Valid range of SQLite rowid?
Row IDs are 64-bit signed integers, so the maximum is 0x7FFFFFFFFFFFFFFFLL. But unless a negative or zero row ID has been entered explicitly, auto-generated row IDs are always greater than zero. If you can be certain that row IDs will always be generated automatically then zero or -1 would be safe values to for error status returns.
Thinking further, I realise that the sqlite3_last_insert_rowid API call returns zero if nothing has ever been inserted into the table, thus making zero a de-facto "invalid" row ID.