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Help: Document language standard meta-features

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Brad King
2016-10-28 09:31:48 -04:00
parent df252db15a
commit 9a8d758c3a
2 changed files with 34 additions and 0 deletions
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27
Help/manual/cmake-compile-features.7.rst
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@@ -84,6 +84,33 @@ Feature requirements are evaluated transitively by consuming the link
implementation. See :manual:`cmake-buildsystem(7)` for more on implementation. See :manual:`cmake-buildsystem(7)` for more on
transitive behavior of build properties and usage requirements. transitive behavior of build properties and usage requirements.
Requiring Language Standards
----------------------------
In projects that use a large number of commonly available features from
a particular language standard (e.g. C++ 11) one may specify a
meta-feature (e.g. ``cxx_std_11``) that requires use of a compiler mode
aware of that standard. This is simpler than specifying all the
features individually, but does not guarantee the existence of any
particular feature. Diagnosis of use of unsupported features will be
delayed until compile time.
For example, if C++ 11 features are used extensively in a project's
header files, then clients must use a compiler mode aware of C++ 11
or above. This can be requested with the code:
.. code-block:: cmake
target_compile_features(mylib PUBLIC cxx_std_11)
In this example, CMake will ensure the compiler is invoked in a mode
that is aware of C++ 11 (or above), adding flags such as
``-std=gnu++11`` if necessary. This applies to sources within ``mylib``
as well as any dependents (that may include headers from ``mylib``).
Availability of Compiler Extensions
-----------------------------------
Because the :prop_tgt:`CXX_EXTENSIONS` target property is ``ON`` by default, Because the :prop_tgt:`CXX_EXTENSIONS` target property is ``ON`` by default,
CMake uses extended variants of language dialects by default, such as CMake uses extended variants of language dialects by default, such as
``-std=gnu++11`` instead of ``-std=c++11``. That target property may be ``-std=gnu++11`` instead of ``-std=c++11``. That target property may be

7
Help/release/dev/compile-features-for-language-standards.rst Normal file
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@@ -0,0 +1,7 @@
compile-features-for-language-standards
---------------------------------------
* The :manual:`Compile Features <cmake-compile-features(7)>` functionality
now offers meta-features that request compiler modes for specific language
standard levels. See :prop_gbl:`CMAKE_C_KNOWN_FEATURES` and
:prop_gbl:`CMAKE_CXX_KNOWN_FEATURES`.