用Visual c++查询操作系统信息

Question

下面的代码是msdn（链接）中关于如何使用WMI查询操作信息的示例代码。当在visual c++2010中运行此代码时，我得到以下错误：

"ProjectTest.exe中0x5a2c47af（msvcr100d.dll）处出现未处理的异常：0xC0000005:读取位置0xccccffff时发生访问冲突。"

有人能帮我解决这个问题吗？

#include "stdafx.h"
#include <iostream>
using namespace std;
#include <comdef.h>
#include <Wbemidl.h>
# pragma comment(lib, "wbemuuid.lib")
int main()
{
    HRESULT hres;
    // 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 1;                  // 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 1;                    // 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 rootcimv2 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 = NULL;
    ULONG uReturn = 0;
    while (pEnumerator)
    {
        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"PAEEnabled", 0, &vtProp, 0, 0);
        wcout << " Is PAE enabled? : " << vtProp.bstrVal << endl;
        VariantClear(&vtProp);
        pclsObj->Release();
    }
    // Cleanup
    // ========
    pSvc->Release();
    pLoc->Release();
    pEnumerator->Release();
    CoUninitialize();
    system("PAUSE");
    return 0;   // Program successfully completed.
}

Answer 1

实际上，它确实返回了完全有效的数据。只是它只为您的调用返回一个布尔值，而不返回bstrVal。

根据vt_BOOLEAN检查vtProp.vt属性。在VARIANT中，您必须始终检查VARIANT所包含的数据类型的vt属性。

---

原始答案：

即使pclsObj->Get（）调用的HRESULT为S_OK，您的vtProp也是一个nullptr。很可能它没有找到PAEEnabled属性。

当您使用MSDN示例中的原始代码时，它使用"Name"而不是"PAEEnabled"，效果很好。