删除 ptr 将解决写入 0 的访问冲突异常

Question

我得到以下代码，其中最后一条语句我尝试删除指向动态创建的内存的指针。

但是，一旦我到达指令，就会引发访问冲突异常，并显示：

0x0094c91f 处未处理的异常 Server.exe：0xC0000005：访问 违规读取位置 0x00000000。

但是当我使用调试器单步执行它时，它包含一个有效地址，其中包含有效数据...我没有意识到我在这里做的致命错误...

有什么建议吗？

void CServer::HandleAcceptRequest(ACCEPT_REQUEST* pRequest)
{
    //Add the new connection socket to the connection handler
    m_pConnectionHandler->AddConnection(pRequest->m_NewConnection);
    //Associate the new connections´ socket handle with the IOCP
    if(!m_pCompletionPort->AssociateHandle((HANDLE)pRequest->m_NewConnection, 0))
    {
        MessageBox(NULL, "Could not associate a socket handle with the completion port", "", MB_ICONERROR | MB_OK);
        DebugBreak();
    }


    //Create a new COMM_REQUEST and initialize a Recv-Request
    COMM_REQUEST* pCommRequest = new COMM_REQUEST;
    memset(pCommRequest, 0, sizeof(COMM_REQUEST));
    pCommRequest->Socket = pRequest->m_NewConnection;
    pCommRequest->m_RequestType = BASIC_REQUEST::RECV;

    WSABUF* buf = new WSABUF;
    buf->buf = pCommRequest->cBuf;
    buf->len = Inc::COMMUNICATION_BUFFER_SIZE;
    DWORD dwFlags = 0;
    if(WSARecv(pCommRequest->Socket, buf, 1, NULL, &dwFlags, pCommRequest, NULL))
    {
        DWORD dwRet = WSAGetLastError();
        if(dwRet != WSA_IO_PENDING)
        {
            MessageBox(NULL, "WSARecv() failed", "", MB_ICONERROR | MB_OK);
            DebugBreak();
        }
    };

    //Delete the old ACCEPT_REQUEST structure
    delete pRequest;
}

编辑：我确实在主线程中的另一个函数中分配了内存

bool CConnectionHandler::AcceptNewConnection(SOCKET ListenSocket, unsigned nCount)
{
    DWORD dwBytesReceived = 0;
    ACCEPT_REQUEST* pOverlapped = nullptr;

    for(unsigned n = 0; n < nCount; n++)
    {
        dwBytesReceived = 0;
        pOverlapped = new ACCEPT_REQUEST;
        memset(pOverlapped, 0, sizeof(ACCEPT_REQUEST));
        pOverlapped->m_RequestType = ACCEPT_REQUEST::ACCEPT;

        //add the ListenSocket to the request
        pOverlapped->m_ListenSocket = ListenSocket;
        //invalidate the new connection socket
        pOverlapped->m_NewConnection = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
        if(pOverlapped->m_NewConnection == INVALID_SOCKET)
        {
            delete pOverlapped;
            return false;
        }

        // call 'AcceptEx'
        if(m_lpfnAcceptEx(pOverlapped->m_ListenSocket, pOverlapped->m_NewConnection, pOverlapped->cOutputBuffer, 0, sizeof(sockaddr_in) + 16, sizeof(sockaddr_in) + 16, &dwBytesReceived, pOverlapped) == FALSE)
        {
            DWORD dwRet = WSAGetLastError();
            if(dwRet == ERROR_IO_PENDING)
                continue;
            else
                return false;
        }
    }

    return true;
};

编辑2：与向函数提供参数有关的线程代码...

unsigned int WINAPI ServerThreadFunc(void* pvArgs)
{
    CServer* pServer = (CServer*)pvArgs;        // pointer to the server object
    DWORD dwBytes = 0;
    ULONG_PTR ulKey;
    OVERLAPPED* pOverlapped = nullptr;
    bool bLooping = true;

    while(bLooping)
    {
        //TODO: Add code (ServerThreadFunc)
        if(!pServer->m_pCompletionPort->GetCompletionStatus(&dwBytes, &ulKey, &pOverlapped, INFINITE))
        {
            //TODO: Set some error variable or flag an error event to notify the main thread
            DebugBreak();
        }

        //check type of request
        switch(((BASIC_REQUEST*)pOverlapped)->m_RequestType)
        {
        case BASIC_REQUEST::ACCEPT:
            {
                // TODO: Handle AcceptEx-request
                pServer->HandleAcceptRequest(static_cast<ACCEPT_REQUEST*>(pOverlapped));

Answer 1

抱歉，无法从您提供的零碎内容中真正弄清楚任何内容。

但是，在第三段代码中，您有此调用。

pServer->HandleAcceptRequest(static_cast<ACCEPT_REQUEST*>(pOverlapped));

此调用将通过调用 delete 来销毁 *pOverlapped 对象。 （请记住，在 HandleAcceptRequest 的最后，您要删除 pRequest，其中 pRequest 是 HandleAcceptRequest 的参数） 。

这将使 pOverlapped 成为指向死内存的悬空指针。我在代码中没有看到任何地方可以重新初始化悬空指针或将其设置为空。

如果您不重新初始化它，则循环中对 *pOverlapped 的下一次访问将访问死内存（这可能看起来“有效”），并且下一次尝试删除< /code> 它很可能再次崩溃。如果下一次删除尝试再次发生在HandleAcceptRequest末尾，那么行为可能与您最初描述的完全一样。

Answer 2

OVERLAPPED* pOverlapped = nullptr;
..
pServer->m_pCompletionPort->GetCompletionStatus(&dwBytes, &ulKey, &pOverlapped, INFINITE);

好的。看来您删除了错误的指针。您在 HandleAcceptRequest() 中删除的不再是指向 OVERLAPPED 的指针，因为该指针已从 OVERLAPPED* 转换为 ACCEPT_REQUEST*。

GetCompletionStatus() 是你自己的吗？