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fix pointer aliasing in in_parallel.rs #1115

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Merged
merged 1 commit into from
Nov 16, 2023
Merged

fix pointer aliasing in in_parallel.rs #1115

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9 changes: 5 additions & 4 deletions gix-features/src/parallel/in_parallel.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -229,11 +229,12 @@ where
.expect("valid name");

let input_len = input.len();
struct Input<I>(*mut [I])
struct Input<I>(*mut I)
where
I: Send;

// SAFETY: I is Send + Sync, so is a *mut [I]
// SAFETY: I is Send, and we only use the pointer for creating new
// pointers (within the input slice) from the threads.
#[allow(unsafe_code)]
unsafe impl<I> Send for Input<I> where I: Send {}

Expand All @@ -245,7 +246,7 @@ where
let new_thread_state = new_thread_state.clone();
let state_to_rval = state_to_rval.clone();
let mut consume = consume.clone();
let input = Input(input as *mut [I]);
let input = Input(input.as_mut_ptr());
move || {
let _ = &input;
threads_left.fetch_sub(1, Ordering::SeqCst);
Expand All @@ -264,7 +265,7 @@ where
let item = {
#[allow(unsafe_code)]
unsafe {
&mut (&mut *input.0)[input_index]
&mut *input.0.add(input_index)
}
};
if let Err(err) = consume(item, &mut state, threads_left, stop_everything) {
Expand Down