调试空指针错误

最新推荐文章于 2021-04-08 22:06:14 发布

jasonvip_c

最新推荐文章于 2021-04-08 22:06:14 发布

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CC 4.0 BY-SA版权

文章标签： exception string byte null

本文链接：https://blog.youkuaiyun.com/jasonvip_c/article/details/5073202

本文介绍了一种通过分析异常调用堆栈和中间语言(IL)代码来精确定位异常源头的方法。具体步骤包括获取异常堆栈跟踪、提取IL代码及偏移量，并通过解析指令码来追溯引发异常的具体操作。

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思路大概是：

1. 获取exception的调用堆栈。

2. 获取exception相关的这个方法的方法的IL代码

3. 结合excpetion的IL偏移量和方法的IL，把调用源找出来。

代码

    class Program
    {
        static void Main(string[] args)
        {
            try
            {
                string hello3 = null;

                hello3 = hello3.ToUpper();
            }
            catch (Exception ex)
            {
                //获取调用堆栈

                StackTrace trace = new StackTrace(ex, true);

                StackFrame frame = trace.GetFrame(0);

                int offset = frame.GetILOffset();

                byte[] il = frame.GetMethod().GetMethodBody().GetILAsByteArray();

                //获取调用指令

                offset++;

                ushort instruction = il[offset++];

                //打开潘多拉魔盒

                ILGlobals global = new ILGlobals();

                global.LoadOpCodes();

                //翻译

                OpCode code = OpCodes.Nop;

                if (instruction != 0xfe)
                {
                    code = global.SingleByteOpCodes[(int)instruction];
                }
                else
                {
                    instruction = il[offset++];
                    code = global.MultiByteOpCodes[(int)instruction];
                    instruction = (ushort)(instruction | 0xfe00);
                }

                //获取方法信息

                int metadataToken = ReadInt32(il, ref offset);

                MethodBase callmethod = frame.GetMethod().Module.ResolveMethod(metadataToken,
                     frame.GetMethod().DeclaringType.GetGenericArguments(),
                     frame.GetMethod().GetGenericArguments());

                //完成

                Console.WriteLine(callmethod.DeclaringType + "." + callmethod.Name);

                Console.Read();
            }

        }

        private static int ReadInt32(byte[] il, ref int position)
        {
            return (((il[position++] | (il[position++] << 8)) | (il[position++] << 0x10)) | (il[position++] << 0x18));
        }

    }

    public class ILGlobals
    {
        private OpCode[] multiByteOpCodes;

        private OpCode[] singleByteOpCodes;

        /// <summary>
        /// Loads the OpCodes for later use.
        /// </summary>
        public void LoadOpCodes()
        {
            singleByteOpCodes = new OpCode[0x100];
            multiByteOpCodes = new OpCode[0x100];
            FieldInfo[] infoArray1 = typeof(OpCodes).GetFields();
            for (int num1 = 0; num1 < infoArray1.Length; num1++)
            {
                FieldInfo info1 = infoArray1[num1];
                if (info1.FieldType == typeof(OpCode))
                {
                    OpCode code1 = (OpCode)info1.GetValue(null);
                    ushort num2 = (ushort)code1.Value;
                    if (num2 < 0x100)
                    {
                        singleByteOpCodes[(int)num2] = code1;
                    }
                    else
                    {
                        if ((num2 & 0xff00) != 0xfe00)
                        {
                            throw new Exception("Invalid OpCode.");
                        }
                        multiByteOpCodes[num2 & 0xff] = code1;
                    }
                }
            }
        }

        /// <summary>
        /// Retrieve the friendly name of a type
        /// </summary>
        /// <param name="typeName">
        /// The complete name to the type
        /// </param>
        /// <returns>
        /// The simplified name of the type (i.e. "int" instead f System.Int32)
        /// </returns>
        public static string ProcessSpecialTypes(string typeName)
        {
            string result = typeName;
            switch (typeName)
            {
                case "System.string":
                case "System.String":
                case "String":
                    result = "string"; break;
                case "System.Int32":
                case "Int":
                case "Int32":
                    result = "int"; break;
            }
            return result;
        }

        public OpCode[] MultiByteOpCodes
        {
            get { return multiByteOpCodes; }
        }

        public OpCode[] SingleByteOpCodes
        {
            get { return singleByteOpCodes; }
        }
    }