SQLite C/C++ API unsigned char *
From the SQLite documentation:
(H13821) The sqlite3_column_text(S,N) interface converts the Nth column in the current row of the result set for the prepared statement S into a zero-terminated UTF-8 string and returns a pointer to that string.
UTF-8 wants byte values ranging from 0x00 to 0xFF. char can range from -0x80 to 0x7F (signed) or 0x00 to 0xFF (unsigned). Forcing unsigned allows the proper encoding of a UTF-8 string.