Objc2 foundation not working with MacOS 26 / Xcode 26

[zmarlon]

When I want to use objc2_founation with macOS 26, I get the following error message:

/src/generated/NSEnumerator.rs:7:1:
invalid message send to -[_TtGCs23_ContiguousArrayStorageCSo8NSScreen_$ countByEnumeratingWithState:objects:count:]: expected return to have type code 'q', but found 'Q'
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

[karolisr]

Same here.

[zmarlon]

Any news about this? Nearly no rust program works because of this issue.

[Neirth]

I had a project that collapsed a few hours before presenting it to investors because of this bug...

[simlay]

This looks like a runtime bug. I don't have a spare mac to run beta macOS and there's no github runners that run macOS beta so it's tough to fix this without more context. Is there more detailed repro case or specific project?

I am currently running macOS 15.5 and xcode 26 beta and have not noticed anything similar to this.

#762 is to add support for xcode 26 beta but like I said, it's not using on macOS 26.

[simlay]

bevyengine/bevy#19567 is relevant for future reference.

[Zanderwohl]

I also have this issue on an m3 Pro with Version 26.0 Beta (25A5279m). I have another Mac still on Sequoia and can confirm the same code runs fine on that.

Here is "minimal" code to reproduce this in bevy:

use bevy::prelude::*;
use bevy::winit::{WakeUp, WinitPlugin};


fn main() {
    App::new()
        .add_plugins((
            AssetPlugin::default(),
            WinitPlugin::<WakeUp>::default(),
        ))
        .run();
}

Based on debugging, the error originates in objc2/src/verify.rs:123, which in turn descends from the initial call to self.app.run() in winit's src/macos/event_loop.rs:299 which calls the external method NSApplication::run.

However, the winit minimal "Event handling" example here compiles and runs as expected. I suspect this has something to do with bevy's params starting the window. Sorry if this isn't helpful, I'm not at all familiar with how this crate works or these Objective C methods.

[madsmtm]

The underlying issue seems to be the same as #671 and #566 (#754 is also related), and the solutions there would probably work:

1. Disable signed encoding checks.

   # Cargo.toml
   [dependencies]
   objc2 = { version = "0.6.1", features = ["relax-sign-encoding"] }

2. Disable all encoding assertions:

   # Cargo.toml
   [dependencies]
   objc2 = { version = "0.6.1", features = ["disable-encoding-assertions"] }

3. Disable debug assertions in objc2 altogether.

   # Top-level Cargo.toml
   [profile.dev.package.objc2]
   debug-assertions = false

4. Run with --release.