How should I use FormatMessage() properly in C++?

Question

Without:

• MFC
• ATL

How can I use FormatMessage() to get the error text for a HRESULT?

 HRES         


        

Answer 1

Keep in mind that you cannot do the following:

{
   LPCTSTR errorText = _com_error(hresult).ErrorMessage();

   // do something with the error...

   //automatic cleanup when error goes out of scope
}

As the class is created and destroyed on the stack leaving errorText to point to an invalid location. In most cases this location will still contain the error string, but that likelihood falls away fast when writing threaded applications.

So always do it as follows as answered by Shog9 above:

{
   _com_error error(hresult);
   LPCTSTR errorText = error.ErrorMessage();

   // do something with the error...

   //automatic cleanup when error goes out of scope
}