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Firefox crashes - assertation failed

  • 5 replies
  • 2 have this problem
  • Last reply by guigs

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I am experiencing random occasional crashes with new Firefox versions 40 (40.0.2 , 40.0.3 both so far). They just happen randomly after a while of browsing. Sometimes it's triggered by just a mere mouse cursor movement (really strange..). Anyway here are some details.

This is what I see in .xsession-errors file after a crash:

case 1) firefox: ../../src/XlibInt.c:595: _XPrivSyncFunction: Assertion `dpy->synchandler == _XPrivSyncFunction' failed.

case 2) firefox: ../../src/xcb_io.c:385: _XAllocID: Assertion `ret != inval_id' failed.

The 2nd case happens much more often than the 1st one.

$ uname -a Linux bt 3.2.6 #1 SMP Fri Feb 17 10:34:20 EST 2012 x86_64 GNU/Linux

I'm using a bit old linux distro backtrack 5 R2. I know this is kinda outdated distro and you will probably not gonna rash into fixing this, but I just couldn't find any info about those failed assertions, so I'm posting it here. In case you find out how to fix it or workaround it (so the new version of Firefox do not crash for me), please let me know.. Thank you!

All Replies (5)

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Start Firefox in Safe Mode {web Link} by holding down the <Shift>
(Mac Options)
key, and then starting Firefox. Is the problem still there?

While still in Safe Mode,

In the address bar, type about:crashes<enter>. Note: If any reports do not have BP in front of the numbers/letters, click it and select Submit.

Using your mouse, mark the most resent 7 - 10 crash reports, and copy them. Now go to the reply box below and paste them in.

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He is is using linux and he has no safemode and gave the kernel details by using "uname -a" command the new stable kernel is 4.1.6 that you can find and you download from here:

You can see this thread in here and is a bit funny

jmurcko gave me a crash report and i was be able to find the library that was missing i told him to type


This way the terminal is used as output of errors and the errors appear with the pid they get from the process that running in the background like

(firefox:1784): Gtk-CRITICAL **: IA__gtk_clipboard_set_with_data: assertion 'targets != NULL' failed (firefox:1784): Gtk-CRITICAL **: IA__gtk_clipboard_set_with_data: assertion 'targets != NULL' failed

Is the best way to detect all the type of errors and to find the missing libraries also you can see this link here

I used a virtual machine and I did compiled nightly 40.0b9i in debian 8.1 is the best way to find out how many new libraries are missing in the end I did download and install 26 new libraries but in the end the effort was worth it as I was be able to view even the mobile version of this webside.

I like to do the same and to a real pc but in the end is whatever you decide.

Modified by user1241316

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Here are my crash reports regarding this issue: Report ID Date Submitted bp-d2f79487-2276-4177-8261-0a6382151111 11/11/2015 04:02 PM bp-d16bbb0e-0b1b-4891-8b23-6bbec2151111 11/11/2015 01:32 PM bp-fa5212a5-3379-4d7e-9815-e859f2151111 11/11/2015 12:00 PM bp-50625559-fcca-451d-8431-10e3e2151111 11/11/2015 11:58 AM bp-eede310b-7598-4698-8f18-2acc82151111 11/11/2015 11:57 AM bp-d5993ec5-ac77-4b57-bce5-4d61f2151110 11/10/2015 09:18 AM bp-234a7c38-7b99-4e0c-8930-fd3702151110 11/10/2015 08:54 AM bp-7d6b0900-f415-4111-8258-2063a2151110 11/10/2015 08:50 AM bp-3ce2537a-efec-4f89-91bd-3e8922151110 11/10/2015 07:50 AM bp-55822110-9fe4-415c-b7e3-ade2d2151110 11/10/2015 07:31 AM bp-045e01b7-f4cd-4b80-97c1-3d1172151109 11/09/2015 01:06 PM bp-fa0079a7-9043-41a7-a67b-f2c2a2151109 11/09/2015 12:39 PM bp-102f8f34-ae1d-4b34-8250-01dee2151106 11/06/2015 04:06 PM bp-c7951db1-cdff-4a1c-8e83-930272151106 11/06/2015 11:26 AM bp-3948bfa1-64c7-4068-a088-0b6be2151106 11/06/2015 08:58 AM bp-e248772a-c577-42f1-aca1-6dccd2151106 11/06/2015 07:53 AM bp-e397667f-099f-42f5-9ad5-b301c2151106 11/06/2015 07:45 AM bp-d041a6c1-bc88-438f-b206-046dc2151106 11/06/2015 07:40 AM bp-988773a4-4e37-4d8c-953e-30be32151105 11/05/2015 03:40 PM

Modified by cor-el

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Product Firefox Version 42.0

Release Channel release OS Linux OS Version 0.0.0 Linux 2.6.32-220.27.1.el6.x86_64 #1 SMP Wed Sep 12 16:38:37 EDT 2012 x86_64


The crash report flagged these programs;

I've called the big guys to help you. Good luck.

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For case 1-> "case 1) firefox: ../../src/XlibInt.c:595: _XPrivSyncFunction: Assertion `dpy->synchandler == _XPrivSyncFunction' failed. "

That is the old sync engine failing I am assuming. Have you recently signed up for a new account: How do I set up Sync on my computer? (ignore this, best way to check if you are on the new on is to see if you are signed in on

The second I think you have already tried Safe Mode to eliminate if its a driver issue or an addon in your profile (though I would first recommend to the latest version, if its available for your version of Linux...should be): Troubleshoot Firefox issues using Safe Mode