NVDA crashes at Startup with BRLTTY enabled

[nvaccessAuto]

Reported by laughingthunder on 2015-04-16 06:24
There is a message posted to the NVDA user mailing list regarding NVDA crashing at Startup with BRLTTY enabled. I am posting it here for tracking purposes.

--Begin Message--

NVDA crashes when it starts up and the selected braille display is Brltty.  It crashes so hard that you either have to hit the power switch, or change to a different user account, kill nvda.exe and then switch back. I managed to capture a log file of the crash. I don't know how much use it'll be, but below are the relevant sections.
INFO - main (13:00:06):
Starting NVDA
INFO - core.main (13:00:06):
Config dir: C:\Users\asterisk\AppData\Roaming\nvda
INFO - core.main (13:00:06):
NVDA version 2015.1
INFO - core.main (13:00:06):
Using Windows version sys.getwindowsversion(major=6, minor=1, build=7601, platform=2, service_pack='Service Pack 1')
INFO - core.main (13:00:06):
Using Python version 2.7.9 (default, Dec 10 2014, 12:24:55) v.1500 32 bit (Intel)
INFO - core.main (13:00:06):
Using comtypes version 0.6.2
NFO - braille.initialize (13:00:06):
Using liblouis version 2.6.0
INFO - braille.BrailleHandler.setDisplayByName (13:00:06):
Loaded braille display driver brltty, current display has 80 cells.
INFO - brailleInput.initialize (13:00:06):
Braille input initialized
ERROR - eventHandler.executeEvent (13:00:06):
error executing event: becomeNavigatorObject on <NVDAObjects.window.Desktop object at 0x05728FB0> with extra args of {}
Traceback (most recent call last):
  File "eventHandler.pyo", line 141, in executeEvent
  File "eventHandler.pyo", line 89, in init
  File "eventHandler.pyo", line 96, in next
  File "NVDAObjects__init__.pyo", line 875, in event_becomeNavigatorObject
  File "braille.pyo", line 1478, in handleReviewMove
  File "braille.pyo", line 1402, in doNewObject
  File "braille.pyo", line 1192, in getFocusRegions
  File "braille.pyo", line 549, in update
  File "braille.pyo", line 394, in update
  File "louis__init_.pyo", line 136, in translate
WindowsError: exception: access violation reading 0x67205645
ERROR - eventHandler.executeEvent (13:00:06):
error executing event: becomeNavigatorObject on <NVDAObjects.window.Desktop object at 0x05728FB0> with extra args of {}
Traceback (most recent call last):
  File "eventHandler.pyo", line 141, in executeEvent
  File "eventHandler.pyo", line 89, in init
  File "eventHandler.pyo", line 96, in next
  File "NVDAObjects__init__.pyo", line 875, in event_becomeNavigatorObject
  File "braille.pyo", line 1478, in handleReviewMove
  File "braille.pyo", line 1402, in doNewObject
  File "braille.pyo", line 1192, in getFocusRegions
  File "braille.pyo", line 549, in update
  File "braille.pyo", line 394, in update
  File "louis__init_.pyo", line 136, in translate
WindowsError: exception: access violation reading 0x6745DA0D
If you start Brltty while NVDA is loaded, there is no crash. This crash only happens when NVDA is started while Brltty is enabled. I do not know if a similar crash happens if another braille display is loaded.
I hope something can be done about this, because Brltty is the only service which supports my current desktop display.

--End Message--

[nvaccessAuto]

Comment 1 by jteh on 2015-04-17 05:53
From the log, this actually looks like a problem related to braille translation (liblouis), not BRLTTY. It'd be good to know what NVDA language and braille translation table the user is using.

[nvaccessAuto]

Comment 2 by asterisk (in reply to comment 1) on 2015-04-17 17:44
Replying to jteh:

From the log, this actually looks like a problem related to braille translation (liblouis), not BRLTTY. It'd be good to know what NVDA language and braille translation table the user is using.

I am the one who posted the original message. The NVDA language is English, and the translation table is U.S. English Grade Two.

[nvaccessAuto]

Comment 3 by jteh on 2015-04-20 23:26
That's very odd. I haven't seen any issues with that table before, but there are nasty braille translation errors in your log. Perhaps BRLAPI is somehow corrupting memory, but that would suggest a very severe issue in BRLAPI.

[nvaccessAuto]

Attachment nvda-old.log added by dkager on 2015-05-27 10:38
Description:
Crash log without BRLTTY.

[nvaccessAuto]

Comment 4 by dkager on 2015-05-27 10:43
This doesn't appear to be specific to BRLTTY (see attachment). I'm running master with liblouis 2.6.2, Alva BC640 display, en-us-comp8.ctb table.
I haven't been able to reproduce this in the precompiled next builds, but in master from source this crash often occurs when OK'ing the Braille Settings dialog. I've seen this happen when changing tables so am guessing it's not specific to the table you are using but rather that it has to do with setting/compiling the table or initializing the braille display driver.

[jcsteh]

We believe this to be the same underlying cause as #4457. A fix is now available for testing in the latest "next" branch snapshots.