RegisterClass for window class returning "file already exists" error

Question

At the moment I am simply trying to create a blank window as part of a DLL that provides behind the scenes communication with our platform. No other part of this DLL will ever display anything.

Currently I instantiate the window class as such:

WNDCLASS wc;

wc.cbClsExtra = 0;
wc.style = 0;
wc.hInstance = hInstance;
wc.lpszClassName = "Preview";

I then register the class:

if((RegisterClass(&wc)) == 0)
{
   DWORD dwErrorNum = GetLastError();
   **some logging function here**
   return;
}

Registering the class results in GetLastError() returning 0x57 which translates to "Cannot create a file when that file already exists" which is horribly cryptic at best as I am not directly writing to any files.

Is there a better way for me to create this simple, blank window, or a better way for me to debug this beyond what I've already done?

Answer 1

Error code 0x57 does not have anything to do with files. It is ERROR_INVALID_PARAMETER.

Looking at your code, you have only filled in four of the ten members of WNDCLASS. Fill in the rest as well, and you should be fine.