Debugging C++ inside Python (pybind11)

[k0nze]

Hello,

I currently work on a project which uses a library written in C++ which can be used in Python with pybind11. To debug the C++ code, I currently use ipython together with lldb. Which works as follows:

• Start ipython and get the process id with !ps aux | grep -i ipython
• Start lldb in another terminal and connect to ipyhton with attach --pid $PID and continue
• Set a breakpoint in lldb to a class method, e.g. breakpoint -n Cat::purr
• In ipython launch the Python script with run examples/example.py
• Now lldb breaks at the breakpoint and I can step through the code in lldb which is possible but also a bit tedious.

Is there a way to set a breakpoint through nvim-dap in C++ and then launch the Python script through nvim-dap-python and have it recognize the C++ breakpoint when running the Python script?

PS:
I prepared a little example project https://github.com/k0nze/nvim_cpp_python_debugging which can be set up as follows:

cd $REPO_DIR
python -m venv .venv
source .venv/bin/activate
python -m pip install .

An example which instantiates the C++ classes in Python can be run with:

python examples/example.py

The C++ file in which I would like to set a breakpoint in is located under:

src/backend/cat.cc

Additionally, I added a minimal nvim config which installs plugins into a temporary directory which can be launched with:

nvim -lu minimal.lua

If the plugins don't install automatically, you can use :PackerSync

When started you can launch nvim-dap with nvim-dap-ui with [SPACE]+[d] and use the usual commands for setting breakpoints, and stepping though code.

Thank you in advance!

[theHamsta]

It's not possible with nvim-dap-python (as far as I Know). But you can set the break points in your c++ files and use lldb-vscode or one of the other debug adapters for c++. Just use python3 + args to start the script as the executable to debug. The c++ breakpoints get resolved as soon as the c++ module gets loaded

[k0nze]

Thank you for the tip, I'm able to pass the path of python3 interpreter to the prompt of nvim-dap-uito lldb-vscode which opens Python interactive mode. However, I can't figure out how to pass an argument to the python interpreter to run my Python script?

[theHamsta]

I'm using a configuration similar to https://github.com/mfussenegger/nvim-dap/wiki/Debug-Adapter-installation#ccrust-via-lldb-vscode.

I've created myself a command to launch lldb like I would do with gdb/lldb from command line https://github.com/theHamsta/dotfiles/blob/eca0f8ac905074b58f059bcdccf0c5cbcab3de3c/.config/nvim/lua/my_debug.lua#L143-L194 / https://github.com/theHamsta/dotfiles/blob/eca0f8ac905074b58f059bcdccf0c5cbcab3de3c/.config/nvim/lua/init.lua#L683-L708 https://github.com/theHamsta/dotfiles/blob/eca0f8ac905074b58f059bcdccf0c5cbcab3de3c/.config/nvim/lua/init.lua#L1108-L1110

Now, I can do :DebugLLDB cmd arg1 arg2 arg3, e.g. :DebugLLDB python3 % to debug the current Python file. Sorry, for my config being so messy. nvim-dap didn't have many of the convenience functions it now has back then.

[theHamsta]

Would you find this useful enough for to wrap it up in a nice form for a nvim-dap-native extension that wraps all that recipes for native debuggers with maybe some pre-debug build triggers?

[k0nze]

That would be incredibly useful for me!

[Sahas-Ananth]

Hello, I am new(ish) to Neovim, and for one of my project I have to do this. Can you help me through this? My config is a fork of kickstart.nvim and I use mason-nvim-dap which I believe does the dap configurations automatically. Thanks in advance!