is | |
equivalent to the original flags. | |
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 | |
must be used throughout the tree. In projects that have nested projects | |
in subdirectories, be sure to convert everything together. | |
The ``OLD`` behavior for this policy is to place MSVC runtime library | |
flags in the default :variable:`CMAKE_<LANG>_FLAGS_<CONFIG>` cache | |
entries and ignore the :variable:`CMAKE_MSVC_RUNTIME_LIBRARY` abstraction. | |
The ``NEW`` behavior for this policy is to *not* place MSVC runtime | |
library flags in the default cache entries and use the abstraction instead. | |
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 |