Constify ptr::read and ptr::read_unaligned

Author: usbalbin

library/core/src/lib.rs

@@ -73,6 +73,7 @@
 #![feature(const_assert_type)]
 #![feature(const_discriminant)]
 #![feature(const_cell_into_inner)]
+#![feature(const_intrinsic_copy)]
 #![feature(const_checked_int_methods)]
 #![feature(const_euclidean_int_methods)]
 #![feature(const_float_classify)]

library/core/src/ptr/mod.rs

@@ -685,7 +685,8 @@ pub unsafe fn replace<T>(dst: *mut T, mut src: T) -> T {
 /// [valid]: self#safety
 #[inline]
 #[stable(feature = "rust1", since = "1.0.0")]
-pub unsafe fn read<T>(src: *const T) -> T {
+#[rustc_const_unstable(feature = "const_ptr_read", issue = "none")]
+pub const unsafe fn read<T>(src: *const T) -> T {
     // `copy_nonoverlapping` takes care of debug_assert.
     let mut tmp = MaybeUninit::<T>::uninit();
     // SAFETY: the caller must guarantee that `src` is valid for reads.
@@ -784,7 +785,8 @@ pub unsafe fn read<T>(src: *const T) -> T {
 /// ```
 #[inline]
 #[stable(feature = "ptr_unaligned", since = "1.17.0")]
-pub unsafe fn read_unaligned<T>(src: *const T) -> T {
+#[rustc_const_unstable(feature = "const_ptr_read", issue = "none")]
+pub const unsafe fn read_unaligned<T>(src: *const T) -> T {
     // `copy_nonoverlapping` takes care of debug_assert.
     let mut tmp = MaybeUninit::<T>::uninit();
     // SAFETY: the caller must guarantee that `src` is valid for reads.