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.

5 files changed, 73 insertions, 11 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;
+}