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Merge topic 'cmp0128-fixup'

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e47dfce75d CMP0128: Enable/disable extensions if standard same as default

Acked-by: Kitware Robot <kwrobot@kitware.com>
Acked-by: buildbot <buildbot@kitware.com>
Merge-request: !6723
This commit is contained in:
Brad King
2021-11-12 14:02:23 +00:00
committed by Kitware Robot
parent 9f6c91eb30 e47dfce75d
commit 648b66a1d3
7 changed files with 47 additions and 28 deletions
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Help/policy/CMP0128.rst
+13 -22
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@@ -9,8 +9,8 @@ When this policy is set to ``NEW``:
: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.
* Extensions are correctly enabled/disabled if :prop_tgt:`<LANG>_STANDARD` is
unset or satisfied by the default.
* Standard mode-affecting flags aren't added unless necessary to achieve the
specified mode.
@@ -33,26 +33,6 @@ The ``OLD`` behavior:
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.
@@ -64,6 +44,17 @@ Code may need to be updated for the ``NEW`` behavior in the following cases:
* Or ensure the manually-specified flags are used during compiler detection.
* If extensions were disabled without :prop_tgt:`<LANG>_STANDARD` being set
CMake previously wouldn't actually disable extensions.
Such code should be updated to not disable extensions if they are required.
* If extensions were enabled/disabled when :prop_tgt:`<LANG>_STANDARD` was
satisfied by the compiler's default CMake previously wouldn't actually
enable/disable extensions.
Such code should be updated to set the correct extensions mode.
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