.net - Mono.Cecil:注入(inject)try/finally？

Question

在 Mono.Cecil was answered here 中实现 try/catch 的良好概述，但他在一次完整的尝试/捕捉/最后停下来。那么如何使用 Mono.Cecil 实现 try/finally？

Answer 1

这里是如何注入(inject)finally。

首先，您需要修复您的退货声明。你只想要一个。

Instruction FixReturns()
{
    if (Method.ReturnType == TypeSystem.Void)
    {
        var instructions = body.Instructions;
        var lastRet = Instruction.Create(OpCodes.Ret);
        instructions.Add(lastRet);

        for (var index = 0; index < instructions.Count - 1; index++)
        {
            var instruction = instructions[index];
            if (instruction.OpCode == OpCodes.Ret)
            {
                instructions[index] = Instruction.Create(OpCodes.Leave, lastRet);
            }
        }
        return lastRet;
    }
    else
    {
        var instructions = body.Instructions;
        var returnVariable = new VariableDefinition("methodTimerReturn", Method.ReturnType);
        body.Variables.Add(returnVariable);
        var lastLd = Instruction.Create(OpCodes.Ldloc, returnVariable);
        instructions.Add(lastLd);
        instructions.Add(Instruction.Create(OpCodes.Ret));

        for (var index = 0; index < instructions.Count - 2; index++)
        {
            var instruction = instructions[index];
            if (instruction.OpCode == OpCodes.Ret)
            {
                instructions[index] = Instruction.Create(OpCodes.Leave, lastLd);
                instructions.Insert(index, Instruction.Create(OpCodes.Stloc, returnVariable));
                index++;
            }
        }
        return lastLd;
    }
}

然后找到第一条指令。如果它是实例构造函数，则需要跳过 2。

Instruction FirstInstructionSkipCtor()
{
    if (Method.IsConstructor && !Method.IsStatic)
    {
        return body.Instructions.Skip(2).First();
    }
    return body.Instructions.First();
}

然后缝合在一起

void InnerProcess()
{
    body = Method.Body;
    body.SimplifyMacros();
    ilProcessor = body.GetILProcessor();

    var returnInstruction = FixReturns();

    var firstInstruction = FirstInstructionSkipCtor();

    var beforeReturn = Instruction.Create(OpCodes.Nop);
    ilProcessor.InsertBefore(returnInstruction, beforeReturn);

    InjectIlForFinaly(returnInstruction);

    var handler = new ExceptionHandler(ExceptionHandlerType.Finally)
        {
            TryStart = firstInstruction,
            TryEnd = beforeReturn,
            HandlerStart = beforeReturn,
            HandlerEnd = returnInstruction,
        };

    body.ExceptionHandlers.Add(handler);
    body.InitLocals = true;
    body.OptimizeMacros();
}