UB when using observers with `OnAdd`

[AlfredAn]

use flecs_ecs::prelude::*;

#[derive(Component, Debug)]
pub struct Foo(u8);

fn main() {
    let world = World::new();

    world.observer::<flecs::OnAdd, &Foo>().each(|bar: &Foo| {
        println!("OnAdd {bar:?}");
    });

    world.entity().set(Foo(0));
}

This prints:

OnAdd Foo(224)

OnAdd Foo(160)

OnAdd Foo(48)

when run three separate times, which suggests that there is UB somewhere. OnSet and OnRemove seem to work fine.

[Indra-db]

Yes, that's correct, in Flecs Core, OnAdd is triggered before the value is initialized.

It seems like behavior might need to change within Flecs itself to make it safe for the Rust binding. I will update you once this problem is discussed with Sander.

It was overlooked that this is UB in rust

[Indra-db]

completed, thanks for the issue!

This will panic now.