Exception when trying to execute generated code

Question

I'm implementing a constructor for a dynamic type but when i'm executing the code it throws me a exception that the IL-Code is corrupted ( FatalExecutionError ).

IL-Code

Working part:

.method assembly specialname rtspecialname 
instance void .ctor (
    object '',
    object '',
    string ''
) cil managed 
{
// Method begins at RVA 0xa370
// Code size 36 (0x24)
.maxstack 2
.locals init (
    [0] class [mscorlib]System.Collections.IList,
    [1] class [mscorlib]System.Collections.IList
)

IL_0000: ldarg.0
IL_0001: ldarg.1
IL_0002: stfld object HIDDEN.PropertyComparison::_Object0
IL_0007: ldarg.0
IL_0008: ldarg.2
IL_0009: stfld object HIDDEN.PropertyComparison::_Object1
IL_000e: ldarg.0
IL_000f: ldarg.3
IL_0010: stfld string HIDDEN.PropertyComparison::_Name
// Return is here normally when not using the following code

When adding the following IL-code the error occurs. It must have something to do with the code or it's some other strange behaviour which only occurs with the code before this code.

IL_0015: ldarg.1
IL_0016: isinst [mscorlib]System.Collections.IList
IL_001b: stloc.0
IL_001c: ldarg.2
IL_001d: isinst [mscorlib]System.Collections.IList
IL_0022: stloc.1
IL_0023: ret
} // end of method PropertyComparison::.ctor

The point is the lines which cause the error ( it seems they are the reason for the error ) are just a simple as, when speaking of C#, nothing more. Would be great if anyone has a idea to solve this issue.

Generating code

PropertyComparisonType = _Module.DefineType("HIDDEN.PropertyComparison", TypeAttributes.Public, typeof(Object));
FieldBuilder object0Field = PropertyComparisonType.DefineField("_Object0", typeof(Object), FieldAttributes.Private);
FieldBuilder object1Field = PropertyComparisonType.DefineField("_Object1", typeof(Object), FieldAttributes.Private);
FieldBuilder equalField = PropertyComparisonType.DefineField("_Equal", typeof(Boolean), FieldAttributes.Private);
FieldBuilder nameField = PropertyComparisonType.DefineField("_Name", typeof(String), FieldAttributes.Private);
FieldBuilder childsField = PropertyComparisonType.DefineField("_Childs", typeof(IEnumerable<>).MakeGenericType(PropertyComparisonType), FieldAttributes.Private);

PropertyBuilder object0Property = PropertyComparisonType.DefineProperty("Object0", object0Field, setter: false);
PropertyBuilder object1Property = PropertyComparisonType.DefineProperty("Object1", object1Field, setter: false);
PropertyBuilder equalProperty = PropertyComparisonType.DefineProperty("Equal", equalField, setter: false);
PropertyBuilder nameProperty = PropertyComparisonType.DefineProperty("Name", nameField, setter: false);
PropertyBuilder childsProperty = PropertyComparisonType.DefineProperty("Childs", childsField, setter: false);

PropertyComparisonConstructor = PropertyComparisonType.DefineConstructor(MethodAttributes.Assembly, CallingConventions.Standard, new[] { typeof(Object), typeof(Object), typeof(String) });
ILGenerator il = PropertyComparisonConstructor.GetILGenerator();


il.Emit(OpCodes.Ldarg_0);
il.Emit(OpCodes.Ldarg_1);
il.Emit(OpCodes.Stfld, object0Field);

il.Emit(OpCodes.Ldarg_0);
il.Emit(OpCodes.Ldarg_2);
il.Emit(OpCodes.Stfld, object1Field);

il.Emit(OpCodes.Ldarg_0);
il.Emit(OpCodes.Ldarg_3);
il.Emit(OpCodes.Stfld, nameField);

LocalBuilder localList0 = il.DeclareLocal(typeof(IList));
LocalBuilder localList1 = il.DeclareLocal(typeof(IList));

il.Emit(OpCodes.Ldarg_1);
il.Emit(OpCodes.Isinst, typeof(IList));
il.Emit(OpCodes.Stloc, localList0);
il.Emit(OpCodes.Ldarg_2);
il.Emit(OpCodes.Isinst, typeof(IList));
il.Emit(OpCodes.Stloc, localList1);

Castclass ( Edit )

I noticed that OpCodes.Castclass doesn't throws the error but of course throws a runtime-error when the runtime is trying to cast a invalid object.

Another crazy thing ( Edit 2 )

I noticed also that it works when i exchange the last Isinst with Castclass it works without throwing any error. This makes me even more wondering about this error. When comment out the lines which generate castclass the error is back again.

Kirk Woll · Accepted Answer · 2012-03-01 17:04:35Z

1

I tried your code (had to change the constructor to MethodAttributes.Public to get it to work) and it worked flawlessly. I apologize that this isn't really an answer, but wanted to show the code that I used in case it points to any differences that might be helpful:

class Program
{
    static void Main(string[] args)
    {
        var assembly = AppDomain.CurrentDomain.DefineDynamicAssembly(new AssemblyName("foo"), AssemblyBuilderAccess.RunAndSave);
        var _Module = assembly.DefineDynamicModule("fooModule");

        var PropertyComparisonType = _Module.DefineType("HIDDEN.PropertyComparison", TypeAttributes.Public, typeof(Object));
        FieldBuilder object0Field = PropertyComparisonType.DefineField("_Object0", typeof(Object), FieldAttributes.Private);
        FieldBuilder object1Field = PropertyComparisonType.DefineField("_Object1", typeof(Object), FieldAttributes.Private);
        FieldBuilder equalField = PropertyComparisonType.DefineField("_Equal", typeof(Boolean), FieldAttributes.Private);
        FieldBuilder nameField = PropertyComparisonType.DefineField("_Name", typeof(String), FieldAttributes.Private);
        FieldBuilder childsField = PropertyComparisonType.DefineField("_Childs", typeof(IEnumerable<>).MakeGenericType(PropertyComparisonType), FieldAttributes.Private);

        var PropertyComparisonConstructor = PropertyComparisonType.DefineConstructor(MethodAttributes.Public, CallingConventions.Standard, new[] { typeof(Object), typeof(Object), typeof(String) });
        ILGenerator il = PropertyComparisonConstructor.GetILGenerator();


        il.Emit(OpCodes.Ldarg_0);
        il.Emit(OpCodes.Ldarg_1);
        il.Emit(OpCodes.Stfld, object0Field);

        il.Emit(OpCodes.Ldarg_0);
        il.Emit(OpCodes.Ldarg_2);
        il.Emit(OpCodes.Stfld, object1Field);

        il.Emit(OpCodes.Ldarg_0);
        il.Emit(OpCodes.Ldarg_3);
        il.Emit(OpCodes.Stfld, nameField);

        LocalBuilder localList0 = il.DeclareLocal(typeof(IList));
        LocalBuilder localList1 = il.DeclareLocal(typeof(IList));

        il.Emit(OpCodes.Ldarg_1);
        il.Emit(OpCodes.Isinst, typeof(IList));
        il.Emit(OpCodes.Stloc, localList0);
        il.Emit(OpCodes.Ldarg_2);
        il.Emit(OpCodes.Isinst, typeof(IList));
        il.Emit(OpCodes.Stloc, localList1);
        il.Emit(OpCodes.Ret);

        var type = PropertyComparisonType.CreateType();

        var list1 = new List<string>();
        var list2 = new List<string>();
        var s = "prop";
        var instance = Activator.CreateInstance(type, list1, list2, s);
    }
}

answered Mar 1, 2012 at 17:04

Kirk Woll

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6 Comments

Kirk Woll Over a year ago

@Felix, can you elaborate? What do you mean by "a previous code"?

Felix K. Over a year ago

I mean a previous method which calls the constructor.

Kirk Woll Over a year ago

I'm not sure -- the fully self-contained sample I provided above works perfectly for me every time. Does it work for you?

Felix K. Over a year ago

Thanks for your help, it turned out that i forget to box a value type and this causes the exception at this point.

Kirk Woll Over a year ago

@Felix, ah, yeah, I've had some gnarly errors when forgetting to do that. I wish the CLR was more helpful when the IL is off.

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