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Hot reload crashes editor when UPROPERTY value is changed

Most of the objects in my scene are blueprints based on a custom AActor subclass with the following structure:

     |- UStaticMeshComponent (root)
         |- UMyCustomSceneComponent

I can add whatever code I like in the constructor of my custom USceneComponent (declare variables, print messages, and so on), and hot-reload works fine. As soon as I touch any of the UPROPERTY values in the constructor, however, hot-reload crashes with the following stacktrace:


If I compile with the editor closed, I have no issues or crashes at all and everything works as expected. It just seems that there's a problem to do with refreshing the blueprints and/or the actors using them.

Product Version: Not Selected
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asked Apr 28 '15 at 05:04 AM in C++ Programming

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Hello, rohoon

Sorry to hear about the crash, but please note that Hot Reload should only be used for minor code changes, that don't affect UPROPERTIES (UFUNCTIONS).

Thus, when you add/remove a function and change some Blueprint-exposed behavior, closing the editor and recompiling would be the correct solution.

Hope this helped! Good luck!

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answered May 08 '15 at 12:40 PM

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Andrii Melnyk
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avatar image rohoon May 10 '15 at 10:02 PM

Hi Andrew,

I should have phrased my question better. What I mean is this: If I have the class hierarchy I described before, then add the following line to the constructor the of the nested USceneComponent:

 MySimpleIntProperty = 5;

From that point on, hot-reload will ALWAYS crash the editor. As long as that line of code exists in my project, hot-reload will never work again, even if the next change I make is to simply add whitespace or a comment somewhere..

On a side note, I would have thought that changing the default value of existing UPROPERTYs would have been a perfect use case for hot-reloading (and it certainly works in all other scenarios I've tested). In any case, surely there's a better way for the editor to handle this than crashing with an Access Violation error.

avatar image rohoon May 13 '15 at 11:38 PM


I created a test project to demonstrate another bug, but it also demonstrates this hot-reload crash. Try making a whitespace-only change to the code and then recompile with the editor open.

bugtest.zip (444.5 kB)
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