Linux

Debugging Linux applications

LDD

Linux LDD is just a wrapper for:

LD_TRACE_LOADED_OBJECTS=1 <cmd>

Core dumps

To check core dump handler:

cat /proc/sys/kernel/core_pattern
|/usr/sbin/coredump-handler %h_%t_%p.core

Valgrind

valgrind --trace-children=yes --leak-check=full --show-leak-kinds=all <binary>

Configuring Linux

Disable Nvidia drivers and enable Intel embedded HD graphics driver

sudo apt-get purge nvidia-*
sudo apt-get install --reinstall xserver-xorg-video-intel libgl1-mesa-glx libgl1-mesa-dri mesa-utils xserver-xorg-core
sudo dpkg-reconfigure xserver-xorg
sudo update-alternatives --remove gl_conf /usr/lib/nvidia-current/ld.so.conf
reboot

Switch default compiler

(cc --version;c++ --version;gcc --version;g++ --version) | grep Debian
 cc (Debian 6.1.1-11) 6.1.1 20160802
 c++ (Debian 6.1.1-11) 6.1.1 20160802
 gcc (Debian 6.1.1-11) 6.1.1 20160802
 g++ (Debian 6.1.1-11) 6.1.1 20160802

sudo apt-get install gcc-4.9 g++-4.9

gcc-4.9 --version
 gcc-4.9 (Debian 4.9.3-14) 4.9.3

g++-4.9 --version
 g++-4.9 (Debian 4.9.3-14) 4.9.3

gcc-5 --version
 gcc-5 (Debian 5.4.1-1) 5.4.1 20160803

g++-5 --version
 g++-5 (Debian 5.4.1-1) 5.4.1 20160803

sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-5 10
sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-4.9 20
sudo update-alternatives --install /usr/bin/g++ g++ /usr/bin/g++-5 10
sudo update-alternatives --install /usr/bin/g++ g++ /usr/bin/g++-4.9 20
sudo update-alternatives --install /usr/bin/cc cc /usr/bin/gcc 30
sudo update-alternatives --set cc /usr/bin/gcc
sudo update-alternatives --install /usr/bin/c++ c++ /usr/bin/g++ 30
sudo update-alternatives --set c++ /usr/bin/g++

(cc --version;c++ --version;gcc --version;g++ --version) | grep Debian
 cc (Debian 4.9.3-14) 4.9.3
 c++ (Debian 4.9.3-14) 4.9.3
 gcc (Debian 4.9.3-14) 4.9.3
 g++ (Debian 4.9.3-14) 4.9.3

To go back:

sudo update-alternatives --config gcc
sudo update-alternatives --config g++

Console is not filling the screen completely

This may be due to that the console thinks it is connected to a different display device than it actually is. This can be fixed by adding kernel command line parameters to disable that specific video mode.

ls /sys/class/drm
card0@  card0-DisplayPort-1@  card0-DisplayPort-2@  card0-DisplayPort-3@  card0-HDMI Type A-1@  card0-HDMI Type A-2@  card0-LVDS-1@  card0-SVIDEO-1@  card0-VGA-1@  controlD64@  version

Now check the different "modes" and "connected" and "enabled" nodes under each device to figure out which needs to be disabled. Then add to your kernel command line things such as

video=LVDS-1:d video=SVIDEO-1:d video=TV-1:d

More information: https://bbs.archlinux.org/viewtopic.php?id=94990

udev

udev rules

Some sample udev rules which might come handy:

KERNEL=="tty*", GROUP="dialout", MODE="0660"
SUBSYSTEM=="gpio", GROUP:="gpio", MODE:="0660"

udev debugging

Command to test udev rules:

udevadm test --action=add /class/gpio