Debugging i3: How To
-==================
+====================
Michael Stapelberg <michael+i3@stapelberg.de>
-April 2009
+March 2010
-This document describes how to debug i3 suitably for sending us useful bug reports, even
-if you have no clue of C programming.
+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!
+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!
== Enabling logging
-i3 spits out much information onto stdout. To have a clearly defined place where logfiles
-will be saved, you should redirect stdout and stderr in xsession. While you’re at it,
-putting each run of i3 in a separate logfile with date/time in it is a good idea to not
-get confused about the different logfiles later on.
+i3 spits out much information onto stdout, if told so. To have a clearly
+defined place where log files will be saved, you should redirect stdout and
+stderr in xsession. While you’re at it, putting each run of i3 in a seperate
+log file with date/time in it is a good idea to not get confused about the
+different log files later on.
--------------------------------------------------------------------
-exec /usr/bin/i3 >/home/michael/i3/i3log-$(date +'%F-%k-%M-%S') 2>&1
+exec /usr/bin/i3 -V -d all >/home/michael/i3/i3log-$(date +'%F-%k-%M-%S') 2>&1
--------------------------------------------------------------------
-== Enabling coredumps
+== Enabling core dumps
-When i3 crashes, often you have the chance of getting a coredump (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 coredumps, use the following command (in your .xsession, before
-starting i3):
+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:
+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+.
+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 coredumps, you should make sure that your version of i3 is compiled
-with debug symbols, that is, that they are not stripped during the build process. You
-can check whether your executable contains symbols by issuing the following command:
+To actually get useful core dumps, you should make sure that your version of i3
+is compiled with debug symbols, that is, that they are not stripped during the
+build process. You can check whether your executable contains symbols by
+issuing the following command:
----------------
file $(which i3)
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.
+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 coredumps
-are enabled, you can start getting some sense out of the coredumps.
+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 coredump 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 coredump might
-be useless afterwards.
+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 coredump of
-course):
+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
----------
-
-Also, getting an overview of the local variables might help:
------------
-info locals
------------
-
-If your backtrace looks like this:
----------------------------------------------------------------------------------------------------
-(gdb) backtrace
-#0 0x041b1a01 in vfprintf () from /lib/libc.so.6
-#1 0x041b2f80 in vprintf () from /lib/libc.so.6
-#2 0x080555de in slog (fmt=0x8059ba0 "%s:%s:%d - Name should change to \"%s\"\n") at src/util.c:60
-#3 0x0804fa73 in handle_windowname_change_legacy (data=0x0, conn=0x42da908,
- state=0 '\0', window=8389918, atom=39, prop=0x4303f90) at src/handlers.c:752
-#4 0x0406cace in ?? () from /usr/lib/libxcb-property.so.1
-#5 0x00000000 in ?? ()
----------------------------------------------------------------------------------------------------
-
-you need to find the first frame which actually belongs to i3 code. You can easily spot them, as
-their filename starts with src/ and has a line number. In this case, frame 2 would be the correct
-frame, so before getting the local variables, switch to frame 2:
-
------------
-frame 2
-info locals
------------
-
-== Sending bugreports/debugging on IRC
-
-When sending bugreports, 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 coredump).
-
-When debugging with us in IRC, be prepared to use a so called nopaste service such as http://nopaste.info
-because pasting large amounts of text in IRC sometimes leads to incomplete lines (servers have line
+--------------
+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.
projects / i3 / i3 / blobdiff