Stabilize dyn subset of Allocator as core::alloc::Alloc

Author: jmillikin

library/alloc/src/alloc.rs

@@ -45,13 +45,10 @@ unsafe extern "Rust" {
 
 /// The global memory allocator.
 ///
-/// This type implements the [`Allocator`] trait by forwarding calls
+/// This type implements the [`Alloc`] trait by forwarding calls
 /// to the allocator registered with the `#[global_allocator]` attribute
 /// if there is one, or the `std` crate’s default.
-///
-/// Note: while this type is unstable, the functionality it provides can be
-/// accessed through the [free functions in `alloc`](self#functions).
-#[unstable(feature = "allocator_api", issue = "32838")]
+#[stable(feature = "allocator_api_mvp", since = "CURRENT_RUSTC_VERSION")]
 #[derive(Copy, Clone, Default, Debug)]
 // the compiler needs to know when a Box uses the global allocator vs a custom one
 #[lang = "global_alloc_ty"]
@@ -202,14 +199,14 @@ pub unsafe fn alloc_zeroed(layout: Layout) -> *mut u8 {
 impl Global {
     #[inline]
     #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
-    fn alloc_impl_runtime(layout: Layout, zeroed: bool) -> Result<NonNull<[u8]>, AllocError> {
+    fn alloc_impl_runtime(layout: Layout, zeroed: bool) -> Result<NonNull<u8>, AllocError> {
         match layout.size() {
-            0 => Ok(layout.dangling_ptr().cast_slice(0)),
+            0 => Ok(layout.dangling_ptr()),
             // SAFETY: `layout` is non-zero in size,
-            size => unsafe {
+            _ => unsafe {
                 let raw_ptr = if zeroed { alloc_zeroed(layout) } else { alloc(layout) };
                 let ptr = NonNull::new(raw_ptr).ok_or(AllocError)?;
-                Ok(ptr.cast_slice(size))
+                Ok(ptr)
             },
         }
     }
@@ -224,13 +221,13 @@ impl Global {
             //   "fit" always means a layout that is equal to the original, because our
             //   `allocate()`, `grow()`, and `shrink()` implementations never returns a larger
             //   allocation than requested.
-            // * Other conditions must be upheld by the caller, as per `Allocator::deallocate()`'s
+            // * Other conditions must be upheld by the caller, as per `Alloc::deallocate()`'s
             //   safety documentation.
             unsafe { dealloc_nonnull(ptr, layout) }
         }
     }
 
-    // SAFETY: Same as `Allocator::grow`
+    // SAFETY: Same as `Alloc::grow`
     #[inline]
     #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
     fn grow_impl_runtime(
@@ -239,7 +236,7 @@ impl Global {
         old_layout: Layout,
         new_layout: Layout,
         zeroed: bool,
-    ) -> Result<NonNull<[u8]>, AllocError> {
+    ) -> Result<NonNull<u8>, AllocError> {
         debug_assert!(
             new_layout.size() >= old_layout.size(),
             "`new_layout.size()` must be greater than or equal to `old_layout.size()`"
@@ -261,7 +258,7 @@ impl Global {
                 if zeroed {
                     raw_ptr.add(old_size).write_bytes(0, new_size - old_size);
                 }
-                Ok(ptr.cast_slice(new_size))
+                Ok(ptr)
             },
 
             // SAFETY: because `new_layout.size()` must be greater than or equal to `old_size`,
@@ -271,14 +268,14 @@ impl Global {
             // for `dealloc` must be upheld by the caller.
             old_size => unsafe {
                 let new_ptr = self.alloc_impl(new_layout, zeroed)?;
-                ptr::copy_nonoverlapping(ptr.as_ptr(), new_ptr.as_mut_ptr(), old_size);
+                ptr::copy_nonoverlapping(ptr.as_ptr(), new_ptr.as_ptr(), old_size);
                 self.deallocate(ptr, old_layout);
                 Ok(new_ptr)
             },
         }
     }
 
-    // SAFETY: Same as `Allocator::grow`
+    // SAFETY: Same as `Alloc::grow`
     #[inline]
     #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
     fn shrink_impl_runtime(
@@ -287,7 +284,7 @@ impl Global {
         old_layout: Layout,
         new_layout: Layout,
         _zeroed: bool,
-    ) -> Result<NonNull<[u8]>, AllocError> {
+    ) -> Result<NonNull<u8>, AllocError> {
         debug_assert!(
             new_layout.size() <= old_layout.size(),
             "`new_layout.size()` must be smaller than or equal to `old_layout.size()`"
@@ -297,7 +294,7 @@ impl Global {
             // SAFETY: conditions must be upheld by the caller
             0 => unsafe {
                 self.deallocate(ptr, old_layout);
-                Ok(new_layout.dangling_ptr().cast_slice(0))
+                Ok(new_layout.dangling_ptr())
             },
 
             // SAFETY: `new_size` is non-zero. Other conditions must be upheld by the caller
@@ -307,7 +304,7 @@ impl Global {
 
                 let raw_ptr = realloc_nonnull(ptr, old_layout, new_size);
                 let ptr = NonNull::new(raw_ptr).ok_or(AllocError)?;
-                Ok(ptr.cast_slice(new_size))
+                Ok(ptr)
             },
 
             // SAFETY: because `new_size` must be smaller than or equal to `old_layout.size()`,
@@ -317,26 +314,26 @@ impl Global {
             // for `dealloc` must be upheld by the caller.
             new_size => unsafe {
                 let new_ptr = self.allocate(new_layout)?;
-                ptr::copy_nonoverlapping(ptr.as_ptr(), new_ptr.as_mut_ptr(), new_size);
+                ptr::copy_nonoverlapping(ptr.as_ptr(), new_ptr.as_ptr(), new_size);
                 self.deallocate(ptr, old_layout);
                 Ok(new_ptr)
             },
         }
     }
 
-    // SAFETY: Same as `Allocator::allocate`
+    // SAFETY: Same as `Alloc::allocate`
     #[inline]
     #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
     #[rustc_const_unstable(feature = "const_heap", issue = "79597")]
-    const fn alloc_impl(&self, layout: Layout, zeroed: bool) -> Result<NonNull<[u8]>, AllocError> {
+    const fn alloc_impl(&self, layout: Layout, zeroed: bool) -> Result<NonNull<u8>, AllocError> {
         core::intrinsics::const_eval_select(
             (layout, zeroed),
             Global::alloc_impl_const,
             Global::alloc_impl_runtime,
         )
     }
 
-    // SAFETY: Same as `Allocator::deallocate`
+    // SAFETY: Same as `Alloc::deallocate`
     #[inline]
     #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
     #[rustc_const_unstable(feature = "const_heap", issue = "79597")]
@@ -348,7 +345,7 @@ impl Global {
         )
     }
 
-    // SAFETY: Same as `Allocator::grow`
+    // SAFETY: Same as `Alloc::grow`
     #[inline]
     #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
     #[rustc_const_unstable(feature = "const_heap", issue = "79597")]
@@ -358,15 +355,15 @@ impl Global {
         old_layout: Layout,
         new_layout: Layout,
         zeroed: bool,
-    ) -> Result<NonNull<[u8]>, AllocError> {
+    ) -> Result<NonNull<u8>, AllocError> {
         core::intrinsics::const_eval_select(
             (self, ptr, old_layout, new_layout, zeroed),
             Global::grow_shrink_impl_const,
             Global::grow_impl_runtime,
         )
     }
 
-    // SAFETY: Same as `Allocator::shrink`
+    // SAFETY: Same as `Alloc::shrink`
     #[inline]
     #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
     #[rustc_const_unstable(feature = "const_heap", issue = "79597")]
@@ -375,7 +372,7 @@ impl Global {
         ptr: NonNull<u8>,
         old_layout: Layout,
         new_layout: Layout,
-    ) -> Result<NonNull<[u8]>, AllocError> {
+    ) -> Result<NonNull<u8>, AllocError> {
         core::intrinsics::const_eval_select(
             (self, ptr, old_layout, new_layout, false),
             Global::grow_shrink_impl_const,
@@ -386,9 +383,9 @@ impl Global {
     #[inline]
     #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
     #[rustc_const_unstable(feature = "const_heap", issue = "79597")]
-    const fn alloc_impl_const(layout: Layout, zeroed: bool) -> Result<NonNull<[u8]>, AllocError> {
+    const fn alloc_impl_const(layout: Layout, zeroed: bool) -> Result<NonNull<u8>, AllocError> {
         match layout.size() {
-            0 => Ok(layout.dangling_ptr().cast_slice(0)),
+            0 => Ok(layout.dangling_ptr()),
             // SAFETY: `layout` is non-zero in size,
             size => unsafe {
                 let raw_ptr = core::intrinsics::const_allocate(layout.size(), layout.align());
@@ -397,7 +394,7 @@ impl Global {
                     // SAFETY: the pointer returned by `const_allocate` is valid to write to.
                     ptr.write_bytes(0, size);
                 }
-                Ok(ptr.cast_slice(size))
+                Ok(ptr)
             },
         }
     }
@@ -423,13 +420,13 @@ impl Global {
         old_layout: Layout,
         new_layout: Layout,
         zeroed: bool,
-    ) -> Result<NonNull<[u8]>, AllocError> {
+    ) -> Result<NonNull<u8>, AllocError> {
         let new_ptr = self.alloc_impl(new_layout, zeroed)?;
         // SAFETY: both pointers are valid and this operations is in bounds.
         unsafe {
             ptr::copy_nonoverlapping(
                 ptr.as_ptr(),
-                new_ptr.as_mut_ptr(),
+                new_ptr.as_ptr(),
                 cmp::min(old_layout.size(), new_layout.size()),
             );
         }
@@ -440,18 +437,18 @@ impl Global {
     }
 }
 
-#[unstable(feature = "allocator_api", issue = "32838")]
+#[stable(feature = "allocator_api_mvp", since = "CURRENT_RUSTC_VERSION")]
 #[rustc_const_unstable(feature = "const_heap", issue = "79597")]
-const unsafe impl Allocator for Global {
+const unsafe impl Alloc for Global {
     #[inline]
     #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
-    fn allocate(&self, layout: Layout) -> Result<NonNull<[u8]>, AllocError> {
+    fn allocate(&self, layout: Layout) -> Result<NonNull<u8>, AllocError> {
         self.alloc_impl(layout, false)
     }
 
     #[inline]
     #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
-    fn allocate_zeroed(&self, layout: Layout) -> Result<NonNull<[u8]>, AllocError> {
+    fn allocate_zeroed(&self, layout: Layout) -> Result<NonNull<u8>, AllocError> {
         self.alloc_impl(layout, true)
     }
 
@@ -469,7 +466,7 @@ const unsafe impl Allocator for Global {
         ptr: NonNull<u8>,
         old_layout: Layout,
         new_layout: Layout,
-    ) -> Result<NonNull<[u8]>, AllocError> {
+    ) -> Result<NonNull<u8>, AllocError> {
         // SAFETY: all conditions must be upheld by the caller
         unsafe { self.grow_impl(ptr, old_layout, new_layout, false) }
     }
@@ -481,7 +478,7 @@ const unsafe impl Allocator for Global {
         ptr: NonNull<u8>,
         old_layout: Layout,
         new_layout: Layout,
-    ) -> Result<NonNull<[u8]>, AllocError> {
+    ) -> Result<NonNull<u8>, AllocError> {
         // SAFETY: all conditions must be upheld by the caller
         unsafe { self.grow_impl(ptr, old_layout, new_layout, true) }
     }
@@ -493,12 +490,16 @@ const unsafe impl Allocator for Global {
         ptr: NonNull<u8>,
         old_layout: Layout,
         new_layout: Layout,
-    ) -> Result<NonNull<[u8]>, AllocError> {
+    ) -> Result<NonNull<u8>, AllocError> {
         // SAFETY: all conditions must be upheld by the caller
         unsafe { self.shrink_impl(ptr, old_layout, new_layout) }
     }
 }
 
+#[unstable(feature = "allocator_api", issue = "32838")]
+#[rustc_const_unstable(feature = "const_heap", issue = "79597")]
+const unsafe impl Allocator for Global {}
+
 // # Allocation error handler
 
 #[cfg(not(no_global_oom_handling))]

library/alloc/src/boxed.rs

@@ -206,7 +206,7 @@ use core::task::{Context, Poll};
 
 #[cfg(not(no_global_oom_handling))]
 use crate::alloc::handle_alloc_error;
-use crate::alloc::{AllocError, Allocator, Global, Layout};
+use crate::alloc::{Alloc, AllocError, Allocator, Global, Layout};
 use crate::raw_vec::RawVec;
 #[cfg(not(no_global_oom_handling))]
 use crate::str::from_boxed_utf8_unchecked;
@@ -246,7 +246,7 @@ pub struct Box<
 #[cfg(not(no_global_oom_handling))]
 fn box_new_uninit(layout: Layout) -> *mut u8 {
     match Global.allocate(layout) {
-        Ok(ptr) => ptr.as_mut_ptr(),
+        Ok(ptr) => ptr.as_ptr(),
         Err(_) => handle_alloc_error(layout),
     }
 }
@@ -801,7 +801,6 @@ impl<T: ?Sized + CloneToUninit> Box<T> {
     ///
     /// ```
     /// #![feature(clone_from_ref)]
-    /// #![feature(allocator_api)]
     ///
     /// let hello: Box<str> = Box::try_clone_from_ref("hello")?;
     /// # Ok::<(), std::alloc::AllocError>(())
@@ -1537,12 +1536,12 @@ impl<T: ?Sized, A: Allocator> Box<T, A> {
     /// ```
     /// Manually create a `Box` from scratch by using the system allocator:
     /// ```
-    /// #![feature(allocator_api, slice_ptr_get)]
+    /// #![feature(allocator_api)]
     ///
-    /// use std::alloc::{Allocator, Layout, System};
+    /// use std::alloc::{Alloc, Layout, System};
     ///
     /// unsafe {
-    ///     let ptr = System.allocate(Layout::new::<i32>())?.as_mut_ptr() as *mut i32;
+    ///     let ptr = System.allocate(Layout::new::<i32>())?.as_ptr() as *mut i32;
     ///     // In general .write is required to avoid attempting to destruct
     ///     // the (uninitialized) previous contents of `ptr`, though for this
     ///     // simple example `*ptr = 5` would have worked as well.
@@ -1596,7 +1595,7 @@ impl<T: ?Sized, A: Allocator> Box<T, A> {
     /// ```
     /// #![feature(allocator_api)]
     ///
-    /// use std::alloc::{Allocator, Layout, System};
+    /// use std::alloc::{Alloc, Layout, System};
     ///
     /// unsafe {
     ///     let non_null = System.allocate(Layout::new::<i32>())?.cast::<i32>();
@@ -1651,7 +1650,7 @@ impl<T: ?Sized, A: Allocator> Box<T, A> {
     /// ```
     /// #![feature(allocator_api)]
     ///
-    /// use std::alloc::{Allocator, Layout, System};
+    /// use std::alloc::{Alloc, Layout, System};
     /// use std::ptr::{self, NonNull};
     ///
     /// let x = Box::new_in(String::from("Hello"), System);
@@ -1713,7 +1712,7 @@ impl<T: ?Sized, A: Allocator> Box<T, A> {
     /// ```
     /// #![feature(allocator_api)]
     ///
-    /// use std::alloc::{Allocator, Layout, System};
+    /// use std::alloc::{Alloc, Layout, System};
     ///
     /// let x = Box::new_in(String::from("Hello"), System);
     /// let (non_null, alloc) = Box::into_non_null_with_allocator(x);
@@ -2434,15 +2433,15 @@ impl<E: Error> Error for Box<E> {
     }
 }
 
-#[unstable(feature = "allocator_api", issue = "32838")]
-unsafe impl<T: ?Sized + Allocator, A: Allocator> Allocator for Box<T, A> {
+#[stable(feature = "allocator_api_mvp", since = "CURRENT_RUSTC_VERSION")]
+unsafe impl<T: ?Sized + Alloc, A: Allocator> Alloc for Box<T, A> {
     #[inline]
-    fn allocate(&self, layout: Layout) -> Result<NonNull<[u8]>, AllocError> {
+    fn allocate(&self, layout: Layout) -> Result<NonNull<u8>, AllocError> {
         (**self).allocate(layout)
     }
 
     #[inline]
-    fn allocate_zeroed(&self, layout: Layout) -> Result<NonNull<[u8]>, AllocError> {
+    fn allocate_zeroed(&self, layout: Layout) -> Result<NonNull<u8>, AllocError> {
         (**self).allocate_zeroed(layout)
     }
 
@@ -2458,7 +2457,7 @@ unsafe impl<T: ?Sized + Allocator, A: Allocator> Allocator for Box<T, A> {
         ptr: NonNull<u8>,
         old_layout: Layout,
         new_layout: Layout,
-    ) -> Result<NonNull<[u8]>, AllocError> {
+    ) -> Result<NonNull<u8>, AllocError> {
         // SAFETY: the safety contract must be upheld by the caller
         unsafe { (**self).grow(ptr, old_layout, new_layout) }
     }
@@ -2469,7 +2468,7 @@ unsafe impl<T: ?Sized + Allocator, A: Allocator> Allocator for Box<T, A> {
         ptr: NonNull<u8>,
         old_layout: Layout,
         new_layout: Layout,
-    ) -> Result<NonNull<[u8]>, AllocError> {
+    ) -> Result<NonNull<u8>, AllocError> {
         // SAFETY: the safety contract must be upheld by the caller
         unsafe { (**self).grow_zeroed(ptr, old_layout, new_layout) }
     }
@@ -2480,8 +2479,11 @@ unsafe impl<T: ?Sized + Allocator, A: Allocator> Allocator for Box<T, A> {
         ptr: NonNull<u8>,
         old_layout: Layout,
         new_layout: Layout,
-    ) -> Result<NonNull<[u8]>, AllocError> {
+    ) -> Result<NonNull<u8>, AllocError> {
         // SAFETY: the safety contract must be upheld by the caller
         unsafe { (**self).shrink(ptr, old_layout, new_layout) }
     }
 }
+
+#[unstable(feature = "allocator_api", issue = "32838")]
+unsafe impl<T: ?Sized + Allocator, A: Allocator> Allocator for Box<T, A> {}