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4.5.1 hot reload causes UE Editor to hang / freeze

Hot reloading either through the 'Compile' button inside the UE Editor or 'Build' in Visual Studio causes the editor to hang. I am able to reproduce this consistently while making changes to any header file, eg: addition of a new UProperty or changing the visibility property of an existing UProperty.

The only way to recover is to kill the UE4Editor process. I've tried this in the following combinations: a)Launch editor from Visual Studio in "Development Editor" mode b)Launch editor from Visual Studio in "Debug" mode c)Launch editor directly from the uproject file.

In all three cases hot reloading either through Editor or Visual Studio caused the editor to hang.

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asked Nov 13 '14 at 06:31 PM in Bug Reports

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avatar image Tim C ♦♦ STAFF Nov 15 '14 at 12:11 AM


I have not been able to reproduce this issue. Would you be able to provide some more information?

  • Are you using the binary version installed by the Launcher, or did you build the Engine from source code?

  • Does this only happen in your own project, or do you see this in a new project as well? If so, can you tell me exactly what steps you are following from creating the project to when the Editor freezes?

  • Would you be able to provide your dxdiag information?

avatar image VSZ Nov 15 '14 at 02:14 PM

Tim you're right, I'm not able to reproduce this in a new project at all. I tried various combinations of adding new UPROPERTY/UFUNCTION(s) and hot-reload worked both when I hit F7 in Visual Studio and when I hit 'Recompile' in the Editor (BTW what's the difference between these two methods? I wasn't able to find documentation on when we should be using which approach to hot reload)

To your other questions:

  1. I've been using the binary version installed by the launcher

  2. Should I attach my dxdiag using the attachment tools of the Answers hub or is there a way to send it directly to you?

It seems like there's something in my project that is causing the Editor to crash on hot reload. I don't recollect seeing anything useful in the logs but I'll check the logs one more time today.

avatar image Tim C ♦♦ STAFF Nov 17 '14 at 11:44 PM

You can attach the dxdiag information as a text file on AnswerHub. The information it contains generally is not sensitive, but if you would prefer that it not be publicly available you can instead send it to me via a private message on the forums (my username there is the same as it is here).

The terms "Hot Recompile" and "Hot Reload" are typically used interchangeably, and essentially perform the same function. Hot Recompile is performed in the Editor after making changes to code in Visual Studio, and Hot Reload is performed in Visual Studio in the same situation. As far as I am aware, the end result is the same. I will check to see if there are any important differences, though. Which one you use seems to be a matter of preference. I typically find myself using Hot Reload much more often.

One other thing you can try with the project that is having this issue would be to make a copy of it and, using the copy, slowly strip parts out of it until the issue no longer occurs. That could help us pinpoint where the issue originates.

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Thanks Tim, I have PM-ed my dxdiag to you.

Fortunately I haven't had this issue for the past few days but if I see it again I'll be sure to check the logs and also duplicate the project and try to narrow the scope down as you suggest.

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answered Nov 18 '14 at 08:03 AM

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avatar image Tim C ♦♦ STAFF Nov 18 '14 at 03:08 PM

I don't see anything in your dxdiag that throws up any red flags, so you should be fine in that regard.

I will set this question as resolved for now, but please feel free to re-open it at any time if you find any new information that may help us track it down.

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