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

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

On Wed, Dec 06, 2017 at 08:22:35AM -0600, Eric Blake wrote:
> On 12/06/2017 05:57 AM, Daniel P. Berrange 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(-)
> 
> >      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) {
> 
> Should we instead be looking for a match against the current termios()
> c_cc[VEOF] setting, in case the user prefers something other than ^D via
> stty?  Does readline provide any functionality for automating this?

I was afraid someone was going to suggest doing that. I was being lazy by
hardcoding Ctrl-D, but yes the real readline() library will honour the
VEOF value.  QEMU though is using a home-grown reimpl of readline...

Regards,
Daniel
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