DumpIL SOS command does not properly handle DynamicMethods in .NET Core

[davidwrighton]

Description

• Create a DynamicMethod
• Use the !dumpil command to examine the IL of the associated MethodDesc
• This will fail with a message indicating "Error gathering dynamic info from object at ADDRESS"

Configuration

Any vaguely recent .NET Core build.

Regression?

This probably works targeting the .NET Framework

Other information

It appears that at some point in time the fields on the System.Reflection.Emit.DynamicMethod object were changed to change the m_ prefix to _. In addition, a few other fields look to have changed their name entirely. GatherDynamicInfo in the SOS codebase appears to need to be updated to handle the newer paths, and we probably need some testing for this scenario.

[mikem8361]

Do you have a simple test app that creates a dynamic method?

[davidwrighton]

Here's a simple test app I wrote recently that generates a continuous stream of DynamicMethod objects. You should be able to tweak this to your needs.

using System.Reflection.Emit;
using System.Runtime.CompilerServices;

namespace TestInfiniteDynamicMethods
{
    internal class Program
    {
        [MethodImpl(MethodImplOptions.NoInlining)]
        static Func<int, int> GetFibDynamicMethod()
        {
            DynamicMethod dynamicMethod = new DynamicMethod("Fibonacci", typeof(int), new Type[] { typeof(int) });
            ILGenerator ilgen = dynamicMethod.GetILGenerator();
            Label labelAfterCmp0 = ilgen.DefineLabel();
            ilgen.Emit(OpCodes.Ldarg_0);
            ilgen.Emit(OpCodes.Ldc_I4_0);
            ilgen.Emit(OpCodes.Bne_Un_S, labelAfterCmp0);
            ilgen.Emit(OpCodes.Ldc_I4_0);
            ilgen.Emit(OpCodes.Ret);
            ilgen.MarkLabel(labelAfterCmp0);

            Label labelAfterCmp1 = ilgen.DefineLabel();
            ilgen.Emit(OpCodes.Ldarg_0);
            ilgen.Emit(OpCodes.Ldc_I4_1);
            ilgen.Emit(OpCodes.Bne_Un_S, labelAfterCmp1);
            ilgen.Emit(OpCodes.Ldc_I4_1);
            ilgen.Emit(OpCodes.Ret);
            ilgen.MarkLabel(labelAfterCmp1);

            ilgen.Emit(OpCodes.Ldarg_0);
            ilgen.Emit(OpCodes.Ldc_I4_1);
            ilgen.Emit(OpCodes.Sub);
            ilgen.Emit(OpCodes.Call, dynamicMethod);

            ilgen.Emit(OpCodes.Ldarg_0);
            ilgen.Emit(OpCodes.Ldc_I4_2);
            ilgen.Emit(OpCodes.Sub);
            ilgen.Emit(OpCodes.Call, dynamicMethod);

            ilgen.Emit(OpCodes.Add);
            ilgen.Emit(OpCodes.Ret);

            return dynamicMethod.CreateDelegate<Func<int, int>>();
        }

        static void Main(string[] args)
        {
            Console.WriteLine("Hello, World!");

            int count = 0;
            while (true)
            {
                GetFibDynamicMethod()(4);

                if (((++count) % 200) == 0)
                {
                    GC.Collect();
                    GC.WaitForPendingFinalizers();
                }

                if (((++count) % 1000) == 0)
                    Console.WriteLine(count);
            }
        }
    }
}