InvalidOperationException: Failed to Free handle with Index=0 Version=0 at UnityEngine.UIElements.

Unity Engine
,
1

Hi,

I’m on WebGL and using Addressables to load uxml files.
I’m loading and instatiating one element 6 times and the first time I get the following error, but the other 5 times it works fine:

InvalidOperationException: Failed to Free handle with Index=0 Version=0
  at UnityEngine.UIElements.Layout.LayoutDataStore.Free (UnityEngine.UIElements.Layout.LayoutHandle& handle) [0x00000] in <00000000000000000000000000000000>:0

What’s interesting is that it was working fine before and I’ve been reverting back and forth the changes when this started happing, but there’s no pattern.

I was close to identify the issue, but without any luck:
Maybe it was using Addressable Asset Settings - Catalog - Player Version Override (I switched back and fourth, it was fixed at some point, but the issue came back)
Maybe because intially the VisualElement - display is none (so hidden) and mayb the Layout issue, thought it doesn’t seem to be, since the other elements work fine.

2

Started having the same issue.

Still can’t identify it. Do you mind sharing if you managed to resolve it?
I can’t reproduce in Unity 2022.x LTS. Can easily reproduce in 2023.1.x and 2023.2.x.

Will share a bug report if there’s no follow up later this week.

3

I have the same issue but I don’t really need a webgl build right now so I didn’t investigate much and I didn’t submit a bug report.
EDIT: I don’t use Addressables to load uxml files, I use Resources.Load (not sure if it’s different)

4

Bug report here: (2023.2.x, 2023.1.x) IndexOutOfRangeException in Layout.LayoutManager.DestroyNode when changing UXML

It’s weird, I don’t get the error often but it appears randomly while I was investigating the issue linked above.

5

I have this error now after Upgradeing to Unity 2023.2.0 when UIElements are created.

I use Resource.Load for that like this:

 public MyButton()
{
     if (MyButton.tree == null)
     {
         MyButton.tree = Resources.Load<VisualTreeAsset>("MyButton");
     }

     MyButton.tree.CloneTree(this);

     OuterButton = this.Q<ButtonTranslatable>("outerButton");
     HoverButton = this.Q<Button>("hoverButton");

}

Is there a different way to do something like this?

I made further tests, and it also crashes when I create the elements via c# code

6

There seems to be a serious bug somewhere, when creating VisualElements during runtime.
Sometimes it works fine, sometimes I get errors like

IndexOutOfRangeException: Index was outside the bounds of the array.
  at System.Collections.Generic.Stack`1[T].PushWithResize (T item) [0x00000] in <00000000000000000000000000000000>:0
  at System.Collections.Generic.Stack`1[T].Push (T item) [0x00000] in <00000000000000000000000000000000>:0
  at UnityEngine.UIElements.Layout.LayoutManager.DestroyNode (UnityEngine.UIElements.Layout.LayoutNode& node) [0x00000] in <00000000000000000000000000000000>:0
  at UnityEngine.UIElements.VisualElement.Finalize () [0x00000] in <00000000000000000000000000000000>:0

and this:

System.InvalidOperationException: Failed to Free handle with Index=0 Version=0
  at UnityEngine.UIElements.Layout.LayoutDataStore.Free (UnityEngine.UIElements.Layout.LayoutHandle& handle) [0x00000] in <00000000000000000000000000000000>:0
  at UnityEngine.UIElements.Layout.LayoutManager.FreeNode (UnityEngine.UIElements.Layout.LayoutHandle handle) [0x00000] in <00000000000000000000000000000000>:0
  at UnityEngine.UIElements.Layout.LayoutManager.TryFreeNodes () [0x00000] in <00000000000000000000000000000000>:0
  at UnityEngine.UIElements.Layout.LayoutManager.CreateNodeInternal (UnityEngine.UIElements.Layout.LayoutHandle configHandle) [0x00000] in <00000000000000000000000000000000>:0
  at UnityEngine.UIElements.Layout.LayoutManager.CreateNode () [0x00000] in <00000000000000000000000000000000>:0

And different browsers have different results:
Often Chrome and Edge work fine, but Firefox throws those exceptions every time.

And sometime when I open the browser and start the app everything works fine. Then I reload the page and the error occurs.

7

Today I tried something new:
Since It seems to be memory related I switched in the player publishing settings from “full stacktrace” to “Exceptions only”.
Then I get no errors in Firefox but in Chrome and Edge the whole app crashes with a javascript error popup:

vishow_1_22_3_a.framework.js:9  System.InvalidOperationException: Stack empty.
  at System.Collections.Generic.Stack`1[T].ThrowForEmptyStack () [0x00000] in <00000000000000000000000000000000>:0
8

The only thing you can do is vote here Unity Issue Tracker - &quot;IndexOutOfRangeException&quot; in &quot;UIElements.Layout.LayoutManager.DestroyNode&quot; when changing UXMLs and wait for Unity to fix it. It’s been 4 months and it doesn’t seem any progress has been made though.
EDIT: It looks like a dev from unity is working on it so maybe a fix will be released soon

9

I don’t know if it is the same bug (but i voted anyway).
When I compare code code of 2022.3. with 2023.2.1 there are significant changes in the memory handling of ui elements. I don’t know when those where added.

10

Hey there, I am the one who reported that bug. Here’s the WebGL thread if you want to add your voice;

If you’re not getting the error in 2022.x it is probably the same error, the call stack looks very similar to what I reported.

11

I had to downgrade to 2022.3.14, since no workaround worked…

12

Same, stuck on 2022.x until it is fixed…

13

I’ve been dealing with the same problem for a few days. I think the problem is caused by the LayoutManager.TryFreeNodes() method. I was getting the error on the line VisualElement choiceElement = new VisualElement(); .

As far as I understand, webgl gets a Timeout error from threading because it runs slower than the editor.

As a temporary solution, I caught the error with Try-catch and called the method again with the same parameters in the catch, and it is now working despite receiving an error.

1 Like
14

I will add this to the bug report - thank you.