Using Valgrind and gdb in Scratchbox

Some hints for using valgrind tools in Scratchbox+Maemo

These commands work in the 386 scratchbox target.

First, standard way to use valgrind and gdb. af-sb-init.sh supports parameters for using these tools with a piece of software we want to study:

af-sb-init.sh start --valgrind=my_app
af-sb-init.sh start --gdb=my_app

Valgrind will store the results in /tmp/valgrind-my_app.log*. Gdb will show its prompt on load of my_app. This way you can debug/valgrind the program you want.

An interesting example would be: "I want to valgrind my status bar applet". And this is easy:

af-sb-init.sh start --valgrind=maemo_af_desktop

You'll get the results in /tmp/valgrind-maemo_af_desktop.log*

If you want to run other valgrind tools, you would better use these environment variables: * VALGRINDCMD: the command you want to run inside valgrind. * VALGRIND: the valgrind command and parameters.

For example, if you want to run massif of maemo_af_desktop, you would run:

export VALGRINDCMD=maemo_af_desktop
export VALGRIND="valgrind tool=massif num-callers=50
       trace-children=yes depth=5 format=html log-file=/tmp/massif
       alloc-fn=g_malloc alloc-fn=g_malloc0 --alloc-fn=g_realloc
       alloc-fn=g_slice_alloc alloc-fn=g_try_malloc
      - -alloc-fn=g_slice_alloc0"
af-sb-init.sh start
... do your stuff ...
af-sb-init.sh stop

And you'll get your massif reports in /tmp (logs) and $PWD (html and postscripts).

If you want valgrind and gdb to find debug packages in Scratchbox, you need to do something like this:

#!/bin/sh
# symlinks for debug symfiles in sbox
mkdir -p /usr/lib/debug/targets
cd /usr/lib/debug/targets
ln -sf /usr/lib/debug $(sh -c '. /targets/links/scratchbox.config;echo $SBOX_TARGET_NAME')

This is because when Gdb uses "realpath" on libraries in Sbox it gets a path starting with /targets//... You can see the effect of this if you "strace" Valgrind (or Gdb).

When using Valgrind, you need to remember to use:

export G_SLICE="always-malloc"

Otherwise Valgrind will report bogus leaks (see Gnome Bugzilla for more information on Glib Gslice and Valgrind).

Another thing to remember about Gdb is that the Maemo Sbox cross-gdb cannot debug ARM (EABI) core dumps. You need target Gdb for this. However, because Sbox will use the host (cross-gdb) binary if it exists, you need to tell Sbox to ignore that:

#!/bin/sh
# use native Gdb in Scratchbox
SBOX_REDIRECT_IGNORE=/usr/bin/gdb /usr/bin/gdb $*

You can check which Gdb is used with "gdb -v". If it says "--host=i686-pc-linux-gnu" on ARM target, it's a cross-gdb.