RE: Brainstorming a fix for CTRL-C handling in an emacs shell buf fer (non-TTY)

[Troy Noble <troy dot noble at channelpoint dot com>]

Christopher,

Here's yet another patch (hopefully at the location of the
root problem this time).

I'd like to see if you come to the same conclusion as I did.

$ diff -b --unified=3 dtable.cc-orig dtable.cc
--- dtable.cc-orig      Sat Apr 28 17:48:27 2001
+++ dtable.cc   Tue May  8 06:36:00 2001
@@ -120,7 +120,7 @@
       cygheap->fdtab.init_std_file_from_handle (2, err, GENERIC_WRITE,
"{stderr}");
       /* Assign the console as the controlling tty for this process if we
actually
         have a console and no other controlling tty has been assigned. */
-      if (myself->ctty < 0 && GetConsoleCP () > 0)
+      if (ISSTATE(myself,PID_USETTY) && myself->ctty < 0 && GetConsoleCP ()
> 0)
        set_console_ctty ();
     }
 }


Below is the stack trace when stdin is a pipe.  Bottom line
(I think) is that we should never get into any of the code
that sets ctty or the tty's pgid for a pipe.  I suspect the
missing check above is the reason we got to
fhandler_termios.cc:101 which is where the pgid is
actually getting set.

(gdb) n
101               setpgid (myself->pgid);
(gdb) p myself->procinfo->pgid
$24 = 1116
(gdb) p myself->procinfo->ctty
$25 = 1073741824
(gdb) bt
#0  tty_min::set_ctty (this=0x1c520000, ttynum=1073741824, flags=0)
    at /work/build/src/winsup/cygwin/fhandler_termios.cc:101
#1  0x61014b79 in get_tty_stuff (flags=0)
    at /work/build/src/winsup/cygwin/fhandler_console.cc:112
#2  0x61014b94 in set_console_ctty ()
    at /work/build/src/winsup/cygwin/fhandler_console.cc:119
#3  0x61006f74 in stdio_init () at
/work/build/src/winsup/cygwin/dtable.cc:124
#4  0x6100394f in dll_crt0_1 () at
/work/build/src/winsup/cygwin/dcrt0.cc:815
#5  0x61003d51 in _dll_crt0 () at /work/build/src/winsup/cygwin/dcrt0.cc:928
#6  0x61003d90 in dll_crt0 (uptr=0x0)
    at /work/build/src/winsup/cygwin/dcrt0.cc:940
#7  0x469dfb in _size_of_heap_reserve__ ()
#8  0x40103d in _size_of_heap_reserve__ ()
#9  0x77e992a6 in _libkernel32_a_iname ()


-----Original Message-----
From: Christopher Faylor [mailto:cgf@redhat.com]
Sent: Monday, May 07, 2001 11:23 AM
To: 'cygwin@cygwin.com'
Subject: Re: Brainstorming a fix for CTRL-C handling in an emacs shell
buf fer (non-TTY)


On Sun, May 06, 2001 at 10:16:38PM -0600, Troy Noble wrote:
>Christopher,
>
>Looks like t->getpgid() is OK,  it's the
>
>   t->getpgid () != myself->pid
>
>that's causing the behavior... and I think I understand why
>now.  Thanks for leading me in the right direction.
>
>What do you think about the patch below for exceptions.cc
>instead?  No extra environment variables required this time ;->

You're still fixing the symptom rather than the problem.

If the program doesn't have a controlling tty then t->getpgid should be
zero.  If it isn't zero, then I want to know why it isn't zero.

>to kill other non-cygwin child processes (like java.exe for example)
>when running bash in a shell buffer.  They probably had CYGWIN=tty
>set.  You probably already knew that,

No, I didn't know that.  It's difficult to understand why anyone would
do something that dumb.  If they do, they get what they paid for.

Or, rather, I guess I'll get what they paid for because then they'll
send email whining about cygwin instabilities.

cgf


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