remove the c code path

tinyxml2.cpp

@@ -36,38 +36,20 @@ distribution.
 #ifndef __has_attribute
 #   define __has_attribute(x) 0
 #endif
-#ifdef __cplusplus
-#   ifndef __has_cpp_attribute
-#      define __has_cpp_attribute(x) 0
-#   endif
-#else
-#   ifndef __has_c_attribute
-#      define __has_c_attribute(x) 0
-#   endif
+#ifndef __has_cpp_attribute
+#  define __has_cpp_attribute(x) 0
 #endif
 
-#ifdef __cplusplus
-#   if defined(_MSC_VER)
-#      define TIXML_FALLTHROUGH (void(0))
-#   elif (__cplusplus >= 201703L && __has_cpp_attribute(fallthrough))
-#      define TIXML_FALLTHROUGH [[fallthrough]]
-#   elif __has_cpp_attribute(clang::fallthrough)
-#      define TIXML_FALLTHROUGH [[clang::fallthrough]]
-#   elif __has_attribute(fallthrough)
-#      define TIXML_FALLTHROUGH __attribute__((fallthrough))
-#   else
-#      define TIXML_FALLTHROUGH (void(0))
-#   endif
+#if defined(_MSC_VER)
+#   define TIXML_FALLTHROUGH (void(0))
+#elif (__cplusplus >= 201703L && __has_cpp_attribute(fallthrough))
+#   define TIXML_FALLTHROUGH [[fallthrough]]
+#elif __has_cpp_attribute(clang::fallthrough)
+#   define TIXML_FALLTHROUGH [[clang::fallthrough]]
+#elif __has_attribute(fallthrough)
+#   define TIXML_FALLTHROUGH __attribute__((fallthrough))
 #else
-#   if defined(_MSC_VER)
-#      define TIXML_FALLTHROUGH (void(0))
-#   elif __has_c_attribute(fallthrough)
-#      define TIXML_FALLTHROUGH [[fallthrough]]
-#   elif __has_attribute(fallthrough)
-#      define TIXML_FALLTHROUGH __attribute__((fallthrough))
-#   else
-#      define TIXML_FALLTHROUGH (void(0))
-#   endif
+#   define TIXML_FALLTHROUGH (void(0))
 #endif