Posts about Mono

A bug story about named mutex on Mono



When you write some multithreading magic on .NET, you can use a cool synchronization primitive called Mutex:

var mutex = new Mutex(false, "Global\\MyNamedMutex");

You also can make it named (and share the mutex between processes) which works perfectly on Windows:

However, today the .NET Framework is cross-platform, so this code should work on any operation system. What will happen if you use named mutex on Linux or MacOS with the help of Mono or CoreCLR? Is it possible to create some tricky bug based on this case? Of course, it does. Today I want to tell you a story about such bug in Rider which was a headache for several weeks.

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About UTF-8 conversions in Mono



This post is a logical continuation of the Jon Skeet's blog post “When is a string not a string?”. Jon showed very interesting things about behavior of ill-formed Unicode strings in .NET. I wondered about how similar examples will work on Mono. And I have got very interesting results.

Experiment 1: Compilation

Let's take the Jon's code with a small modification. We will just add text null check in DumpString:

using System;
using System.ComponentModel;
using System.Text;
using System.Linq;
[Description(Value)]
class Test
{
    const string Value = "X\ud800Y";
    static void Main()
    {
        var description = (DescriptionAttribute)typeof(Test).
            GetCustomAttributes(typeof(DescriptionAttribute), true)[0];
        DumpString("Attribute", description.Description);
        DumpString("Constant", Value);
    }
    static void DumpString(string name, string text)
    {
        Console.Write("{0}: ", name);
        if (text != null)
        {
            var utf16 = text.Select(c => ((uint) c).ToString("x4"));
            Console.WriteLine(string.Join(" ", utf16));
        }
        else
            Console.WriteLine("null");
    }
}

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