Make pointer related code in std and compiler nicer

compiler/rustc_arena/src/lib.rs

@@ -16,6 +16,7 @@
 #![feature(maybe_uninit_slice)]
 #![feature(min_specialization)]
 #![feature(decl_macro)]
+#![feature(pointer_byte_offsets)]
 #![feature(rustc_attrs)]
 #![cfg_attr(test, feature(test))]
 #![feature(strict_provenance)]
@@ -209,15 +210,15 @@ impl<T> TypedArena<T> {
 
         unsafe {
             if mem::size_of::<T>() == 0 {
-                self.ptr.set((self.ptr.get() as *mut u8).wrapping_offset(1) as *mut T);
+                self.ptr.set(self.ptr.get().wrapping_byte_add(1));
                 let ptr = ptr::NonNull::<T>::dangling().as_ptr();
                 // Don't drop the object. This `write` is equivalent to `forget`.
                 ptr::write(ptr, object);
                 &mut *ptr
             } else {
                 let ptr = self.ptr.get();
                 // Advance the pointer.
-                self.ptr.set(self.ptr.get().offset(1));
+                self.ptr.set(self.ptr.get().add(1));
                 // Write into uninitialized memory.
                 ptr::write(ptr, object);
                 &mut *ptr

compiler/rustc_codegen_cranelift/example/alloc_system.rs

@@ -94,7 +94,7 @@ mod platform {
     struct Header(*mut u8);
     const HEAP_ZERO_MEMORY: DWORD = 0x00000008;
     unsafe fn get_header<'a>(ptr: *mut u8) -> &'a mut Header {
-        &mut *(ptr as *mut Header).offset(-1)
+        &mut *(ptr as *mut Header).sub(1)
     }
     unsafe fn align_ptr(ptr: *mut u8, align: usize) -> *mut u8 {
         let aligned = ptr.add(align - (ptr as usize & (align - 1)));

compiler/rustc_codegen_gcc/example/alloc_system.rs

@@ -156,7 +156,7 @@ mod platform {
     struct Header(*mut u8);
     const HEAP_ZERO_MEMORY: DWORD = 0x00000008;
     unsafe fn get_header<'a>(ptr: *mut u8) -> &'a mut Header {
-        &mut *(ptr as *mut Header).offset(-1)
+        &mut *(ptr as *mut Header).sub(1)
     }
     unsafe fn align_ptr(ptr: *mut u8, align: usize) -> *mut u8 {
         let aligned = ptr.add(align - (ptr as usize & (align - 1)));

compiler/rustc_serialize/src/serialize.rs

@@ -273,7 +273,7 @@ impl<D: Decoder, T: Decodable<D>> Decodable<D> for Vec<T> {
         unsafe {
             let ptr: *mut T = vec.as_mut_ptr();
             for i in 0..len {
-                std::ptr::write(ptr.offset(i as isize), Decodable::decode(d));
+                std::ptr::write(ptr.add(i), Decodable::decode(d));
             }
             vec.set_len(len);
         }

library/alloc/src/alloc/tests.rs

@@ -15,7 +15,7 @@ fn allocate_zeroed() {
         let end = i.add(layout.size());
         while i < end {
             assert_eq!(*i, 0);
-            i = i.offset(1);
+            i = i.add(1);
         }
         Global.deallocate(ptr.as_non_null_ptr(), layout);
     }

library/alloc/src/collections/vec_deque/mod.rs

@@ -2447,8 +2447,8 @@ impl<T, A: Allocator> VecDeque<T, A> {
                     let mut right_offset = 0;
                     for i in left_edge..right_edge {
                         right_offset = (i - left_edge) % (cap - right_edge);
-                        let src: isize = (right_edge + right_offset) as isize;
-                        ptr::swap(buf.add(i), buf.offset(src));
+                        let src = right_edge + right_offset;
+                        ptr::swap(buf.add(i), buf.add(src));
                     }
                     let n_ops = right_edge - left_edge;
                     left_edge += n_ops;

library/alloc/src/ffi/c_str.rs

@@ -436,9 +436,9 @@ impl CString {
     ///
     /// unsafe {
     ///     assert_eq!(b'f', *ptr as u8);
-    ///     assert_eq!(b'o', *ptr.offset(1) as u8);
-    ///     assert_eq!(b'o', *ptr.offset(2) as u8);
-    ///     assert_eq!(b'\0', *ptr.offset(3) as u8);
+    ///     assert_eq!(b'o', *ptr.add(1) as u8);
+    ///     assert_eq!(b'o', *ptr.add(2) as u8);
+    ///     assert_eq!(b'\0', *ptr.add(3) as u8);
     ///
     ///     // retake pointer to free memory
     ///     let _ = CString::from_raw(ptr);

library/alloc/src/slice.rs

@@ -1024,7 +1024,7 @@ where
             // Consume the greater side.
             // If equal, prefer the right run to maintain stability.
             unsafe {
-                let to_copy = if is_less(&*right.offset(-1), &*left.offset(-1)) {
+                let to_copy = if is_less(&*right.sub(1), &*left.sub(1)) {
                     decrement_and_get(left)
                 } else {
                     decrement_and_get(right)
@@ -1038,12 +1038,12 @@ where
 
     unsafe fn get_and_increment<T>(ptr: &mut *mut T) -> *mut T {
         let old = *ptr;
-        *ptr = unsafe { ptr.offset(1) };
+        *ptr = unsafe { ptr.add(1) };
         old
     }
 
     unsafe fn decrement_and_get<T>(ptr: &mut *mut T) -> *mut T {
-        *ptr = unsafe { ptr.offset(-1) };
+        *ptr = unsafe { ptr.sub(1) };
         *ptr
     }
 

library/alloc/src/vec/in_place_collect.rs

@@ -267,7 +267,7 @@ where
             // one slot in the underlying storage will have been freed up and we can immediately
             // write back the result.
             unsafe {
-                let dst = dst_buf.offset(i as isize);
+                let dst = dst_buf.add(i);
                 debug_assert!(dst as *const _ <= end, "InPlaceIterable contract violation");
                 ptr::write(dst, self.__iterator_get_unchecked(i));
                 // Since this executes user code which can panic we have to bump the pointer

library/alloc/src/vec/into_iter.rs

@@ -4,7 +4,6 @@ use crate::alloc::{Allocator, Global};
 use crate::raw_vec::RawVec;
 use core::array;
 use core::fmt;
-use core::intrinsics::arith_offset;
 use core::iter::{
     FusedIterator, InPlaceIterable, SourceIter, TrustedLen, TrustedRandomAccessNoCoerce,
 };
@@ -148,19 +147,19 @@ impl<T, A: Allocator> Iterator for IntoIter<T, A> {
 
     #[inline]
     fn next(&mut self) -> Option<T> {
-        if self.ptr as *const _ == self.end {
+        if self.ptr == self.end {
             None
         } else if mem::size_of::<T>() == 0 {
             // purposefully don't use 'ptr.offset' because for
             // vectors with 0-size elements this would return the
             // same pointer.
-            self.ptr = unsafe { arith_offset(self.ptr as *const i8, 1) as *mut T };
+            self.ptr = self.ptr.wrapping_byte_add(1);
 
             // Make up a value of this ZST.
             Some(unsafe { mem::zeroed() })
         } else {
             let old = self.ptr;
-            self.ptr = unsafe { self.ptr.offset(1) };
+            self.ptr = unsafe { self.ptr.add(1) };
 
             Some(unsafe { ptr::read(old) })
         }
@@ -184,7 +183,7 @@ impl<T, A: Allocator> Iterator for IntoIter<T, A> {
             // SAFETY: due to unchecked casts of unsigned amounts to signed offsets the wraparound
             // effectively results in unsigned pointers representing positions 0..usize::MAX,
             // which is valid for ZSTs.
-            self.ptr = unsafe { arith_offset(self.ptr as *const i8, step_size as isize) as *mut T }
+            self.ptr = self.ptr.wrapping_byte_add(step_size);
         } else {
             // SAFETY: the min() above ensures that step_size is in bounds
             self.ptr = unsafe { self.ptr.add(step_size) };
@@ -217,7 +216,7 @@ impl<T, A: Allocator> Iterator for IntoIter<T, A> {
                 return Err(unsafe { array::IntoIter::new_unchecked(raw_ary, 0..len) });
             }
 
-            self.ptr = unsafe { arith_offset(self.ptr as *const i8, N as isize) as *mut T };
+            self.ptr = self.ptr.wrapping_byte_add(N);
             // Safety: ditto
             return Ok(unsafe { MaybeUninit::array_assume_init(raw_ary) });
         }
@@ -267,12 +266,12 @@ impl<T, A: Allocator> DoubleEndedIterator for IntoIter<T, A> {
             None
         } else if mem::size_of::<T>() == 0 {
             // See above for why 'ptr.offset' isn't used
-            self.end = unsafe { arith_offset(self.end as *const i8, -1) as *mut T };
+            self.end = self.ptr.wrapping_byte_sub(1);
 
             // Make up a value of this ZST.
             Some(unsafe { mem::zeroed() })
         } else {
-            self.end = unsafe { self.end.offset(-1) };
+            self.end = unsafe { self.end.sub(1) };
 
             Some(unsafe { ptr::read(self.end) })
         }
@@ -283,12 +282,10 @@ impl<T, A: Allocator> DoubleEndedIterator for IntoIter<T, A> {
         let step_size = self.len().min(n);
         if mem::size_of::<T>() == 0 {
             // SAFETY: same as for advance_by()
-            self.end = unsafe {
-                arith_offset(self.end as *const i8, step_size.wrapping_neg() as isize) as *mut T
-            }
+            self.end = self.end.wrapping_byte_sub(step_size);
         } else {
             // SAFETY: same as for advance_by()
-            self.end = unsafe { self.end.offset(step_size.wrapping_neg() as isize) };
+            self.end = unsafe { self.end.sub(step_size) };
         }
         let to_drop = ptr::slice_from_raw_parts_mut(self.end as *mut T, step_size);
         // SAFETY: same as for advance_by()

library/alloc/src/vec/mod.rs

@@ -59,7 +59,7 @@ use core::cmp::Ordering;
 use core::convert::TryFrom;
 use core::fmt;
 use core::hash::{Hash, Hasher};
-use core::intrinsics::{arith_offset, assume};
+use core::intrinsics::assume;
 use core::iter;
 #[cfg(not(no_global_oom_handling))]
 use core::iter::FromIterator;
@@ -542,8 +542,8 @@ impl<T> Vec<T> {
     ///
     /// unsafe {
     ///     // Overwrite memory with 4, 5, 6
-    ///     for i in 0..len as isize {
-    ///         ptr::write(p.offset(i), 4 + i);
+    ///     for i in 0..len {
+    ///         ptr::write(p.add(i), 4 + i);
     ///     }
     ///
     ///     // Put everything back together into a Vec
@@ -702,8 +702,8 @@ impl<T, A: Allocator> Vec<T, A> {
     ///
     /// unsafe {
     ///     // Overwrite memory with 4, 5, 6
-    ///     for i in 0..len as isize {
-    ///         ptr::write(p.offset(i), 4 + i);
+    ///     for i in 0..len {
+    ///         ptr::write(p.add(i), 4 + i);
     ///     }
     ///
     ///     // Put everything back together into a Vec
@@ -1393,7 +1393,7 @@ impl<T, A: Allocator> Vec<T, A> {
                 if index < len {
                     // Shift everything over to make space. (Duplicating the
                     // `index`th element into two consecutive places.)
-                    ptr::copy(p, p.offset(1), len - index);
+                    ptr::copy(p, p.add(1), len - index);
                 } else if index == len {
                     // No elements need shifting.
                 } else {
@@ -1455,7 +1455,7 @@ impl<T, A: Allocator> Vec<T, A> {
                 ret = ptr::read(ptr);
 
                 // Shift everything down to fill in that spot.
-                ptr::copy(ptr.offset(1), ptr, len - index - 1);
+                ptr::copy(ptr.add(1), ptr, len - index - 1);
             }
             self.set_len(len - 1);
             ret
@@ -2408,7 +2408,7 @@ impl<T, A: Allocator> Vec<T, A> {
             // Write all elements except the last one
             for _ in 1..n {
                 ptr::write(ptr, value.next());
-                ptr = ptr.offset(1);
+                ptr = ptr.add(1);
                 // Increment the length in every step in case next() panics
                 local_len.increment_len(1);
             }
@@ -2677,7 +2677,7 @@ impl<T, A: Allocator> IntoIterator for Vec<T, A> {
             let alloc = ManuallyDrop::new(ptr::read(me.allocator()));
             let begin = me.as_mut_ptr();
             let end = if mem::size_of::<T>() == 0 {
-                arith_offset(begin as *const i8, me.len() as isize) as *const T
+                begin.wrapping_byte_add(me.len())
             } else {
                 begin.add(me.len()) as *const T
             };

library/alloc/src/vec/spec_extend.rs

@@ -39,7 +39,7 @@ where
                 let mut local_len = SetLenOnDrop::new(&mut self.len);
                 iterator.for_each(move |element| {
                     ptr::write(ptr, element);
-                    ptr = ptr.offset(1);
+                    ptr = ptr.add(1);
                     // Since the loop executes user code which can panic we have to bump the pointer
                     // after each step.
                     // NB can't overflow since we would have had to alloc the address space

library/alloc/tests/lib.rs

@@ -38,6 +38,7 @@
 #![feature(const_str_from_utf8)]
 #![feature(nonnull_slice_from_raw_parts)]
 #![feature(panic_update_hook)]
+#![feature(pointer_is_aligned)]
 #![feature(slice_flatten)]
 #![feature(thin_box)]
 #![feature(bench_black_box)]

library/alloc/tests/str.rs

@@ -1010,11 +1010,11 @@ fn test_as_bytes_fail() {
 fn test_as_ptr() {
     let buf = "hello".as_ptr();
     unsafe {
-        assert_eq!(*buf.offset(0), b'h');
-        assert_eq!(*buf.offset(1), b'e');
-        assert_eq!(*buf.offset(2), b'l');
-        assert_eq!(*buf.offset(3), b'l');
-        assert_eq!(*buf.offset(4), b'o');
+        assert_eq!(*buf.add(0), b'h');
+        assert_eq!(*buf.add(1), b'e');
+        assert_eq!(*buf.add(2), b'l');
+        assert_eq!(*buf.add(3), b'l');
+        assert_eq!(*buf.add(4), b'o');
     }
 }
 

library/alloc/tests/thin_box.rs

@@ -48,11 +48,11 @@ fn verify_aligned<T>(ptr: *const T) {
     // practice these checks are mostly just smoke-detectors for an extremely
     // broken `ThinBox` impl, since it's an extremely subtle piece of code.
     let ptr = core::hint::black_box(ptr);
-    let align = core::mem::align_of::<T>();
     assert!(
-        (ptr.addr() & (align - 1)) == 0 && !ptr.is_null(),
-        "misaligned ThinBox data; valid pointers to `{}` should be aligned to {align}: {ptr:p}",
-        core::any::type_name::<T>(),
+        ptr.is_aligned() && !ptr.is_null(),
+        "misaligned ThinBox data; valid pointers to `{ty}` should be aligned to {align}: {ptr:p}",
+        ty = core::any::type_name::<T>(),
+        align = core::mem::align_of::<T>(),
     );
 }