comments and another test

Author: RalfJung

tests/run-pass/align_offset.rs

@@ -5,15 +5,15 @@ fn test_align_offset() {
 
     assert_eq!(raw.align_offset(2), 0);
     assert_eq!(raw.align_offset(4), 0);
-    assert_eq!(raw.align_offset(8), usize::max_value());
+    assert_eq!(raw.align_offset(8), usize::max_value()); // requested alignment higher than allocation alignment
 
     assert_eq!(raw.wrapping_offset(1).align_offset(2), 1);
     assert_eq!(raw.wrapping_offset(1).align_offset(4), 3);
-    assert_eq!(raw.wrapping_offset(1).align_offset(8), usize::max_value());
+    assert_eq!(raw.wrapping_offset(1).align_offset(8), usize::max_value()); // requested alignment higher than allocation alignment
 
     assert_eq!(raw.wrapping_offset(2).align_offset(2), 0);
     assert_eq!(raw.wrapping_offset(2).align_offset(4), 2);
-    assert_eq!(raw.wrapping_offset(2).align_offset(8), usize::max_value());
+    assert_eq!(raw.wrapping_offset(2).align_offset(8), usize::max_value()); // requested alignment higher than allocation alignment
 }
 
 fn test_align_to() {
@@ -54,6 +54,13 @@ fn test_align_to() {
         assert_eq!(r.len(), 3);
         assert_eq!(raw.wrapping_offset(4), m.as_ptr() as *const u8);
     }
+
+    {
+        let (l, m, r) = unsafe { s.align_to::<u64>() }; // requested alignment higher than allocation alignment
+        assert_eq!(l.len(), 4*N);
+        assert_eq!(r.len(), 0);
+        assert_eq!(m.len(), 0);
+    }
 }
 
 fn test_from_utf8() {