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Rollup merge of #119158 - JohnTheCoolingFan:arc-weak-clone-pretty, r=cuviper

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Clean up alloc::sync::Weak Clone implementation

Since both return points (tail and early return) return the same expression and the only difference is whether inner is available, the code that does the atomic operations and checks on inner was moved into the if body and the only return is at the tail. Original comments preserved.
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Matthias Krüger 2023-12-30 11:42:02 +01:00 committed by GitHub
commit c67ab2e0b4
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1 changed files with 10 additions and 13 deletions
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23
library/alloc/src/sync.rs
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@ -2917,20 +2917,17 @@ impl<T: ?Sized, A: Allocator + Clone> Clone for Weak<T, A> {
/// ```
#[inline]
fn clone(&self) -> Weak<T, A> {
let inner = if let Some(inner) = self.inner() {
inner
} else {
return Weak { ptr: self.ptr, alloc: self.alloc.clone() };
};
// See comments in Arc::clone() for why this is relaxed. This can use a
// fetch_add (ignoring the lock) because the weak count is only locked
// where are *no other* weak pointers in existence. (So we can't be
// running this code in that case).
let old_size = inner.weak.fetch_add(1, Relaxed);
if let Some(inner) = self.inner() {
// See comments in Arc::clone() for why this is relaxed. This can use a
// fetch_add (ignoring the lock) because the weak count is only locked
// where are *no other* weak pointers in existence. (So we can't be
// running this code in that case).
let old_size = inner.weak.fetch_add(1, Relaxed);
// See comments in Arc::clone() for why we do this (for mem::forget).
if old_size > MAX_REFCOUNT {
abort();
// See comments in Arc::clone() for why we do this (for mem::forget).
if old_size > MAX_REFCOUNT {
abort();
}
}
Weak { ptr: self.ptr, alloc: self.alloc.clone() }