I don't have a C standard handy, but it's been suggested to me in
private mail that a compiler could choose to use -1 as the value of an
equality boolean value.

If it were to do so (or even if it chooses any non-1 value for TRUE), then
rcmd.c will fail to do what it's intended to do because it currently
negates the value of a boolean test and compares it with -1.

==John