added a comment

Zend/zend_virtual_cwd.c

@@ -983,6 +983,7 @@ static int tsrm_realpath_r(char *path, int start, int len, int *ll, time_t *t, i
 				memcpy(substitutename, path, len + 1);
 				substitutename_len = len;
 			} else {
+				/* XXX this might be not the end, restart handling with REPARSE_GUID_DATA_BUFFER should be implemented. */
 				free_alloca(pbuffer, use_heap_large);
 				return -1;
 			}