#define GET_NEXT_WCHAR() do { \
prev_c = next_c; pos += pos_add_next; \
if ((pos_add_next = mbtowc(&next_c, str_byte, MB_LEN_MAX)) <= 0) { \
#define GET_NEXT_WCHAR() do { \
prev_c = next_c; pos += pos_add_next; \
if ((pos_add_next = mbtowc(&next_c, str_byte, MB_LEN_MAX)) <= 0) { \