127 lines
5.1 KiB
Plaintext
127 lines
5.1 KiB
Plaintext
|
Debugging i3: How To (release version)
|
|||
|
|
======================================
|
|||
|
|
Michael Stapelberg <michael@i3wm.org>
|
|||
|
|
February 2012
|
|||
|
|
|
|||
|
|
This document describes how to debug i3 suitably for sending us useful bug
|
|||
|
|
reports, even if you have no clue of C programming.
|
|||
|
|
|
|||
|
|
First of all: Thank you for being interested in debugging i3. It really means
|
|||
|
|
something to us to get your bug fixed. If you have any questions about the
|
|||
|
|
debugging and/or need further help, do not hesitate to contact us!
|
|||
|
|
|
|||
|
|
NOTE: This document is for the release version of i3. If you are using a
|
|||
|
|
development version, please see link:debugging.html[Debugging i3: How To]
|
|||
|
|
instead.
|
|||
|
|
|
|||
|
|
== Consider using the development version
|
|||
|
|
|
|||
|
|
This document is for the release version of i3. In many cases, bugs are already
|
|||
|
|
fixed in the development version of i3. If they aren’t, we will still ask you
|
|||
|
|
to reproduce your error with the most recent development version of i3.
|
|||
|
|
Therefore, please upgrade to a development version and continue reading at
|
|||
|
|
link:debugging.html[Debugging i3: How To].
|
|||
|
|
|
|||
|
|
If you absolutely cannot upgrade to a development version of i3, you may
|
|||
|
|
continue reading this document.
|
|||
|
|
|
|||
|
|
== Enabling logging
|
|||
|
|
|
|||
|
|
i3 logs useful information to stdout. To have a clearly defined place where log
|
|||
|
|
files will be saved, you should redirect stdout and stderr in your
|
|||
|
|
+~/.xsession+. While you’re at it, putting each run of i3 in a separate log
|
|||
|
|
file with date/time in its filename is a good idea to not get confused about
|
|||
|
|
the different log files later on.
|
|||
|
|
|
|||
|
|
--------------------------------------------------------------------
|
|||
|
|
exec /usr/bin/i3 >~/i3log-$(date +'%F-%k-%M-%S') 2>&1
|
|||
|
|
--------------------------------------------------------------------
|
|||
|
|
|
|||
|
|
To enable verbose output and all levels of debug output (required when
|
|||
|
|
attaching logfiles to bugreports), add the parameters +-V -d all+, like this:
|
|||
|
|
|
|||
|
|
--------------------------------------------------------------------
|
|||
|
|
exec /usr/bin/i3 -V -d all >~/i3log-$(date +'%F-%k-%M-%S') 2>&1
|
|||
|
|
--------------------------------------------------------------------
|
|||
|
|
|
|||
|
|
== Enabling core dumps
|
|||
|
|
|
|||
|
|
When i3 crashes, often you have the chance of getting a 'core dump' (an image
|
|||
|
|
of the memory of the i3 process which can be loaded into a debugger). To get a
|
|||
|
|
core dump, you have to make sure that the user limit for core dump files is set
|
|||
|
|
high enough. Many systems ship with a default value which even forbids core
|
|||
|
|
dumps completely. To disable the limit completely and thus enable core dumps,
|
|||
|
|
use the following command (in your +~/.xsession+, before starting i3):
|
|||
|
|
|
|||
|
|
-------------------
|
|||
|
|
ulimit -c unlimited
|
|||
|
|
-------------------
|
|||
|
|
|
|||
|
|
Furthermore, to easily recognize core dumps and allow multiple of them, you
|
|||
|
|
should set a custom core dump filename pattern, using a command like the
|
|||
|
|
following:
|
|||
|
|
|
|||
|
|
---------------------------------------------
|
|||
|
|
sudo sysctl -w kernel.core_pattern=core.%e.%p
|
|||
|
|
---------------------------------------------
|
|||
|
|
|
|||
|
|
This will generate files which have the executable’s file name (%e) and the
|
|||
|
|
process id (%p) in it. You can save this setting across reboots using
|
|||
|
|
+/etc/sysctl.conf+.
|
|||
|
|
|
|||
|
|
== Compiling with debug symbols
|
|||
|
|
|
|||
|
|
To actually get useful core dumps, you should make sure that your version of i3
|
|||
|
|
is compiled with debug symbols, that is, that the symbols are not stripped
|
|||
|
|
during the build process. You can check whether your executable contains
|
|||
|
|
symbols by issuing the following command:
|
|||
|
|
|
|||
|
|
----------------
|
|||
|
|
file $(which i3)
|
|||
|
|
----------------
|
|||
|
|
|
|||
|
|
You should get an output like this:
|
|||
|
|
------------------------------------------------------------------------------
|
|||
|
|
/usr/bin/i3: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), dynamically
|
|||
|
|
linked (uses shared libs), for GNU/Linux 2.6.18, not stripped
|
|||
|
|
------------------------------------------------------------------------------
|
|||
|
|
|
|||
|
|
Notice the +not stripped+, which is the important part. If you have a version
|
|||
|
|
which is stripped, please have a look if your distribution provides debug
|
|||
|
|
symbols (package +i3-wm-dbg+ on Debian for example) or if you can turn off
|
|||
|
|
stripping. If nothing helps, please build i3 from source.
|
|||
|
|
|
|||
|
|
== Generating a backtrace
|
|||
|
|
|
|||
|
|
Once you have made sure that your i3 is compiled with debug symbols and that
|
|||
|
|
core dumps are enabled, you can start making sense out of the core dumps.
|
|||
|
|
|
|||
|
|
Because the core dump depends on the original executable (and its debug
|
|||
|
|
symbols), please do this as soon as you encounter the problem. If you
|
|||
|
|
re-compile i3, your core dump might be useless afterwards.
|
|||
|
|
|
|||
|
|
Please install +gdb+, a debugger for C. No worries, you don’t need to learn it
|
|||
|
|
now. Start gdb using the following command (replacing the actual name of the
|
|||
|
|
core dump of course):
|
|||
|
|
|
|||
|
|
----------------------------
|
|||
|
|
gdb $(which i3) core.i3.3849
|
|||
|
|
----------------------------
|
|||
|
|
|
|||
|
|
Then, generate a backtrace using:
|
|||
|
|
|
|||
|
|
--------------
|
|||
|
|
backtrace full
|
|||
|
|
--------------
|
|||
|
|
|
|||
|
|
== Sending bug reports/debugging on IRC
|
|||
|
|
|
|||
|
|
When sending bug reports, please paste the relevant part of the log (if in
|
|||
|
|
doubt, please send us rather too much information than too less) and the whole
|
|||
|
|
backtrace (if there was a core dump).
|
|||
|
|
|
|||
|
|
When debugging with us in IRC, be prepared to use a so called nopaste service
|
|||
|
|
such as http://nopaste.info or http://pastebin.com because pasting large
|
|||
|
|
amounts of text in IRC sometimes leads to incomplete lines (servers have line
|
|||
|
|
length limitations) or flood kicks.
|