c6ba3d31cf
2 Commits
| Author | SHA1 | Message | Date | |
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SpecificProtagonist
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13e89a1678
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Fix EntityMeta.spawned_or_despawned unsoundness (#19350)
# Objective #19047 added an `MaybeUninit` field to `EntityMeta`, but did not guarantee that it will be initialized before access: ```rust let mut world = World::new(); let id = world.entities().reserve_entity(); world.flush(); world.entity(id); ``` <details> <summary>Miri Error</summary> ``` error: Undefined Behavior: using uninitialized data, but this operation requires initialized memory --> /home/vj/workspace/rust/bevy/crates/bevy_ecs/src/entity/mod.rs:1121:26 | 1121 | unsafe { meta.spawned_or_despawned.assume_init() } | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ using uninitialized data, but this operation requires initialized memory | = help: this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior = help: see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information = note: BACKTRACE: = note: inside closure at /home/vj/workspace/rust/bevy/crates/bevy_ecs/src/entity/mod.rs:1121:26: 1121:65 = note: inside `std::option::Option::<&bevy_ecs::entity::EntityMeta>::map::<bevy_ecs::entity::SpawnedOrDespawned, {closure@bevy_ecs::entity::Entities::entity_get_spawned_or_despawned::{closure#1}}>` at /home/vj/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/option.rs:1144:29: 1144:33 = note: inside `bevy_ecs::entity::Entities::entity_get_spawned_or_despawned` at /home/vj/workspace/rust/bevy/crates/bevy_ecs/src/entity/mod.rs:1112:9: 1122:15 = note: inside closure at /home/vj/workspace/rust/bevy/crates/bevy_ecs/src/entity/mod.rs:1094:13: 1094:57 = note: inside `bevy_ecs::change_detection::MaybeLocation::<std::option::Option<&std::panic::Location<'_>>>::new_with_flattened::<{closure@bevy_ecs::entity::Entities::entity_get_spawned_or_despawned_by::{closure#0}}>` at /home/vj/workspace/rust/bevy/crates/bevy_ecs/src/change_detection.rs:1371:20: 1371:24 = note: inside `bevy_ecs::entity::Entities::entity_get_spawned_or_despawned_by` at /home/vj/workspace/rust/bevy/crates/bevy_ecs/src/entity/mod.rs:1093:9: 1096:11 = note: inside `bevy_ecs::entity::Entities::entity_does_not_exist_error_details` at /home/vj/workspace/rust/bevy/crates/bevy_ecs/src/entity/mod.rs:1163:23: 1163:70 = note: inside `bevy_ecs::entity::EntityDoesNotExistError::new` at /home/vj/workspace/rust/bevy/crates/bevy_ecs/src/entity/mod.rs:1182:22: 1182:74 = note: inside `bevy_ecs::world::unsafe_world_cell::UnsafeWorldCell::<'_>::get_entity` at /home/vj/workspace/rust/bevy/crates/bevy_ecs/src/world/unsafe_world_cell.rs:368:20: 368:73 = note: inside `<bevy_ecs::entity::Entity as bevy_ecs::world::WorldEntityFetch>::fetch_ref` at /home/vj/workspace/rust/bevy/crates/bevy_ecs/src/world/entity_fetch.rs:207:21: 207:42 = note: inside `bevy_ecs::world::World::get_entity::<bevy_ecs::entity::Entity>` at /home/vj/workspace/rust/bevy/crates/bevy_ecs/src/world/mod.rs:911:18: 911:42 note: inside `main` --> src/main.rs:12:15 | 12 | world.entity(id); | ``` </details> ## Solution - remove the existing `MaybeUninit` in `EntityMeta.spawned_or_despawned` - initialize during flush. This is not needed for soundness, but not doing this means we can't return a sensible location/tick for flushed entities. ## Testing Test via the snippet above (also added equivalent test). --------- Co-authored-by: urben1680 <55257931+urben1680@users.noreply.github.com> |
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urben1680
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732b2e0c79
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Track spawn Tick of entities, offer methods, query data SpawnDetails and query filter Spawned (#19047)
# Objective In my own project I was encountering the issue to find out which entities were spawned after applying commands. I began maintaining a vector of all entities with generational information before and after applying the command and diffing it. This was awfully complicated though and has no constant complexity but grows with the number of entities. ## Solution Looking at `EntyMeta` it seemed obvious to me that struct can track the tick just as it does with `MaybeLocation`, updated from the same call. After that it became almost a given to also introduce query data `SpawnDetails` which offers methods to get the spawn tick and location, and query filter `Spawned` that filters entities out that were not spawned since the last run. ## Testing I expanded a few tests and added new ones, though maybe I forgot a group of tests that should be extended too. I basically searched `bevy_ecs` for mentions of `Changed` and `Added` to see where the tests and docs are. Benchmarks of spawn/despawn can be found [here](https://github.com/bevyengine/bevy/pull/19047#issuecomment-2852181374). --- ## Showcase From the added docs, systems with equal complexity since the filter is not archetypal: ```rs fn system1(q: Query<Entity, Spawned>) { for entity in &q { /* entity spawned */ } } fn system2(query: Query<(Entity, SpawnDetails)>) { for (entity, spawned) in &query { if spawned.is_spawned() { /* entity spawned */ } } } ``` `SpawnedDetails` has a few more methods: ```rs fn print_spawn_details(query: Query<(Entity, SpawnDetails)>) { for (entity, spawn_details) in &query { if spawn_details.is_spawned() { print!("new "); } println!( "entity {:?} spawned at {:?} by {:?}", entity, spawn_details.spawned_at(), spawn_details.spawned_by() ); } } ``` ## Changes No public api was changed, I only added to it. That is why I added no migration guide. - query data `SpawnDetails` - query filter `Spawned` - method `Entities::entity_get_spawned_or_despawned_at` - method `EntityRef::spawned_at` - method `EntityMut::spawned_at` - method `EntityWorldMut::spawned_at` - method `UnsafeEntityCell::spawned_at` - method `FilteredEntityRef::spawned_at` - method `FilteredEntityMut::spawned_at` - method `EntityRefExcept::spawned_at` - method `EntityMutExcept::spawned_at` --------- Co-authored-by: Eagster <79881080+ElliottjPierce@users.noreply.github.com> Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com> |