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Mark TableRow and TableId as repr(transparent) (#7166)
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# Objective
Following #6681, both `TableRow` and `TableId` are now part of `EntityLocation`. However, the safety invariant on `EntityLocation` requires that all of the constituent fields are `repr(transprent)` or `repr(C)` and the bit pattern of all 1s must be valid. This is not true for `TableRow` and `TableId` currently.

## Solution
Mark `TableRow` and `TableId` to satisfy the safety requirement. Add safety comments on `ArchetypeId`, `ArchetypeRow`, `TableId` and `TableRow`.
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james7132 committed Jan 11, 2023
1 parent dfc4f05 commit f4920bb
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Showing 2 changed files with 6 additions and 0 deletions.
2 changes: 2 additions & 0 deletions crates/bevy_ecs/src/archetype.rs
Original file line number Diff line number Diff line change
Expand Up @@ -40,6 +40,7 @@ use std::{
/// [`World`]: crate::world::World
/// [`Entities::get`]: crate::entity::Entities
#[derive(Debug, Copy, Clone, Eq, PartialEq)]
// SAFETY: Must be repr(transparent) due to the safety requirements on EntityLocation
#[repr(transparent)]
pub struct ArchetypeRow(u32);

Expand Down Expand Up @@ -68,6 +69,7 @@ impl ArchetypeRow {
/// [`World`]: crate::world::World
/// [`EMPTY`]: crate::archetype::ArchetypeId::EMPTY
#[derive(Debug, Copy, Clone, Eq, PartialEq, Hash)]
// SAFETY: Must be repr(transparent) due to the safety requirements on EntityLocation
#[repr(transparent)]
pub struct ArchetypeId(u32);

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4 changes: 4 additions & 0 deletions crates/bevy_ecs/src/storage/table.rs
Original file line number Diff line number Diff line change
Expand Up @@ -26,6 +26,8 @@ use std::{
/// [`Archetype`]: crate::archetype::Archetype
/// [`Archetype::table_id`]: crate::archetype::Archetype::table_id
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
// SAFETY: Must be repr(transparent) due to the safety requirements on EntityLocation
#[repr(transparent)]
pub struct TableId(u32);

impl TableId {
Expand Down Expand Up @@ -64,6 +66,8 @@ impl TableId {
/// [`Archetype::table_id`]: crate::archetype::Archetype::table_id
/// [`Entity`]: crate::entity::Entity
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
// SAFETY: Must be repr(transparent) due to the safety requirements on EntityLocation
#[repr(transparent)]
pub struct TableRow(u32);

impl TableRow {
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