Build and Debugging Exercism Problems within Visual Studio Code

I’ve been working my way through Exercism’s C Track to sharpen my programming skills. I like how Exercism provides a CLI you can use to write and submit programs from your own machine. Handy!

Exercism uses Unity as a testing framework and heavily encourages Test-Driven Development as part of the problem solving process. One issue I have encountered with the way Exercism solutions are run is that I do not have access to stdout. My machine might not be configured correctly but I’m inclined to think this behavior is intentional.

I’m an electronics engineer by profession, but software isn’t the main thing we do in my office and most of my software and firmware projects are the “figure it out yourself” kind of situations. I admittedly haven’t had any mentorship in proper software design and testing. For software projects, I tend to overuse console logging as the primary way to figure out what the heck is going on behind the scenes.

Without access to my handy printf, I figured it was time to figure out how to used Visual Studio Code’s debugging functionality.

Configuring Visual Studio Code

Note: my host machine runs Fedora and I’m using GCC and GDB to build and debug. Things will be different with other configurations.

After using the Exercism CLI tool to download the problem files, your directory will look something like this:

problem/
    .exercism/
        config.json
        metadata.json
    test_framework/
        unity_internals.h
        unity.h
        unity.c
    HELP.md
    makefile
    problem.c
    problem.h
    README.md
    test_problem.c

Create a new folder .vscode/ in the problem’s root directory. Create two new files in this folder - tasks.json and launch.json. Your directory will now look something like this:

problem/
    .exercism/
        config.json
        metadata.json
    .vscode/
        launch.json
        tasks.json
    test_framework/
        unity_internals.h
        unity.h
        unity.c
    HELP.md
    makefile
    problem.c
    problem.h
    README.md
    test_problem.c

Building

The makefile is already configured to build & test, clean, and build without testing. The makefile also passes the -g flag to the compiler by default, enabling debugging symbols in the output. These tasks can be launched through VSCode by adding these tasks to tasks.json:

// tasks.json
{
    // See https://go.microsoft.com/fwlink/?LinkId=733558
    // for the documentation about the tasks.json format
    "version": "2.0.0",
    "tasks": [
        {
            "label": "exercism: test",
            "type": "shell",
            "command": "make",
            "args": [
                "test"
            ],
            "group": {
                "kind": "build",
                "isDefault": true
            }
        },
        {
            "label": "exercism: clean",
            "type": "shell",
            "command": "make",
            "args": [
                "clean"
            ]
        },
        {
            "label": "exercism: compile",
            "type": "shell",
            "command": "make",
            "args": [
                "tests.out"
            ],
            "group": {
                "kind": "build"
            }
        }
    ]
}

Debugging

To compile the code and launch the debugger, modify launch.json as such:

// launch.json
{
    // 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) Launch",
            "type": "cppdbg",
            "request": "launch",
            "program": "${workspaceFolder}/tests.out",
            "args": [],
            "stopAtEntry": false,
            "cwd": "${fileDirname}",
            "environment": [],
            "externalConsole": false,
            "MIMode": "gdb",
            "setupCommands": [
                {
                    "description": "Enable pretty-printing for gdb",
                    "text": "-enable-pretty-printing",
                    "ignoreFailures": true
                }
            ],
            "preLaunchTask": "exercism: compile"
        }
    ]
}