actually, i suspect that one subtle point here is that char in Plan 9 (and Inferno) C is
always signed, which (i recall) ANSI C does not guarantee one way or the other.
there is no warranty of fitness for purpose; some such thing.
i can't be certain because my new C standard hasn't arrived owing to
the application by my credit card company of AI for Internet sales.
well, it's obvious the first thing a villain would buy is a copy of
the C99 standard, isn't it?