From Fedora Project Wiki

This article helps affected users in reporting of Firefox and Thunderbird bugs and ease package maintainers fixing them.

Application crash

Application crash can occur during runtime. Application window simply disappear and bug report dialog will show up. By accepting this dialog crash will be reported to Mozilla crashstat servers. You can see list of submitted crashes on about:crashes page. If you want to report this crash to Fedora bugzilla you need to do few additional steps described in following subsections.

Installing debug info packages

Debug info packages which contains source files are required to create meaningful bug report. To install them you need to execute following command as root:

debuginfo install firefox

for Firefox,

debuginfo install thunderbird

for Thunderbird.

Running application in debugger

To run application in gnu debugger you need to run command:

firefox -g -d gdb

for Firefox,

thunderbird -g -d gdb

After debugger is started which is indicated by line:


To run program use command:


Obtain crash stack trace

Then bring application to crash. This should be indicated by (gdb) prompt. Type:

set logging on crash_bt
thread apply all bt full
print DumpJSStack()
set logging off

to store stack and Javascript trace into crash_bt. Don't forget to attach this file to bug report.

Application freeze

If you are able to reproduce freeze you can follow #Application crash steps. There is only one difference in #Obtain crash stack trace section where (gdb) prompt is missing. To get prompt you have to press Ctrl-C.

Attach debugger to running application

Before you can attach to running application you need to have # When the freeze occurs randomly and/or difficult to predict you can attach to running application by

Basically there are two types of problems which can occur in Mozilla products: Application doesn't work as expected, application crashes , Freeze and application .


We need to determine whenever crash has been infliced by third party plugin or addon, or by application itself.


Application stops responding to user action for a long time. In this case we need to attach debugger to running process and get stack trace

Doesn't work as expected

Figuring out whose fault is it

Some crashes and problems come from installed addons or 3rd party plugins. To determine if that's the case run Mozilla products with -safe-mode parameter:

firefox -safe-mode


thunderbird -safe-mode

Then Disable all add-ons needs to be checked and Make Changes and Restart pressed.

Error creating thumbnail: File missing
This setting disables all your add-ons and plugins until you manually re-enable them.

If problem still persist it isn't most likely related to addons or plugins and you can proceed to Bugs in gecko. Otherwise go to Reporting addons and plugins issues. . In that case proceed to Plugins and Addons problems section.

Reporting addons and plugins issues

Error creating thumbnail: File missing
Reenable plugins and addons
At first don't forget to reenable all plugins and addons in Tools/Add-ons/Extensions and Plugins menu and restart application.

Then set your location to about:plugins page, save it (by File/Save Page As...) to file and attach it to bug report. This page contains information about all installed plugins and it may help us in resolving your issue. Attach also output of following commands:

rpm -q firefox xulrunner flash-plugin gnash google-talkplugin nspluginwrapper
ls /usr/lib64/mozilla/plugins/
ls /usr/lib/mozilla/plugins/

You may also run Firefox or Thunderbird by strace. This help us to track which dynamic libraries are loaded during startup. Strace usage:

strace firefox &>strace_output

or in case of Thunderbird:

strace thunderbird &> strace_output

and don't forget to attach created strace_output file to bug report. If application crash or freeze stack trace is also very useful, for instruction how to obtain stacktrace go here.

Bugs in core

How to get stacktrace