Remove the impl Alloc for System

See rust-lang/wg-allocators#2

Author: glandium

src/liballoc/tests/heap.rs

@@ -1,26 +1,21 @@
-use std::alloc::{Global, Alloc, Layout, System};
+use std::alloc::{GlobalAlloc, Layout, System};
 
 /// Issue #45955.
 #[test]
 fn alloc_system_overaligned_request() {
     check_overalign_requests(System)
 }
 
-#[test]
-fn std_heap_overaligned_request() {
-    check_overalign_requests(Global)
-}
-
-fn check_overalign_requests<T: Alloc>(mut allocator: T) {
+fn check_overalign_requests<T: GlobalAlloc>(allocator: T) {
     let size = 8;
     let align = 16; // greater than size
     let iterations = 100;
     unsafe {
         let pointers: Vec<_> = (0..iterations).map(|_| {
-            allocator.alloc(Layout::from_size_align(size, align).unwrap()).unwrap()
+            allocator.alloc(Layout::from_size_align(size, align).unwrap())
         }).collect();
         for &ptr in &pointers {
-            assert_eq!((ptr.as_ptr() as usize) % align, 0,
+            assert_eq!((ptr as usize) % align, 0,
                        "Got a pointer less aligned than requested")
         }
 

src/libstd/alloc.rs

@@ -63,7 +63,6 @@
 
 use core::sync::atomic::{AtomicPtr, Ordering};
 use core::{mem, ptr};
-use core::ptr::NonNull;
 
 use crate::sys_common::util::dumb_print;
 
@@ -133,33 +132,6 @@ pub use alloc_crate::alloc::*;
 #[derive(Debug, Default, Copy, Clone)]
 pub struct System;
 
-// The Alloc impl just forwards to the GlobalAlloc impl, which is in `std::sys::*::alloc`.
-#[unstable(feature = "allocator_api", issue = "32838")]
-unsafe impl Alloc for System {
-    #[inline]
-    unsafe fn alloc(&mut self, layout: Layout) -> Result<NonNull<u8>, AllocErr> {
-        NonNull::new(GlobalAlloc::alloc(self, layout)).ok_or(AllocErr)
-    }
-
-    #[inline]
-    unsafe fn alloc_zeroed(&mut self, layout: Layout) -> Result<NonNull<u8>, AllocErr> {
-        NonNull::new(GlobalAlloc::alloc_zeroed(self, layout)).ok_or(AllocErr)
-    }
-
-    #[inline]
-    unsafe fn dealloc(&mut self, ptr: NonNull<u8>, layout: Layout) {
-        GlobalAlloc::dealloc(self, ptr.as_ptr(), layout)
-    }
-
-    #[inline]
-    unsafe fn realloc(&mut self,
-                      ptr: NonNull<u8>,
-                      layout: Layout,
-                      new_size: usize) -> Result<NonNull<u8>, AllocErr> {
-        NonNull::new(GlobalAlloc::realloc(self, ptr.as_ptr(), layout, new_size)).ok_or(AllocErr)
-    }
-}
-
 static HOOK: AtomicPtr<()> = AtomicPtr::new(ptr::null_mut());
 
 /// Registers a custom allocation error hook, replacing any that was previously registered.

src/test/run-pass/allocator/custom.rs

@@ -7,14 +7,14 @@
 
 extern crate helper;
 
-use std::alloc::{self, Global, Alloc, System, Layout};
+use std::alloc::{Global, Alloc, GlobalAlloc, System, Layout};
 use std::sync::atomic::{AtomicUsize, Ordering};
 
 static HITS: AtomicUsize = AtomicUsize::new(0);
 
 struct A;
 
-unsafe impl alloc::GlobalAlloc for A {
+unsafe impl GlobalAlloc for A {
     unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
         HITS.fetch_add(1, Ordering::SeqCst);
         System.alloc(layout)
@@ -49,7 +49,7 @@ fn main() {
         drop(s);
         assert_eq!(HITS.load(Ordering::SeqCst), n + 4);
 
-        let ptr = System.alloc(layout.clone()).unwrap();
+        let ptr = System.alloc(layout.clone());
         assert_eq!(HITS.load(Ordering::SeqCst), n + 4);
         helper::work_with(&ptr);
         System.dealloc(ptr, layout);

src/test/run-pass/allocator/xcrate-use.rs

@@ -9,7 +9,7 @@
 extern crate custom;
 extern crate helper;
 
-use std::alloc::{Global, Alloc, System, Layout};
+use std::alloc::{Global, Alloc, GlobalAlloc, System, Layout};
 use std::sync::atomic::{Ordering, AtomicUsize};
 
 #[global_allocator]
@@ -26,7 +26,7 @@ fn main() {
         Global.dealloc(ptr, layout.clone());
         assert_eq!(GLOBAL.0.load(Ordering::SeqCst), n + 2);
 
-        let ptr = System.alloc(layout.clone()).unwrap();
+        let ptr = System.alloc(layout.clone());
         assert_eq!(GLOBAL.0.load(Ordering::SeqCst), n + 2);
         helper::work_with(&ptr);
         System.dealloc(ptr, layout);