CreateFile()返回INVALID_HANDLE_VALUE但GetLastError()返回ERROR_SUCCESS

Question

CreateFile()返回INVALID_HANDLE_VALUE但GetLastError()返回ERROR_SUCCESS

winapiserial-portcreatefileiocpgetlasterror

8

我正在使用CreateFile()打开一个串口。我有一个测试用例（过于复杂，无法重新分发），该测试用例始终导致CreateFile()返回INVALID_HANDLE_VALUE和GetLastError()返回ERROR_SUCCESS。看起来，只有当一个线程在另一个端口关闭它的同时打开端口时，才会出现此错误。打开端口的线程遇到了这个问题。

我不知道这是否有区别，但稍后在代码中，我使用CreateIoCompletionPort将端口与CompletionPort相关联。

以下是我的代码：

HANDLE port = CreateFile(L"\\\\.\\COM1",
                         GENERIC_READ | GENERIC_WRITE,
                         0,                    // must be opened with exclusive-access
                         0,                    // default security attributes
                         OPEN_EXISTING,        // must use OPEN_EXISTING
                         FILE_FLAG_OVERLAPPED, // overlapped I/O
                         0);                   // hTemplate must be NULL for comm devices
if (port == INVALID_HANDLE_VALUE)
{
    DWORD errorCode = GetLastError();
    cerr << L"CreateFile() failed with error: " << errorCode << endl;
}

我相信这种情况不应该发生。我做错了什么？如何让API返回正确的结果？

更多细节: 这段代码来自我开发的串口库: JPeripheral 下面是实际的（未经过处理的）源代码：

JLong SerialChannel::nativeOpen(String name)
{
    cerr << "nativeOpen(" << name << ")" << endl;
    wstring nameWstring = name;
    HANDLE port = CreateFile((L"\\\\.\\" + nameWstring).c_str(),
        GENERIC_READ | GENERIC_WRITE,
        0,                                          // must be opened with exclusive-access
        0,                                          // default security attributes
        OPEN_EXISTING,                  // must use OPEN_EXISTING
        FILE_FLAG_OVERLAPPED,       // overlapped I/O
        0);                                         // hTemplate must be NULL for comm devices
    cerr << "nativeOpen.afterCreateFile(" << name << ")" << endl;
    cerr << "port: " << port << ", errorCode: " << GetLastError() << endl;
    if (port == INVALID_HANDLE_VALUE)
    {
        DWORD errorCode = GetLastError();

        switch (errorCode)
        {
            case ERROR_FILE_NOT_FOUND:
                throw PeripheralNotFoundException(jace::java_new<PeripheralNotFoundException>(name, Throwable()));
            case ERROR_ACCESS_DENIED:
            case ERROR_SHARING_VIOLATION:
                throw PeripheralInUseException(jace::java_new<PeripheralInUseException>(name, Throwable()));
            default:
            {
                throw IOException(jace::java_new<IOException>(L"CreateFile() failed with error: " +
                    getErrorMessage(GetLastError())));
            }
        }
    }

    // Associate the file handle with the existing completion port
    HANDLE completionPort = CreateIoCompletionPort(port, ::jperipheral::worker->completionPort, Task::COMPLETION, 0);
    if (completionPort==0)
    {
        throw AssertionError(jace::java_new<AssertionError>(L"CreateIoCompletionPort() failed with error: " +
            getErrorMessage(GetLastError())));
    }
    cerr << "nativeOpen.afterCompletionPort(" << name << ")" << endl;

    // Bind the native serial port to Java serial port
    SerialPortContext* result = new SerialPortContext(port);
    cerr << "nativeOpen.afterContext(" << name << ")" << endl;
    return reinterpret_cast<intptr_t>(result);
}

这是我得到的实际输出结果：

nativeOpen(COM1)
nativeOpen.afterCreateFile(COM1)
port: 00000374, errorCode: 0
nativeOpen.afterCompletionPort(COM1)
nativeOpen.afterContext(COM1)
[...]
nativeOpen(COM1)
nativeOpen.afterCreateFile(COM1)
port: FFFFFFFF, errorCode: 0
java.io.IOException: CreateFile() failed with error: The operation completed successfully.

- Gili

你要访问的硬件是什么？ - Gabe

@Gabe：我正在访问我们内部开发的一个嵌入式设备。它有一个标准的DB9串口连接，我已将其连接到我的电脑上（这里没有USB-RS232适配器）。 - Gili

@David：我已经发布了完整的源代码供您审查。 - Gili

5

在CreateFile失败后，必须立即调用GetLastError，中间不要加入<<。 - Roman R.

@Gili：是的，你的简化隐藏了问题。你在调用“<<”之后调用了“GetLastError”。你需要在调用“CreateFile”之后调用“GetLastError”。 - David Schwartz

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1个回答

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- Hans Passant · Accepted Answer

 HANDLE port = CreateFile(...);
 cerr << "nativeOpen.afterCreateFile(" << name << ")" << endl;
 cerr << "port: " << port << ", errorCode: " << GetLastError() << endl;
 if (port == INVALID_HANDLE_VALUE)
 {
    DWORD errorCode = GetLastError();

输出到cerr会在底层调用winapi函数，这会重置由GetLastError()返回的线程错误值。修复方法：

 HANDLE port = CreateFile(...);
 int err = GetLastError();
 // etc, use err instead...