The buffer-full branch writes the forced '\r' to command[sizeof-1], but the
line-complete check below tests command[len-1] (== sizeof-2 when the buffer
is full), so the line never completes: the read loop's condition
(len < sizeof-1) stays false forever and the CLI stops reading serial input
until reboot. Writing at [sizeof-1] also overwrites the string's NUL
terminator, so the next strlen() reads past the buffer (UB).
Write the '\r' at command[sizeof-2] instead — exactly the position the
completion check tests. The overflowed input is then processed as an
(unknown) command, the buffer resets, and the CLI keeps working.
Reproduced on hardware (T1000-E repeater): ~53 arrow-key presses in an
attached terminal (3-byte ESC[A escape sequences, 159 bytes with no CR)
filled the buffer and the CLI never accepted a command again until reboot.
The same copy-pasted pattern is fixed in simple_repeater, simple_sensor,
simple_room_server and simple_secure_chat.
Fedor Kallay
f76c46565a