Following up to my previous answer, I’ve managed to create a basic exception finder. It utilises a reflection-based ILReader class, available here on Haibo Luo’s MSDN blog. (Just add a reference to the project.)
Updates:
- Now handles local variables and the stack.
- Correctly detects exceptions returned from method calls or fields and later thrown.
- Now handles stack pushes/pops fully and appropiately.
Here is the code, in full. You simply want to use the GetAllExceptions(MethodBase) method either as an extension or static method.
using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Linq;
using System.Reflection;
using System.Reflection.Emit;
using System.Text;
using ClrTest.Reflection;
public static class ExceptionAnalyser
{
public static ReadOnlyCollection<Type> GetAllExceptions(this MethodBase method)
{
var exceptionTypes = new HashSet<Type>();
var visitedMethods = new HashSet<MethodBase>();
var localVars = new Type[ushort.MaxValue];
var stack = new Stack<Type>();
GetAllExceptions(method, exceptionTypes, visitedMethods, localVars, stack, 0);
return exceptionTypes.ToList().AsReadOnly();
}
public static void GetAllExceptions(MethodBase method, HashSet<Type> exceptionTypes,
HashSet<MethodBase> visitedMethods, Type[] localVars, Stack<Type> stack, int depth)
{
var ilReader = new ILReader(method);
var allInstructions = ilReader.ToArray();
ILInstruction instruction;
for (int i = 0; i < allInstructions.Length; i++)
{
instruction = allInstructions[i];
if (instruction is InlineMethodInstruction)
{
var methodInstruction = (InlineMethodInstruction)instruction;
if (!visitedMethods.Contains(methodInstruction.Method))
{
visitedMethods.Add(methodInstruction.Method);
GetAllExceptions(methodInstruction.Method, exceptionTypes, visitedMethods,
localVars, stack, depth + 1);
}
var curMethod = methodInstruction.Method;
if (curMethod is ConstructorInfo)
stack.Push(((ConstructorInfo)curMethod).DeclaringType);
else if (method is MethodInfo)
stack.Push(((MethodInfo)curMethod).ReturnParameter.ParameterType);
}
else if (instruction is InlineFieldInstruction)
{
var fieldInstruction = (InlineFieldInstruction)instruction;
stack.Push(fieldInstruction.Field.FieldType);
}
else if (instruction is ShortInlineBrTargetInstruction)
{
}
else if (instruction is InlineBrTargetInstruction)
{
}
else
{
switch (instruction.OpCode.Value)
{
// ld*
case 0x06:
stack.Push(localVars[0]);
break;
case 0x07:
stack.Push(localVars[1]);
break;
case 0x08:
stack.Push(localVars[2]);
break;
case 0x09:
stack.Push(localVars[3]);
break;
case 0x11:
{
var index = (ushort)allInstructions[i + 1].OpCode.Value;
stack.Push(localVars[index]);
break;
}
// st*
case 0x0A:
localVars[0] = stack.Pop();
break;
case 0x0B:
localVars[1] = stack.Pop();
break;
case 0x0C:
localVars[2] = stack.Pop();
break;
case 0x0D:
localVars[3] = stack.Pop();
break;
case 0x13:
{
var index = (ushort)allInstructions[i + 1].OpCode.Value;
localVars[index] = stack.Pop();
break;
}
// throw
case 0x7A:
if (stack.Peek() == null)
break;
if (!typeof(Exception).IsAssignableFrom(stack.Peek()))
{
//var ops = allInstructions.Select(f => f.OpCode).ToArray();
//break;
}
exceptionTypes.Add(stack.Pop());
break;
default:
switch (instruction.OpCode.StackBehaviourPop)
{
case StackBehaviour.Pop0:
break;
case StackBehaviour.Pop1:
case StackBehaviour.Popi:
case StackBehaviour.Popref:
case StackBehaviour.Varpop:
stack.Pop();
break;
case StackBehaviour.Pop1_pop1:
case StackBehaviour.Popi_pop1:
case StackBehaviour.Popi_popi:
case StackBehaviour.Popi_popi8:
case StackBehaviour.Popi_popr4:
case StackBehaviour.Popi_popr8:
case StackBehaviour.Popref_pop1:
case StackBehaviour.Popref_popi:
stack.Pop();
stack.Pop();
break;
case StackBehaviour.Popref_popi_pop1:
case StackBehaviour.Popref_popi_popi:
case StackBehaviour.Popref_popi_popi8:
case StackBehaviour.Popref_popi_popr4:
case StackBehaviour.Popref_popi_popr8:
case StackBehaviour.Popref_popi_popref:
stack.Pop();
stack.Pop();
stack.Pop();
break;
}
switch (instruction.OpCode.StackBehaviourPush)
{
case StackBehaviour.Push0:
break;
case StackBehaviour.Push1:
case StackBehaviour.Pushi:
case StackBehaviour.Pushi8:
case StackBehaviour.Pushr4:
case StackBehaviour.Pushr8:
case StackBehaviour.Pushref:
case StackBehaviour.Varpush:
stack.Push(null);
break;
case StackBehaviour.Push1_push1:
stack.Push(null);
stack.Push(null);
break;
}
break;
}
}
}
}
}
To summarise, this algorithm recursively enumerates (depth-first) any methods called within the specified one, by reading the CIL instructions (as well as keeping track of methods already visited). It maintains a single list of collections that can be thrown using a HashSet<T> object, which is returned at the end. It additionally maintains an array of local variables and a stack, in order to keep track of exceptions that aren’t thrown immediately after they are created.
Of course, this code isn’t infallible in it’s current state. There are a few improvements that I need to make for it to be robust, namely:
Detect exceptions that aren’t thrown directly using an exception constructor. (i.e. The exception is retrieved from a local variable or a method call.)Support exceptions popped off the stack then later pushed back on.- Add flow-control detection. Try-catch blocks that handle any thrown exception should remove the appropiate exception from the list, unless a
rethrowinstruction is detected.
Apart from that, I believe the code is reasonably complete. It may take a bit more investigation before I figure out exactly how to do the flow-control detection (though I believe I can see how it operates at the IL-level now).
These functions could probably be turned into an entire library if one was to create a full-featured “exception analyser”, but hopefully this will at least provide a sound starting point for such a tool, if not already good enough in its current state.
Anyway, hope that helps!