# 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
# Valgrind
brew install valgrind
or
sudo apt-get install valgrind
To use valgrind during the SITL simulation:
make px4_sitl_default jmavsim___valgrind
# Start combinations
SITL can be launched with and without debugger attached and with either jMAVSim or Gazebo as simulation backend. This results in the start options below:
make px4_sitl_default jmavsim
make px4_sitl_default jmavsim___gdb
make px4_sitl_default jmavsim___lldb
make px4_sitl_default gazebo
make px4_sitl_default gazebo___gdb
make px4_sitl_default gazebo___lldb
where the last parameter is the <viewer_model_debugger> triplet (using three underscores implies the default 'iris' model).
This will start the debugger and launch the SITL application. In order to break into the debugger shell and halt the execution, hit CTRL-C
:
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 jmavsim___gdb
is equivalent with
make px4_sitl_default # Configure with cmake
make -C build/px4_sitl_default jmavsim___gdb
A full list of the available make targets in the build directory can be obtained with:
make help
but for your convenience, a list with just the <viewer_model_debugger> triplets is printed with the command
make list_vmd_make_targets
# Compiler optimization
It is possible to suppress compiler optimization for given executables and/or
modules (as added by cmake with add_executable
or add_library
) when configuring
for posix_sitl_*
. 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 posix_sitl_*
.
For example,
export PX4_NO_OPTIMIZATION='px4;^modules__uORB;^modules__systemlib$'
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