Question

I have this C# code to get Processor ID but I’m not able to pass it to C++, I tried a lot but I really can’t, I just started in C++ and I would like to be able to get the CPU ID with C++ like I used to get with C#

This is the code I have in C#:

public static string GetProcessorID()
{
  string sProcessorID = "";
  string sQuery = "SELECT ProcessorId FROM Win32_Processor";
  ManagementObjectSearcher oManagementObjectSearcher = new ManagementObjectSearcher(sQuery);
  ManagementObjectCollection oCollection = oManagementObjectSearcher.Get();
  foreach (ManagementObject oManagementObject in oCollection)
  {
    sProcessorID = (string)oManagementObject["ProcessorId"];
  }

  return (sProcessorID);
}

Answer 1

It’s a little bit longer in C++! This is a full working example, note that if you change the query from

SELECT ProcessorId FROM Win32_Processor

to

SELECT * FROM Win32_Processor

Then you can use the QueryValue function to query any property value.

HRESULT GetCpuId(char* cpuId, int bufferLength)
{
    HRESULT result = InitializeCom();
    if (FAILED(result))
        return result;

    IWbemLocator* pLocator = NULL;
    IWbemServices* pService = NULL;
    result = GetWbemService(&pLocator, &pService);
    if (FAILED(result))
    {
        CoUninitialize();
        return result;
    }

    memset(cpuId, 0, bufferLength);
    result = QueryValue(pService, 
            L"SELECT ProcessorId FROM Win32_Processor", L"ProcessorId",
            cpuId, bufferLength);

    if (FAILED(result))
    {
        pService->Release();
        pLocator->Release();
        CoUninitialize();

        return result;
    }

    pService->Release();
    pLocator->Release();
    CoUninitialize();

    return NOERROR;
}

First you have to do all the initialization stuffs, they’re packed into these two functions:

HRESULT InitializeCom()
{
    HRESULT result = CoInitializeEx(0, COINIT_APARTMENTTHREADED); 
    if (FAILED(result))
        return result;

    result = CoInitializeSecurity(
        NULL,                           // pSecDesc
        -1,                             // cAuthSvc (COM authentication)
        NULL,                           // asAuthSvc
        NULL,                           // pReserved1
        RPC_C_AUTHN_LEVEL_DEFAULT,      // dwAuthnLevel
        RPC_C_IMP_LEVEL_IMPERSONATE,    // dwImpLevel
        NULL,                           // pAuthList
        EOAC_NONE,                      // dwCapabilities
        NULL                            // Reserved
        );

    if (FAILED(result) && result != RPC_E_TOO_LATE)
    {
        CoUninitialize();

        return result;
    }

    return NOERROR;
}

HRESULT GetWbemService(IWbemLocator** pLocator, IWbemServices** pService)
{
    HRESULT result = CoCreateInstance(CLSID_WbemLocator, 0, CLSCTX_INPROC_SERVER, 
        IID_IWbemLocator, reinterpret_cast<LPVOID*>(pLocator));

    if (FAILED(result))
    {
        return result;
    }

    result = (*pLocator)->ConnectServer(
        _bstr_t(L"ROOT\\CIMV2"),    // strNetworkResource
        NULL,                       // strUser  
        NULL,                       // strPassword
        NULL,                       // strLocale
        0,                          // lSecurityFlags
        NULL,                       // strAuthority
        NULL,                       // pCtx
        pService                    // ppNamespace
        );

    if (FAILED(result))
    {
        (*pLocator)->Release();     

        return result;
    }

    result = CoSetProxyBlanket(
        *pService,                      // pProxy
        RPC_C_AUTHN_WINNT,              // dwAuthnSvc
        RPC_C_AUTHZ_NONE,               // dwAuthzSvc
        NULL,                           // pServerPrincName
        RPC_C_AUTHN_LEVEL_CALL,         // dwAuthnLevel
        RPC_C_IMP_LEVEL_IMPERSONATE,    // dwImpLevel
        NULL,                           // pAuthInfo
        EOAC_NONE                       // dwCapabilities
        );

    if (FAILED(result))
    {
        (*pService)->Release();
        (*pLocator)->Release();     

        return result;
    }

    return NOERROR;
}

That done you can run your WQL query then you have to enumerate returned properties to find the one you need (you can make it simpler but in this way you can query multiple values). Note that if you query ALL values from Win32_Processor you’ll get a lot of data. On some systems I saw it takes even 2 seconds to complete the query and to enumerate properties (so filter your query to include only data you need).

HRESULT QueryValue(IWbemServices* pService, const wchar_t* query, const wchar_t* propertyName, char* propertyValue, int maximumPropertyValueLength)
{
    USES_CONVERSION;

    IEnumWbemClassObject* pEnumerator = NULL;
    HRESULT result = pService->ExecQuery(
        bstr_t(L"WQL"),                                         // strQueryLanguage
        bstr_t(query),                                          // strQuery
        WBEM_FLAG_FORWARD_ONLY | WBEM_FLAG_RETURN_IMMEDIATELY,  // lFlags
        NULL,                                                   // pCtx
        &pEnumerator                                            // ppEnum
        );

    if (FAILED(result))
        return result;

    IWbemClassObject *pQueryObject = NULL;
    while (pEnumerator)
    {
        try
        {
            ULONG returnedObjectCount = 0;
            result = pEnumerator->Next(WBEM_INFINITE, 1, &pQueryObject, &returnedObjectCount);

            if (returnedObjectCount == 0)
                break;

            VARIANT objectProperty;
            result = pQueryObject->Get(propertyName, 0, &objectProperty, 0, 0);
            if (FAILED(result))
            {
                if (pEnumerator != NULL)
                    pEnumerator->Release();

                if (pQueryObject != NULL)
                    pQueryObject->Release();

                return result;
            }

            if ((objectProperty.vt & VT_BSTR) == VT_BSTR)
            {
                strcpy_s(propertyValue, maximumPropertyValueLength, OLE2A(objectProperty.bstrVal));
                break;
            }

            VariantClear(&objectProperty);
        }
        catch (...)
        {
            if (pEnumerator != NULL)
                pEnumerator->Release();

            if (pQueryObject != NULL)
                pQueryObject->Release();

            return NOERROR;
        }
    } 

    if (pEnumerator != NULL)
        pEnumerator->Release();

    if (pQueryObject != NULL)
        pQueryObject->Release();

    return NOERROR;
}

NOTE: this code is useful if you need to gather more informations than the simple ID of the CPU. It’s a generic example to get one (or more) properties from a WQL query (as you did in C#). If you do not need to get any other information (and you do not think to use WMI in your C++ programs) then you may use the __cpuid() intrinsic as posted in a comment.

__cpuid()

The ProcessorId property from WMI has following description:

Processor information that describes the processor features. For an
x86 class CPU, the field format depends on the processor support of
the CPUID instruction. If the instruction is supported, the property
contains 2 (two) DWORD formatted values. The first is an offset of
08h-0Bh, which is the EAX value that a CPUID instruction returns with
input EAX set to 1. The second is an offset of 0Ch-0Fh, which is the
EDX value that the instruction returns. Only the first two bytes of
the property are significant and contain the contents of the DX
register at CPU reset—all others are set to 0 (zero), and the contents
are in DWORD format.

A good implementation should check more about strange cases but a naive implementation may be:

std::string GetProcessorId()
{
 int info[4] = { -1 };

 __cpuid(info, 0);
 if (info[0] < 1)
  return ""; // Not supported?!

 // Up to you...you do not need to mask results and you may use
 // features bits "as is".    
 __cpuid(info, 1);
 int family = info[0];
 int features = info[3];

 std::stringstream id;
 id << std::hex << std::setw(4) << std::setfill('0') << family << features;

 return id.str();
}

See also this post for a better C++-ish implementation.