VSCode is NOT crashing when running a shallow copies program

[Alexander Anthon (AAnthon1985)]

Hi,
Learning C++, I am currently looking at the pitfalls when using shallow copy constructors. The program compiles well, and, unfortunately, it also runs well in VSCode, while it should crash. Is this VSCode specific? Running the program in my console CMD, the program crashes. Running the program in an online compiler, I get the feedback of memory violation. Thank you,

#include <iostream>
#include <vector>

using std::cin;
using std::cout;
using std::endl;
using std::string;
using std::vector;

class Shallow
{
private:
    int *data;
public:
    void set_data(int d)
    {
        *data = d;
    }
    int get_data_value()
    {
        return *data;
    }

    // Constructor
    Shallow(int d);
    // Copy constructor
    Shallow(const Shallow &source);
    //Destructor
    ~Shallow();
};

// Constructor
Shallow::Shallow(int d)
{
    data = new int;
    *data = d;
}

// Copy constructor
Shallow::Shallow(const Shallow &source)
: data(source.data)
{
    cout << "Copy constructor - shallow copy" << endl;
}

// Destructor
Shallow::~Shallow()
{
    delete data;
    cout << "Destructor freeing data" << endl;
}

void display_shallow(Shallow s)
{
    cout << s.get_data_value() << endl;
}

int main()
{
    Shallow obj1(100);
    display_shallow(obj1);

    Shallow obj2(obj1);
    obj2.set_data(1000);
    
    return 0;
}

My tasks.json file:

{
	"version": "2.0.0",
	"tasks": [
		{
			"type": "cppbuild",
			"label": "C/C++: g++.exe build active file",
			"command": "C:\\MinGW\\bin\\g++.exe",
			"args": [
				"-g",
				"${workspaceFolder}\\*.cpp",
				// "${workspaceFolder}\\src\\*.cpp",
				"-I",
				"${workspaceFolder}\\inc\\",
				"-o",
				"${fileDirname}\\${fileBasenameNoExtension}.exe"
			],
			"options": {
				"cwd": "${workspaceFolder}"
			},
			"problemMatcher": [
				"$gcc"
			],
			"group": {
				"kind": "build",
				"isDefault": true
			},
			"detail": "compiler: C:\\MinGW\\bin\\g++.exe"
		}
	]
}

[Sean McManus (sean-mcmanus)]

It crashes for me in VS Code. Are you sure you're running the app until it runs the destructor?

[Alexander Anthon (AAnthon1985)]

Okay, so now I am getting confused. First of all, my msvcrt.dll is dated 11/02/2021, so pretty new. Also, perhaps worth to mention, is that my machine is pretty new (less than 6 weeks old). I think/thought I have all the windows updates. At least there are no updates shown to be installed on my Windows update.
Anyways...
Once I found out that there was no appverif.exe in my System32 folder, I googled it and found out that I did not have the Windows 10 SDK (and hence no Application Verifier) on my machine. So I downloaded Windows 10 SDK, and tried to debug the main.exe file while logging the execution with appverif.exe.
I crashed during debug.

So here comes the mysterious part:
Whenever I am now compiling and running my code in the VSCode terminal (refer to Step 4 and Step 5 from above), I now get the following output:

PS C:\Users\Alexander\Documents\GitHub\CPP_Projects\01_beginning_cpp_programming_course\148_Shallow_copy> .\main
Copy constructor - shallow copy
100
Destructor freeing data        
Copy constructor - shallow copy
PS C:\Users\Alexander\Documents\GitHub\CPP_Projects\01_beginning_cpp_programming_course\148_Shallow_copy> 

Look at that: The program ends without having the last two destructors executed.

In fact, I'm getting the same output as you do.

Not sure what changed on my machine after I installed Windows 10 SDK. Do you perhaps have an explanation?

Cheers,

[Sean McManus (sean-mcmanus)]

Yeah, your C runtime that was being used by mingw must have been some old version (not sure where from). The Windows SDK's C runtime is at a path like C:\Program Files (x86)\Windows Kits\10\Include\10.0.19041.0\ucrt and C:\Program Files (x86)\Windows Kits\10\Lib\10.0.19041.0\ucrt\x86.

[Alexander Anthon (AAnthon1985)]

Thank you, I'm getting closer here, but there are still some things not entirely understandable for me.

I basically blindly followed the instructions from here:
https://code.visualstudio.com/docs/cpp/config-mingw
Which forwarded me to the following website to download Mingw-w64
https://sourceforge.net/projects/mingw-w64/

So I downloaded and installed mingw-w64 and continued following the instruction from here:
https://code.visualstudio.com/docs/cpp/config-mingw

I did nothing more, and I did nothing less. With that in mind, I am confused that I was running into these problems with the shallow copying.

Let me ask the other way around:
Is Windows 10 SDK a requirement in order to run Mingw-w64 properly, or is something wrong my Mingw-w64? You mentioned that you used gdb/c++ 10.1:

Where did you get that one from? I couldn't see any option as of which gdb/c++ to use.

The reason why I am asking:
What is it that I need to be aware of in the future when programming in C++ to make sure that things run properly. Clearly, installing Mingw-w64 and VSCode alone is not enough (in my case at least).

Thank you,

[Sean McManus (sean-mcmanus)]

Those docs needs to be updated. The version of mingw described there is old -- see #6536 . I recommend using msys2 to get gcc 10.2 compilers (or using WSL2 with Ubuntu 20). I'm not entirely sure which components of mingw or msys2 rely on installed Windows 10 SDK (my guess is it might bundle an older version if a newer version isn't found on your system). I always have the Windows 10 SDK installed as part of my VS install.

[Alexander Anthon (AAnthon1985)]

Sean McManus (@sean-mcmanus) That's great to hear. Thank you very much (once again), for your help and support. Although with SDK and G++ 8.1.0 it works fine as expected, it's good to know that there is a G++10.2 and that the docs should be updated.

Good job. Issue is resolved and answered from my side here.

Cheers,