Visual Debugging on VS Code Using GDB

If you’re already developing a C/C++ project in VS Code, configuring the built-in debugger will allow you to fully use features already within the IDE with only a single configuration file. To those are used to debugging in IDEs like IntelliJ or Visual Studio, this is a much more familiar and pleasant experience. Additionally, this can be done both locally and over SSH via the Remote - SSH extension.

For Computer Science & Engineering courses at the UW, I typically open the folder containing my entire repo in VS Code (i.e. ~/code/cse3xx-21au-username), which contains all of the course’s projects. This makes configuring debugging easier since you don’t have to copy this JSON file into every folder if you typically just open a project’s folder directly (i.e. ~/code/cse3xx-21au-username/hw1 ), as the configuration is expected to be found in a folder at the highest level with the current workspace.

Configuring Visual Debugging

To open the default configuration file, click the Run and Debug icon (or Ctrl+Shift+d), then click the cog icon at the top of the sidebar that opens. A file titled launch.json should be created and opened.

Here’s an example debugging configuration for an executable called test_suite in a CentOS 8 based environment (as used in the course CSE 333):

Simple launch.json Example

{
    "version": "0.2.0",
    "configurations": [
        {
            "name": "Run & Debug test_suite",
            "type": "cppdbg",
            "request": "launch",
            "program": "${fileDirname}/test_suite",
            "args": [],
            "stopAtEntry": false,
            "cwd": "${fileDirname}",
            "environment": [],
            "externalConsole": false,
            "MIMode": "gdb",
            "setupCommands": [
                {
                    "description": "Enable pretty-printing for gdb",
                    "text": "-enable-pretty-printing",
                    "ignoreFailures": true
                }
            ],
            "preLaunchTask": "",
            "miDebuggerPath": "/opt/rh/gcc-toolset-9/root/usr/bin/gdb"
        }
		]
}

Save this file, and if everything is configured correctly, you should be ready to debug.

Debugging is now as easy as clicking the Run and Debug icon (or Ctrl+Shift+d), selecting the configuration named Run & Debug test_suite in the dropdown box that appears at the top of the sidebar, then pressing the Play/Run button (or F5).

Important note: this setup requires that you have a file open in the correct hw folder before running the debugger. This configuration depends on the path of that open file to find the path of the test_suite executable. For example, if you want to debug the executable test_suite in a folder named hw1, you would simply have open a file within the directory containing that executable, such as ~/cse3xx-21au-username/hw1/LinkedList.c, before starting a debugging session.

Creating breakpoints and adding a variable to the watchlist is similar other IDEs (see more: https://code.visualstudio.com/Docs/editor/debugging).

You can add more configs to target different executables, and edit the args field to append arguments just like you would on the command line. Here’s another launch.json configuration that runs only a specific set of test cases from the test_suite, and adds another configuration to debug an executable named server:

Example launch.json with Multiple Configurations

{
    "version": "0.2.0",
    "configurations": [
        {
            "name": "Run & Debug test_suite",
            "type": "cppdbg",
            "request": "launch",
            "program": "${fileDirname}/test_suite",
            "args": [
                "--gtest_filter=Test_SomeTestCase.*"

            "stopAtEntry": false,
            "cwd": "${fileDirname}",
            "environment": [],
            "externalConsole": false,
            "MIMode": "gdb",
            "setupCommands": [
                {
                    "description": "Enable pretty-printing for gdb",
                    "text": "-enable-pretty-printing",
                    "ignoreFailures": true
                }
            ],
            "preLaunchTask": "",
            "miDebuggerPath": "/opt/rh/gcc-toolset-9/root/usr/bin/gdb"
        },
        {
            "name": "Run & Debug server",
            "type": "cppdbg",
            "request": "launch",
            "program": "${fileDirname}/server",
            "stopAtEntry": false,
            "cwd": "${fileDirname}",
            "environment": [],
            "externalConsole": false,
            "MIMode": "gdb",
            "setupCommands": [
                {
                    "description": "Enable pretty-printing for gdb",
                    "text": "-enable-pretty-printing",
                    "ignoreFailures": true
                }
            ],
            "preLaunchTask": "",
            "miDebuggerPath": "/opt/rh/gcc-toolset-9/root/usr/bin/gdb"
        }
    ]
}

Additional Resources

Overview on Microsoft’s website: https://code.visualstudio.com/docs/cpp/config-linux#_debug-helloworldcpp