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

This answer assumes that you are not trying to do anything with multiple containers... I'm assuming that you just want to use a single container to build some C++ code, and that all of your code is in a folder called C:\vsc_docker_cc_gdb. I also assume you have the C++ and Docker extensions from Microsoft installed in Visual Studio Code.

Let's start with a simple C++ file, called hello.cc:

#include 
int main(int argc, char **argv) {
  std::cout << "Hello from Docker" << std::endl;
}

Let's also add a Makefile:

CXXFLAGS = -O3 -ggdb -m64
LDFLAGS  = -m64

all: hello.exe
.PRECIOUS: hello.exe hello.o
.PHONY: all clean

%.o: %.cc
    $(CXX) -c $< -o $@ $(CXXFLAGS)

%.exe: %.o
    $(CXX) $^ -o $@ $(LDFLAGS)

clean:
    rm -f hello.o hello.exe

Here's a Dockerfile that extends gcc:latest by adding GDB and gdbserver (note: I'm not sure gdbserver is needed):

FROM gcc:latest
LABEL Name=vsc_docker_cc_gdb Version=0.0.2
RUN apt-get -y update
RUN apt-get -y install gdb gdbserver
WORKDIR /root

Here's .vscode/tasks.json:

{
    "version": "2.0.0",
    "tasks": [
        {
            "label": "build (in container)",
            "type": "shell",
            "command": "docker run --privileged -v c:/vsc_docker_cc_gdb/:/root vsc_docker_cc_gdb make",
            "group": {
                "kind": "build",
                "isDefault": true
            },
            "problemMatcher": {
                "owner": "cpp",
                "fileLocation": [
                    "relative",
                    "${workspaceFolder}"
                ],
                "pattern": {
                    "regexp": "^(.*):(\\d+):(\\d+):\\s+(warning|error):\\s+(.*)$",
                    "file": 1,
                    "line": 2,
                    "column": 3,
                    "severity": 4,
                    "message": 5
                }
            }
        },
        {
            "label": "clean (in container)",
            "type": "shell",
            "command": "docker run --privileged -v c:/vsc_docker_cc_gdb/:/root vsc_docker_cc_gdb make clean",
            "group": "build",
            "problemMatcher": []
        },
        {
            "label": "remove containers",
            "type": "shell",
            "command": "docker ps -a -q | % { docker rm $_ }",
            "problemMatcher": []
        },
        {
            "label": "run the code",
            "type": "shell",
            "command": "docker run --privileged -v c:/vsc_docker_cc_gdb/:/root vsc_docker_cc_gdb ./hello.exe",
            "group": "build",
            "problemMatcher": []
        },
        {
            "label": "prepare to debug",
            "type": "shell",
            "command": "docker run --privileged -v c:/vsc_docker_cc_gdb/:/root --name debug_vsc -it vsc_docker_cc_gdb ",
            "group": "build",
            "problemMatcher": []
        }
    ]
}

And finally, .vscode/launch.json:

{
    "version": "0.2.0",
    "configurations": [{
        "name": "(gdb) Pipe Launch",
        "type": "cppdbg",
        "request": "launch",
        "program": "/root/hello.exe",
        "cwd": "/root",
        "args": [],
        "stopAtEntry": true,
        "environment": [],
        "externalConsole": true,
        "pipeTransport": {
            "debuggerPath": "/usr/bin/gdb",
            "pipeProgram": "docker.exe",
            "pipeArgs": ["exec", "-i", "debug_vsc", "sh", "-c"],
            "pipeCwd": "${workspaceRoot}"
        },
        "MIMode": "gdb",
        "setupCommands": [{
            "description": "Enable pretty-printing for gdb",
            "text": "-enable-pretty-printing",
            "ignoreFailures": true
        }]
    }, ]
}

There are two important things here. The first is that you'll notice that parts of launch.json are referring to paths in the container (/root/) and others are referring to paths on the Windows host (workspaceRoot). That is important.

The second is that you'll need to have a container running, and then you can launch a debug process into it. Here's a recipe to go from zero to starting that special container and launching a debugger in it.

• From PowerShell: docker pull gcc
• From Visual Studio Code: F1, Docker: Build Image (pick vsc_docker_cc_gdb:latest)
• From Visual Studio Code: Ctrl + Shift + B to build the code
• From Visual Studio Code: F1, Tasks: Run Task (pick "remove containers")
• From Visual Studio Code: F1, Tasks: Run Task (pick "prepare to debug")
• From Visual Studio Code: F5 to start the debugger

From there, the Visual Studio Code Debug Console should work, and you should be able to set breakpoints, watch variables, and enter debug commands.