Backtraces

2005-07-29T12:29:38Z

217.237.149.162: according to Kry's post this is neccessary for kad-enabled aMule

== Introduction ==

Well, not hard to guess, this is about backtraces.

Usually, it should not be necessary for the normal user to do this. However, we might have a bad day and release a somewhat buggy version or you are running [http://www.gnu.org/software/cvs CVS] which can also be unstable sometimes.
This is where the backtraces come in: if [[aMule]] crashes, and you get an "OOPS - aMule crashed" and so on, we'd like to know. The backtrace [[aMule]] provides is not always very usefull as it contains little information, but, as usual, there's a better way: A *real* backtrace.

== The GNU Debugger ==

First of all, you need the [http://www.gnu.org/software/gdb/gdb.html GNU Debugger] installed. It's called ''gdb'' and you could check for that by typing ''which gdb'' in a console window. You should see something like this:

''<pre>
$ which gdb
/usr/bin/gdb
</pre>''

If you don't have [http://www.gnu.org/software/gdb/gdb.html GDB] installed, you will get a message like this:<br>

''<pre>
$ which gdb
which: no gdb in (/bin:/usr/bin:[etc])
</pre>''

If that is the case, the [http://www.gnu.org/software/gdb/gdb.html GNU Debugger] is most likely not installed on your system and you should install it before you proceed.

If your OS is [http://www.gentoo.org Gentoo Linux] you have just to type this:
''<pre>
# emerge -av gdb
</pre>''

== Compiling [[aMule]] ==

Then, compile [[aMule]] with debugging information:

''<pre>
$ ./configure --enable-debug --disable-optimize --prefix=/where/to/install/aMule
$ make
$ make install
</pre>''

If you do not want to overwrite you old copy of [[aMule]], simply do this instead:

''<pre>
$ ./configure --enable-debug --disable-optimize
$ make
</pre>''

[[aMule]] can then be run by going into the dir ''src'' and typing ''./amule''

If you are unable or unwilling to recompile, or are running a RPM version, proceed anyway, but be aware that backtraces from debugging enabled builds are much more useful to us.

== Create a backtrace ==

Now create in your home directory the file ''.gdbinit'' and put these lines into it (or you can type them in at the ''(gdb)'' prompt later):
''<pre>
ha SIGPIPE nostop noprint pass
ha SIG32 nostop noprint pass
</pre>''

For those who want to know the meaning of the previous lines:
the first one avoid [http://www.gnu.org/software/gdb/gdb.html GDB] stopping at broken pipes;
the second one avoid [http://www.gnu.org/software/gdb/gdb.html GDB] stopping at new thread.

To create a backtrace, open a console and do the following:

''<pre>
$ gdb /where/to/install/aMule/bin/amule
(gdb) run
</pre>''

Now use [[aMule]] normally until it crashes. If it crashes do the following:

''<pre>
(gdb) bt
(gdb) bt full
(gdb) thread apply all bt
</pre>''

Post the output of the last three commands in the [http://www.amule.org/amule/board.php?boardid=33 backtraces forum] with some additional comment about the circumstances the segfault happened and what [[aMule]] version you used (or checkout time for [http://www.gnu.org/software/cvs CVS]).

== The core file ==

If your [[aMule]] executable has been compiled with debug information (''--enable-debug'' configure flag), but you were not running it from within [http://www.gnu.org/software/gdb/gdb.html GDB], there is still a way to generate a backtrace, if your system was configured to generate '''core files'''.

Core files are the full memory image of a process that crashed. Your session must be properly configured, so that the system generates core files. Add the following command to ''~/.bashrc'':

''ulimit -c unlimited''

Now, when a program crashes, suppose it generate the file ''core.1234'' (this name can be different, but usually will start with 'core') you can enter [http://www.gnu.org/software/gdb/gdb.html GDB] like that:

''$ gdb /path/to/amule /path/to/core/file/core.1234''

and then proceed as in the last session and issue 'bt' and 'bt full'.

So, that's it, have fun with [[aMule]]

Greetings, [[User:Citroklar|Citroklar]] & [[User:Phoenix|Phoenix]]

(Most of the above shamelessly stolen from pure_ascii's post in backtraces forum, thanks, pure!)

Please read [[Using_gdb_and_valgrind|this]] to learn more about [http://www.gnu.org/software/gdb/gdb.html GDB] and [http://valgrind.kde.org Valgrind].

AMule Project FAQ - User contributions [en]

Backtraces