| Message ID | 20171206115726.5237-1-berrange@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
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?
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
On 12/06/2017 08:25 AM, Daniel P. Berrange wrote: >> 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... I understand why we can't use modern libreadline (it is licensed GPLv3+, making it impossible to use with our GPLv2-only code) - but doesn't BSD have a readline-alike library with BSD licensing that we could use instead of implementing readline ourselves? (Was it named libinput?)
Eric Blake <eblake@redhat.com> writes: > On 12/06/2017 08:25 AM, Daniel P. Berrange wrote: > >>> 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... > > I understand why we can't use modern libreadline (it is licensed GPLv3+, > making it impossible to use with our GPLv2-only code) - but doesn't BSD > have a readline-alike library with BSD licensing that we could use > instead of implementing readline ourselves? (Was it named libinput?) We've discussed this before. Short story: we can't use the original due to our foolish licensing mistake, and the clones don't cut the mustard. Long story: http://lists.gnu.org/archive/html/qemu-devel/2016-10/msg02697.html
* 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 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) Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com> > break; > } > readline_handle_byte(readline_state, ch); > -- > 2.14.3 > > -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
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
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) { break; } readline_handle_byte(readline_state, ch);
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(-)