Update to use the new allocator APIs.

Author: Mark-Simulacrum

src/destructors.md

@@ -26,24 +26,23 @@ this is totally fine.
 For instance, a custom implementation of `Box` might write `Drop` like this:
 
 ```rust
-#![feature(alloc, heap_api, unique)]
+#![feature(alloc, heap_api, unique, allocator_api)]
 
 extern crate alloc;
 
 use std::ptr::{drop_in_place, Unique};
 use std::mem;
 
-use alloc::heap;
+use alloc::allocator::{Layout, Alloc};
+use alloc::heap::Heap;
 
 struct Box<T>{ ptr: Unique<T> }
 
 impl<T> Drop for Box<T> {
     fn drop(&mut self) {
         unsafe {
             drop_in_place(self.ptr.as_ptr());
-            heap::deallocate(self.ptr.as_ptr() as *mut u8,
-                             mem::size_of::<T>(),
-                             mem::align_of::<T>());
+            Heap.dealloc(self.ptr.as_ptr() as *mut u8, Layout::new::<T>())
         }
     }
 }
@@ -57,24 +56,23 @@ use-after-free the `ptr` because when drop exits, it becomes inaccessible.
 However this wouldn't work:
 
 ```rust
-#![feature(alloc, heap_api, unique)]
+#![feature(alloc, allocator_api, heap_api, unique)]
 
 extern crate alloc;
 
 use std::ptr::{drop_in_place, Unique};
 use std::mem;
 
-use alloc::heap;
+use alloc::allocator::{Layout, Alloc};
+use alloc::heap::Heap;
 
 struct Box<T>{ ptr: Unique<T> }
 
 impl<T> Drop for Box<T> {
     fn drop(&mut self) {
         unsafe {
             drop_in_place(self.ptr.as_ptr());
-            heap::deallocate(self.ptr.as_ptr() as *mut u8,
-                             mem::size_of::<T>(),
-                             mem::align_of::<T>());
+            Heap.dealloc(self.ptr.as_ptr() as *mut u8, Layout::new::<T>());
         }
     }
 }
@@ -86,9 +84,7 @@ impl<T> Drop for SuperBox<T> {
         unsafe {
             // Hyper-optimized: deallocate the box's contents for it
             // without `drop`ing the contents
-            heap::deallocate(self.my_box.ptr.as_ptr() as *mut u8,
-                             mem::size_of::<T>(),
-                             mem::align_of::<T>());
+            Heap.dealloc(self.my_box.ptr.as_ptr() as *mut u8, Layout::new::<T>());
         }
     }
 }
@@ -135,24 +131,23 @@ The classic safe solution to overriding recursive drop and allowing moving out
 of Self during `drop` is to use an Option:
 
 ```rust
-#![feature(alloc, heap_api, unique)]
+#![feature(alloc, allocator_api, heap_api, unique)]
 
 extern crate alloc;
 
 use std::ptr::{drop_in_place, Unique};
 use std::mem;
 
-use alloc::heap;
+use alloc::allocator::{Layout, Alloc};
+use alloc::heap::Heap;
 
 struct Box<T>{ ptr: Unique<T> }
 
 impl<T> Drop for Box<T> {
     fn drop(&mut self) {
         unsafe {
             drop_in_place(self.ptr.as_ptr());
-            heap::deallocate(self.ptr.as_ptr() as *mut u8,
-                             mem::size_of::<T>(),
-                             mem::align_of::<T>());
+            Heap.dealloc(self.ptr.as_ptr() as *mut u8, Layout::new::<T>());
         }
     }
 }
@@ -166,9 +161,7 @@ impl<T> Drop for SuperBox<T> {
             // without `drop`ing the contents. Need to set the `box`
             // field as `None` to prevent Rust from trying to Drop it.
             let my_box = self.my_box.take().unwrap();
-            heap::deallocate(my_box.ptr.as_ptr() as *mut u8,
-                             mem::size_of::<T>(),
-                             mem::align_of::<T>());
+            Heap.dealloc(my_box.ptr.as_ptr() as *mut u8, Layout::new::<T>());
             mem::forget(my_box);
         }
     }

src/vec-final.md

@@ -2,7 +2,7 @@
 
 ```rust
 #![feature(unique)]
-#![feature(alloc, heap_api)]
+#![feature(alloc, allocator_api, heap_api)]
 
 extern crate alloc;
 
@@ -11,7 +11,8 @@ use std::mem;
 use std::ops::{Deref, DerefMut};
 use std::marker::PhantomData;
 
-use alloc::heap;
+use alloc::allocator::{Layout, Alloc};
+use alloc::heap::Heap;
 
 struct RawVec<T> {
     ptr: Unique<T>,
@@ -35,22 +36,22 @@ impl<T> RawVec<T> {
             // 0, getting to here necessarily means the Vec is overfull.
             assert!(elem_size != 0, "capacity overflow");
 
-            let align = mem::align_of::<T>();
-
             let (new_cap, ptr) = if self.cap == 0 {
-                let ptr = heap::allocate(elem_size, align);
+                let ptr = Heap.alloc(Layout::array::<T>(1).unwrap());
                 (1, ptr)
             } else {
                 let new_cap = 2 * self.cap;
-                let ptr = heap::reallocate(self.ptr.as_ptr() as *mut _,
-                                            self.cap * elem_size,
-                                            new_cap * elem_size,
-                                            align);
+                let ptr = Heap.realloc(self.ptr.as_ptr() as *mut _,
+                                       Layout::array::<T>(self.cap).unwrap(),
+                                       Layout::array::<T>(new_cap).unwrap());
                 (new_cap, ptr)
             };
 
-            // If allocate or reallocate fail, we'll get `null` back
-            if ptr.is_null() { oom() }
+            // If allocate or reallocate fail, oom
+            let ptr = match ptr {
+                Ok(ptr) => ptr,
+                Err(err) => Heap.oom(err),
+            };
 
             self.ptr = Unique::new(ptr as *mut _);
             self.cap = new_cap;
@@ -62,11 +63,8 @@ impl<T> Drop for RawVec<T> {
     fn drop(&mut self) {
         let elem_size = mem::size_of::<T>();
         if self.cap != 0 && elem_size != 0 {
-            let align = mem::align_of::<T>();
-
-            let num_bytes = elem_size * self.cap;
             unsafe {
-                heap::deallocate(self.ptr.as_ptr() as *mut _, num_bytes, align);
+                Heap.dealloc(self.ptr.as_ptr() as *mut _, Layout::array::<T>(self.cap).unwrap());
             }
         }
     }