Re: [Qemu-devel] [PATCH] qemu-io: fix EOF Ctrl-D handling in qemu-io readline code

["Daniel P. Berrange" <berrange@redhat.com>]

On Fri, Dec 08, 2017 at 12:15:21PM +0000, Dr. David Alan Gilbert wrote:
> * Daniel P. Berrange (berrange@redhat.com) wrote:
> > qemu-io puts the TTY into non-canonical mode, which means no EOF processing is
> > done and thus getchar() will never return the EOF constant. Instead we have to
> > check for an explicit Ctrl-D, aka  0x4, to detect EOF and exit the qemu-io
> > shell. This fixes the regression that prevented Ctrl-D from triggering an exit
> > of qemu-io that has existed since readline was first added in
> > 
> >   commit 0cf17e181798063c3824c8200ba46f25f54faa1a
> >   Author: Stefan Hajnoczi <stefanha@redhat.com>
> >   Date:   Thu Nov 14 11:54:17 2013 +0100
> > 
> >     qemu-io: use readline.c
> > 
> > Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
> > ---
> >  qemu-io.c | 4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> > 
> > diff --git a/qemu-io.c b/qemu-io.c
> > index c70bde3eb1..2ea0bfbaf8 100644
> > --- a/qemu-io.c
> > +++ b/qemu-io.c
> > @@ -322,7 +322,9 @@ static char *fetchline_readline(void)
> >      readline_start(readline_state, get_prompt(), 0, readline_func, &line);
> >      while (!line) {
> >          int ch = getchar();
> > -        if (ch == EOF) {
> > +        /* In non-canon tty mode we get 0x4 (Ctrl-D), not the stdio "EOF"
> > +         * constant */
> > +        if (ch == 0x4) {
> 
> Personally I'd have made that EOF or 0x4  - but that's fine

I thought about that, but it is impossible to get 'EOF' when the terminal
is in raw mode, so there's little point.

> (I don't see the point of reading the ioctl to figure out which EOF
> char we're using; it seems to turn a trivial check into something much
> more complex)

I'd already done the work to read termios settings by time I read this
comment, so I've sent a v2 anyway :-)

> Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

Regards,
Daniel
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