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.

33 files changed, 258 insertions, 17 deletions

diff --git a/Tests/CMakeCommands/target_compile_features/CMakeLists.txt b/Tests/CMakeCommands/target_compile_features/CMakeLists.txt
index 62e3ce0..9b35f27 100644
--- a/Tests/CMakeCommands/target_compile_features/CMakeLists.txt
+++ b/Tests/CMakeCommands/target_compile_features/CMakeLists.txt
@@ -1,7 +1,7 @@
 cmake_minimum_required(VERSION 3.0)
 project(target_compile_features)
 
-if (NOT CMAKE_CXX_COMPILE_FEATURES)
+if (NOT CMAKE_CXX_COMPILE_FEATURES AND NOT CMAKE_C_COMPILE_FEATURES)
   file(WRITE "${CMAKE_CURRENT_BINARY_DIR}/test_dummy.cpp"
     "int main(int,char**) { return 0; }\n"
   )
@@ -11,15 +11,35 @@ endif()
 
 set(CMAKE_VERBOSE_MAKEFILE ON)
 
-add_executable(target_compile_features main.cpp)
-target_compile_features(target_compile_features
-  PRIVATE cxx_auto_type
-)
+if (CMAKE_C_COMPILE_FEATURES)
+  add_executable(target_compile_features main.c)
+  target_compile_features(target_compile_features
+    PRIVATE c_restrict
+  )
 
-add_library(lib_auto_type lib_auto_type.cpp)
-target_compile_features(lib_auto_type
-  PUBLIC cxx_auto_type
-)
+  add_library(lib_restrict lib_restrict.c)
+  target_compile_features(lib_restrict
+    PUBLIC c_restrict
+  )
 
-add_executable(lib_user lib_user.cpp)
-target_link_libraries(lib_user lib_auto_type)
+  add_executable(restrict_user restrict_user.c)
+  target_link_libraries(restrict_user lib_restrict)
+endif()
+
+if (CMAKE_CXX_COMPILE_FEATURES)
+  if (CMAKE_C_COMPILE_FEATURES)
+    set(target_suffix _cxx)
+  endif()
+  add_executable(target_compile_features${target_suffix} main.cpp)
+  target_compile_features(target_compile_features${target_suffix}
+    PRIVATE cxx_auto_type
+  )
+
+  add_library(lib_auto_type lib_auto_type.cpp)
+  target_compile_features(lib_auto_type
+    PUBLIC cxx_auto_type
+  )
+
+  add_executable(lib_user lib_user.cpp)
+  target_link_libraries(lib_user lib_auto_type)
+endif()
diff --git a/Tests/CMakeCommands/target_compile_features/lib_restrict.c b/Tests/CMakeCommands/target_compile_features/lib_restrict.c
new file mode 100644
index 0000000..049c1b0
--- /dev/null
+++ b/Tests/CMakeCommands/target_compile_features/lib_restrict.c
@@ -0,0 +1,9 @@
+
+#include "lib_restrict.h"
+
+int foo(int * restrict a, int * restrict b)
+{
+  (void)a;
+  (void)b;
+  return 0;
+}
diff --git a/Tests/CMakeCommands/target_compile_features/lib_restrict.h b/Tests/CMakeCommands/target_compile_features/lib_restrict.h
new file mode 100644
index 0000000..eca22be
--- /dev/null
+++ b/Tests/CMakeCommands/target_compile_features/lib_restrict.h
@@ -0,0 +1,7 @@
+
+#ifndef LIB_RESTRICT_H
+#define LIB_RESTRICT_H
+
+int foo(int * restrict a, int * restrict b);
+
+#endif
diff --git a/Tests/CMakeCommands/target_compile_features/main.c b/Tests/CMakeCommands/target_compile_features/main.c
new file mode 100644
index 0000000..831c5eb2
--- /dev/null
+++ b/Tests/CMakeCommands/target_compile_features/main.c
@@ -0,0 +1,12 @@
+
+int foo(int * restrict a, int * restrict b)
+{
+  (void)a;
+  (void)b;
+  return 0;
+}
+
+int main()
+{
+  return 0;
+}
diff --git a/Tests/CMakeCommands/target_compile_features/restrict_user.c b/Tests/CMakeCommands/target_compile_features/restrict_user.c
new file mode 100644
index 0000000..d47b847
--- /dev/null
+++ b/Tests/CMakeCommands/target_compile_features/restrict_user.c
@@ -0,0 +1,14 @@
+
+#include "lib_restrict.h"
+
+int bar(int * restrict a, int * restrict b)
+{
+  (void)a;
+  (void)b;
+  return foo(a, b);
+}
+
+int main()
+{
+  return 0;
+}
diff --git a/Tests/CompileFeatures/CMakeLists.txt b/Tests/CompileFeatures/CMakeLists.txt
index adf50d5..0e1e6c9 100644
--- a/Tests/CompileFeatures/CMakeLists.txt
+++ b/Tests/CompileFeatures/CMakeLists.txt
@@ -3,7 +3,7 @@ cmake_minimum_required(VERSION 3.0)
 
 project(CompileFeatures)
 
-if (NOT CMAKE_CXX_COMPILE_FEATURES)
+if (NOT CMAKE_C_COMPILE_FEATURES AND NOT CMAKE_CXX_COMPILE_FEATURES)
   file(WRITE "${CMAKE_CURRENT_BINARY_DIR}/dummy.cpp"
     "int main(int,char**) { return 0; }\n"
   )
@@ -22,6 +22,10 @@ macro(run_test feature lang)
   endif()
 endmacro()
 
+get_property(c_features GLOBAL PROPERTY CMAKE_C_KNOWN_FEATURES)
+foreach(feature ${c_features})
+  run_test(${feature} C)
+endforeach()
 get_property(cxx_features GLOBAL PROPERTY CMAKE_CXX_KNOWN_FEATURES)
 foreach(feature ${cxx_features})
   run_test(${feature} CXX)
@@ -34,9 +38,11 @@ if (CMAKE_CXX_COMPILER_ID STREQUAL GNU
   )
 endif()
 
+set(C_ext c)
+set(C_standard_flag 11)
 set(CXX_ext cpp)
 set(CXX_standard_flag 11)
-foreach(lang CXX)
+foreach(lang CXX C)
   if (CMAKE_${lang}_COMPILE_FEATURES)
     foreach(feature ${${lang}_non_features})
       message("Testing feature : ${feature}")
diff --git a/Tests/CompileFeatures/c_function_prototypes.c b/Tests/CompileFeatures/c_function_prototypes.c
new file mode 100644
index 0000000..ab3c948
--- /dev/null
+++ b/Tests/CompileFeatures/c_function_prototypes.c
@@ -0,0 +1,9 @@
+
+int someFunc(int a, int b);
+
+int someFunc(int a, int b)
+{
+  (void)a;
+  (void)b;
+  return 0;
+}
diff --git a/Tests/CompileFeatures/c_restrict.c b/Tests/CompileFeatures/c_restrict.c
new file mode 100644
index 0000000..7bc7566
--- /dev/null
+++ b/Tests/CompileFeatures/c_restrict.c
@@ -0,0 +1,7 @@
+
+int f (int * restrict a, int * restrict b)
+{
+  (void)a;
+  (void)b;
+  return 0;
+}
diff --git a/Tests/CompileFeatures/c_static_assert.c b/Tests/CompileFeatures/c_static_assert.c
new file mode 100644
index 0000000..afab504
--- /dev/null
+++ b/Tests/CompileFeatures/c_static_assert.c
@@ -0,0 +1,2 @@
+
+_Static_assert(1, "Static assert test");
diff --git a/Tests/CompileFeatures/c_variadic_macros.c b/Tests/CompileFeatures/c_variadic_macros.c
new file mode 100644
index 0000000..4da111e
--- /dev/null
+++ b/Tests/CompileFeatures/c_variadic_macros.c
@@ -0,0 +1,15 @@
+
+int someFunc(int i1, char c, int i2)
+{
+  (void)i1;
+  (void)c;
+  (void)i2;
+  return 0;
+}
+
+#define FUNC_WRAPPER(...) someFunc(__VA_ARGS__)
+
+void otherFunc()
+{
+  FUNC_WRAPPER(42, 'a', 7);
+}
diff --git a/Tests/CompileFeatures/main.c b/Tests/CompileFeatures/main.c
new file mode 100644
index 0000000..831c5eb2
--- /dev/null
+++ b/Tests/CompileFeatures/main.c
@@ -0,0 +1,12 @@
+
+int foo(int * restrict a, int * restrict b)
+{
+  (void)a;
+  (void)b;
+  return 0;
+}
+
+int main()
+{
+  return 0;
+}
diff --git a/Tests/ExportImport/Export/Interface/CMakeLists.txt b/Tests/ExportImport/Export/Interface/CMakeLists.txt
index 1b653eb..523fc29 100644
--- a/Tests/ExportImport/Export/Interface/CMakeLists.txt
+++ b/Tests/ExportImport/Export/Interface/CMakeLists.txt
@@ -26,7 +26,10 @@ target_link_libraries(sharediface INTERFACE sharedlib)
 add_library(use_auto_type INTERFACE)
 target_compile_features(use_auto_type INTERFACE cxx_auto_type)
 
-install(TARGETS headeronly sharediface use_auto_type
+add_library(use_c_restrict INTERFACE)
+target_compile_features(use_c_restrict INTERFACE c_restrict)
+
+install(TARGETS headeronly sharediface use_auto_type use_c_restrict
   EXPORT expInterface
 )
 install(TARGETS sharedlib
diff --git a/Tests/ExportImport/Import/Interface/CMakeLists.txt b/Tests/ExportImport/Import/Interface/CMakeLists.txt
index 18d9b76..4028405 100644
--- a/Tests/ExportImport/Import/Interface/CMakeLists.txt
+++ b/Tests/ExportImport/Import/Interface/CMakeLists.txt
@@ -17,6 +17,7 @@ set_property(TARGET bld::sharediface APPEND PROPERTY INTERFACE_LINK_LIBRARIES de
 add_executable(interfacetest_bld interfacetest.cpp)
 target_link_libraries(interfacetest_bld bld::sharediface)
 
+include(CheckCSourceCompiles)
 include(CheckCXXSourceCompiles)
 
 macro(do_try_compile prefix)
@@ -41,6 +42,26 @@ macro(do_try_compile prefix)
     message(SEND_ERROR "${prefix} try_compile with IMPORTED INTERFACE target failed!\n\n${OUTPUT}")
   endif()
 
+  if (";${CMAKE_C_COMPILE_FEATURES};" MATCHES ";c_restrict;")
+    set(CMAKE_REQUIRED_LIBRARIES ${prefix}::use_c_restrict)
+    check_c_source_compiles(
+      "
+    int foo(int * restrict a, int * restrict b)
+    {
+      (void)a;
+      (void)b;
+      return 0;
+    }
+    int main()
+    {
+      return 0;
+    }
+    " ${prefix}IMPORTED_IFACE_C_RESTRICT)
+
+    if(NOT ${prefix}IMPORTED_IFACE_C_RESTRICT)
+      message(SEND_ERROR "${prefix} try_compile with IMPORTED INTERFACE target failed!\n\n${OUTPUT}")
+    endif()
+  endif()
   if (";${CMAKE_CXX_COMPILE_FEATURES};" MATCHES ";cxx_auto_type;")
     set(CMAKE_REQUIRED_LIBRARIES ${prefix}::use_auto_type)
     check_cxx_source_compiles(
diff --git a/Tests/Module/WriteCompilerDetectionHeader/CMakeLists.txt b/Tests/Module/WriteCompilerDetectionHeader/CMakeLists.txt
index 6c5e0be..8dd262e 100644
--- a/Tests/Module/WriteCompilerDetectionHeader/CMakeLists.txt
+++ b/Tests/Module/WriteCompilerDetectionHeader/CMakeLists.txt
@@ -6,6 +6,7 @@ set(CMAKE_INCLUDE_CURRENT_DIR ON)
 include(WriteCompilerDetectionHeader)
 
 get_property(cxx_known_features GLOBAL PROPERTY CMAKE_CXX_KNOWN_FEATURES)
+get_property(c_known_features GLOBAL PROPERTY CMAKE_C_KNOWN_FEATURES)
 
 write_compiler_detection_header(
   FILE "${CMAKE_CURRENT_BINARY_DIR}/test_compiler_detection.h"
@@ -15,10 +16,10 @@ write_compiler_detection_header(
   PROLOG "// something"
   EPILOG "// more"
   FEATURES
-    ${cxx_known_features}
+    ${cxx_known_features} ${c_known_features}
 )
 
-if (NOT CMAKE_CXX_COMPILE_FEATURES)
+if (NOT CMAKE_CXX_COMPILE_FEATURES AND NOT CMAKE_C_COMPILE_FEATURES)
   file(WRITE "${CMAKE_CURRENT_BINARY_DIR}/dummy.cpp"
     "int main(int,char**) { return 0; }\n"
   )
diff --git a/Tests/RunCMake/CompileFeatures/NoSupportedCFeatures-result.txt b/Tests/RunCMake/CompileFeatures/NoSupportedCFeatures-result.txt
new file mode 100644
index 0000000..d00491f
--- /dev/null
+++ b/Tests/RunCMake/CompileFeatures/NoSupportedCFeatures-result.txt
@@ -0,0 +1 @@
+1
diff --git a/Tests/RunCMake/CompileFeatures/NoSupportedCFeatures-stderr.txt b/Tests/RunCMake/CompileFeatures/NoSupportedCFeatures-stderr.txt
new file mode 100644
index 0000000..fd18c88
--- /dev/null
+++ b/Tests/RunCMake/CompileFeatures/NoSupportedCFeatures-stderr.txt
@@ -0,0 +1,8 @@
+CMake Error at NoSupportedCFeatures.cmake:[0-9]+ \(target_compile_features\):
+  target_compile_features no known features for C compiler
+
+  "[^"]*"
+
+  version *[.0-9]+\.
+Call Stack \(most recent call first\):
+  CMakeLists.txt:3 \(include\)
diff --git a/Tests/RunCMake/CompileFeatures/NoSupportedCFeatures.cmake b/Tests/RunCMake/CompileFeatures/NoSupportedCFeatures.cmake
new file mode 100644
index 0000000..3624d4b
--- /dev/null
+++ b/Tests/RunCMake/CompileFeatures/NoSupportedCFeatures.cmake
@@ -0,0 +1,5 @@
+
+enable_language(C)
+
+add_library(no_features empty.c)
+target_compile_features(no_features PRIVATE c_static_assert)
diff --git a/Tests/RunCMake/CompileFeatures/NoSupportedCFeaturesGenex-result.txt b/Tests/RunCMake/CompileFeatures/NoSupportedCFeaturesGenex-result.txt
new file mode 100644
index 0000000..d00491f
--- /dev/null
+++ b/Tests/RunCMake/CompileFeatures/NoSupportedCFeaturesGenex-result.txt
@@ -0,0 +1 @@
+1
diff --git a/Tests/RunCMake/CompileFeatures/NoSupportedCFeaturesGenex-stderr.txt b/Tests/RunCMake/CompileFeatures/NoSupportedCFeaturesGenex-stderr.txt
new file mode 100644
index 0000000..df647e8
--- /dev/null
+++ b/Tests/RunCMake/CompileFeatures/NoSupportedCFeaturesGenex-stderr.txt
@@ -0,0 +1,6 @@
+CMake Error in CMakeLists.txt:
+  No known features for C compiler
+
+  "[^"]*"
+
+  version *[.0-9]+\.
diff --git a/Tests/RunCMake/CompileFeatures/NoSupportedCFeaturesGenex.cmake b/Tests/RunCMake/CompileFeatures/NoSupportedCFeaturesGenex.cmake
new file mode 100644
index 0000000..b6053aa
--- /dev/null
+++ b/Tests/RunCMake/CompileFeatures/NoSupportedCFeaturesGenex.cmake
@@ -0,0 +1,5 @@
+
+enable_language(C)
+
+add_library(no_features empty.c)
+target_compile_features(no_features PRIVATE $<1:c_static_assert>)
diff --git a/Tests/RunCMake/CompileFeatures/RunCMakeTest.cmake b/Tests/RunCMake/CompileFeatures/RunCMakeTest.cmake
index bb4e0f9..a23d44f 100644
--- a/Tests/RunCMake/CompileFeatures/RunCMakeTest.cmake
+++ b/Tests/RunCMake/CompileFeatures/RunCMakeTest.cmake
@@ -10,10 +10,19 @@ run_cmake(NotAFeature_OriginDebug_target_compile_features)
 
 run_cmake(generate_feature_list)
 file(READ
+  "${RunCMake_BINARY_DIR}/generate_feature_list-build/c_features.txt"
+  C_FEATURES
+)
+file(READ
   "${RunCMake_BINARY_DIR}/generate_feature_list-build/cxx_features.txt"
   CXX_FEATURES
 )
 
+if (NOT C_FEATURES)
+  run_cmake(NoSupportedCFeatures)
+  run_cmake(NoSupportedCFeaturesGenex)
+endif()
+
 if (NOT CXX_FEATURES)
   run_cmake(NoSupportedCxxFeatures)
   run_cmake(NoSupportedCxxFeaturesGenex)
diff --git a/Tests/RunCMake/CompileFeatures/empty.c b/Tests/RunCMake/CompileFeatures/empty.c
new file mode 100644
index 0000000..bfbbdde
--- /dev/null
+++ b/Tests/RunCMake/CompileFeatures/empty.c
@@ -0,0 +1,7 @@
+#ifdef _WIN32
+__declspec(dllexport)
+#endif
+int empty()
+{
+  return 0;
+}
diff --git a/Tests/RunCMake/CompileFeatures/generate_feature_list.cmake b/Tests/RunCMake/CompileFeatures/generate_feature_list.cmake
index beb15fc..09e17b1 100644
--- a/Tests/RunCMake/CompileFeatures/generate_feature_list.cmake
+++ b/Tests/RunCMake/CompileFeatures/generate_feature_list.cmake
@@ -1,4 +1,10 @@
 
+enable_language(C)
+
+file(WRITE "${CMAKE_CURRENT_BINARY_DIR}/c_features.txt"
+  "${CMAKE_C_COMPILE_FEATURES}"
+)
+
 file(WRITE "${CMAKE_CURRENT_BINARY_DIR}/cxx_features.txt"
   "${CMAKE_CXX_COMPILE_FEATURES}"
 )
diff --git a/Tests/RunCMake/Configure/FailCopyFileABI-stdout.txt b/Tests/RunCMake/Configure/FailCopyFileABI-stdout.txt
index bb87f4c..92fe233 100644
--- a/Tests/RunCMake/Configure/FailCopyFileABI-stdout.txt
+++ b/Tests/RunCMake/Configure/FailCopyFileABI-stdout.txt
@@ -1,4 +1,4 @@
 -- Detecting C compiler ABI info
--- Detecting C compiler ABI info - failed
+-- Detecting C compiler ABI info - failed.*
 -- Configuring done
 -- Generating done
diff --git a/Tests/RunCMake/target_compile_features/RunCMakeTest.cmake b/Tests/RunCMake/target_compile_features/RunCMakeTest.cmake
index f2abef7..33faf2b 100644
--- a/Tests/RunCMake/target_compile_features/RunCMakeTest.cmake
+++ b/Tests/RunCMake/target_compile_features/RunCMakeTest.cmake
@@ -9,3 +9,5 @@ run_cmake(imported_target)
 run_cmake(no_target)
 run_cmake(not_a_cxx_feature)
 run_cmake(no_matching_cxx_feature)
+run_cmake(not_a_c_feature)
+run_cmake(no_matching_c_feature)
diff --git a/Tests/RunCMake/target_compile_features/empty.c b/Tests/RunCMake/target_compile_features/empty.c
new file mode 100644
index 0000000..bfbbdde
--- /dev/null
+++ b/Tests/RunCMake/target_compile_features/empty.c
@@ -0,0 +1,7 @@
+#ifdef _WIN32
+__declspec(dllexport)
+#endif
+int empty()
+{
+  return 0;
+}
diff --git a/Tests/RunCMake/target_compile_features/no_matching_c_feature-result.txt b/Tests/RunCMake/target_compile_features/no_matching_c_feature-result.txt
new file mode 100644
index 0000000..d00491f
--- /dev/null
+++ b/Tests/RunCMake/target_compile_features/no_matching_c_feature-result.txt
@@ -0,0 +1 @@
+1
diff --git a/Tests/RunCMake/target_compile_features/no_matching_c_feature-stderr.txt b/Tests/RunCMake/target_compile_features/no_matching_c_feature-stderr.txt
new file mode 100644
index 0000000..96b959c
--- /dev/null
+++ b/Tests/RunCMake/target_compile_features/no_matching_c_feature-stderr.txt
@@ -0,0 +1,8 @@
+CMake Error at no_matching_c_feature.cmake:[0-9][0-9]? \((target_compile_features|message)\):
+  The compiler feature "gnu_c_dummy" is not known to C compiler
+
+  "GNU"
+
+  version 4.8.1.
+Call Stack \(most recent call first\):
+  CMakeLists.txt:3 \(include\)
diff --git a/Tests/RunCMake/target_compile_features/no_matching_c_feature.cmake b/Tests/RunCMake/target_compile_features/no_matching_c_feature.cmake
new file mode 100644
index 0000000..a44caf2
--- /dev/null
+++ b/Tests/RunCMake/target_compile_features/no_matching_c_feature.cmake
@@ -0,0 +1,15 @@
+
+if (NOT ";${CMAKE_C_COMPILE_FEATURES};" MATCHES ";gnu_c_typeof;")
+  # Simulate passing the test.
+  message(SEND_ERROR
+    "The compiler feature \"gnu_c_dummy\" is not known to C compiler\n\"GNU\"\nversion 4.8.1."
+  )
+  return()
+endif()
+
+add_executable(main empty.c)
+
+target_compile_features(main
+  PRIVATE
+    gnu_c_typeof
+)
diff --git a/Tests/RunCMake/target_compile_features/not_a_c_feature-result.txt b/Tests/RunCMake/target_compile_features/not_a_c_feature-result.txt
new file mode 100644
index 0000000..d00491f
--- /dev/null
+++ b/Tests/RunCMake/target_compile_features/not_a_c_feature-result.txt
@@ -0,0 +1 @@
+1
diff --git a/Tests/RunCMake/target_compile_features/not_a_c_feature-stderr.txt b/Tests/RunCMake/target_compile_features/not_a_c_feature-stderr.txt
new file mode 100644
index 0000000..6dd00f3
--- /dev/null
+++ b/Tests/RunCMake/target_compile_features/not_a_c_feature-stderr.txt
@@ -0,0 +1,5 @@
+CMake Error at not_a_c_feature.cmake:3 \(target_compile_features\):
+  target_compile_features specified unknown feature "c_not_a_feature" for
+  target "main".
+Call Stack \(most recent call first\):
+  CMakeLists.txt:3 \(include\)
diff --git a/Tests/RunCMake/target_compile_features/not_a_c_feature.cmake b/Tests/RunCMake/target_compile_features/not_a_c_feature.cmake
new file mode 100644
index 0000000..0420698
--- /dev/null
+++ b/Tests/RunCMake/target_compile_features/not_a_c_feature.cmake
@@ -0,0 +1,6 @@
+
+add_executable(main empty.c)
+target_compile_features(main
+  PRIVATE
+    c_not_a_feature
+)
diff --git a/Tests/SystemInformation/SystemInformation.in b/Tests/SystemInformation/SystemInformation.in
index 9966e8d..7e1ee24 100644
--- a/Tests/SystemInformation/SystemInformation.in
+++ b/Tests/SystemInformation/SystemInformation.in
@@ -19,6 +19,16 @@ CMAKE_COMPILER_IS_GNUCC == "${CMAKE_COMPILER_IS_GNUCC}"
 CMAKE_COMPILER_IS_GNUCXX == "${CMAKE_COMPILER_IS_GNUCXX}"
 CMAKE_C_COMPILER_ID == "${CMAKE_C_COMPILER_ID}"
 CMAKE_C_COMPILER_VERSION == "${CMAKE_C_COMPILER_VERSION}"
+CMAKE_C90_STANDARD_COMPILE_OPTION == "${CMAKE_C90_STANDARD_COMPILE_OPTION}"
+CMAKE_C99_STANDARD_COMPILE_OPTION == "${CMAKE_C99_STANDARD_COMPILE_OPTION}"
+CMAKE_C11_STANDARD_COMPILE_OPTION == "${CMAKE_C11_STANDARD_COMPILE_OPTION}"
+CMAKE_C90_EXTENSION_COMPILE_OPTION == "${CMAKE_C90_EXTENSION_COMPILE_OPTION}"
+CMAKE_C99_EXTENSION_COMPILE_OPTION == "${CMAKE_C99_EXTENSION_COMPILE_OPTION}"
+CMAKE_C11_EXTENSION_COMPILE_OPTION == "${CMAKE_C11_EXTENSION_COMPILE_OPTION}"
+CMAKE_C_COMPILE_FEATURES == "${CMAKE_C_COMPILE_FEATURES}"
+CMAKE_C90_COMPILE_FEATURES == "${CMAKE_C90_COMPILE_FEATURES}"
+CMAKE_C99_COMPILE_FEATURES == "${CMAKE_C99_COMPILE_FEATURES}"
+CMAKE_C11_COMPILE_FEATURES == "${CMAKE_C11_COMPILE_FEATURES}"
 CMAKE_CXX_COMPILER_ID == "${CMAKE_CXX_COMPILER_ID}"
 CMAKE_CXX_COMPILER_VERSION == "${CMAKE_CXX_COMPILER_VERSION}"
 CMAKE_CXX98_STANDARD_COMPILE_OPTION == "${CMAKE_CXX98_STANDARD_COMPILE_OPTION}"