remove the c code path

tinyxml2.cpp

@@ -36,17 +36,10 @@ 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
-#endif
 
-#ifdef __cplusplus
 #if defined(_MSC_VER)
 #   define TIXML_FALLTHROUGH (void(0))
 #elif (__cplusplus >= 201703L && __has_cpp_attribute(fallthrough))
@@ -58,17 +51,6 @@ distribution.
 #else
 #   define TIXML_FALLTHROUGH (void(0))
 #endif
-#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
-#endif
 
 
 #if defined(_MSC_VER) && (_MSC_VER >= 1400 ) && (!defined WINCE)