User Agent: Mozilla/5.0 (Windows NT 6.2; WOW64; rv:20.0) Gecko/20130105 Firefox/20.0 Build ID: 20130105030839 Steps to reproduce: Launch Firefox after updating to the latest nightly build. It crashes in a few seconds. After reporting the issue and re-open Firefox, and it crashes again. Actual results: Crashed. At last it offers me a dialog to choose to start in Safe Mode or Reset my profile. Choose Safe Mode will open the browser and run without any crash again. Expected results: Nightly would not crash.

Can you link to one of your crash reports?

Hmm, well, maybe you can't. If you run Firefox in an older version that doesn't crash immediately, then you can go to about:crashes, and it will give links to your crash reports. I was unable to find any such reports at Crash-Stats.mozilla.com, but I'm not very skilled at using it, so that could just be my fault.

Oh, so it does work in safe mode. Okay. That's good. What addons are you using? You can get this information in about:support under Extensions.

Extensions Name Version Enabled ID Abduction! 3.0.16 false {b0e1b4a6-2c6f-4e99-94f2-8e625d7ae255} Adblock Plus 2.2.2a.3606 false {d10d0bf8-f5b5-c8b4-a8b2-2b9879e08c5d} Add-on Compatibility Reporter 2.0 false compatibility@addons.mozilla.org Add-on Update Checker 2.1 false {891f0410-aaa2-11e0-9f1c-0800200c9a66} Adobe Acrobat - Create PDF 2.0 false web2pdfextension@web2pdf.adobedotcom Anti-Aliasing Tuner 11.12.01.01 false aatuner@hotmint.com DownThemAll! *nightly* 3.0b1pre.20130105.3375 false dta@downthemall.net Element Hiding Helper for Adblock Plus 1.2.4a.446 false elemhidehelper@adblockplus.org Firebug 1.11.1 false firebug@software.joehewitt.com Firefox Share (alpha) 0.2.3 false fx-share-addon@mozilla.org Nightly Tester Tools 3.4pre false {8620c15f-30dc-4dba-a131-7c5d20cf4a29} OpenAttribute 0.9.8 false firefox@openattribute.com PDF Viewer 0.7.45 false uriloader@pdf.js Status-4-Evar 2012.11.11.16b false status4evar@caligonstudios.com

And a few of my reports. https://crash-stats.mozilla.com/report/index/bp-c72885bf-e8bd-471a-aff0-37d972130105 https://crash-stats.mozilla.com/report/index/bp-a25a5661-cba7-4833-8509-ddd1c2130105 https://crash-stats.mozilla.com/report/index/bp-11104e45-d841-402c-95e4-3b8a02130105 https://crash-stats.mozilla.com/report/index/bp-9e674fab-e2f6-440f-8f60-36c362130105

Looks like mRoot is null. I was wondering if that might be a problem...

Thanks for the reports! Windows build: https://tbpl.mozilla.org/?tree=Try&rev=a27d33a46501 I'll try to link to the installation when it is finished. This patch does a null check, but also asserts in debug builds, to make it easier to tell if the condition is hit. Could you try disabling a few addons at a time to figure out which one might be causing the problem? Thanks.

Seems like the extension "Adobe Acrobat - Create PDF" caused this issue. Have tried to disable all extensions and enabled one at a time. Got crash after enabling this one. Disabled all extensions again and only enabled Acrobat - and crashed. Got the same signature. https://crash-stats.mozilla.com/report/index/bp-b4ac0a8e-f27b-483b-82b4-9fdd92130105

Untested, but it should be okay, at least in terms of passing tests. https://tbpl.mozilla.org/?tree=Try&rev=40b9fe590403 Thanks for figuring out what addon caused it! Unfortunately, I don't have Acrobat so I won't be able to confirm the fix locally.

Comment on attachment 698302 [details] [diff] [review] null check Sorry that I missed this while reviewing.

Andrew, will you be able to land this to m-c soon? If not, I could, so that the fix would be in the next nightly.

Yeah, I can do that in an hour or so, when the try run finishes. Good point, I'll land directly on m-c.

Thanks again for the report, Xavier Fung. If you could confirm with tomorrow's Nightly that this works (or with the build here: http://ftp-scl3.mozilla.com/pub/mozilla.org/firefox/try-builds/amccreight@mozilla.com-a27d33a46501/try-win32/ ) that would be useful. https://hg.mozilla.org/mozilla-central/rev/16574882a159

Can confirm that today's nightly (Jan 6) does not crash. Thanks Andrew!

I confirm the fix is verified on Latest Nightly 22.0a1 and on FF 20.b1 on Windows 8 x64. Mozilla/5.0 (Windows NT 6.2; WOW64; rv:20.0) Gecko/20100101 Firefox/20.0(20130220104816) Mozilla/5.0 (Windows NT 6.2; WOW64; rv:22.0) Gecko/20130220 Firefox/22.0(20130220031126) Update to FF 20.b1 works only if you modify channel from Firefox/defaults/pref/channel-pref.js from beta to betatest. Based on my verifications and on Comment 14 this issue looks to be verified. Thanks Xavier for Confirm!