Unity Issue Tracker - Struct field value corrupts when invoking a generic delegate with a large struct by value

Third Party Issue

6.6.X

6.5.X

6.4.X

6.3.X

6.0.X

6000.0.38f1 onwards

Thank you for reporting a bug to Unity. Our investigation indicates the issue originates from a third-party compiler issue in NDK 27. Because the problem lies outside our codebase, we're unable to address it directly at the moment, but it will be addressed in the future by an NDK 29 update. When Writer<TestStruct>.write = DebugStruct is assigned in C#, IL2CPP stores it as an open static delegate. The Action_2_Invoke system routes through a generated OpenStatic trampoline. In NDK 27, the compiler incorrectly reordered a dependent store-then-load pair. - Option 1: Pass by Reference: Change the delegate to use ref T. This avoids large-struct register splitting. delegate void RefAction<A, B>(A a, ref B b); - Option 2: Use Reference Types Wrap the large internal State struct in a class. This shrinks the parent struct size to 8 bytes, keeping it in registers and avoiding the buggy stack-split path. - Option 3: Avoid Generic Delegate Trampolines Call the method directly (DebugStruct(writer, item)) rather than through a generic Action<T> field.

Reproduction steps:
1. Open the attached “IN-133974“ project
2. In the Android Player Settings, make sure that IL2CPP is selected as the Scripting backend and that only ARMv7 is selected as the Target Architecture (Project Settings > Player Settings > Other Settings)
3. Build and Run the Android Player
4. In the Player, click the “Test” button
5. Observe the result text field under the button

Actual result: The provided result is a random number, not equal to “300”
Expected result: The provided result is “300”

Reproducible with: 6000.0.67f1, 6000.2.0a2, 6000.3.8f1, 6000.4.0b8, 6000.5.0a6
Not reproducible with: 2022.3.71f1, 6000.2.0a1

Reproducible environments: macOS 26.2
Not reproducible environments: No other environments tested

Reproducible with these devices:
VLNQA00336 - HUAWEI Y6p (MED-LX9N), CPU: MediaTek MT6762R, GPU: PowerVR Rogue GE8320, OS: 10
VLNQA00583 - Xiaomi Redmi 9A (M2006C3LG), CPU: MediaTek Helio G25 (MT6762G), GPU: PowerVR Rogue GE8320, OS: 11
VLNQA00422 - Galaxy S21 Ultra 5G (SM-G998B), CPU: Exynos 2100, GPU: Mali-G78, OS: 11 (When only ARMv7 is enabled, when ARM64 is enabled, issue does not reproduce)

Struct field value corrupts when invoking a generic delegate with a large struct by value

Unity: Android

Third Party Issue

Prioritise and Follow this issue

Have a workaround or additional info about this issue?

Struct field value corrupts when invoking a generic delegate with a large struct by value

Unity: Android

Statuses

Third Party Issue

Resolution Notes

Description

Prioritise and Follow this issue

Have a workaround or additional info about this issue?