Undefined reference to vtable when functions are defined in VS Code

Question

I've seen a lot of questions about this, but can't seem to see what I'm missing. I am fairly new at C++. I am using Visual Studio Code with G++ and MINGW32 10.3.0. When I attempt to run test.cpp (below) I receive two errors:

...test.cpp:7: undefined reference to 'QData::getDataPacket(void*)

...undefined reference to 'vtable for QData'

// qdata.h
#ifndef QDATA_H_
#define QDATA_H_

//Define generic queue data
class QData {
    private:
        int data = 17;                                                               
    public:
        void virtual getDataPacket(void* dataptr);                                 
        void virtual setDataPacket(void* dataptr);                                 
};

#endif

// qdata.cpp
#include "qdata.h"

void QData::getDataPacket(void* dataptr) {                                 
    *(int*)dataptr = data;                                                  
}

void QData::setDataPacket(void* dataptr) {                                 
    data = *(int*)dataptr;                                                  
}

// test.cpp
#include <iostream>
#include "qdata.h"

int main() {
    QData qqq;
    int a;
    qqq.getDataPacket(&a);
    std::cout << a << std::endl;

    return 0;
}

I know the code works because it was originally all in one file and compiled fine. From my research this is maybe a linking issue? Most questions related to this refer to needing to define your virtual functions, but I have already done that.

If I use the following command in the terminal, binary.exe runs correctly (the output is 17): g++ -o binary test.cpp qdata.cpp

Is there a way to get this to compile and run correctly without manually typing in a list of cpp files?

Edit: Since there seems to be some confusion, typically in VSCode you can compile and debug in one go by pushing F5. This is the part where I get the errors above. I am hoping someone can help me understand why that is failing and how to fix it so I can continue testing/debugging in VSCode.

Edit: I'm still voting that this question is unique since I was simply following the trace of the compile error in VS Code. I had actually found this article before, and it did not solve my problem. It is also extremely dense and as a beginner was difficult to understand how it might explain my problem. I will add a visual studio code tag to help people find this question. But every other reference to the vtable error I found was to do with the vtable itself and not following the troubleshooting path to a solution in VS Code.

Answer 1

@JaMiT shared a link that helped me get to the answer. As it turns out, the code is fine but the issue is with how VisualStudio Code is configured in the tasks.json file. If you want to compile multiple cpp files with g++ (assuming you used the Using GCC with MINGW getting started guide) you need to modify the "args". Here is my tasks.json that specifies which cpp files to compile:

tasks.json

{
"tasks": [
    {
        "type": "cppbuild",
        "label": "C/C++: g++.exe build active file",
        "command": "C:\\msys64\\mingw64\\bin\\g++.exe",
        "args": [
            "-g",
            "test.cpp",
            "qdata.cpp",
            "-o",
            "${fileDirname}\\${fileBasenameNoExtension}.exe"
        ],
        "options": {
            "cwd": "${fileDirname}"
        },
        "problemMatcher": [
            "$gcc"
        ],
        "group": {
            "kind": "build",
            "isDefault": true
        },
        "detail": "Task generated by Debugger."
    }
],
"version": "2.0.0"

}

If you simply want to compile all cpp files in the active directory, then you can modify it as follows:

{
"tasks": [
    {
        "type": "cppbuild",
        "label": "C/C++: g++.exe build active file",
        "command": "C:\\msys64\\mingw64\\bin\\g++.exe",
        "args": [
            "-g",
            "*.cpp",
            "-o",
            "${fileDirname}\\${fileBasenameNoExtension}.exe"
        ],
        "options": {
            "cwd": "${fileDirname}"
        },
        "problemMatcher": [
            "$gcc"
        ],
        "group": {
            "kind": "build",
            "isDefault": true
        },
        "detail": "Task generated by Debugger."
    }
],
"version": "2.0.0"

}

Notice that "${file}" has been removed from the "args" in the default tasks.json file.