Re: dialog --pause not timing out on serial console (dialog 1.2)

[Stefan Puiu]

Hi Thomas,

Sorry for resurrecting an old thread, but I dug a bit deeper into this
and was wondering if the new info rings any bells.

On Thu, Jan 28, 2021 at 9:59 PM Thomas Dickey <dickey@his.com> wrote:
>
[...]
> > > > We have dialog 1.2 (release 4.20130902.fc20) and ncurses 5.9 (release
> > > > 12.20130511.fc20), I know, ancient stuff.
> > >
> > > yes, that's known and supposed to have been fixed.
> > > This appears to be relevant:
> > >
> > > https://invisible-island.net/dialog/CHANGES.html#t20030818
> > >         + better solution for initializing curses when "--stdout" option 
> > > is
> > >           used, e.g., use stderr for the output if it is a tty.  Also 
> > > correct
> > >           the error handling, so dialog exits with an error if it cannot
> > >           find a way to do output (Debian #205509).
> >
> > Thanks for the pointer. I think that change is a bit old, though, the
> > Fedora package seems to be from 2013, and from the look of the release
> > tag (and the RPM changelog), I think it's based on
> > dialog-1.2.20130902.
>
> agreed - I mentioned it because I didn't notice further change notes
> for this issue (though I seem to recall some followup).

Somebody managed to reproduce this again, and this time I debugged
dialog a bit with gdb, and it seems to be stuck inside a tcsetattr
call:

(gdb) bt
#0  0x0000003b96aeb5cc in __GI_tcsetattr (fd=1,
optional_actions=optional_actions@entry=1,
    termios_p=termios_p@entry=0x7fff17feba40) at
../sysdeps/unix/sysv/linux/tcsetattr.c:83
#1  0x0000003b98e1677a in _nc_set_tty_mode
(buf=buf@entry=0x7fff17feba40) at
../../ncurses/tinfo/lib_ttyflags.c:108
#2  0x0000003b98e10d8c in cbreak () at ../../ncurses/tinfo/lib_raw.c:155
#3  0x0000003b97214f33 in _nc_initscr () at ../../ncurses/base/lib_newterm.c:79
#4  newterm (name=<optimized out>, ofp=<optimized out>, ifp=<optimized
out>) at ../../ncurses/base/lib_newterm.c:332
#5  0x0000003b97211343 in initscr () at ../../ncurses/base/lib_initscr.c:87
#6  0x0000003e24225f5d in init_dialog (input=<optimized out>,
output=0x3b96db81c0 <_IO_2_1_stderr_>) at util.c:385
#7  0x0000000000402351 in main (argc=12, argv=0x7fff17fec638) at dialog.c:1844

(gdb) info locals
resultvar = 18446744073709551104
k_termios = {c_iflag = 21504, c_oflag = 5, c_cflag = 7346, c_lflag =
2105, c_line = 0 '\000',
  c_cc = 
"\003\034\177\025\004\000\001\000\021\023\032\000\022\017\027\026\000\000"}
cmd = <optimized out>
retval = <optimized out>


As far as I can tell, it's trying to call ioctl 0x5043 (TCSETSW) on fd
1 (stdout), and that call blocks. Maybe the serial driver in the
kernel is getting blocked on something? Any ideas?

Thanks in advance,
Stefan.