The putc macro is specified as returning an int, but our
type conversion rules turned it into a uint. Put in the
appropriate cast to make the type what we want.
When calling putc, we need to return either EOF
or the character returned. To distinguish the
two, we need to avoid sign extending 0xff. The
code attempted to do this, but the order of
operations was wrong, so we ended up masking,
setting a character, and then sign extending
the character.
This fixes things so we mask after assignment.
