Problems creating Blueprint Function Libraries on Windows 10

So previously I was able to create blueprint function libraries just fine. I was using 4.8.3 on Windows 8.1. The same workflow I was using then no longer works ever since I moved to Windows 10.

The process is:

  • Start a new project (either C++ or BP empty project, doesn’t matter which, no starter content just a fresh project, both 4.8.3 and 4.9, makes no difference)
  • Project is generated, C++ projects generate the VS project files here no problem. VS opens.
  • Create a new C++ class, BP Function Library. BP project generates the VS project files here no problem.
  • Compile in both editor and build in VS work at this point without issues.
  • Add the below code to the cpp and h files the function lib generated.
  • Re-build in VS. Link error (as below) This causes the “Compile” button to disappear from the editor until it is restarted.
  • Building again apparently succeeds for some reason.
  • Functions do not show up in the blueprint editor as they did before this started happening.

Link errors: Hastebin: Send and Save Text or Code Snippets for Free | Toptal®

h file:

    UFUNCTION(BlueprintCallable, meta = (DisplayName = "TestFunction"), Category = "ATestCategory")
    static void TestFunction();

cpp file:

void TestFunction() {


This happens regardless of whether I select “public” or “private” or nothing during creation of the class, and regardless of whether I add the “public:” line, or “static” before the function declaration.

I thought it might be due to the fact that I didn’t do a fresh install of 10. So I completely uninstalled UE4 and Visual Studio and all of their dependencies (which took forever filtering through the installed programs list, ■■■■ it all) and rebooted, then reinstalled both from scratch. The latest version of VS2013 Community, Update 5, and reinstalled UE4.

Nothing changed. At this point I’m considering completely reinstalling Windows…

I’ve uploaded a video where the issues take place:

This happening to anyone else?

Does anyone have any idea why the compile button disappears if the linker fails in VS?

Am I doing something wrong with my workflow that was working before?

You’re not defining the function.

In your CPP you have made a global function instead of a member of UTestFunctions.

Change it to

void UTestFunctions::TestFunction()

This is 100% the correct answer and now I feel like an idiot for missing that.

The compile button disappearing is still weird, is that also normal?