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.

8 files changed, 45 insertions, 0 deletions

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
+)