C# CreatePipe() -> protected 内存错误

Question

我尝试使用 C# 创建管道。代码非常简单，但是当执行带有 CreatePipe() 调用的行时，我得到一个 System.AccessViolationException 并显示以下错误消息:

Attempted to read or write protected memory. This is often an indication that other memory is corrupt.

这是我表单的完整代码:

public partial class Form1 : Form
{
    [DllImport("kernel32.dll", CharSet = CharSet.Auto, SetLastError = true)]
    public static extern bool CreatePipe(out SafeFileHandle hReadPipe, out SafeFileHandle hWritePipe, SECURITY_ATTRIBUTES lpPipeAttributes, int nSize);

    [StructLayout(LayoutKind.Sequential)]
    public struct SECURITY_ATTRIBUTES
    {
        public DWORD nLength;
        public IntPtr lpSecurityDescriptor;
        public bool bInheritHandle;
    }

    public Form1()
    {
        InitializeComponent();
    }

    private void btCreate_Click(object sender, EventArgs e)
    {
        SECURITY_ATTRIBUTES sa = new SECURITY_ATTRIBUTES();
        sa.nLength = (DWORD)System.Runtime.InteropServices.Marshal.SizeOf(sa);
        sa.lpSecurityDescriptor = IntPtr.Zero;
        sa.bInheritHandle = true;

        SafeFileHandle hWrite = null;
        SafeFileHandle hRead = null;

        if (CreatePipe(out hRead, out hWrite, sa, 4096))
        {
            MessageBox.Show("Pipe created !");
        }
        else
            MessageBox.Show("Error : Pipe not created !");
    }   
}

在顶部我声明:using DWORD = System.UInt32;

如果有人能提供帮助，非常感谢。

Answer 1

protected 内存冲突的原因是因为 CreatePipe 的 Windows API 需要一个指向内存区域的指针值，该函数将用作安全属性结构的跳板。简单地传入 SECURITY_ATTRIBUTES 结构将覆盖安全内存(页面尚未分配给您的应用程序)，因此出现 protected 内存错误。

传入一个 IntPtr 来表示这个指针，解决了你的问题。

    [DllImport("kernel32.dll", CharSet = CharSet.Auto, SetLastError = true)]
    public static extern bool CreatePipe(ref IntPtr hReadPipe, ref IntPtr hWritePipe, IntPtr  lpPipeAttributes, int nSize);

    [StructLayout(LayoutKind.Sequential)]
    public struct SECURITY_ATTRIBUTES
    {
        public DWORD nLength;
        public IntPtr lpSecurityDescriptor;
        [MarshalAs(UnmanagedType.Bool)]
        public bool bInheritHandle;
    }

    public Form1()
    {
        InitializeComponent();
    }

    private void btnCreate_Click(object sender, EventArgs e)
    {

        SECURITY_ATTRIBUTES sa = new SECURITY_ATTRIBUTES();
        sa.nLength = (DWORD)System.Runtime.InteropServices.Marshal.SizeOf(sa);
        sa.lpSecurityDescriptor = IntPtr.Zero;
        sa.bInheritHandle = true;

        IntPtr attr = Marshal.AllocHGlobal(Marshal.SizeOf(sa));
        Marshal.StructureToPtr(sa, attr, true);

        IntPtr hWrite = new IntPtr();
        IntPtr hRead = new IntPtr();

        if (CreatePipe(ref hRead, ref hWrite, attr, 4096))
        {
            MessageBox.Show("Pipe created !");
        }
        else
        {
            int error = Marshal.GetLastWin32Error();
            MessageBox.Show("Error : Pipe not created ! LastError= " + error);
        }
    }