Features: Extend concept to C language.

Add properties and variables corresponding to CXX equivalents.

Add features for c_function_prototypes (C90), c_restrict (C99),
c_variadic_macros (C99) and c_static_assert (C11). This feature
set can be extended later.

Add a <PREFIX>_RESTRICT symbol define to WriteCompilerDetectionHeader
to conditionally represent the c_restrict feature.

1 files changed, 25 insertions, 0 deletions

diff --git a/Help/prop_gbl/CMAKE_C_KNOWN_FEATURES.rst b/Help/prop_gbl/CMAKE_C_KNOWN_FEATURES.rst
new file mode 100644
index 0000000..c57bc73
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+++ b/Help/prop_gbl/CMAKE_C_KNOWN_FEATURES.rst
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+CMAKE_C_KNOWN_FEATURES
+----------------------
+
+List of C features known to this version of CMake.
+
+The features listed in this global property may be known to be available to the
+C compiler.  If the feature is available with the C compiler, it will
+be listed in the :variable:`CMAKE_C_COMPILE_FEATURES` variable.
+
+The features listed here may be used with the :command:`target_compile_features`
+command.
+
+The features known to this version of CMake are:
+
+``c_function_prototypes``
+  Function prototypes, as defined in ``ISO/IEC 9899:1990``.
+
+``c_restrict``
+  ``restrict`` keyword, as defined in ``ISO/IEC 9899:1999``.
+
+``c_static_assert``
+  Static assert, as defined in ``ISO/IEC 9899:2011``.
+
+``c_variadic_macros``
+  Variadic macros, as defined in ``ISO/IEC 9899:1999``.