> > Because it has to restore any registers saved by intermediate call
> > frames (in the "normal" case, that is).  Arguably all registers should
> > be saved into the jmp_buf; I don't know why that isn't how it's done.
> 
> setjmp/longjmp aren't required to preserve general registers; that's
> why setjmp(3) says that values of all non-volatile autos modified
> between the setjmp and longjmp are unpredictable.  

I screwed up here.  The setjmp/longjmp combination *does* have to
preserve the general registers that must normally be preserved across
any function call.  The non-volatile autos being unpredictable is not
tied to that; that just happens whenever you mess with flow control.

To track pth not working, I filed port-vax/11698.  There's patches
in there for setjmp/longjmp that get pth working for me.

Matt

--
Matt Fredette
fredette@aquery.com, fredette@mit.edu, fredette@theory.lcs.mit.edu
http://mit.edu/fredette/www
"If you understood everything I said, you'd be me."  - Miles Davis