+/* Checks whether if UTF-8 string ID is an acceptable identifier in encoding
+ DICT_ENCODING (UTF-8 if null). Returns NULL if it is acceptable, otherwise
+ an error message that the caller must free(). */
+char * WARN_UNUSED_RESULT
+id_is_valid__ (const char *id, const char *dict_encoding)
+{
+ char *error = id_is_plausible__ (id);
+ if (error)
+ return error;