Rollup merge of #76993 - blitzerr:alloc-ref, r=Amanieu

Changing the alloc() to accept &self instead of &mut self

Fixes: [#55](https://github.com/rust-lang/wg-allocators/issues/55)

This is the first cut. It only makes the change for `alloc` method.

library/alloc/src/alloc.rs

@@ -145,7 +145,7 @@ pub unsafe fn alloc_zeroed(layout: Layout) -> *mut u8 {
 
 impl Global {
     #[inline]
-    fn alloc_impl(&mut self, layout: Layout, zeroed: bool) -> Result<NonNull<[u8]>, AllocErr> {
+    fn alloc_impl(&self, layout: Layout, zeroed: bool) -> Result<NonNull<[u8]>, AllocErr> {
         match layout.size() {
             0 => Ok(NonNull::slice_from_raw_parts(layout.dangling(), 0)),
             // SAFETY: `layout` is non-zero in size,
@@ -160,7 +160,7 @@ impl Global {
     // SAFETY: Same as `AllocRef::grow`
     #[inline]
     unsafe fn grow_impl(
-        &mut self,
+        &self,
         ptr: NonNull<u8>,
         old_layout: Layout,
         new_layout: Layout,
@@ -208,17 +208,17 @@ impl Global {
 #[unstable(feature = "allocator_api", issue = "32838")]
 unsafe impl AllocRef for Global {
     #[inline]
-    fn alloc(&mut self, layout: Layout) -> Result<NonNull<[u8]>, AllocErr> {
+    fn alloc(&self, layout: Layout) -> Result<NonNull<[u8]>, AllocErr> {
         self.alloc_impl(layout, false)
     }
 
     #[inline]
-    fn alloc_zeroed(&mut self, layout: Layout) -> Result<NonNull<[u8]>, AllocErr> {
+    fn alloc_zeroed(&self, layout: Layout) -> Result<NonNull<[u8]>, AllocErr> {
         self.alloc_impl(layout, true)
     }
 
     #[inline]
-    unsafe fn dealloc(&mut self, ptr: NonNull<u8>, layout: Layout) {
+    unsafe fn dealloc(&self, ptr: NonNull<u8>, layout: Layout) {
         if layout.size() != 0 {
             // SAFETY: `layout` is non-zero in size,
             // other conditions must be upheld by the caller
@@ -228,7 +228,7 @@ unsafe impl AllocRef for Global {
 
     #[inline]
     unsafe fn grow(
-        &mut self,
+        &self,
         ptr: NonNull<u8>,
         old_layout: Layout,
         new_layout: Layout,
@@ -239,7 +239,7 @@ unsafe impl AllocRef for Global {
 
     #[inline]
     unsafe fn grow_zeroed(
-        &mut self,
+        &self,
         ptr: NonNull<u8>,
         old_layout: Layout,
         new_layout: Layout,
@@ -250,7 +250,7 @@ unsafe impl AllocRef for Global {
 
     #[inline]
     unsafe fn shrink(
-        &mut self,
+        &self,
         ptr: NonNull<u8>,
         old_layout: Layout,
         new_layout: Layout,

library/alloc/src/raw_vec.rs

@@ -170,7 +170,7 @@ impl<T, A: AllocRef> RawVec<T, A> {
         Self::allocate_in(capacity, AllocInit::Zeroed, alloc)
     }
 
-    fn allocate_in(capacity: usize, init: AllocInit, mut alloc: A) -> Self {
+    fn allocate_in(capacity: usize, init: AllocInit, alloc: A) -> Self {
         if mem::size_of::<T>() == 0 {
             Self::new_in(alloc)
         } else {

library/alloc/src/raw_vec/tests.rs

@@ -1,4 +1,5 @@
 use super::*;
+use std::cell::Cell;
 
 #[test]
 fn allocator_param() {
@@ -17,32 +18,32 @@ fn allocator_param() {
     // A dumb allocator that consumes a fixed amount of fuel
     // before allocation attempts start failing.
     struct BoundedAlloc {
-        fuel: usize,
+        fuel: Cell<usize>,
     }
     unsafe impl AllocRef for BoundedAlloc {
-        fn alloc(&mut self, layout: Layout) -> Result<NonNull<[u8]>, AllocErr> {
+        fn alloc(&self, layout: Layout) -> Result<NonNull<[u8]>, AllocErr> {
             let size = layout.size();
-            if size > self.fuel {
+            if size > self.fuel.get() {
                 return Err(AllocErr);
             }
             match Global.alloc(layout) {
                 ok @ Ok(_) => {
-                    self.fuel -= size;
+                    self.fuel.set(self.fuel.get() - size);
                     ok
                 }
                 err @ Err(_) => err,
             }
         }
-        unsafe fn dealloc(&mut self, ptr: NonNull<u8>, layout: Layout) {
+        unsafe fn dealloc(&self, ptr: NonNull<u8>, layout: Layout) {
             unsafe { Global.dealloc(ptr, layout) }
         }
     }
 
-    let a = BoundedAlloc { fuel: 500 };
+    let a = BoundedAlloc { fuel: Cell::new(500) };
     let mut v: RawVec<u8, _> = RawVec::with_capacity_in(50, a);
-    assert_eq!(v.alloc.fuel, 450);
+    assert_eq!(v.alloc.fuel.get(), 450);
     v.reserve(50, 150); // (causes a realloc, thus using 50 + 150 = 200 units of fuel)
-    assert_eq!(v.alloc.fuel, 250);
+    assert_eq!(v.alloc.fuel.get(), 250);
 }
 
 #[test]

library/alloc/tests/heap.rs

@@ -11,7 +11,7 @@ fn std_heap_overaligned_request() {
     check_overalign_requests(Global)
 }
 
-fn check_overalign_requests<T: AllocRef>(mut allocator: T) {
+fn check_overalign_requests<T: AllocRef>(allocator: T) {
     for &align in &[4, 8, 16, 32] {
         // less than and bigger than `MIN_ALIGN`
         for &size in &[align / 2, align - 1] {

library/core/src/alloc/mod.rs

@@ -109,7 +109,7 @@ pub unsafe trait AllocRef {
     /// call the [`handle_alloc_error`] function, rather than directly invoking `panic!` or similar.
     ///
     /// [`handle_alloc_error`]: ../../alloc/alloc/fn.handle_alloc_error.html
-    fn alloc(&mut self, layout: Layout) -> Result<NonNull<[u8]>, AllocErr>;
+    fn alloc(&self, layout: Layout) -> Result<NonNull<[u8]>, AllocErr>;
 
     /// Behaves like `alloc`, but also ensures that the returned memory is zero-initialized.
     ///
@@ -126,7 +126,7 @@ pub unsafe trait AllocRef {
     /// call the [`handle_alloc_error`] function, rather than directly invoking `panic!` or similar.
     ///
     /// [`handle_alloc_error`]: ../../alloc/alloc/fn.handle_alloc_error.html
-    fn alloc_zeroed(&mut self, layout: Layout) -> Result<NonNull<[u8]>, AllocErr> {
+    fn alloc_zeroed(&self, layout: Layout) -> Result<NonNull<[u8]>, AllocErr> {
         let ptr = self.alloc(layout)?;
         // SAFETY: `alloc` returns a valid memory block
         unsafe { ptr.as_non_null_ptr().as_ptr().write_bytes(0, ptr.len()) }
@@ -142,7 +142,7 @@ pub unsafe trait AllocRef {
     ///
     /// [*currently allocated*]: #currently-allocated-memory
     /// [*fit*]: #memory-fitting
-    unsafe fn dealloc(&mut self, ptr: NonNull<u8>, layout: Layout);
+    unsafe fn dealloc(&self, ptr: NonNull<u8>, layout: Layout);
 
     /// Attempts to extend the memory block.
     ///
@@ -183,7 +183,7 @@ pub unsafe trait AllocRef {
     ///
     /// [`handle_alloc_error`]: ../../alloc/alloc/fn.handle_alloc_error.html
     unsafe fn grow(
-        &mut self,
+        &self,
         ptr: NonNull<u8>,
         old_layout: Layout,
         new_layout: Layout,
@@ -244,7 +244,7 @@ pub unsafe trait AllocRef {
     ///
     /// [`handle_alloc_error`]: ../../alloc/alloc/fn.handle_alloc_error.html
     unsafe fn grow_zeroed(
-        &mut self,
+        &self,
         ptr: NonNull<u8>,
         old_layout: Layout,
         new_layout: Layout,
@@ -308,7 +308,7 @@ pub unsafe trait AllocRef {
     ///
     /// [`handle_alloc_error`]: ../../alloc/alloc/fn.handle_alloc_error.html
     unsafe fn shrink(
-        &mut self,
+        &self,
         ptr: NonNull<u8>,
         old_layout: Layout,
         new_layout: Layout,
@@ -337,35 +337,35 @@ pub unsafe trait AllocRef {
     ///
     /// The returned adaptor also implements `AllocRef` and will simply borrow this.
     #[inline(always)]
-    fn by_ref(&mut self) -> &mut Self {
+    fn by_ref(&mut self) -> &Self {
         self
     }
 }
 
 #[unstable(feature = "allocator_api", issue = "32838")]
-unsafe impl<A> AllocRef for &mut A
+unsafe impl<A> AllocRef for &A
 where
     A: AllocRef + ?Sized,
 {
     #[inline]
-    fn alloc(&mut self, layout: Layout) -> Result<NonNull<[u8]>, AllocErr> {
+    fn alloc(&self, layout: Layout) -> Result<NonNull<[u8]>, AllocErr> {
         (**self).alloc(layout)
     }
 
     #[inline]
-    fn alloc_zeroed(&mut self, layout: Layout) -> Result<NonNull<[u8]>, AllocErr> {
+    fn alloc_zeroed(&self, layout: Layout) -> Result<NonNull<[u8]>, AllocErr> {
         (**self).alloc_zeroed(layout)
     }
 
     #[inline]
-    unsafe fn dealloc(&mut self, ptr: NonNull<u8>, layout: Layout) {
+    unsafe fn dealloc(&self, ptr: NonNull<u8>, layout: Layout) {
         // SAFETY: the safety contract must be upheld by the caller
         unsafe { (**self).dealloc(ptr, layout) }
     }
 
     #[inline]
     unsafe fn grow(
-        &mut self,
+        &self,
         ptr: NonNull<u8>,
         old_layout: Layout,
         new_layout: Layout,
@@ -376,7 +376,7 @@ where
 
     #[inline]
     unsafe fn grow_zeroed(
-        &mut self,
+        &self,
         ptr: NonNull<u8>,
         old_layout: Layout,
         new_layout: Layout,
@@ -387,7 +387,7 @@ where
 
     #[inline]
     unsafe fn shrink(
-        &mut self,
+        &self,
         ptr: NonNull<u8>,
         old_layout: Layout,
         new_layout: Layout,

library/std/src/alloc.rs

@@ -133,7 +133,7 @@ pub struct System;
 
 impl System {
     #[inline]
-    fn alloc_impl(&mut self, layout: Layout, zeroed: bool) -> Result<NonNull<[u8]>, AllocErr> {
+    fn alloc_impl(&self, layout: Layout, zeroed: bool) -> Result<NonNull<[u8]>, AllocErr> {
         match layout.size() {
             0 => Ok(NonNull::slice_from_raw_parts(layout.dangling(), 0)),
             // SAFETY: `layout` is non-zero in size,
@@ -152,7 +152,7 @@ impl System {
     // SAFETY: Same as `AllocRef::grow`
     #[inline]
     unsafe fn grow_impl(
-        &mut self,
+        &self,
         ptr: NonNull<u8>,
         old_layout: Layout,
         new_layout: Layout,
@@ -190,7 +190,7 @@ impl System {
             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);
-                self.dealloc(ptr, old_layout);
+                AllocRef::dealloc(&self, ptr, old_layout);
                 Ok(new_ptr)
             },
         }
@@ -202,17 +202,17 @@ impl System {
 #[unstable(feature = "allocator_api", issue = "32838")]
 unsafe impl AllocRef for System {
     #[inline]
-    fn alloc(&mut self, layout: Layout) -> Result<NonNull<[u8]>, AllocErr> {
+    fn alloc(&self, layout: Layout) -> Result<NonNull<[u8]>, AllocErr> {
         self.alloc_impl(layout, false)
     }
 
     #[inline]
-    fn alloc_zeroed(&mut self, layout: Layout) -> Result<NonNull<[u8]>, AllocErr> {
+    fn alloc_zeroed(&self, layout: Layout) -> Result<NonNull<[u8]>, AllocErr> {
         self.alloc_impl(layout, true)
     }
 
     #[inline]
-    unsafe fn dealloc(&mut self, ptr: NonNull<u8>, layout: Layout) {
+    unsafe fn dealloc(&self, ptr: NonNull<u8>, layout: Layout) {
         if layout.size() != 0 {
             // SAFETY: `layout` is non-zero in size,
             // other conditions must be upheld by the caller
@@ -222,7 +222,7 @@ unsafe impl AllocRef for System {
 
     #[inline]
     unsafe fn grow(
-        &mut self,
+        &self,
         ptr: NonNull<u8>,
         old_layout: Layout,
         new_layout: Layout,
@@ -233,7 +233,7 @@ unsafe impl AllocRef for System {
 
     #[inline]
     unsafe fn grow_zeroed(
-        &mut self,
+        &self,
         ptr: NonNull<u8>,
         old_layout: Layout,
         new_layout: Layout,
@@ -244,7 +244,7 @@ unsafe impl AllocRef for System {
 
     #[inline]
     unsafe fn shrink(
-        &mut self,
+        &self,
         ptr: NonNull<u8>,
         old_layout: Layout,
         new_layout: Layout,
@@ -257,7 +257,7 @@ unsafe impl AllocRef for System {
         match new_layout.size() {
             // SAFETY: conditions must be upheld by the caller
             0 => unsafe {
-                self.dealloc(ptr, old_layout);
+                AllocRef::dealloc(&self, ptr, old_layout);
                 Ok(NonNull::slice_from_raw_parts(new_layout.dangling(), 0))
             },
 
@@ -277,9 +277,9 @@ unsafe impl AllocRef for System {
             // `new_ptr`. Thus, the call to `copy_nonoverlapping` is safe. The safety contract
             // for `dealloc` must be upheld by the caller.
             new_size => unsafe {
-                let new_ptr = self.alloc(new_layout)?;
+                let new_ptr = AllocRef::alloc(&self, new_layout)?;
                 ptr::copy_nonoverlapping(ptr.as_ptr(), new_ptr.as_mut_ptr(), new_size);
-                self.dealloc(ptr, old_layout);
+                AllocRef::dealloc(&self, ptr, old_layout);
                 Ok(new_ptr)
             },
         }

src/test/ui/allocator/custom.rs

@@ -10,6 +10,7 @@ extern crate helper;
 
 use std::alloc::{self, AllocRef, Global, Layout, System};
 use std::sync::atomic::{AtomicUsize, Ordering};
+use std::ptr::NonNull;
 
 static HITS: AtomicUsize = AtomicUsize::new(0);
 
@@ -18,12 +19,12 @@ struct A;
 unsafe impl alloc::GlobalAlloc for A {
     unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
         HITS.fetch_add(1, Ordering::SeqCst);
-        System.alloc(layout)
+        alloc::GlobalAlloc::alloc(&System, layout)
     }
 
     unsafe fn dealloc(&self, ptr: *mut u8, layout: Layout) {
         HITS.fetch_add(1, Ordering::SeqCst);
-        System.dealloc(ptr, layout)
+        AllocRef::dealloc(&System, NonNull::new(ptr).unwrap(), layout)
     }
 }