Macro and Interface "library" causes crash with blueprints

I shut down the editor and pc with a perfectly working game , now 2h later the editor cannot open a single BP even a new empty one.

I opened some example projects and the first couple of times it couldn’t open their BP too but after few tries it started working OK.

Now it wont open any BP which is in my project. I create an empty BP and cannot open it , I migrate the whole project and cannot open anything.

When I migrate 1 Random BP I can open and edit it without any problem. I am using interfaces and macros

Edit: Since I don’t post until I spend a good hour looking at the problem I found that my “Macro Library” was killing the build and this is not the first time… last time it was an “Interface library” so Epic take a look into this.

here is a download link FIXED Dropbox - Error

Edtit 2: after I remade all the corrupted files i made an “Interface library” which killed the BP that had it. They became uneditable (double clicking on them crashes the engine)

To recreate the events you need to make 2 or more BP that share the same Macros or Interfaces and they have been plugged in and compiled ,saved and work correctly. Than start editing the library’s contents (not adding) rename or delete a macro/interface. Even if I Clear the BP of the interface events first it sill manages to kill it …


Unreal Engine savew backups in saved directory, you can revive corrapted files from there… or else they been overwriten by your trys to retrive

Hi Midnight640,

This is very concerning to hear. First off, I am sorry that this gave you so much trouble. We’re going to have someone dig into this and hopefully we can get to the bottom of what’s going on.

Thanks for providing us with the problematic asset. To repro this we should drop that asset into our project, and use a macro from it in a blueprint of our own?

Hi Midnight640,

The link is broken, could you paste it again?


Hello to you all , I was busy and I just see the answers.

here is the link , I have no Idea why it got messed up …

To reproduce the results just make a simple library(macro or interface) with 2 or 3 functions. In Edit 2 my interface had only 1 function. Then make sure that these functions are used in some BP. Then start deleting/editing them and the BP.

What I think I did was: (I was working on Pawn and HUD)
I removed the Interface actions from my pawn , then i removed the interface and clicked compile


What is the call-stack, when engine crashes?


Hello kaziu I am currently out of the city for the holidays and I cannot tell you , but I also  don’t understand the question, Do you mean the “autoreport” message or is it  something like a Log file hidden in the depths of the engine?

Also if you manage to replicate the error please keep me up to date, interfaces and macros are very usefull and I would like to continue using them but for now I can’t knowing the progress I lost .

Hi Midnight640,

The “autoreport” message would be fine. It contains the call-stack. The log file also contains the call stack (but it could be hard to find the proper log file). They are stored in “[game_name]\Saved\Logs” directory.

I could not reproduce the error so far. So it was hopefully fixed on our branch, OR repro-steps are more complex.


Hello I managed to reproduce the error on 4.1 this is the call stack

"We apologize for the inconvenience.
Please send this crash report to help improve our software.


What I did was have the interface with function 444 in the character BP and the projectile BP.
Then in the interface if you delete 444 and click compile the editor crashes BUT your work is safe,
IF you DELETE 444 THEN SAVE and then COMPILE the editor continues to work but as soon as you open the character BP it crashes ( the character has the Event444 node and the projectile has the "triger " for 444)

Hi Midnight640,

Thanks for reporting the issue. I was able to reproduce the crash. It was fixed in CL#2063447.