Question

I’m emitting some IL, here my code:

mgen.Emit(OpCodes.Ldc_I4,0);
mgen.Emit(OpCodes.Newarr, typeof(object));
mgen.Emit(OpCodes.Stloc_1); // THIS SHOULD                       


mgen.Emit(OpCodes.Ldloc_1); // MATCH THIS ONE
mgen.Emit(OpCodes.Callvirt, typeof(IInternalFactory).GetMethod("Create"));
mgen.Emit(OpCodes.Castclass, method.ReturnType);
mgen.Emit(OpCodes.Ret);

This is a work in progress, I’ve create an array, and now I’m preparing to do somethings with it, so I decided to store it ( Stloc_1 ) and then push it back onto the stack (Ldloc_1) as soon I did these instruction the IL is signaled to be invalid, but if I understood correctly, these instruction should leave the stack unmodified. Without these two instruction the IL works perfectly. So I can’t unserstand why a pop with a subsequent push does not work.

Answer 1

Before you can store values in a local, you must declare the local using the ILGenerator.DeclareLocal method. Referring to locals that don’t exist will cause the JIT compiler to declare the program invalid.