# Simulation Debugging
As the simulation is running on the host machine, all the desktop development tools are available.
# CLANG Address Sanitizer (Mac OS, Linux)
The Clang address sanitizer can help to find alignment (bus) errors and other memory faults like segmentation faults. The command below sets the right compile options.
make clean # only required on first address sanitizer run after a normal build PX4_ASAN=1 make px4_sitl jmavsim
brew install valgrind
sudo apt-get install valgrind
To use valgrind during the SITL simulation:
make px4_sitl_default jmavsim___valgrind
# Launch Gazebo Classic SITL Without Debugger
By default SITL is launched without a debugger attached when using any simulator backend:
make px4_sitl_default gz make px4_sitl_default gazebo-classic make px4_sitl_default jmavsim
For Gazebo Classic (only) you can also start the simulator with a debugger attached. Note however, that you must provide the vehicle type in the simulator target, as shown below:
make px4_sitl_default gazebo-classic_iris_gdb make px4_sitl_default gazebo-classic_iris_lldb
This will start the debugger and launch the SITL application with Gazebo and the Iris simulator.
In order to break into the debugger shell and halt the execution, hit
Process 16529 stopped * thread #1: tid = 0x114e6d, 0x00007fff90f4430a libsystem_kernel.dylib`__read_nocancel + 10, name = 'px4', queue = 'com.apple.main-thread', stop reason = signal SIGSTOP frame #0: 0x00007fff90f4430a libsystem_kernel.dylib`__read_nocancel + 10 libsystem_kernel.dylib`__read_nocancel: -> 0x7fff90f4430a <+10>: jae 0x7fff90f44314 ; <+20> 0x7fff90f4430c <+12>: movq %rax, %rdi 0x7fff90f4430f <+15>: jmp 0x7fff90f3fc53 ; cerror_nocancel 0x7fff90f44314 <+20>: retq (lldb)
In order to not have the DriverFrameworks scheduling interfere with the debugging session
SIGCONT should be masked in LLDB and GDB:
(lldb) process handle SIGCONT -n false -p false -s false
Or in the case of GDB:
(gdb) handle SIGCONT noprint nostop
After that the lldb or gdb shells behave like normal sessions, please refer to the LLDB / GDB documentation.
The last parameter, the <viewer_model_debugger> triplet, is actually passed to make in the build directory, so
make px4_sitl_default gazebo-classic_iris_gdb
is equivalent with
make px4_sitl_default # Configure with cmake make -C build/px4_sitl_default classic_iris_gdb
A full list of the available make targets in the build directory can be obtained with:
# Attaching GDB to running SITL
You can also start your simulation, and then attach
In one terminal screen enter the command to start your simulation:
make px4_sitl_default gazebo-classic
As the script runs, note the SITL COMMAND: output text located right above the large "PX4" text. It will list the location of your px4 bin file for later use.
SITL COMMAND: "<px4 bin file>" "<build dir>"/etc ______ __ __ ___ | ___ \ \ \ / / / | | |_/ / \ V / / /| | | __/ / \ / /_| | | | / /^\ \ \___ | \_| \/ \/ |_/ px4 starting. INFO [px4] startup script: /bin/sh etc/init.d-posix/rcS 0 INFO [init] found model autostart file as SYS_AUTOSTART=10015
Open another terminal and type:
You will want to note the PID of the process named "PX4"
(In this example it is 14149)
atlas:~/px4/main/PX4-Autopilot$ ps -a PID TTY TIME CMD 1796 tty2 00:01:59 Xorg 1836 tty2 00:00:00 gnome-session-b 14027 pts/1 00:00:00 make 14077 pts/1 00:00:00 sh 14078 pts/1 00:00:00 cmake 14079 pts/1 00:00:00 ninja 14090 pts/1 00:00:00 sh 14091 pts/1 00:00:00 bash 14095 pts/1 00:01:23 gzserver 14149 pts/1 00:02:48 px4 14808 pts/2 00:00:00 ps
Then type in the same window
sudo gdb [px4 bin file path (from step 1) here]
sudo gdb /home/atlas/px4/base/PX4-Autopilot/build/px4_sitl_default/bin/px4
Now, you can attach to the PX4 instance by entering the PID noted in step 2.
attach [PID on px4]
You should now have a GDB interface to debug with.
# Compiler optimization
It is possible to suppress compiler optimization for given executables and/or modules (as added by cmake with
add_library) when configuring
This can be handy when it is necessary to step through code with a debugger or print variables that would otherwise be optimized out.
To do so, set the environment variable
PX4_NO_OPTIMIZATION to be a semi-colon separated list of regular expressions that match the targets that need to be compiled without optimization.
This environment variable is ignored when the configuration isn't
would suppress optimization of the targets: platforms__posix__px4_layer, modules__systemlib, modules__uORB, examples__px4_simple_app, modules__uORB__uORB_tests and px4.
The targets that can be matched with these regular expressions can be printed with the command:
make -C build/posix_sitl_* list_cmake_targets