Debugging guidelines for Mozilla products

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

Using Mozilla crash reporter

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. To view and submit the crash info please do:

Open about:crashes page
If there is any crash report, submit them (the 'Submit All' button).
Paste all crash ID to bugreport.

Using local debugging

Installing debug info packages

Debug info packages which contains source files are required to create meaningful bug report (unless you use Mozilla crash reporter). To install them you need to execute following command as root:

debuginfo-install firefox

for Firefox,

debuginfo-install thunderbird

for Thunderbird.

Using coredumpctl to get backtrace

You can use coredumpctl to get backtrace. Run on terminal:

coredumpctl list

and find Firefox crash there and get crash ID. Then launch gdb on it by

coredumpctl debug ID

you should get a gdb session and you should be able to get backtrace by

thread apply all bt full

gdb command.

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:

(gdb)

To run program use command:

run

Obtain crash stack trace

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

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

to store stack and Javascript trace into crash_bt.log file. 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 debug symbols installed.

When the freeze occurs randomly and/or difficult to predict you can attach to running application when it freezes by:

gdb firefox `ps ax|grep firefox/firefox|grep -v grep|grep -v "contentproc"|cut -d ' ' -f3`

for Firefox.

gdb thunderbird `ps ax|grep thunderbird/thunderbird|grep -v grep|grep -v "contentproc"|cut -d ' ' -f3`

for Thunderbird.

Then you can continue by #Obtain crash stack trace

Figuring out what is responsible for crash

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

firefox -safe-mode

or

thunderbird -safe-mode

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

Note
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 just simply follow instructions in #Application crash. Otherwise continue to next section.

Reporting addons and plugins issues

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.

For Firefox set your location to about:plugins page. This page contains information about all installed plugins and it may help us in resolving your issue. Save it by File/Save Page As... to file and attach saved file to bug report.

For Thunderbird make screenshot of Tools/Addons/Extensions and Tools/Addons/Plugins, dialogs and attach images to bugzilla.

Attach also output of following commands:

rpm -q firefox xulrunner thunderbird flash-plugin gnash google-talkplugin nspluginwrapper thunderbird-lightning thunderbird-enigmail flash-plugin
ls -l /usr/lib64/mozilla/plugins/
ls -l /usr/lib/mozilla/plugins/
ls -l /usr/share/mozilla/extensions

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 instructions see #Application crash section.

Bug report attachment in a nutshell

To make long story short, execute following commands and attach ~/bug-report file to bugzilla:

rpm -q firefox xulrunner thunderbird flash-plugin gnash google-talkplugin nspluginwrapper thunderbird-lightning thunderbird-enigmail flash-plugin > ~/bug-report
ls -l /usr/lib64/mozilla/plugins/   >> ~/bug-report
ls -l /usr/lib/mozilla/plugins/     >> ~/bug-report
ls -l /usr/share/mozilla/extensions >> ~/bug-report

For Firefox go to about:support and about:plugins pages, save them and attach to bug report.