Crash when compiling Blueprint

Development Programming & Scripting Blueprint
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1

Ever since I started using Blueprints that derive from other Blueprints, UE4 Editor crashes nearly every time I compile Blueprint.

I’ve attached crash report data. If you need project, I can get it to you with repro steps.

I really hope this has already been fixed in 4.9 because working with these frequent crashes is very difficult.

link text

2

I don’t know how to read output log, that’s Unreal’s business but I’ve had same problem before. I remember that I did something stupid and there was a bug related to animations.

I’m not really sure anymore but I think mine crashed due to fact that my parent called a function directly that was located in child. Of course that doesn’t work because a parent does not see it’s child, it’s child only sees parent.

So make sure you did not do something like that :wink:

3

Hi sranck,

I’m taking a look at crash reports we’ve gotten from you (thanks for submitting them!), and it looks like majority do indeed involve an Anim Blueprint, though perhaps its source is simply a BP derived from Pawn or something. Please check suggestion Serellyn made above and see if there are any calls to a function in a child from its parent, and let us know if there is.

Otherwise, this crash does not look familiar, and I can’t find another in our database for it. Would you mind uploading project somewhere and getting me a download link? You can send it privately via PM on , if you’d prefer:

https://.unrealengine.com/member.php?32–

Thanks!

4

Thanks for replies. I don’t quite understand what you’d like me to check, but I did PM a link to crashing project and provided repro steps.

5

Hi sranck,

I tested each Case in both your original project and a new, “clean,” project I created with 4.8.3’s Third Person Blueprint Template, migrating your agents assets over. results are as follows:

(A) CRASH 1

  • Case #1: REPRO’S in original / Not in Clean version
  • Case #2: REPRO’S in original / Not in Clean version

(B) CRASH 2

  • Case #1: REPRO’S in original / Not in Clean version
  • Case #2: REPRO’S in original / Not in Clean version (Does not crash but Node gives error)
  • Case #3: REPRO’S in original / Not in Clean version (Does not crash but Node gives error)
  • Case #4: REPRO’S in original / Not in Clean version (Does not crash but Node gives error)

This tells us that there’s some conflict or something is corrupted in your master project, but if you *migrate your agent assets to a clean Third Person Blueprint project this will take care of crashes.

*[Migrating Assets][1]

[1]:

6

It’s disconcerting that a UE4 project can suddenly become corrupted to point where it’s unusable, and only solutions are to either migrate everything to a clean project, or revert to an earlier backup. I’m hoping you can provide my corrupted project to one of your programmers to take a look at and perhaps discover what exactly became corrupted. Perhaps it would provide enough information to track down bug and fix it in a future release. This seems like a very important bug to fix.

7

Unfortunately, due to vast quantities of assets in your project, we simply do not have resources to debug your project to isolate why crash is occurring. For instance, you have included entire Kite demo, among numerous other asset packs, and your project only appears to be referencing grass from that pack.

By testing your assets with your repro steps in a new project, we have isolated cause to be not that of engine itself. So saying project has become “corrupt” is a general statement as there is likely some reference to an asset engine cannot find. This may be sole cause of crash or in additon to errors generated by blend nodes discussed in your previous thread. (ie “conflict.”)

next steps I’d recommend to debug on your own are to:

  1. Make a back up of your project then
  2. Systemmatically remove assets (or entire asset packs) one at a time, trying 1 repro case after each removal to see if it still crashes until you find asset or assets that are causing problem
8

Missing assets (“reference to an asset engine cannot find”) should never cause UE4 Editor to crash & become permanently unusable. Missing assets usually produce a warning message, so I assume that whatever’s causing Editor to crash is a bug in engine itself.

crashes literally started happening instant I introduced another layer to my Character BP and Anim BP, and started adding functionality to new layers, which involved renaming some functions. From that point on, compiling my Character BP began crashing Editor, and my Anim BP became so unstable that I couldn’t even delete a node without Editor crashing. This really appears to be a bug in engine itself.

fact that my testbed project has entire Kite demo in it shouldn’t make it any more difficult for a programmer to track down a crash. Visual Studio will just trigger an exception, and from there programmer can take a look at what caused crash.

I would think that your engine programmers would want to know that there’s a defect in engine that can cause Editor to become permanently unstable, and would be glad to have a project where crashes can be reproduced so that they can track down cause and fix bug.

9

We are interested in getting to bottom of this whether it’s a bug with engine or resolving issue so you can continue your project. You wrote," crashes literally started happening instant I introduced another layer to my Character BP and Anim BP, and started adding functionality to new layers, which involved renaming some functions."

  1. What do you mean by you “introduced another layer to your Character Blueprint and Anim Blueprint?” Please be specific.
  2. If you renamed some functions, engine may still be trying to call those functions somewhere in your Blueprints by their original name.
  3. Are you able to revert your Character and Animation Blueprints to a state before you added functionality? If so, does engine crash?
  4. Was this project started in a previous version of Engine before opening in version 4.8?

Please answer with as much detailed information as possible.

Thanks.

10

Thanks, . FWIW, we are a paying UE4 support client, so if you’d prefer that I post this on UDN, please let me know.

-1-
Before things started crashing, AgentAR2_CharacterBlueprint’s parent class was Character. I created a new BP called Agent_CharacterBP, whose parent class was Character, and then reparented AgentAR2_CharacterBlueprint to Agent_CharacterBP. After doing reparenting, I relocated some functions and probably some variables from AgentAR2_CharacterBlueprint to Agent_CharacterBP. I don’t recall which. I also introduced virtual functions such as GetAgentWeaponBP in Agent_CharacterBP, but where implementation is actually in AgentAR2_CharacterBlueprint.

Also, AgentAR2_AnimBP’s parent class was originally AnimInstance. I renamed AgentAR2_AnimBP to Agent_AnimBP (because it already had a lot of functionality that I needed to keep), and then created a new BP called AgentAR2_AnimBP and parented it to Agent_AnimBP. idea was that AgentAR2_AnimBP could then use its own unique set of animations by specifying those animation names as variables ( K_* variables found in “Anims” section of Agent_AnimBP).

-2-
Sure, if that’s case then there’s likely a bug in engine’s renaming functionality. Recall, however, that crash occurs when I compile Agent_CharacterBP or AgentAR2_CharacterBlueprint, and not when game is run. If engine is trying to call a stale function, wouldn’t that occur when game is running as opposed to BP being compiled?

One side note is that when I compiled my BP and editor would crash, when I then relaunched editor, BP had already been compiled successfully and I wouldn’t have to recompile it again (until I made another change, of course). game ran fine.

-3-
No, project was initially started with 4.8.

11

Thanks, . FWIW, we are a paying UE4 support client, so if you’d prefer that I post this on UDN, please let me know.

Hi sranck,

Please post this issue in UDN. AnswerHub is a hub for community driven support.

Thanks,

Sean

12

Thanks Sean. Done.