Using mimalloc with bevy reveals unsoundness.

[moonheart08]

Bevy version

0.15.3

Relevant system information

• Windows 11
• cargo 1.86.0-nightly (ce948f461 2025-02-14)

What you did

Compiled and ran the following test, with dynamic_linking enabled:

//! A simple 3D scene with light shining over a cube sitting on a plane.

use bevy::prelude::*;
use mimalloc::MiMalloc;

#[global_allocator]
static GLOBAL: MiMalloc = MiMalloc;

fn main() {
    let mut a = App::new();
    a.add_plugins(DefaultPlugins);

    std::mem::drop(a); // exercise allocating a bit.
    App::new()
        .add_plugins(DefaultPlugins)
        .add_systems(Startup, setup)
        .run();
}

/// set up a simple 3D scene
fn setup(
    mut commands: Commands,
    mut meshes: ResMut<Assets<Mesh>>,
    mut materials: ResMut<Assets<StandardMaterial>>,
) {
    // circular base
    commands.spawn((
        Mesh3d(meshes.add(Circle::new(4.0))),
        MeshMaterial3d(materials.add(Color::WHITE)),
        Transform::from_rotation(Quat::from_rotation_x(-std::f32::consts::FRAC_PI_2)),
    ));
    // cube
    commands.spawn((
        Mesh3d(meshes.add(Cuboid::new(1.0, 1.0, 1.0))),
        MeshMaterial3d(materials.add(Color::srgb_u8(124, 144, 255))),
        Transform::from_xyz(0.0, 0.5, 0.0),
    ));
    // light
    commands.spawn((
        PointLight {
            shadows_enabled: true,
            ..default()
        },
        Transform::from_xyz(4.0, 8.0, 4.0),
    ));
    // camera
 
   commands.spawn((
        Camera3d::default(),
        Transform::from_xyz(-2.5, 4.5, 9.0).looking_at(Vec3::ZERO, Vec3::Y),
    ));
}

For ease of reproduction, a repo with settings necessary to make dylink work on windows is here: https://github.com/moonheart08/bevy-crash-repro

What went wrong

Immediate segmentation fault.

[moonheart08]

Can't reproduce this without the dylib feature ftr, which has me Slightly Concerned about the stability of that feature

[mockersf]

Can you reproduce with dynamic linking and without mimalloc?

[moonheart08]

So upon further reading, I found rust-lang/rust#100781

It looks like global allocators and dylibs are unsound/unsupported at this time and there's not much to be done here.

Bevy should probably attach a warning to dynamic_linking for this, but otherwise not much to do.