UE5.6 Linux - wrong Cross-Compile Toolchain

Development Getting Started & Setup
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1

I downloaded and installed Cross-Compile Toolchain v25 from Epic’s CDN, but it actually contains the v23 toolchain inside (folder name and version.txt both confirm it’s v23).

When trying to package a plugin for Linux using UE 5.6, I get fatal errors anywhere CoreMinimal.h is included.

for example:

UATHelper: Package Plugin Task (Windows): In file included from C:\Program Files\Epic Games\UE_5.6\Engine\Source\Runtime\Core\Public\CoreMinimal.h:9:
UATHelper: Package Plugin Task (Windows): In file included from C:\Program Files\Epic Games\UE_5.6\Engine\Source\Runtime\Core\Public\CoreTypes.h:10:
UATHelper: Package Plugin Task (Windows): C:\Program Files\Epic Games\UE_5.6\Engine\Source\Runtime\Core\Public\HAL\Platform.h(7,10): fatal error: 'type_traits' file not found

Workaround available, or just wait for the proper v25?

4 Likes
2

Hello, Same issue.

image
image1590×191 9.88 KB

1 Like
3

same problem

1 Like
4

Same issue,

I’ve managed to get a little further by installing the unlisted https://cdn.unrealengine.com/CrossToolchain_Linux/v25_clang-18.1.0-rockylinux8.exe

To match what’s in the submission history in mainline but then run into a crash on linking:

12>ASSERT : error : Access violation writing at address: 0x00000252D4000A90
12> CALLSTACK:
12>   _mi_free_block_mt (alloc.c:446)
12>   _mi_heap_realloc_zero (alloc.c:735)
12>   ucrtbase.dll: +0x3d189
12>   ucrtbase.dll: +0x14a0c
12>   ucrtbase.dll: +0x1488b
12>   ucrtbase.dll: +0x14844
12>   ucrtbase.dll: +0x14e01
12>   combase.dll: +0x18889d
12>   combase.dll: +0x1888bd
12>   combase.dll: +0xc8d5c
12>   combase.dll: +0xc8833
12>   combase.dll: +0xc837b
12>   combase.dll: +0xc7923
12>   combase.dll: +0x1da4ee
12>   combase.dll: +0x6cdb0
12>   combase.dll: +0x6d7a6
1 Like
5

The link already has the correct toolchain. Everything works as it should.

1 Like
7

Hey we have the exact same issue tryin to cross compile I get a crash exactly as you do…

V25 of cross compile tools…

I’ll let you know if we get anywhere

So far it looks like it might be .psym file not getting generated … which I think is some debug symbol dumper … I’m going to look today it may be crashing with wrong dwarf format ( v4 vs v5 ) … just guessing from the digging I’ve been doing …

Let me know if you get anywhere!

9

Screenshot 2025-06-08 191010
Screenshot 2025-06-08 1910102198×1094 229 KB

This fixed it for me… turn OFF UBA … the build accelerator is crashing…

it was not the toolchain as I had the right stuff.. it was UBA.

1 Like
10

The issue we think is within UbaDetours and “Update for Microsoft Windows (KB5058499)”
Uninstalling this update makes everything work.

If you can’t do that (like us without IT permission) then you can still use UBA and bypass the detours crash by using -UBANoDetour

Should sort you while Epic work on a fix.

2 Likes
11

Same cross compiler toolchain crash here. I do not have KB5058499 installed on my computer.

Indeed this is the workaround, but it’s better to modify the file in “%AppData%\Roaming\Unreal Engine\UnrealBuildTool” instead of modifying the one in UE installation directory:

<?xml version="1.0" encoding="utf-8" ?>
<Configuration xmlns="https://www.unrealengine.com/BuildConfiguration">
    <BuildConfiguration>
        <bAllowUBALocalExecutor>false</bAllowUBALocalExecutor>
    </BuildConfiguration>
</Configuration>
12

Thank you!

1 Like
14

I had same problem.
For me working:

  1. Download and install
    https://cdn.unrealengine.com/CrossToolchain_Linux/v25_clang-18.1.0-rockylinux8.exe
  2. Add LINUX_MULTIARCH_TOOLS in Environment variables
    image
  3. Go to %AppData%\Roaming\Unreal Engine\UnrealBuildTool and add:
    <BuildConfiguration>
        <bAllowUBALocalExecutor>false</bAllowUBALocalExecutor>
    </BuildConfiguration>
15

It worked once for one of my plugin, then the error was back for another one. I don’t have explanation…

One month this error is here… Seriously.