This function does not behave as expected when unknown escape sequences
are sent to it:
- it fails to store (and thus echo) the last character of the invalid
sequence
- it fails to set esc_len to 0 when it finishes emitting the invalid
sequence, meaning that the following character will appear to be part
of a new escape sequence
- it processes the first character of the rejected sequence as a valid
character, just starting the sequence all over again
The last two bugs conspire to produce an "impossible condition #876"
message which is the main symptom of this behaviour.
Fix these bugs and add a test to verify the behaviour.
Signed-off-by: Simon Glass <sjg@chromium.org>
Reported-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
