Public functions without tests
These symbols were not removed while working on #157 (closed) (dead code removal), because they appear in public headers and are not prefix by _
.
sion_free_io_info
sion_set_fp_closed
sion_get_dfile
sion_isdebug
sion_debug_off
sion_generic_register_get_multi_filename_cb
They should probably be called from the test suite.