Windows SDK: How to get the reason for a failure of a SDK function?

[ovidiucucu]

Q: How to get the reason for a failure of a SDK function?

A: First of all, take a look in MSDN and read the documentation of the function. See the meaning of the returned value.

Most Windows SDK functions return a value showing if the function succeeded or failed (in our example 0 if failed and nonzero if succeeded).

Usually, next is written in MSDN: To get extended error information, call 'GetLastError()'.

BOOL bRet = CreateDirectory(_T("X:\\MyApp\\Bin\\Shared"), NULL);
if(!bRet)
{
  DWORD dwError = GetLastError();
  // put a breakpoint here and type the value of dwError in Error Lookup tool
}

Also, we can get the error text using 'FormatMessage()':

void ReportLastError()
{
  LPCTSTR pszCaption = _T("Windows SDK Error Report");
  DWORD dwError      = GetLastError();

  if(NOERROR == dwError)
  {
    MessageBox(NULL, _T("No error"), pszCaption, MB_OK);
  }
  else
  {
    const DWORD dwFormatControl = FORMAT_MESSAGE_ALLOCATE_BUFFER |
                                  FORMAT_MESSAGE_IGNORE_INSERTS |
                                  FORMAT_MESSAGE_FROM_SYSTEM;

    LPVOID pTextBuffer = NULL;
    DWORD dwCount = FormatMessage(dwFormatControl, 
                                  NULL, 
                                  dwError, 
                                  0, 
                                  (LPTSTR) &pTextBuffer, 
                                  0, 
                                  NULL);
    if(0 != dwCount)
    {
      MessageBox(NULL, (LPCSTR)pTextBuffer, pszCaption, MB_OK|MB_ICONERROR);
      LocalFree(pTextBuffer);
    }
    else
    {
      MessageBox(NULL, _T("Unknown error"), pszCaption, MB_OK|MB_ICONERROR);
    }
  }
}

The following example shows how to use it:

BOOL bRet = CreateDirectory(_T("X:\\MyApp\\Bin\\Shared"), NULL);
if(!bRet)
{
  ReportLastError();
}