why does setjmp return 1 after longjmp(buf,0)?

[Guy Harris]

>>Fortunately, the ANSI C spec forbids that sort of thing, so 4.4BSD
>
>This is fortunate?

It's fortunate that ANSI C is saying *something* about the subject, so
that vendors know what they must do and implementors know what they can
count on.

I don't particular care *what* they say; just about anything will work
without too much pain, I don't ever pass "longjmp" a second argument of
0 anyway, and if something that's not ideal in the technical sense is
necessary to get consensus, I can live with it.