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CMP0128
-------
.. versionadded:: 3.22
When this policy is set to ``NEW``:
* :prop_tgt:`<LANG>_EXTENSIONS` is initialized to
:variable:`CMAKE_<LANG>_EXTENSIONS` if set, otherwise falling back to
:variable:`CMAKE_<LANG>_EXTENSIONS_DEFAULT`.
* Extensions are correctly disabled/enabled if :prop_tgt:`<LANG>_STANDARD` is
unset.
* Standard mode-affecting flags aren't added unless necessary to achieve the
specified mode.
The ``OLD`` behavior:
* Initializes :prop_tgt:`<LANG>_EXTENSIONS` to
:variable:`CMAKE_<LANG>_EXTENSIONS` if set, otherwise falling back to ``ON``.
* Always adds a flag if :prop_tgt:`<LANG>_STANDARD` is set and
:prop_tgt:`<LANG>_STANDARD_REQUIRED` is ``OFF``.
* If :prop_tgt:`<LANG>_STANDARD` is unset:
* Doesn't disable extensions even if :prop_tgt:`<LANG>_EXTENSIONS` is
``OFF``.
* Fails to enable extensions if :prop_tgt:`<LANG>_EXTENSIONS` is ``ON``
except for the ``IAR`` compiler.
Code may need to be updated for the ``NEW`` behavior in the following cases:
* If :prop_tgt:`<LANG>_EXTENSIONS` matches
:variable:`CMAKE_<LANG>_EXTENSIONS_DEFAULT` or is unset and the compiler's
default satisfies :prop_tgt:`<LANG>_STANDARD` but the compiled code requires
the exact standard specified.
Such code should set :prop_tgt:`<LANG>_STANDARD_REQUIRED` to ``ON``.
For example:
.. code-block:: cmake
cmake_minimum_required(VERSION |release|)
project(example C)
add_executable(exe main.c)
set_property(TARGET exe PROPERTY C_STANDARD 99)
If the compiler defaults to C11 then the standard specification for C99 is
satisfied and CMake will pass no flags. ``main.c`` will no longer compile if
it is incompatible with C11.
* If a standard mode flag previously overridden by CMake's and not used during
compiler detection now takes effect due to CMake no longer adding one as the
default detected is appropriate.
Such code should be converted to either:
* Use :prop_tgt:`<LANG>_STANDARD` and :prop_tgt:`<LANG>_EXTENSIONS` instead
of manually adding flags.
* Or ensure the manually-specified flags are used during compiler detection.
If compiler flags affecting the standard mode are used during compiler
detection (for example in :manual:`a toolchain file <cmake-toolchains(7)>`
using :variable:`CMAKE_<LANG>_FLAGS_INIT`) then they will affect the detected
default :variable:`standard <CMAKE_<LANG>_STANDARD_DEFAULT>` and
:variable:`extensions <CMAKE_<LANG>_EXTENSIONS_DEFAULT>`.
Unlike many policies, CMake version |release| does *not* warn when the policy
is not set and simply uses the ``OLD`` behavior. Use the
:command:`cmake_policy` command to set it to ``OLD`` or ``NEW`` explicitly.
See documentation of the
:variable:`CMAKE_POLICY_WARNING_CMP0128 <CMAKE_POLICY_WARNING_CMP<NNNN>>`
variable to control the warning.
.. include:: DEPRECATED.txt
|
