在 IEnumWbemClassObject 处调用 next 会挂起应用程序

Question

我有一个使用 WMI 获取硬盘序列号的简单函数，但以下调用会像进入无限循环一样挂起应用程序：

HRESULT hr = pEnumerator->Next(WBEM_INFINITE, 1, &pclsObj, &uReturn);

完整代码为：

std::string GetHarddiskSerialNumber()
{
        HRESULT hres;

        // No need to initialize COM in openFL, as it seems that its already initialized when starting windows
        // Step 1: --------------------------------------------------
        // Initialize COM. ------------------------------------------

        hres =  CoInitializeEx(0, COINIT_MULTITHREADED); 
        if (FAILED(hres))
        {
            cout << "Failed to initialize COM library. Error code = 0x" 
                << hex << hres << endl;
            return "Failed to initialize COM library. Error code = 0x";                  // Program has failed.
        }

        // Step 2: --------------------------------------------------
        // Set general COM security levels --------------------------
        // Note: If you are using Windows 2000, you need to specify -
        // the default authentication credentials for a user by using
        // a SOLE_AUTHENTICATION_LIST structure in the pAuthList ----
        // parameter of CoInitializeSecurity ------------------------
        hres =  CoInitializeSecurity(
            NULL, 
            -1,                          // COM authentication
            NULL,                        // Authentication services
            NULL,                        // Reserved
            RPC_C_AUTHN_LEVEL_DEFAULT,   // Default authentication 
            RPC_C_IMP_LEVEL_IMPERSONATE, // Default Impersonation  
            NULL,                        // Authentication info
            EOAC_NONE,                   // Additional capabilities 
            NULL                         // Reserved
            );


        if (FAILED(hres))
        {
            cout << "Failed to initialize security. Error code = 0x" 
                << hex << hres << endl;
            CoUninitialize();
            return "Failed to initialize security. Error code = 0x";                    // Program has failed.
        }

        // Step 3: ---------------------------------------------------
        // Obtain the initial locator to WMI -------------------------


        IWbemLocator *pLoc = NULL;

        hres = CoCreateInstance(
            CLSID_WbemLocator,             
            0, 
            CLSCTX_INPROC_SERVER, 
            IID_IWbemLocator, (LPVOID *) &pLoc);

        if (FAILED(hres))
        {
            cout << "Failed to create IWbemLocator object."
                << " Err code = 0x"
                << hex << hres << endl;
            CoUninitialize();
            return "1";                 // Program has failed.
        }

        // Step 4: -----------------------------------------------------
        // Connect to WMI through the IWbemLocator::ConnectServer method

        IWbemServices *pSvc = NULL;

        // Connect to the root\cimv2 namespace with
        // the current user and obtain pointer pSvc
        // to make IWbemServices calls.
        hres = pLoc->ConnectServer(
             _bstr_t(L"ROOT\\CIMV2"), // Object path of WMI namespace
             NULL,                    // User name. NULL = current user
             NULL,                    // User password. NULL = current
             0,                       // Locale. NULL indicates current
             NULL,                    // Security flags.
             0,                       // Authority (for example, Kerberos)
             0,                       // Context object 
             &pSvc                    // pointer to IWbemServices proxy
             );

        if (FAILED(hres))
        {
            cout << "Could not connect. Error code = 0x" 
                 << hex << hres << endl;
            pLoc->Release();     
            CoUninitialize();
            return "1";                // Program has failed.
        }

        //cout << "Connected to ROOT\\CIMV2 WMI namespace" << endl;


        // Step 5: --------------------------------------------------
        // Set security levels on the proxy -------------------------

        hres = CoSetProxyBlanket(
           pSvc,                        // Indicates the proxy to set
           RPC_C_AUTHN_WINNT,           // RPC_C_AUTHN_xxx
           RPC_C_AUTHZ_NONE,            // RPC_C_AUTHZ_xxx
           NULL,                        // Server principal name 
           RPC_C_AUTHN_LEVEL_CALL,      // RPC_C_AUTHN_LEVEL_xxx 
           RPC_C_IMP_LEVEL_IMPERSONATE, // RPC_C_IMP_LEVEL_xxx
           NULL,                        // client identity
           EOAC_NONE                    // proxy capabilities 
        );

        if (FAILED(hres))
        {
            cout << "Could not set proxy blanket. Error code = 0x" 
                << hex << hres << endl;
            pSvc->Release();
            pLoc->Release();     
            CoUninitialize();
            return "1";               // Program has failed.
        }

        // Step 6: --------------------------------------------------
        // Use the IWbemServices pointer to make requests of WMI ----

        // For example, get the name of the operating system
        IEnumWbemClassObject* pEnumerator = NULL;
        hres = pSvc->ExecQuery(
            bstr_t("WQL"), 
            bstr_t("SELECT * FROM Win32_OperatingSystem"),
            WBEM_FLAG_FORWARD_ONLY | WBEM_FLAG_RETURN_IMMEDIATELY, 
            NULL,
            &pEnumerator);

        if (FAILED(hres))
        {
            cout << "Query for operating system name failed."
                << " Error code = 0x" 
                << hex << hres << endl;
            pSvc->Release();
            pLoc->Release();
            CoUninitialize();
            return "1";               // Program has failed.
        }

        // Step 7: -------------------------------------------------
        // Get the data from the query in step 6 -------------------

        IWbemClassObject *pclsObj;
        ULONG uReturn = 0;
        std::string result= "";
        while (pEnumerator)
        {
            // this call will hang the app:
            HRESULT hr = pEnumerator->Next(WBEM_INFINITE, 1, &pclsObj, &uReturn);


            if(0 == uReturn)
            {
                break;
            }

            VARIANT vtProp;

            // Get the value of the Name property
            hr = pclsObj->Get(L"SerialNumber", 0, &vtProp, 0, 0);
            wstring ws(vtProp.bstrVal, SysStringLen(vtProp.bstrVal));
            result = string(ws.begin(), ws.end());
            VariantClear(&vtProp);

            hr = pclsObj->Get(L"Manufacturer", 0, &vtProp, 0, 0);
            wstring ws2(vtProp.bstrVal, SysStringLen(vtProp.bstrVal));
            result+=",";
            result+= string(ws2.begin(), ws2.end());
            VariantClear(&vtProp);





            pclsObj->Release();
        }

        // Cleanup
        // ========

        pSvc->Release();
        pLoc->Release();
        pEnumerator->Release();
        //pclsObj->Release();
        CoUninitialize();
        return result;

    }
}// name space

有什么想法吗？

Answer 1

我不太确定，但您可以使用 0 timeout 进行绑定：

HRESULT hr = pEnumerator->Next(WBEM_NO_WAIT, 1, &pclsObj, &uReturn);

来自MSDN：

指定调用的最长时间（以毫秒为单位） 返回之前的块。如果您使用常量 WBEM_INFINITE (0xFFFFFFFF)，调用阻塞直到对象可用。如果你使用 值为 0 (WBEM_NO_WAIT)，调用立即返回，无论是否有 对象是否可用。