Greetings,
One of the guys on my team is getting a
segfault in Accessible_getChildAtIndex. We've have been trying to track
this down for days and are at wit's end. This is our
environment:
Ubuntu 8.04
Gnome 2.22.3
at-spi 1.22.1
Both he and I run Ubuntu on VMWare
Workstation. We are both running identical Ubuntu images on
VMware. Tthe error does not happen for me, he is getting it all the
time. The main difference between our two laptops: his is
significantly slower than mine.
We have a standalone application that
displays all the apps, (i.e, direct children of desktop), on the
machine. Here is the loop to retrieve them:
1 Accessible
*desktop = SPI_getDesktop(0);
2 int dtChildCount =
Accessible_getChildCount(desktop);
3 int
child;
4 for(child = 0; child < dtChildCount; child++)
{
5 Accessible *desktopChild =
Accessible_getChildAtIndex(desktop,
child);
6 if(desktopChild == 0)
{
7
myLog("getChild returned
0");
8
continue;
9 }
10 ... -- display info
about each app
11 }
This loop in the standalone application works for both of us,
although two of the apps get SPI Exceptions. For app 18 (child == 17) we
get an SPI_Exception (*) and the Accessible_getChildAtIndex returns 0 (the
call on line 6, above). Here is the
output:
app 1/21
(n:x-session-manager,d:,r:application) [actions: ] [subs: Application ]
(children: 0)
app 2/21 (n:gnome-settings-daemon,d:,r:application)
[actions: ] [subs: Application ] (children: 0)
app 3/21
(n:gnome-screensaver,d:,r:application) [actions: ] [subs: Application ]
(children: 0)
app 4/21 (n:gnome-panel,d:,r:application) [actions: ]
[subs: Application ] (children: 2)
app 5/21
(n:nautilus,d:,r:application) [actions: ] [subs: Application ]
(children: 1)
app 6/21 (n:metacity,d:,r:application) [actions: ]
[subs: Application ] (children: 0)
app 7/21
(n:bluetooth-applet,d:,r:application) [actions: ] [subs: Application ]
(children: 0)
app 8/21 (n:update-notifier,d:,r:application) [actions:
] [subs: Application ] (children: 0)
app 9/21
(n:gnome-volume-manager,d:,r:application) [actions: ] [subs: Application
] (children: 0)
app 10/21 (n:gnome-power-manager,d:,r:application)
[actions: ] [subs: Application ] (children: 0)
app 11/21
(n:evolution-alarm-notify,d:,r:application) [actions: ] [subs:
Application ] (children: 0)
app 12/21
(n:tracker-applet,d:,r:application) [actions: ] [subs: Application ]
(children: 0)
app 13/21 (n:applet.py,d:,r:application) [actions: ]
[subs: Application ] (children: 0)
app 14/21
(n:gnome-terminal,d:,r:application) [actions: ] [subs: Application ]
(children: 3)
app 15/21 (n:vmware-user,d:,r:application) [actions: ]
[subs: Application ] (children: 0)
---- spiException on app 15/21
retrieving the attributes: Accessible_getAttributes()
app 16/21
(n:notification-daemon,d:,r:application) [actions: ] [subs: Application
] (children: 0)
app 17/21 (n:nm-applet,d:,r:application) [actions: ]
[subs: Application ] (children: 0)
---- NULL app 18: spiException
app 19/21 (n:Firefox,d:,r:application)
[actions: ] [subs: Application ] (children: 1)
app 19/21 -
[states: enabled, sensitive, showing, visible]
app 20/21
(n:evince,d:,r:application) [actions: ] [subs: Application ] (children:
2)
app 21/21 (n:sbq,d:,r:application) [actions: ] [subs: Application
] (children: 0)
(*) Both exceptions display
as:
TCF 57:30.032: AT-SPI Exception:
IDL:omg.org/CORBA/COMM_FAILURE:1.0
TCF
57:30.032: - Code: unknown type or
doesn't fit the other types
TCF
57:30.032: - Type: Do not know or
cannot tell where the problem is
In our primary application, which is multithreaded, we go
through a loop identical in structure to the one above. This time, when
we get to Gnome desktop app 18 our application gets a SIGSEGV
directly. The SPI_ExceptionHandler we pushed does not get
called. We've put in a SIGSEV handler and a
stack walker to figure out what is going on and we get this stack
dump:
/usr/lib/libcspi.so.0 [0xb78da969] called
by
/usr/lib/libcspi.so.0 [0xb78d6be2] called
by
/usr/lib/libcspi.so.0(Accessible_getChildAtIndex+0x52)
[0xb78d4372] called by <==
Accessible_getChildAtIndex()!
./stp-atspi(getFramesUnderMouse+0x6d)
[0x8063a65] called by
./stp-atspi(stackingOrderUnderMouse+0x9a)
[0x8063c1e] called by
...
Any suggestions for working around
this would be greatly appreciated. Here is some information we've
learned:
If the VMWare image is rebooted and we
comment out all calls to Accessible_getAtttributes(), then we do not get the
segfault (SIGSEGV). However, if we leave the calls in to
Accessible_getAttributes() then we will start getting the SIGSEGV as describe
above. Our theory is that there is a bug in the Accessible_getAttributes
implementation that gets a segfault and leaves some AT-SPI data structure in a
bad state. That bad data structure causes the AT-SPI
implementation to get a suprise SIGSEGV from then on every time we try to
access application 18.
-Sam
PS: Again, this error does not happen
in my VMWare instance, only on my teammate's slower laptop. But one
important fact is that the two of us are running identical Ubuntu
images.
