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

The following instructions were created using VSCode v1.33.1 on Ubuntu 18.04

Prerequisites

VSCode must be run as sudo to debug using GDB. Haven't found a way around this yet.

sudo code . --user-data-dir $TMPDIR

where $TMPDIR is a temporary location for VS Code to place its user data files.

NOTE: Using . as the user-data-dir will litter the current directory with files and folder.

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

4) 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)

5) 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

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

  • Choose GDB
  • This brings up launch.json

7) Add Attach type of configuration

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

8) 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
                }
            ]
        },

    ]
}


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

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

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

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