UsingVSCode

Source level debugging OOT C++ modules with Visual Studio Code

The following instructions were updated using VSCode v1.63.2 on Ubuntu 20.04

Instructions

1) In VSCode Extensions Marketplace, install C++ and GDB Extensions (also Python Debugger for stepping through Python Code)

2) Build the target OOT module and install into the pybombs prefix (or whatever other install method was used for GNU Radio)

• Be sure when building the OOT module, use -DCMAKE_BUILD_TYPE=Debug as one of the cmake flags, e.g:

cmake ../ -DCMAKE_BUILD_TYPE=Debug

3) Create a flowgraph that calls your module

• In GRC, it is helpful to spool a temporary .py by changing the ID in options, generating the flowgraph, then changing the id back, so that direct changes to the python are not overwritten when the flowgraph is run from GRC

Launching from VsCode

The simplest way to achieve source level debugging is to launch the top level flowgraph (python file) from VsCode.

a) Set breakpoints in VSCode that you want to hit

• Like any other IDE with source level debugging, these can also be set while the code is free running

b) In VSCode, Click on the Debug Icon in the left panel (Triangle with a bug), and if one doesn't exist, "create launch.json file"

• Choose "C++ (GDB/LLDB)"
• This brings up launch.json and inserts some code

d) Modify the configuration so that the program to debug is python (either python2 or python3 depending gnuradio branch)

• The launch.json should look like this:

{
    "version": "0.2.0",
    "configurations": [
        
        {
            "name": "(gdb) Launch",
            "type": "cppdbg",
            "request": "launch",
            "program": "/usr/bin/python3",
            "args": ["-u","/path/to/flowgraph.py"],
            "stopAtEntry": false,
            "cwd": "${workspaceFolder}",
            "environment": [],
            "externalConsole": false,
            "MIMode": "gdb",
            "setupCommands": [
                {
                    "description": "Enable pretty-printing for gdb",
                    "text": "-enable-pretty-printing",
                    "ignoreFailures": true
                }
            ]
        },
    ]
}

e) From the menu Debug:Start Debugging (F5) will start the python and land on your breakpoints!

Attaching to Process

Another alternative is to attach to already running process. This is useful for more complicated systems and flowgraphs

a) (optional) Add a sleep into the python file

• Place after the import statement for your module
• If you are debugging the constructors of your module, then place the sleep before your import

import mymodule
import time; time.sleep(15)

b) Set breakpoints in VSCode that you want to hit

• Like any other IDE with source level debugging, these can also be set while the code is free running

c) In VSCode, Debug --> Open Configurations brings up a "Set Environment" selection

• Choose GDB
• This brings up launch.json

d) Add Attach type of configuration

• Debug --> Add Configuration
• Select C/C++ (gdb) Attach
• This inserts some code

e) Modify the configuration so that the program to debug is python (either python2 or python3 depending gnuradio branch)

• The launch.json should look like this:

{
    // Use IntelliSense to learn about possible attributes.
    // Hover to view descriptions of existing attributes.
    // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
    "version": "0.2.0",
    "configurations": [

        { 
            "name": "(gdb) Attach",
            "type": "cppdbg",
            "request": "attach",
            "program": "/usr/bin/python3",
            "processId": "${command:pickProcess}",
            "MIMode": "gdb",
            "setupCommands": [
                {
                    "description": "Enable pretty-printing for gdb",
                    "text": "-enable-pretty-printing",
                    "ignoreFailures": true
                }
            ]
        },

    ]
}

f) From a terminal, launch the python script which uses your module in a flowgraph

g) From VSCode, Start Debugging (F5), and you will be prompted to select the process to attach to

h) Start typing python, and then choose the python instance which is running your flowgraph

i) At this point (or after the script passes time.sleep) GDB should attach and breakpoints will be active