微软MSDN：“Example: Creating a WMI Application”例子代码中的错误

#define _WIN32_DCOM
#include <iostream>
using namespace std;
#include <comdef.h>
#include <Wbemidl.h>

# pragma comment(lib, "wbemuuid.lib")

int main(int argc, char **argv)
{
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 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 (e.g. 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;

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"Name", 0, &vtProp, 0, 0);
wcout << " OS Name : " << vtProp.bstrVal << endl;
VariantClear(&vtProp);

pclsObj->Release();
}

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

pSvc->Release();
pLoc->Release();
pEnumerator->Release();
pclsObj->Release();
CoUninitialize();

return 0;   // Program successfully completed.

}

#define _WIN32_DCOM
#include <iostream>
using namespace std;
#include <comdef.h>
#include <Wbemidl.h>

# pragma comment(lib, "wbemuuid.lib")

int main(int argc, char **argv)
{
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 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 (e.g. 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;	// 秦建辉：移动到while循环内
//    ULONG uReturn = 0;			// 秦建辉：移动到while循环内

while (pEnumerator)
{
IWbemClassObject *pclsObj = NULL;	// 秦建辉：最好初始化
ULONG uReturn = 0;

HRESULT hr = pEnumerator->Next(WBEM_INFINITE, 1,
&pclsObj, &uReturn);	// 秦建辉：如果失败，pclsObj其值将不变

if(0 == uReturn)
{	// 秦建辉：如果pclsObj没有预先初始化，此时其值可能是一个错误的指针
break;
}

VARIANT vtProp;

VariantInit( &vtProp );	// 秦建辉：稳妥起见最好做下初始化
// Get the value of the Name property
hr = pclsObj->Get(L"Name", 0, &vtProp, 0, 0);
wcout << " OS Name : " << vtProp.bstrVal << endl;
VariantClear(&vtProp);

pclsObj->Release();
}

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

pSvc->Release();
pLoc->Release();
pEnumerator->Release();
//  pclsObj->Release();		// 秦建辉：pclsObj可能已经指向一个错误指针
CoUninitialize();

return 0;   // Program successfully completed.

}