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| author | Joshua Wong <joshuawong@anticentri.st> | 2024-10-09 14:24:05 -0400 |
|---|---|---|
| committer | Joshua Wong <joshuawong@anticentri.st> | 2024-10-10 09:50:35 -0400 |
| commit | 5e474f7d83fc931f355cfdadf394313e57290050 (patch) | |
| tree | cd5470a173b6c0b02b29338104e98ccef0aa99cc | |
| parent | dd0620b86721ae8cae86736443acd3f72ba6fc32 (diff) | |
| download | rust-5e474f7d83fc931f355cfdadf394313e57290050.tar.gz rust-5e474f7d83fc931f355cfdadf394313e57290050.zip | |
allocate before calling T::default in <Arc<T>>::default()
Same rationale as in the previous commit.
| -rw-r--r-- | library/alloc/src/lib.rs | 1 | ||||
| -rw-r--r-- | library/alloc/src/sync.rs | 8 | ||||
| -rw-r--r-- | tests/codegen/placement-new.rs | 4 |
3 files changed, 10 insertions, 3 deletions
diff --git a/library/alloc/src/lib.rs b/library/alloc/src/lib.rs index c60c0743c7e..dcfe96be755 100644 --- a/library/alloc/src/lib.rs +++ b/library/alloc/src/lib.rs @@ -104,6 +104,7 @@ #![feature(async_closure)] #![feature(async_fn_traits)] #![feature(async_iterator)] +#![feature(box_uninit_write)] #![feature(clone_to_uninit)] #![feature(coerce_unsized)] #![feature(const_align_of_val)] diff --git a/library/alloc/src/sync.rs b/library/alloc/src/sync.rs index 5d099a49854..0038750d25d 100644 --- a/library/alloc/src/sync.rs +++ b/library/alloc/src/sync.rs @@ -3447,7 +3447,13 @@ impl<T: Default> Default for Arc<T> { /// assert_eq!(*x, 0); /// ``` fn default() -> Arc<T> { - Arc::new(Default::default()) + let x = Box::into_raw(Box::write(Box::new_uninit(), ArcInner { + strong: atomic::AtomicUsize::new(1), + weak: atomic::AtomicUsize::new(1), + data: T::default(), + })); + // SAFETY: `Box::into_raw` consumes the `Box` and never returns null + unsafe { Self::from_inner(NonNull::new_unchecked(x)) } } } diff --git a/tests/codegen/placement-new.rs b/tests/codegen/placement-new.rs index d5c7969dd19..edb25df5eb4 100644 --- a/tests/codegen/placement-new.rs +++ b/tests/codegen/placement-new.rs @@ -19,9 +19,9 @@ pub fn box_default_inplace() -> Box<(String, String)> { // CHECK-LABEL: @arc_default_inplace #[no_mangle] pub fn arc_default_inplace() -> Arc<(String, String)> { - // CHECK: [[ALLOCA:%.*]] = alloca + // CHECK-NOT: alloca // CHECK: [[ARC:%.*]] = {{.*}}call {{.*}}__rust_alloc( - // CHECK: call void @llvm.memcpy + // CHECK-NOT: call void @llvm.memcpy // CHECK: ret ptr [[ARC]] Arc::default() } |