IL Weaving - Mystery wrapped in an Enigma containing Frustration
time to read 15 min | 2858 words

Okay, here is another exampe of using Cecil, but I think that you can figure out what I think about having to deal with raw IL.

Feel free to figure out what this does, and why I would be interested in such a thing. BTW, in Boo to Boo, that sort of thing so painless. Having to deal with the raw IL takes all the fun out of it.

I know about Cecil.FlowControl, but as far as I can find, this is mostly (only?) for reading assemblies. I am looking for a way to have a reasonable AST over cecil. This is not scalable no matter how you cast it.

import Mono.Cecil

import Mono.Cecil.Cil

class DisposableAttribute(Attribute):

      def Process(t as TypeDefinition):

            disposed = FieldDefinition("___was_disposed",t.Module.Import(bool), FieldAttributes.Private)

            t.Fields.Add(disposed)

            t.Interfaces.Add( t.Module.Import(typeof(IDisposable)))

           

            for method as MethodDefinition in t.Methods:

                  cil = method.Body.CilWorker

                  ins = method.Body.Instructions[0];

                 

                  if method.Name=="Dispose":

                        cil.InsertBefore(ins,cil.Create(OpCodes.Ldarg_0))

                        cil.InsertBefore(ins,cil.Create(OpCodes.Ldc_I4_0))

                        cil.InsertBefore(ins,cil.Create(OpCodes.Stfld, disposed))

                        continue

                 

                  wasDisposedLoc = VariableDefinition(t.Module.Import(bool))

                  method.Body.Variables.Add( wasDisposedLoc )

                 

                  cil.InsertBefore(ins,cil.Create(OpCodes.Ldarg_0))

                  cil.InsertBefore(ins,cil.Create(OpCodes.Ldfld,disposed))

                  cil.InsertBefore(ins,cil.Create(OpCodes.Ldc_I4_0))

                  cil.InsertBefore(ins,cil.Create(OpCodes.Ceq))

                  cil.InsertBefore(ins,cil.Create(OpCodes.Stloc_0))

                  cil.InsertBefore(ins,cil.Create(OpCodes.Ldloc_0))

                  cil.InsertBefore(ins, cil.Create(OpCodes.Brtrue_S,ins))

                  cil.InsertBefore(ins,cil.Create(OpCodes.Ldstr, t.FullName))

                  cil.InsertBefore(ins,cil.Create(OpCodes.Newobj,
                                      t.Module.Import(typeof(ObjectDisposedException).GetConstructors()[0]) ))

                  cil.InsertBefore(ins,cil.Create(OpCodes.Throw))

Chris, compiler!

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