Auto merge of #70362 - TimDiekmann:alloc-overhaul, r=Amanieu

Overhaul of the `AllocRef` trait to match allocator-wg's latest consens; Take 2

GitHub won't let me reopen #69889 so I make a new PR.

In addition to #69889 this fixes the unsoundness of `RawVec::into_box` when using allocators supporting overallocating. Also it uses `MemoryBlock` in `AllocRef` to unify `_in_place` methods by passing `&mut MemoryBlock`. Additionally, `RawVec` now checks for `size_of::<T>()` again and ignore every ZST. The internal capacity of `RawVec` isn't used by ZSTs anymore, as `into_box` now requires a length to be specified.

r? @Amanieu

fixes rust-lang/wg-allocators#38
fixes rust-lang/wg-allocators#41
fixes rust-lang/wg-allocators#44
fixes rust-lang/wg-allocators#51

1 files changed, 5 insertions, 3 deletions

diff --git a/src/liballoc/sync.rs b/src/liballoc/sync.rs
index e8985e20256..111a7651b5e 100644
--- a/src/liballoc/sync.rs
+++ b/src/liballoc/sync.rs
@@ -25,7 +25,7 @@ use core::sync::atomic;
 use core::sync::atomic::Ordering::{Acquire, Relaxed, Release, SeqCst};
 use core::{isize, usize};
 
-use crate::alloc::{box_free, handle_alloc_error, AllocRef, Global, Layout};
+use crate::alloc::{box_free, handle_alloc_error, AllocInit, AllocRef, Global, Layout};
 use crate::boxed::Box;
 use crate::rc::is_dangling;
 use crate::string::String;
@@ -814,10 +814,12 @@ impl<T: ?Sized> Arc<T> {
         // reference (see #54908).
         let layout = Layout::new::<ArcInner<()>>().extend(value_layout).unwrap().0.pad_to_align();
 
-        let (mem, _) = Global.alloc(layout).unwrap_or_else(|_| handle_alloc_error(layout));
+        let mem = Global
+            .alloc(layout, AllocInit::Uninitialized)
+            .unwrap_or_else(|_| handle_alloc_error(layout));
 
         // Initialize the ArcInner
-        let inner = mem_to_arcinner(mem.as_ptr());
+        let inner = mem_to_arcinner(mem.ptr.as_ptr());
         debug_assert_eq!(Layout::for_value(&*inner), layout);
 
         ptr::write(&mut (*inner).strong, atomic::AtomicUsize::new(1));