Unable to Build - Multiple "UnknownFunction" Errors

I have been unable to build my project. I can’t seem to find any answers, and the output log doesn’t seem to give me any help with tracking down the problem.

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The project was originally in 4.17. About a week ago I updated the project to 4.19 and added a few widgets and other functionality. The game runs in the PIE editor, but nothing I have done seems to change any of the errors. I have migrated the project to blank projects and still got the same errors. I even deleted the new widgets I created and still no change.

I packaged the game before, when it was 4.17. Attached is the log file.

I appreciate any help. Thanks.

Did you back up your 4.17 version? If so try updating that backup ensuring that the project has the same name (after making another backup of course). If that fails to build properly then we can be certain it’s a migration issue.

If you’re using a C++ project these two migration guides might clue you in to what needs to be changed to get your project to build.



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I found the answer!

This thread pointed me in the right direction:

The error was related to my usage of the Select node. I had multiple instances of arrays of structures plugged into the inputs of a select node. After deleting these select nodes, the packaging was successful.
It appears that this error can also be caused by the output of a select node being plugged into a intIncrease or intDecrease node.

Now I get to redo all of these select nodes as more cumbersome Switch nodes attached to a series of Set Array nodes…

The odd thing about this error (or errors) is that it only arises from packaging or cooking (in my experience); it does not occur when running playing the game in the Unreal Editor. Also, the errors that appear in the output log don’t really give a lot of information (if any) to where to find and fix the error.

I think this should be some kind of error-fix request or feature request:
to either

  1. allow arrays to properly be inputted into select nodes and allow the outputs of select nodes be plugged into ++ and – nodes


  1. disallow the select node from accepting(struct) arrays and disallow the output of the select node to plug into ++ and – nodes.

Thank you for your help!