bug#6413: What does ntdll!DbgUiConnectToDbg mean? (on w32)

bug#6413: What does ntdll!DbgUiConnectToDbg mean? (on w32)

[Lennart Borgman]

I just got this from the gdb running Emacs:

Program received signal SIGTRAP, Trace/breakpoint trap.
[Switching to Thread 372.0xcec]
0x7c90120f in ntdll!DbgUiConnectToDbg () from C:\WINDOWS\system32\ntdll.dll
(gdb) bt
#0  0x7c90120f in ntdll!DbgUiConnectToDbg ()
   from C:\WINDOWS\system32\ntdll.dll
#1  0x7c951e40 in ntdll!KiIntSystemCall () from C:\WINDOWS\system32\ntdll.dll
#2  0x00000005 in ?? ()
#3  0x00000004 in ?? ()
#4  0x00000001 in ?? ()
#5  0x215affd0 in ?? ()
#6  0x00000000 in ?? ()
(gdb) c

Is there anything I can do to look into it further? I can't think of
anything I did in Emacs this time that triggered this so I am a bit
lost.


As I previously mentioned I have added a macro to test system calls
return values and I wonder if this somehow is involved here or if this
is just one of these "doctor watson-crashes" I now and then see, as
seen through gdb.

The macro I added just looks like

  #define W32ASSERT(TEST, WHERE) if (!TEST) DebPrint (("%s: %s\n",
WHERE, w32_strerror(0)))

In the code I write this as something like

  W32ASSERT (0, "w32_SetWindowPos_from_main_thread.PostMessage");

or with 0 replaced by a variable.

This does not look problematic too me, but I wonder if DepPrint can be
called anywhere. Is there some problem calling it inside a BLOCK_INPUT
.. UNBLOCK_INPUT?

bug#6413: What does ntdll!DbgUiConnectToDbg mean? (on w32)

[Eli Zaretskii]

> From: Lennart Borgman <lennart.borgman@gmail.com>
> Date: Sun, 13 Jun 2010 18:58:25 +0200
> Cc: 
> 
> I just got this from the gdb running Emacs:
> 
> Program received signal SIGTRAP, Trace/breakpoint trap.
> [Switching to Thread 372.0xcec]
> 0x7c90120f in ntdll!DbgUiConnectToDbg () from C:\WINDOWS\system32\ntdll.dll
> (gdb) bt
> #0  0x7c90120f in ntdll!DbgUiConnectToDbg ()
>    from C:\WINDOWS\system32\ntdll.dll
> #1  0x7c951e40 in ntdll!KiIntSystemCall () from C:\WINDOWS\system32\ntdll.dll
> #2  0x00000005 in ?? ()
> #3  0x00000004 in ?? ()
> #4  0x00000001 in ?? ()
> #5  0x215affd0 in ?? ()
> #6  0x00000000 in ?? ()
> (gdb) c
> 
> Is there anything I can do to look into it further?

Try "info threads".  I'm guessing you will see a couple more threads,
in which case switch to each one of them and type "bt" to see their
call-stack.

bug#6413: What does ntdll!DbgUiConnectToDbg mean? (on w32)

[Juanma Barranquero]

On Sun, Jun 13, 2010 at 18:58, Lennart Borgman
<lennart.borgman@gmail.com> wrote:

> Is there anything I can do to look into it further? I can't think of
> anything I did in Emacs this time that triggered this so I am a bit
> lost.

Is this bug repeatable, or can we close it?

    Juanma

bug#6413: What does ntdll!DbgUiConnectToDbg mean? (on w32)

[Lennart Borgman]

On Sun, Jul 3, 2011 at 20:49, Juanma Barranquero <lekktu@gmail.com> wrote:
> On Sun, Jun 13, 2010 at 18:58, Lennart Borgman
> <lennart.borgman@gmail.com> wrote:
>
>> Is there anything I can do to look into it further? I can't think of
>> anything I did in Emacs this time that triggered this so I am a bit
>> lost.
>
> Is this bug repeatable, or can we close it?

I saw some more of this, but at the moment I have no setup to repeat it.

You might look at the macro. I would be glad for some comments on it
since I rarely right code like that.

bug#6413: What does ntdll!DbgUiConnectToDbg mean? (on w32)

[Juanma Barranquero]

On Mon, Jul 4, 2011 at 00:39, Lennart Borgman <lennart.borgman@gmail.com> wrote:

> I saw some more of this, but at the moment I have no setup to repeat it.

You also didn't follow Eli's suggestion to try to show backtraces from
other threads, or you didn't report it.

I'm closing this bug. Please reopen it if you have additional info.

    Juanma

bug#6413: What does ntdll!DbgUiConnectToDbg mean? (on w32)

[Juanma Barranquero]

On Mon, Jul 4, 2011 at 00:59, Lennart Borgman <lennart.borgman@gmail.com> wrote:

> You may consider the above information additional info.

No, additional info is something that helps to track or fix a bug, and
I still haven't seen any bug in this report.

    Juanma

bug#6413: What does ntdll!DbgUiConnectToDbg mean? (on w32)

[Lennart Borgman]

On Mon, Jul 4, 2011 at 01:05, Juanma Barranquero <lekktu@gmail.com> wrote:
> On Mon, Jul 4, 2011 at 00:59, Lennart Borgman <lennart.borgman@gmail.com> wrote:
>
>> You may consider the above information additional info.
>
> No, additional info is something that helps to track or fix a bug, and
> I still haven't seen any bug in this report.

Hm, that was what I gave above.

bug#6413: What does ntdll!DbgUiConnectToDbg mean? (on w32)

[Juanma Barranquero]

On Mon, Jul 4, 2011 at 01:19, Lennart Borgman <lennart.borgman@gmail.com> wrote:

> Hm, that was what I gave above.

Sorry, you're right, this bug report is really about a bug, or at
least a crash. I was mixing bug reports :-)

But still, you have said: "It might be that I have fixed this in my
patched version where I did the change I suggested."

The only change you've suggested in this thread is adding a debug
macro. If that really changed things, that would mean that memory is
getting overwritten or some such thing, and without additional
information there's not much to be done.

I think you run Emacs under GDB. If so, when such a crash happens
please don't exit GDB after reporting the bug. Leave it open so
someone knowledgeable can ask you about it.

Thanks,

    Juanma

bug#6413: What does ntdll!DbgUiConnectToDbg mean? (on w32)

[Lennart Borgman]

On Mon, Jul 4, 2011 at 01:29, Juanma Barranquero <lekktu@gmail.com> wrote:
> On Mon, Jul 4, 2011 at 01:19, Lennart Borgman <lennart.borgman@gmail.com> wrote:
>
>> Hm, that was what I gave above.
>
> Sorry, you're right, this bug report is really about a bug, or at
> least a crash. I was mixing bug reports :-)

That is common when you try to fix a lot of things ;-)

> But still, you have said: "It might be that I have fixed this in my
> patched version where I did the change I suggested."
>
> The only change you've suggested in this thread is adding a debug
> macro. If that really changed things, that would mean that memory is
> getting overwritten or some such thing, and without additional
> information there's not much to be done.
>
> I think you run Emacs under GDB. If so, when such a crash happens
> please don't exit GDB after reporting the bug. Leave it open so
> someone knowledgeable can ask you about it.

I can't do that at the moment, but I will do it again when I have time
to set it up.

bug#6413: What does ntdll!DbgUiConnectToDbg mean? (on w32)

[Juanma Barranquero]

On Mon, Jul 4, 2011 at 01:44, Lennart Borgman <lennart.borgman@gmail.com> wrote:

> I can't do that at the moment, but I will do it again when I have time
> to set it up.

Thanks.

    Juanma