匿名管道：当子进程被杀死时，父进程中的 ReadFile 继续等待

Posted 2023-02-16

【中文标题】匿名管道：当子进程被杀死时，父进程中的 ReadFile 继续等待

【英文标题】：Anonymous pipes: ReadFile in parent process keeps on waiting when the child process is killed

【发布时间】：2016-12-27 16:08:18

【问题描述】：

我有一个程序，其中父进程派生出一个子进程，然后与之通信。

父进程是 VB 应用程序，子进程是 C# 控制台应用程序。

父进程（暂时删除错误处理）：

Private Function InitialieExtConversionProcess() As Boolean

Dim lResult As Long
Dim SA As SECURITY_ATTRIBUTES
Dim sInfo As STARTUPINFO
Dim sCommandLine As String

SA.bInheritHandle = True

'Create the pipe that Hyperspace will write to
lResult = CreatePipe(m_pipeOut.hReadPipe, m_pipeOut.hWritePipe, SA, 0)

'Ensure that the read handle is not inherited
lResult = SetHandleInformation(m_pipeOut.hReadPipe, HANDLE_FLAG_INHERIT, 0)


'Create the pipe that Hyperspace will read from
lResult = CreatePipe(m_pipeIn.hReadPipe, m_pipeIn.hWritePipe, SA, 0)

'Ensure that the write handle is not inherited
lResult = SetHandleInformation(m_pipeIn.hWritePipe, HANDLE_FLAG_INHERIT, 0)

'Create the external process
sCommandLine = "some_path\ExtProcess.exe"
sInfo.hStdInput = m_pipeIn.hReadPipe
sInfo.hStdError = m_pipeOut.hWritePipe
sInfo.hStdOutput = m_pipeOut.hWritePipe
sInfo.dwFlags = STARTF_USESTDHANDLES
lResult = CreateProcess(0, sCommandLine, 0, 0, 1, CREATE_NO_WINDOW, 0, 0,   sInfo, m_pInfo)

InitialieExtConversionProcess = True

End Function

然后我使用 WriteFile 和 ReadFile 对子进程进行写入和读取

lResult = WriteFile(m_pipeIn.hWritePipe, sOutput, Len(sOutput), 0, 0)
...
lResult = ReadFile(m_pipeOut.hReadPipe, sInput, Len(sInput), 0, ByVal 0)

子进程（C# 控制台应用程序）：

IntPtr hOutput = GetStdHandle(STD_OUTPUT_HANDLE);
IntPtr hInput = GetStdHandle(STD_INPUT_HANDLE);              
AnonymousPipeClientStream pipeClientRead = new     AnonymousPipeClientStream(PipeDirection.In, hInput.ToString());
AnonymousPipeClientStream pipeClientWrite = new AnonymousPipeClientStream(PipeDirection.Out, hOutput.ToString());

arr = new byte[300];
pipeClientRead.Read(arr, 0, 300);
...
arr = Encoding.ASCII.GetBytes(strResult);
pipeClientWrite.Write(arr, 0, arr.Length);
pipeClientWrite.Flush();

通信在这里按预期工作。我能够成功地读写。

当父进程关闭时，子进程中的Read操作返回false。但是当子进程杀死自己时（如下所示），父进程继续等待 ReadFile。为什么会这样？

arr = new byte[300];
pipeClientRead.Read(arr, 0, 300);
--->Environment.exit(1);<----
arr = Encoding.ASCII.GetBytes(strResult);
pipeClientWrite.Write(arr, 0, arr.Length);
pipeClientWrite.Flush();

我密切关注这个 msdn 示例： https://msdn.microsoft.com/en-us/library/windows/desktop/ms682499(v=vs.85).aspx

【参考方案1】：

我找到了错误的地方。

创建后需要关闭子进程的句柄。

lResult = CreateProcess(0, sCommandLine, 0, 0, 1, CREATE_NO_WINDOW, 0, 0,   sInfo, m_pInfo)
CloseHnadle(m_pipeIn.hReadPipe)
CloseHandle(m_pipeOut.hWritePipe)