some fixes in response to miri

src/machine/heap.rs

@@ -1281,3 +1281,17 @@ pub(crate) fn to_local_code_ptr(heap: &Heap, addr: HeapCellValue) -> Option<usiz
         }
     )
 }
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn heap_manipulation() {
+        let mut heap = Heap::new();
+
+        for idx in 0 .. 10 {
+            heap.push_cell(heap_loc_as_cell!(idx)).unwrap();
+        }
+    }
+}

src/machine/machine_state_impl.rs

@@ -267,16 +267,6 @@ impl MachineState {
         unifier.unify_atom(atom, value);
     }
 
-    pub fn unify_list(&mut self, l1: usize, value: HeapCellValue) {
-        let mut unifier = DefaultUnifier::from(self);
-        unifier.unify_list(l1, value);
-    }
-
-    pub fn unify_partial_string(&mut self, pstr_loc: usize, value: HeapCellValue) {
-        let mut unifier = DefaultUnifier::from(self);
-        unifier.unify_partial_string(pstr_loc, value);
-    }
-
     pub fn unify_char(&mut self, c: char, value: HeapCellValue) {
         let mut unifier = DefaultUnifier::from(self);
         unifier.unify_char(c, value);

src/machine/stack.rs

@@ -228,7 +228,7 @@ impl Stack {
 
             for idx in 0..num_cells {
                 ptr::write(
-                    (new_ptr as usize + offset) as *mut HeapCellValue,
+                    new_ptr.byte_add(offset) as *mut HeapCellValue,
                     stack_loc_as_cell!(OrFrame, b, idx),
                 );