Compiling an actor blueprint crashes to desktop

Development Programming & Scripting Blueprint
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1

Hello! I’ve been doing some work using modular components on actors and have found that under very specific circumstances compilation can trigger a crash to desktop. consistent steps to reproduce crash are:

  1. Attempt to delete a component from content browser.
  2. Cancel deletion.
  3. Open an actor that has same component attached.
  4. Detach (delete) component from actor.
  5. Attempt compile actor blueprint Crash happens before compile finishes

actor in question does not (currently) compile its blueprint due to errors. crash does not happen if step 1) and 2) are not performed, in that case, attempting to detach component and compile work just fine (compilation fails and displays all existing errors).

Hope that helps anyone.

2

I have pinpointed problem to an unimplemented function for specific actor I’m using. When a function is not properly wired, attempting to compile blueprint results in a crash to desktop under multiple conditions, not just one listed above.

above can’t be replicated in copies, instances or new actors. actor I’m using pre-dates version 4.9.

3

Hi GoodOldMalk,

Please copy information in Crash Reporter window and paste it here, including Machine ID. Make sure to hit Send. Then, attach log from project’s \Saved\Logs folder.

I’m not able to reproduce this in a new project with new actors, as you mentioned, nor with an Actor from a project upgraded from 4.8. I’ll see if I can link information from your log and Crash Report to any known issues, otherwise there probably isn’t much we can do if we can’t reproduce it.

If you’re able to reproduce it in a new project at any point, please let us know and upload project someplace we can get at it to look it over. Thanks!

4

I’m unable to paste entirety of crash report here so I’ve attached a text file instead.

MachineId:8C90BD5240B5E75A37D7178D03593FE9

EpicAccountId:44061d6773bf46ac9ca505869bfa1cd9

"Assertion failed: ((UObject*)ContainerPtr)->IsA((UClass*)GetOuter()) [File:D:\BuildFarm\buildmachine_++depot+UE4-Releases+4.9\Engine\Source\Runtime\CoreUObject\Public\UObject\UnrealType.h]

CrashReport.txt

LogFile.log

5

Hey GoodOldMalk,

This looks very similar to another bug report we have (UE-21255), and I see another few projects have reported same crash in 4.9. I’ve created UE-21759 to track issue, and I’ll let you know when I see any update on it. Thanks for report!

6

Hey GoodOldMalk,

developers have requested a repro project. If possible, please project in which this occurs and upload it someplace like Google Drive or Dropbox, and send me a download link via PM on forums:

Please include steps we’d need to reproduce this issue in project you send. Thanks!

7

Regretably for debugging, I’ve done a number of changes that seemed to have removed crash.

I’ve started moving away controller logic from Actor to PlayerController, including components and component interfaces, and in process bug can not be replicated anymore. I’ve also revised my interfaces so that they pass structures (at worst, with default values) instead of arrays (which could possibly be empty), so getting a compilation error from unwired interfaces is no longer possible.

8

Okay, no problem. If you manage to reproduce it again, please send me project. Thanks!