How to compile/debug a C++ application in Docker with Visual Studio Code on Windows

Question

I\'m new on Visual Studio Code and Docker. Now I want to use Visual Studio Code to edit my C++ code and Docker to compile/debug.

I don\'t know how to write the launch.js

Answer 1

I set up a minimal working example on GitHub: https://github.com/fschwaiger/docker-cpp-vscode

The idea is as follows, assuming you have the ms-vscode.cpptools extension:

1. You need containers with gcc and gdb installed (can be the same)
2. You build the application in the container
3. You run gdb from within the container

1. Get the images for gcc and gdb

gcc is available directly from Docker Hub: docker pull gcc. I did not find gdb there, so there is a Dockerfile to build it:

FROM gcc:latest
RUN apt-get update && apt-get install -y gdb
RUN echo "set auto-load safe-path /" >> /root/.gdbinit

It builds on gcc:latest and installs gdb, so you can use the same image to compile and debug. It also sets option set auto-load safe-path / in /root/.gdbinit to suppress a warning when running gdb in the container. Safety should not be a concern for local development.

Build the image using docker build -t gdb . in the working directory, or in Visual Studio Code run the preconfigured task build docker gdb from F1 → Run Task.

2. Building the application

In the project, run docker run --rm -it -v ${pwd}:/work --workdir /work gcc make debug from a PowerShell window in the working directory. Using Visual Studio Code, this can be done by the preconfigured task make debug from F1 → Run Task.

3. Debug the application

You want to configure Visual Studio Code to run /usr/bin/gdb from within the container. You can use the pipeTransport option in launch.json for that and make it run:

docker run --rm --interactive --volume ${workspaceFolder}:/work --workdir /work --privileged gdb sh -c /usr/bin/gdb

Explanation:

• --privileged: allow binary debugging
• --volume ${workspaceFolder}:/work --workdir /work: mount the project folder into the container
• --rm: remove the container after exit
• --interactive: VSCode will issue interactive commands to the gdb shell
• sh -c: defines a shell entrypoint within GDB is run

The overall launch.json looks like follows. Notice that program and cwd are the paths within the container. sourceFileMap allows the debugger to match the breakpoints with the source files. The rest is the default template stuff from the C++ extension.

{
    "version": "0.2.0",
    "configurations": [
        {
            "name": "(gdb) Docker",
            "type": "cppdbg",
            "request": "launch",
            "program": "build/apps/program",
            "args": [],
            "stopAtEntry": true,
            "cwd": "/work",
            "environment": [],
            "externalConsole": true,
            "preLaunchTask": "make debug",
            "targetArchitecture": "x64",
            "sourceFileMap": { "/work": "${workspaceFolder}" },
            "pipeTransport": {
                "debuggerPath": "/usr/bin/gdb",
                "pipeProgram": "docker.exe",
                "pipeArgs": ["run","--rm","--interactive","--volume","${workspaceFolder}:/work","--workdir","/work","--privileged","gdb","sh","-c"],
                "pipeCwd": ""
            },
            "MIMode": "gdb",
            "setupCommands": [
                {
                    "description": "Enable pretty-printing for gdb",
                    "text": "-enable-pretty-printing",
                    "ignoreFailures": true
                }
            ]
        }
    ]
}

With this setup, all you need to do is press play in the debug workspace.