Implement a naive, slow version of undef mask copying.

src/memory.rs

@@ -225,8 +225,10 @@ impl Memory {
             }
         }
 
-        // TODO(tsion): Copy undef ranges from src to dest.
-        self.copy_relocations(src, dest, size)
+        try!(self.copy_undef_mask(src, dest, size));
+        try!(self.copy_relocations(src, dest, size));
+
+        Ok(())
     }
 
     pub fn write_bytes(&mut self, ptr: Pointer, src: &[u8]) -> EvalResult<()> {
@@ -379,6 +381,20 @@ impl Memory {
     // Undefined bytes
     ////////////////////////////////////////////////////////////////////////////////
 
+    // FIXME(tsino): This is a very naive, slow version.
+    fn copy_undef_mask(&mut self, src: Pointer, dest: Pointer, size: usize) -> EvalResult<()> {
+        // The bits have to be saved locally before writing to dest in case src and dest overlap.
+        let mut v = Vec::with_capacity(size);
+        for i in 0..size {
+            let defined = try!(self.get(src.alloc_id)).undef_mask.get(src.offset + i);
+            v.push(defined);
+        }
+        for (i, defined) in v.into_iter().enumerate() {
+            try!(self.get_mut(dest.alloc_id)).undef_mask.set(dest.offset + i, defined);
+        }
+        Ok(())
+    }
+
     fn check_defined(&self, ptr: Pointer, size: usize) -> EvalResult<()> {
         let alloc = try!(self.get(ptr.alloc_id));
         if !alloc.undef_mask.is_range_defined(ptr.offset, ptr.offset + size) {

test/sums.rs

@@ -47,3 +47,8 @@ fn match_opt_some() -> i8 {
         None => 20,
     }
 }
+
+#[miri_run]
+fn two_nones() -> (Option<i16>, Option<i16>) {
+    (None, None)
+}