CodeQL documentation

Unmanaged code

ID: cs/unmanaged-code
Kind: problem
Severity: recommendation
Precision: high
Tags:
   - reliability
   - maintainability
Query suites:
   - csharp-security-and-quality.qls

Click to see the query in the CodeQL repository

Microsoft defines two broad categories for source code. Managed code compiles into bytecode and is then executed by a virtual machine. Unmanaged code is compiled directly into machine code. All C# code is managed but it is possible to call external unmanaged code. This rule finds extern methods that are implemented by unmanaged code. Managed code has many advantages over unmanaged code such as built in memory management performed by the virtual machine and the ability to run compiled programs on a wider variety of architectures.

Recommendation

Consider whether the unmanaged extern methods could be implemented in C# instead.

Example

This example shows a function that displays a message box when clicked. The unmanaged code is shown first and then the same function being performed by managed code is shown after.

// example of using unmanaged code
using System;
using System.Windows.Forms;
using System.Runtime.InteropServices;

public partial class UnmanagedCodeExample : Form
{
    [DllImport("User32.dll")]
    public static extern int MessageBox(int h, string m, string c, int type); // BAD

    private void btnSayHello_Click(object sender, EventArgs e)
    {
        MessageBox(0, "Hello World", "Title", 0);
    }
}



// the same thing in managed code
using System;
using System.Windows.Forms;

public partial class ManagedCodeExample : Form
{
    private void btnSayHello_Click(object sender, EventArgs e)
    {
        MessageBox.Show("Hello World", "Title");
    }
}

References