improve comment wording

Author: RalfJung

compiler/rustc_const_eval/src/interpret/validity.rs

@@ -434,7 +434,8 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValidityVisitor<'rt, 'mir, '
                 found_bytes: has.bytes()
             },
         );
-        // Make sure this is non-null. (ZST references can be dereferenceable and null.)
+        // Make sure this is non-null. We checked dereferenceability above, but if `size` is zero
+        // that does not imply non-null.
         if self.ecx.scalar_may_be_null(Scalar::from_maybe_pointer(place.ptr(), self.ecx))? {
             throw_validation_failure!(self.path, NullPtr { ptr_kind })
         }

library/core/src/intrinsics.rs

@@ -1484,7 +1484,7 @@ extern "rust-intrinsic" {
     /// # Safety
     ///
     /// If the computed offset is non-zero, then both the starting and resulting pointer must be
-    /// either in bounds or one byte past the end of an allocated object. If either pointer is out
+    /// either in bounds or at the end of an allocated object. If either pointer is out
     /// of bounds or arithmetic overflow occurs then any further use of the returned value will
     /// result in undefined behavior.
     ///
@@ -1502,7 +1502,7 @@ extern "rust-intrinsic" {
     /// # Safety
     ///
     /// Unlike the `offset` intrinsic, this intrinsic does not restrict the
-    /// resulting pointer to point into or one byte past the end of an allocated
+    /// resulting pointer to point into or at the end of an allocated
     /// object, and it wraps with two's complement arithmetic. The resulting
     /// value is not necessarily valid to be used to actually access memory.
     ///

library/core/src/ptr/const_ptr.rs

@@ -465,8 +465,8 @@ impl<T: ?Sized> *const T {
     /// If any of the following conditions are violated, the result is Undefined
     /// Behavior:
     ///
-    /// * If the computed offset is non-zero, then both the starting and resulting pointer must be
-    ///   either in bounds or one byte past the end of the same [allocated object].
+    /// * If the computed offset, **in bytes**, is non-zero, then both the starting and resulting
+    ///   pointer must be either in bounds or at the end of the same [allocated object].
     ///   (If it is zero, then the function is always well-defined.)
     ///
     /// * The computed offset, **in bytes**, cannot overflow an `isize`.
@@ -952,8 +952,8 @@ impl<T: ?Sized> *const T {
     /// If any of the following conditions are violated, the result is Undefined
     /// Behavior:
     ///
-    /// * If the computed offset is non-zero, then both the starting and resulting pointer must be
-    ///   either in bounds or one byte past the end of the same [allocated object].
+    /// * If the computed offset, **in bytes**, is non-zero, then both the starting and resulting
+    ///   pointer must be either in bounds or at the end of the same [allocated object].
     ///   (If it is zero, then the function is always well-defined.)
     ///
     /// * The computed offset, **in bytes**, cannot overflow an `isize`.
@@ -1037,8 +1037,8 @@ impl<T: ?Sized> *const T {
     /// If any of the following conditions are violated, the result is Undefined
     /// Behavior:
     ///
-    /// * If the computed offset is non-zero, then both the starting and resulting pointer must be
-    ///   either in bounds or one byte past the end of the same [allocated object].
+    /// * If the computed offset, **in bytes**, is non-zero, then both the starting and resulting
+    ///   pointer must be either in bounds or at the end of the same [allocated object].
     ///   (If it is zero, then the function is always well-defined.)
     ///
     /// * The computed offset cannot exceed `isize::MAX` **bytes**.

library/core/src/ptr/mut_ptr.rs

@@ -480,8 +480,8 @@ impl<T: ?Sized> *mut T {
     /// If any of the following conditions are violated, the result is Undefined
     /// Behavior:
     ///
-    /// * If the computed offset is non-zero, then both the starting and resulting pointer must be
-    ///   either in bounds or one byte past the end of the same [allocated object].
+    /// * If the computed offset, **in bytes**, is non-zero, then both the starting and resulting
+    ///   pointer must be either in bounds or at the end of the same [allocated object].
     ///   (If it is zero, then the function is always well-defined.)
     ///
     /// * The computed offset, **in bytes**, cannot overflow an `isize`.
@@ -1096,8 +1096,8 @@ impl<T: ?Sized> *mut T {
     /// If any of the following conditions are violated, the result is Undefined
     /// Behavior:
     ///
-    /// * If the computed offset is non-zero, then both the starting and resulting pointer must be
-    ///   either in bounds or one byte past the end of the same [allocated object].
+    /// * If the computed offset, **in bytes**, is non-zero, then both the starting and resulting
+    ///   pointer must be either in bounds or at the end of the same [allocated object].
     ///   (If it is zero, then the function is always well-defined.)
     ///
     /// * The computed offset, **in bytes**, cannot overflow an `isize`.
@@ -1181,8 +1181,8 @@ impl<T: ?Sized> *mut T {
     /// If any of the following conditions are violated, the result is Undefined
     /// Behavior:
     ///
-    /// * If the computed offset is non-zero, then both the starting and resulting pointer must be
-    ///   either in bounds or one byte past the end of the same [allocated object].
+    /// * If the computed offset, **in bytes**, is non-zero, then both the starting and resulting
+    ///   pointer must be either in bounds or at the end of the same [allocated object].
     ///   (If it is zero, then the function is always well-defined.)
     ///
     /// * The computed offset cannot exceed `isize::MAX` **bytes**.