rustc: Implement the #[global_allocator] attribute

This PR is an implementation of [RFC 1974] which specifies a new method of
defining a global allocator for a program. This obsoletes the old
`#![allocator]` attribute and also removes support for it.

[RFC 1974]: https://github.com/rust-lang/rfcs/pull/197

The new `#[global_allocator]` attribute solves many issues encountered with the
`#![allocator]` attribute such as composition and restrictions on the crate
graph itself. The compiler now has much more control over the ABI of the
allocator and how it's implemented, allowing much more freedom in terms of how
this feature is implemented.

cc #27389

1 files changed, 8 insertions, 18 deletions

diff --git a/src/liballoc/btree/node.rs b/src/liballoc/btree/node.rs
index 811174b331e..0eaff6f2192 100644
--- a/src/liballoc/btree/node.rs
+++ b/src/liballoc/btree/node.rs
@@ -48,7 +48,7 @@ use core::ptr::{self, Unique};
 use core::slice;
 
 use boxed::Box;
-use heap;
+use heap::{Heap, Alloc, Layout};
 
 const B: usize = 6;
 pub const MIN_LEN: usize = B - 1;
@@ -254,11 +254,7 @@ impl<K, V> Root<K, V> {
         self.as_mut().as_leaf_mut().parent = ptr::null();
 
         unsafe {
-            heap::deallocate(
-                top,
-                mem::size_of::<InternalNode<K, V>>(),
-                mem::align_of::<InternalNode<K, V>>()
-            );
+            Heap.dealloc(top, Layout::new::<InternalNode<K, V>>());
         }
     }
 }
@@ -445,7 +441,7 @@ impl<K, V> NodeRef<marker::Owned, K, V, marker::Leaf> {
     > {
         let ptr = self.as_leaf() as *const LeafNode<K, V> as *const u8 as *mut u8;
         let ret = self.ascend().ok();
-        heap::deallocate(ptr, mem::size_of::<LeafNode<K, V>>(), mem::align_of::<LeafNode<K, V>>());
+        Heap.dealloc(ptr, Layout::new::<LeafNode<K, V>>());
         ret
     }
 }
@@ -466,11 +462,7 @@ impl<K, V> NodeRef<marker::Owned, K, V, marker::Internal> {
     > {
         let ptr = self.as_internal() as *const InternalNode<K, V> as *const u8 as *mut u8;
         let ret = self.ascend().ok();
-        heap::deallocate(
-            ptr,
-            mem::size_of::<InternalNode<K, V>>(),
-            mem::align_of::<InternalNode<K, V>>()
-        );
+        Heap.dealloc(ptr, Layout::new::<InternalNode<K, V>>());
         ret
     }
 }
@@ -1252,16 +1244,14 @@ impl<'a, K, V> Handle<NodeRef<marker::Mut<'a>, K, V, marker::Internal>, marker::
                     ).correct_parent_link();
                 }
 
-                heap::deallocate(
+                Heap.dealloc(
                     right_node.node.get() as *mut u8,
-                    mem::size_of::<InternalNode<K, V>>(),
-                    mem::align_of::<InternalNode<K, V>>()
+                    Layout::new::<InternalNode<K, V>>(),
                 );
             } else {
-                heap::deallocate(
+                Heap.dealloc(
                     right_node.node.get() as *mut u8,
-                    mem::size_of::<LeafNode<K, V>>(),
-                    mem::align_of::<LeafNode<K, V>>()
+                    Layout::new::<LeafNode<K, V>>(),
                 );
             }