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Use ManuallyDrop instead of forget in insert_resource_with_id (#2947)

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# Objective

Calling forget would invalidate the data pointer before it is used.

## Solution

Use `ManuallyDrop` to prevent the value from being dropped without moving it.
This commit is contained in:
bjorn3 2022-02-03 22:34:31 +00:00
parent 6ac9d6876f
commit af22cc1dc3
1 changed files with 4 additions and 3 deletions
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7
crates/bevy_ecs/src/world/mod.rs
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@ -20,6 +20,7 @@ use crate::{
use std::{
any::TypeId,
fmt,
mem::ManuallyDrop,
sync::atomic::{AtomicU32, Ordering},
};
@ -1003,13 +1004,13 @@ impl World {
/// # Safety
/// `component_id` must be valid and correspond to a resource component of type T
#[inline]
unsafe fn insert_resource_with_id<T>(&mut self, component_id: ComponentId, mut value: T) {
unsafe fn insert_resource_with_id<T>(&mut self, component_id: ComponentId, value: T) {
let change_tick = self.change_tick();
let column = self.initialize_resource_internal(component_id);
if column.is_empty() {
let mut value = ManuallyDrop::new(value);
// SAFE: column is of type T and has been allocated above
let data = (&mut value as *mut T).cast::<u8>();
std::mem::forget(value);
let data = (&mut *value as *mut T).cast::<u8>();
column.push(data, ComponentTicks::new(change_tick));
} else {
// SAFE: column is of type T and has already been allocated