MySQL 5.7 C API Developer Guide
MYSQL_ROW_OFFSET mysql_stmt_row_tell(MYSQL_STMT *stmt)
Returns the current position of the row cursor for the last
mysql_stmt_fetch(). This value
can be used as an argument to
mysql_stmt_row_seek().
You should use
mysql_stmt_row_tell() only
after
mysql_stmt_store_result().