Native crash when loading in async function C#

[Martanti]

Godot version

v3.4.4.stable.mono.official [419e713]

System information

Windows 10 64bit, OpenGL ES 3.0 Renderer: NVIDIA GeForce GTX 1060 with Max-Q Design/PCIe/SSE2 OpenGL ES Batching: ON

Issue description

When trying to call var loadedScene = GD.Load<PackedScene>(path); in a Task.Run within an async function the game crashed and the main godot console window printed out :

ERROR: FATAL: Index p_index = 10 is out of bounds (size() = 9).
   at: get (./core/cowdata.h:156)

=================================================================
        Native Crash Reporting
=================================================================
Got a UNKNOWN while executing native code. This usually indicates
a fatal error in the mono runtime or one of the native libraries
used by your application.
=================================================================

=================================================================
        Managed Stacktrace:
=================================================================
=================================================================

Here are the logs:
2022-07-24_10.26.40_18036.log

Steps to reproduce

The ready function:

public override void _Ready()
	{
		_loadFinished = false;
		var dungeonSize = LevelConfig.DungeonSize;
		var powerLevel = LevelConfig.PowerLevel;
		var playerClass = LevelConfig.PlayerClass;

		// Having this in the async function also caused a window freezeup
		var scene = GD.Load<PackedScene>(
				_loadingScreenPath);
		_loadingScreen = scene.Instance();
		AddChild(_loadingScreen);

		_loadingScreenHandling = HandleLoadingScreenAsync();
		_levelLoading = LoadNewLevelAsync(dungeonSize, powerLevel, playerClass);
	}

The LoadNewLevelAsync:

private async Task LoadNewLevelAsync(
		double dungeonSize,
		double powerLevel,
		HeroClasses playerClass)
	{
		await Task.Run(() =>
		{
			// Load player
			LoadPlayer(playerClass);
		});
		_loadFinished = true;
	}

The LoadPlayer function, in which the crash happened:

private void LoadPlayer(HeroClasses playerClass)
	{
		var loadedScene = GD.Load<PackedScene>(_pathsToHeroPrefabs[playerClass]);
		var playerInstance = loadedScene.Instance();
		AddChild(playerInstance);
	}

Minimal reproduction project

No response

[Calinou]

@Martanti Please upload a minimal reproduction project to make this easier to troubleshoot.

[Martanti]

Sorry for the closing and reopening, miss-click.

@Calinou
So it seems that the issue is a composite. When trying to create a minimal reproduction project the async loading worked by itself. But then I introduced a rich text label with a custom font in a custom theme and that made the issue I was facing in my project. Tell me, if I need something more to add.

See the project attached below.
async breaking repro.zip

@tvardero after seeing some kind of correlation with using a custom theme with a font to the crash I am no longer sure if these two issues are related.

[tvardero]

Does the game crash when you make all your code synchronous? @Martanti

[Martanti]

@tvardero I took the code from async calls and called them synchronously and it worked. Mind you, in one of the async calls I do have a while loop that waits for one bool to get set to true at the end of loading, so that was not executed.