RegQueryInfoKey not giving registry key name text

Question

Using the RegQueryInfoKey as in the example available on http://msdn.microsoft.com/en-us/library/windows/desktop/ms724256(v=vs.85).aspx, doesn't give me the registry folder name in the output parameter achClass. I always receive an empty string. My question is: Do I have to call any other function after to get the text of the key name? Or can I use this, but I am missing something?

Side note: machine is Windows 7, 64 bit.

Thanks in advance

UPDATE: code

//Calling site:

HKEY hKey;
LSTATUS status= RegOpenKeyEx(HKEY_CURRENT_USER, InstanceFullName, 0, KEY_ALL_ACCESS, &hKey);
if ( status != ERROR_SUCCESS)
{
    LPVOID lpMsgBuf;
    FormatMessage( 
        FORMAT_MESSAGE_ALLOCATE_BUFFER | 
        FORMAT_MESSAGE_FROM_SYSTEM | 
        FORMAT_MESSAGE_IGNORE_INSERTS,
        NULL,
        status,
        MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT), // Default language
        (LPTSTR) &lpMsgBuf,
        0,
        NULL 
    );

    this->MessageBox( (LPCTSTR)lpMsgBuf, GetProgramTitle(), MB_OK | MB_ICONERROR );
    LocalFree( lpMsgBuf );
    return;     
}

status= MyRegSaveKey(hKey, sTempRegFilePath, NULL);

//Called function

LSTATUS MyRegSaveKey(_In_ HKEY hKey, _In_ LPCTSTR lpFile, _In_opt_ LPSECURITY_ATTRIBUTES lpSecurityAttributes)
{
CXmlWriter xmlWriter;
if(!xmlWriter.Begin(lpFile))
    return ERROR_CANNOT_MAKE;

LSTATUS retCode= _MyRegSaveKey(hKey, lpFile, lpSecurityAttributes, xmlWriter);

xmlWriter.Finish();

return retCode;
}

//Inner called function

LSTATUS _MyRegSaveKey(_In_ HKEY hKey, _In_ LPCTSTR lpFile, _In_opt_ LPSECURITY_ATTRIBUTES lpSecurityAttributes, CXmlWriter& writer)
{
//http://msdn.microsoft.com/en-us/library/windows/desktop/ms724256(v=vs.85).aspx
TCHAR    achKey[MAX_KEY_LENGTH];   // buffer for subkey name
DWORD    cbName;                   // size of name string 
TCHAR    achClass[MAX_PATH] = TEXT("");  // buffer for class name 
achClass[0] = '\0'; 
DWORD    cchClassName = MAX_PATH;  // size of class string 
DWORD    cSubKeys=0;               // number of subkeys 
DWORD    cbMaxSubKey;              // longest subkey size 
DWORD    cchMaxClass;              // longest class string 
DWORD    cValues;              // number of values for key 
DWORD    cchMaxValue;          // longest value name 
DWORD    cbMaxValueData;       // longest value data 
DWORD    cbSecurityDescriptor; // size of security descriptor 
FILETIME ftLastWriteTime;      // last write time 

DWORD i, retCode; 

TCHAR  achValue[MAX_VALUE_NAME]; 
DWORD cchValue = MAX_VALUE_NAME;
DWORD type;
BYTE* pData= NULL;
DWORD size;

// Get the class name and the value count. 
retCode = RegQueryInfoKey(
    hKey,                    // key handle 
    achClass,                // buffer for class name 
    &cchClassName,           // size of class string 
    NULL,                    // reserved 
    &cSubKeys,               // number of subkeys 
    &cbMaxSubKey,            // longest subkey size 
    &cchMaxClass,            // longest class string 
    &cValues,                // number of values for this key 
    &cchMaxValue,            // longest value name 
    &cbMaxValueData,         // longest value data 
    &cbSecurityDescriptor,   // security descriptor 
    &ftLastWriteTime       // last write time 
);

if(retCode != ERROR_SUCCESS)
    return retCode;

//... the rest does not make any difference

return ERROR_SUCCESS;
}

Answer 1

Now that I can see the code, it looks like you expect to get the name of the opened key.

You cannot use the lpClass parameter of RegQueryInfoKey() for this -- see this SO answer; it looks like the example you mentioned uses only the cSubKeys and cValues from the RegQueryInfoKey() call.

From this SO answer [even though the question was for Perl], it doesn't look like the Win32 Registry API has a function will let you take the handle and return the key name.

From the same article, the only two practical solutions are

• Maintain a list of returned objects from Open and the path to them yourself

• extend the Win32::Registry API to call the NtQueryKey exported function in ntdll.dll and do what's shown in this stackoverflow answer