ruby.h: err rb_check_safe_str explicitly

* include/ruby/ruby.h (rb_check_safe_str, Check_SafeStr): show
  error message to update for obsolete function and macro.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@47636 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

include/ruby/ruby.h

@@ -531,6 +531,13 @@ void rb_check_safe_obj(VALUE);
     StringValue(v);\
     rb_check_safe_obj(v);\
 } while (0)
+#if defined(__GNUC__) && (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 4))
+void rb_check_safe_str(VALUE) __attribute__((error("rb_check_safe_str() and Check_SafeStr() are obsolete; use SafeStringValue() instead")));
+# define Check_SafeStr(v) rb_check_safe_str((VALUE)(v))
+#else
+# define rb_check_safe_str(x) [<"rb_check_safe_str() is obsolete; use SafeStringValue() instead">]
+# define Check_SafeStr(v) [<"Check_SafeStr() is obsolete; use SafeStringValue() instead">]
+#endif
 
 VALUE rb_str_export(VALUE);
 #define ExportStringValue(v) do {\