CLR 4.0 拾遗系列1.1 System.AccessViolationException

最新推荐文章于 2023-05-15 11:25:45 发布

转载最新推荐文章于 2023-05-15 11:25:45 发布 · 220 阅读

0 ·

CC 4.0 BY-SA版权

原文链接：http://www.cnblogs.com/pagsun/archive/2011/04/08/clr4_system_access_violation_exception.html

文章标签：

#runtime

本文探讨了在.NET Framework中如何处理AccessViolationException，这种异常通常发生在与未分配的内存或无权限的内存进行读写操作时。文章通过示例代码展示了在C#中调用StgCreateStorageEx函数时可能引发的访问违规异常，并提供了处理此类异常的方法。

Namespace:

System

Class:

System.AccessViolationException

Remarks:

An access violation occurs in unmanaged or unsafe code when the code attempts to read or write to memory that has not been allocated, or to which it does not have access. This usually occurs because a pointer has a bad value. Not all reads or writes through bad pointers lead to access violations, so an access violation usually indicates that several reads or writes have occurred through bad pointers, and that memory might be corrupted. Thus, access violations almost always indicate serious programming errors. In the .NET Framework version 2.0, an AccessViolationException clearly identifies these serious errors.

In programs consisting entirely of verifiable managed code, all references are either valid or null, and access violations are impossible. An AccessViolationException occurs only when verifiable managed code interacts with unmanaged code or with unsafe managed code.

Samples:

using System;
using System.Runtime.ExceptionServices;
using System.Runtime.InteropServices;

class Program
{
    [DllImport("ole32.dll")]
    public static extern UInt32 StgCreateStorageEx(
        [MarshalAs(UnmanagedType.LPWStr), In]
        string pwcsName,
        long grfMode, //TODO grfMode should have been an int not a long
        int stgfmt,
        uint grfAttrs,
        [In]
        IntPtr pStgOptions,
        [In]
        IntPtr reserved2,
        [In]
        ref Guid riid,
        [MarshalAs(UnmanagedType.IUnknown), Out]
        out object ppObjectOpen
        );

    public const int STGM_READWRITE = 0x00000002;
    public const int STGM_SHARE_EXCLUSIVE = 0x00000010;
    public const int STGFMT_STORAGE = 0;

    [HandleProcessCorruptedStateExceptions]
    static void Main(string[] args)
    {
        try
        {
            IntPtr ptr2ptr2ptr = Marshal.AllocHGlobal(IntPtr.Size);
            IntPtr ptr2ptr = Marshal.AllocHGlobal(IntPtr.Size);
            IntPtr ptr2data = Marshal.AllocHGlobal(104857600);
            Marshal.WriteIntPtr(ptr2ptr, ptr2data);
            Marshal.WriteIntPtr(ptr2ptr2ptr, ptr2ptr);
            Guid IID_IStorage = new Guid("0000000B-0000-0000-C000-000000000046");
            UInt32 results;
            object ppObjectOpen;
            results = StgCreateStorageEx(null, STGM_READWRITE + STGM_SHARE_EXCLUSIVE, STGFMT_STORAGE, 0, 
                IntPtr.Zero, IntPtr.Zero, ref IID_IStorage, out ppObjectOpen);
        }
        catch (AccessViolationException ex)
        {
            Console.WriteLine(ex.Message);
            Console.WriteLine(ex.StackTrace);
        }

        Console.WriteLine("Press any key to continue...");
        Console.ReadKey(true);
    }
}