Crash with a PassBy reference wrongly set by engine

Development Programming & Scripting
1

Hello,

Found this crash where a Pin in a custom event was automatically set on Pass-By Reference (drag and drop from a node), which make it crash when triggered ingame. Icon is round instead of diamond, which makes me suspect the automatic pin addition is a bit buggy.

  1. Create a custom event in a Player Controller
  2. Place an ADD node (might happens with other nodes aswel)
  3. Create a variable Player Controller
  4. Connect that variable to the add
  5. Connect the Item pin to the Custom Event
  6. Place the custom event after BeginPlay
  7. Connect a Self reference to the Exposed Pin
  8. Test and crash

It should looks like this

58941-crash_passby_pin.jpg
58941-crash_passby_pin.jpg1531×347 59.7 KB

2

Hi Genova,

I tested your setup but I couldn’t get your results. Could you create a small test project that crashes and upload it here?

Also, please submit and post your full Crash Callstack, Logs, and Dmp files.

3

link text
Here you go.
If you don’t get the crash, just check if the gamemode is properly set.

4

Hi Genova,

Which version of the editor were you using (4.9 or 4.9.1)? If you were using 4.9, please try reproducing it in 4.9.1.

If you were already using 4.9.1, I reproduced the crash in your project but when I attempt to recreate the Custom Event without the diamond pin, I can’t. I get an error message with this warning:

59886-passbyrefcrash01.jpg
59886-passbyrefcrash01.jpg1151×928 171 KB

Which is what you should be getting because it’s not necessary to pass a reference that is already a reference.

Let me know your results.

5

Hi Genova,

We haven’t heard back from you in a few days, so we are marking this post as resolved for tracking purposes. If you’re still experiencing this issue, please feel free to post back here with additional information.

Cheers,

TJ

6

I’m still experiencing this exact same crash in 4.15. Repro steps are still the same like what Genova described.
Connecting a self reference to any pass-by-ref input variable of an event makes the engine crash.

7

Hey John,

Thanks for reporting this for 4.15. I started testing this again and realized what I missed last time. I was able to repro it and created JIRA UE-40861. Our devs will be looking into it further. Like normal, follow that link to monitor the bugs status.