Changes to GlobalAlloc

src/doc/unstable-book/src/language-features/global-allocator.md

@@ -29,17 +29,17 @@ looks like:
 ```rust
 #![feature(global_allocator, allocator_api, heap_api)]
 
-use std::alloc::{GlobalAlloc, System, Layout, Opaque};
+use std::alloc::{AllocErr, GlobalAlloc, System, Layout, Opaque};
 use std::ptr::NonNull;
 
 struct MyAllocator;
 
 unsafe impl GlobalAlloc for MyAllocator {
-    unsafe fn alloc(&self, layout: Layout) -> *mut Opaque {
+    unsafe fn alloc(&self, layout: Layout) -> Result<NonNull<Opaque>, AllocErr> {
         System.alloc(layout)
     }
 
-    unsafe fn dealloc(&self, ptr: *mut Opaque, layout: Layout) {
+    unsafe fn dealloc(&self, ptr: NonNull<Opaque>, layout: Layout) {
         System.dealloc(ptr, layout)
     }
 }
@@ -55,18 +55,15 @@ fn main() {
 ```
 
 And that's it! The `#[global_allocator]` attribute is applied to a `static`
-which implements the `Alloc` trait in the `std::alloc` module. Note, though,
-that the implementation is defined for `&MyAllocator`, not just `MyAllocator`.
-You may wish, however, to also provide `Alloc for MyAllocator` for other use
-cases.
+which implements the `GlobalAlloc` trait in the `std::alloc` module.
 
 A crate can only have one instance of `#[global_allocator]` and this instance
 may be loaded through a dependency. For example `#[global_allocator]` above
 could have been placed in one of the dependencies loaded through `extern crate`.
 
-Note that `Alloc` itself is an `unsafe` trait, with much documentation on the
-trait itself about usage and for implementors. Extra care should be taken when
-implementing a global allocator as well as the allocator may be called from many
-portions of the standard library, such as the panicking routine. As a result it
-is highly recommended to not panic during allocation and work in as many
-situations with as few dependencies as possible as well.
+Note that `GlobalAlloc` itself is an `unsafe` trait, with much documentation on
+the trait itself about usage and for implementors. Extra care should be taken
+when implementing a global allocator as well as the allocator may be called from
+many portions of the standard library, such as the panicking routine. As a
+result it is highly recommended to not panic during allocation and work in as
+many situations with as few dependencies as possible as well.

src/liballoc/alloc.rs

@@ -51,38 +51,46 @@ pub const Heap: Global = Global;
 
 unsafe impl GlobalAlloc for Global {
     #[inline]
-    unsafe fn alloc(&self, layout: Layout) -> *mut Opaque {
-        let ptr = __rust_alloc(layout.size(), layout.align());
-        ptr as *mut Opaque
+    unsafe fn alloc(&self, layout: Layout) -> Result<NonNull<Opaque>, AllocErr> {
+        NonNull::new(__rust_alloc(layout.size(), layout.align()) as *mut Opaque).ok_or(AllocErr)
     }
 
     #[inline]
-    unsafe fn dealloc(&self, ptr: *mut Opaque, layout: Layout) {
-        __rust_dealloc(ptr as *mut u8, layout.size(), layout.align())
+    unsafe fn dealloc(&self, ptr: NonNull<Opaque>, layout: Layout) {
+        __rust_dealloc(ptr.as_ptr() as *mut u8, layout.size(), layout.align())
     }
 
     #[inline]
-    unsafe fn realloc(&self, ptr: *mut Opaque, layout: Layout, new_size: usize) -> *mut Opaque {
-        let ptr = __rust_realloc(ptr as *mut u8, layout.size(), layout.align(), new_size);
-        ptr as *mut Opaque
+    unsafe fn realloc(
+        &self,
+        ptr: NonNull<Opaque>,
+        layout: Layout,
+        new_size: usize,
+    ) -> Result<NonNull<Opaque>, AllocErr> {
+        NonNull::new(__rust_realloc(
+            ptr.as_ptr() as *mut u8,
+            layout.size(),
+            layout.align(),
+            new_size,
+        ) as *mut Opaque).ok_or(AllocErr)
     }
 
     #[inline]
-    unsafe fn alloc_zeroed(&self, layout: Layout) -> *mut Opaque {
-        let ptr = __rust_alloc_zeroed(layout.size(), layout.align());
-        ptr as *mut Opaque
+    unsafe fn alloc_zeroed(&self, layout: Layout) -> Result<NonNull<Opaque>, AllocErr> {
+        NonNull::new(__rust_alloc_zeroed(layout.size(), layout.align()) as *mut Opaque)
+            .ok_or(AllocErr)
     }
 }
 
 unsafe impl Alloc for Global {
     #[inline]
     unsafe fn alloc(&mut self, layout: Layout) -> Result<NonNull<Opaque>, AllocErr> {
-        NonNull::new(GlobalAlloc::alloc(self, layout)).ok_or(AllocErr)
+        GlobalAlloc::alloc(self, layout)
     }
 
     #[inline]
     unsafe fn dealloc(&mut self, ptr: NonNull<Opaque>, layout: Layout) {
-        GlobalAlloc::dealloc(self, ptr.as_ptr(), layout)
+        GlobalAlloc::dealloc(self, ptr, layout)
     }
 
     #[inline]
@@ -92,12 +100,12 @@ unsafe impl Alloc for Global {
                       new_size: usize)
                       -> Result<NonNull<Opaque>, AllocErr>
     {
-        NonNull::new(GlobalAlloc::realloc(self, ptr.as_ptr(), layout, new_size)).ok_or(AllocErr)
+        GlobalAlloc::realloc(self, ptr, layout, new_size)
     }
 
     #[inline]
     unsafe fn alloc_zeroed(&mut self, layout: Layout) -> Result<NonNull<Opaque>, AllocErr> {
-        NonNull::new(GlobalAlloc::alloc_zeroed(self, layout)).ok_or(AllocErr)
+        GlobalAlloc::alloc_zeroed(self, layout)
     }
 }
 
@@ -111,25 +119,22 @@ unsafe fn exchange_malloc(size: usize, align: usize) -> *mut u8 {
         align as *mut u8
     } else {
         let layout = Layout::from_size_align_unchecked(size, align);
-        let ptr = Global.alloc(layout);
-        if !ptr.is_null() {
-            ptr as *mut u8
-        } else {
-            oom(layout)
+        match Global.alloc(layout) {
+            Ok(p) => p.as_ptr() as *mut u8,
+            Err(_) => oom(layout),
         }
     }
 }
 
 #[cfg_attr(not(test), lang = "box_free")]
 #[inline]
 pub(crate) unsafe fn box_free<T: ?Sized>(ptr: Unique<T>) {
-    let ptr = ptr.as_ptr();
-    let size = size_of_val(&*ptr);
-    let align = min_align_of_val(&*ptr);
+    let size = size_of_val(ptr.as_ref());
+    let align = min_align_of_val(ptr.as_ref());
     // We do not allocate for Box<T> when T is ZST, so deallocation is also not necessary.
     if size != 0 {
         let layout = Layout::from_size_align_unchecked(size, align);
-        Global.dealloc(ptr as *mut Opaque, layout);
+        Global.dealloc(NonNull::from(ptr).cast(), layout);
     }
 }
 

src/liballoc/arc.rs

@@ -518,7 +518,7 @@ impl<T: ?Sized> Arc<T> {
 
         if self.inner().weak.fetch_sub(1, Release) == 1 {
             atomic::fence(Acquire);
-            Global.dealloc(self.ptr.as_opaque(), Layout::for_value(self.ptr.as_ref()))
+            Global.dealloc(self.ptr.cast(), Layout::for_value(self.ptr.as_ref()))
         }
     }
 
@@ -638,7 +638,7 @@ impl<T: Clone> ArcFromSlice<T> for Arc<[T]> {
                     let slice = from_raw_parts_mut(self.elems, self.n_elems);
                     ptr::drop_in_place(slice);
 
-                    Global.dealloc(self.mem.as_opaque(), self.layout.clone());
+                    Global.dealloc(self.mem.cast(), self.layout.clone());
                 }
             }
         }
@@ -1157,7 +1157,7 @@ impl<T: ?Sized> Drop for Weak<T> {
         if self.inner().weak.fetch_sub(1, Release) == 1 {
             atomic::fence(Acquire);
             unsafe {
-                Global.dealloc(self.ptr.as_opaque(), Layout::for_value(self.ptr.as_ref()))
+                Global.dealloc(self.ptr.cast(), Layout::for_value(self.ptr.as_ref()))
             }
         }
     }

src/liballoc/btree/node.rs

@@ -287,7 +287,7 @@ impl<K, V> Root<K, V> {
         self.as_mut().as_leaf_mut().parent = ptr::null();
 
         unsafe {
-            Global.dealloc(NonNull::from(top).as_opaque(), Layout::new::<InternalNode<K, V>>());
+            Global.dealloc(NonNull::from(top).cast(), Layout::new::<InternalNode<K, V>>());
         }
     }
 }
@@ -478,7 +478,7 @@ impl<K, V> NodeRef<marker::Owned, K, V, marker::Leaf> {
         debug_assert!(!self.is_shared_root());
         let node = self.node;
         let ret = self.ascend().ok();
-        Global.dealloc(node.as_opaque(), Layout::new::<LeafNode<K, V>>());
+        Global.dealloc(node.cast(), Layout::new::<LeafNode<K, V>>());
         ret
     }
 }
@@ -499,7 +499,7 @@ impl<K, V> NodeRef<marker::Owned, K, V, marker::Internal> {
     > {
         let node = self.node;
         let ret = self.ascend().ok();
-        Global.dealloc(node.as_opaque(), Layout::new::<InternalNode<K, V>>());
+        Global.dealloc(node.cast(), Layout::new::<InternalNode<K, V>>());
         ret
     }
 }
@@ -1321,12 +1321,12 @@ impl<'a, K, V> Handle<NodeRef<marker::Mut<'a>, K, V, marker::Internal>, marker::
                 }
 
                 Global.dealloc(
-                    right_node.node.as_opaque(),
+                    right_node.node.cast(),
                     Layout::new::<InternalNode<K, V>>(),
                 );
             } else {
                 Global.dealloc(
-                    right_node.node.as_opaque(),
+                    right_node.node.cast(),
                     Layout::new::<LeafNode<K, V>>(),
                 );
             }

src/liballoc/raw_vec.rs

@@ -93,7 +93,7 @@ impl<T, A: Alloc> RawVec<T, A> {
 
             // handles ZSTs and `cap = 0` alike
             let ptr = if alloc_size == 0 {
-                NonNull::<T>::dangling().as_opaque()
+                NonNull::<T>::dangling().cast()
             } else {
                 let align = mem::align_of::<T>();
                 let layout = Layout::from_size_align(alloc_size, align).unwrap();
@@ -314,7 +314,7 @@ impl<T, A: Alloc> RawVec<T, A> {
                     let new_cap = 2 * self.cap;
                     let new_size = new_cap * elem_size;
                     alloc_guard(new_size).unwrap_or_else(|_| capacity_overflow());
-                    let ptr_res = self.a.realloc(NonNull::from(self.ptr).as_opaque(),
+                    let ptr_res = self.a.realloc(NonNull::from(self.ptr).cast(),
                                                  cur,
                                                  new_size);
                     match ptr_res {
@@ -373,7 +373,7 @@ impl<T, A: Alloc> RawVec<T, A> {
             let new_cap = 2 * self.cap;
             let new_size = new_cap * elem_size;
             alloc_guard(new_size).unwrap_or_else(|_| capacity_overflow());
-            match self.a.grow_in_place(NonNull::from(self.ptr).as_opaque(), old_layout, new_size) {
+            match self.a.grow_in_place(NonNull::from(self.ptr).cast(), old_layout, new_size) {
                 Ok(_) => {
                     // We can't directly divide `size`.
                     self.cap = new_cap;
@@ -546,7 +546,7 @@ impl<T, A: Alloc> RawVec<T, A> {
             // FIXME: may crash and burn on over-reserve
             alloc_guard(new_layout.size()).unwrap_or_else(|_| capacity_overflow());
             match self.a.grow_in_place(
-                NonNull::from(self.ptr).as_opaque(), old_layout, new_layout.size(),
+                NonNull::from(self.ptr).cast(), old_layout, new_layout.size(),
             ) {
                 Ok(_) => {
                     self.cap = new_cap;
@@ -607,7 +607,7 @@ impl<T, A: Alloc> RawVec<T, A> {
                 let new_size = elem_size * amount;
                 let align = mem::align_of::<T>();
                 let old_layout = Layout::from_size_align_unchecked(old_size, align);
-                match self.a.realloc(NonNull::from(self.ptr).as_opaque(),
+                match self.a.realloc(NonNull::from(self.ptr).cast(),
                                      old_layout,
                                      new_size) {
                     Ok(p) => self.ptr = p.cast().into(),
@@ -667,7 +667,7 @@ impl<T, A: Alloc> RawVec<T, A> {
             let res = match self.current_layout() {
                 Some(layout) => {
                     debug_assert!(new_layout.align() == layout.align());
-                    self.a.realloc(NonNull::from(self.ptr).as_opaque(), layout, new_layout.size())
+                    self.a.realloc(NonNull::from(self.ptr).cast(), layout, new_layout.size())
                 }
                 None => self.a.alloc(new_layout),
             };
@@ -710,7 +710,7 @@ impl<T, A: Alloc> RawVec<T, A> {
         let elem_size = mem::size_of::<T>();
         if elem_size != 0 {
             if let Some(layout) = self.current_layout() {
-                self.a.dealloc(NonNull::from(self.ptr).as_opaque(), layout);
+                self.a.dealloc(NonNull::from(self.ptr).cast(), layout);
             }
         }
     }

src/liballoc/rc.rs

@@ -845,7 +845,7 @@ unsafe impl<#[may_dangle] T: ?Sized> Drop for Rc<T> {
                 self.dec_weak();
 
                 if self.weak() == 0 {
-                    Global.dealloc(self.ptr.as_opaque(), Layout::for_value(self.ptr.as_ref()));
+                    Global.dealloc(self.ptr.cast(), Layout::for_value(self.ptr.as_ref()));
                 }
             }
         }
@@ -1269,7 +1269,7 @@ impl<T: ?Sized> Drop for Weak<T> {
             // the weak count starts at 1, and will only go to zero if all
             // the strong pointers have disappeared.
             if self.weak() == 0 {
-                Global.dealloc(self.ptr.as_opaque(), Layout::for_value(self.ptr.as_ref()));
+                Global.dealloc(self.ptr.cast(), Layout::for_value(self.ptr.as_ref()));
             }
         }
     }