Fix drop fill checking on 32-bit hosts.

Author: solson

src/interpreter.rs

@@ -393,8 +393,9 @@ impl<'a, 'tcx: 'a, 'arena> Interpreter<'a, 'tcx, 'arena> {
                         try!(self.memory.deallocate(contents_ptr));
                     }
                     Err(EvalError::ReadBytesAsPointer) => {
-                        let possible_drop_fill = try!(self.memory.read_usize(ptr));
-                        if possible_drop_fill == mem::POST_DROP_U64 {
+                        let size = self.memory.pointer_size;
+                        let possible_drop_fill = try!(self.memory.read_bytes(ptr, size));
+                        if possible_drop_fill.iter().all(|&b| b == mem::POST_DROP_U8) {
                             return Ok(());
                         } else {
                             return Err(EvalError::ReadBytesAsPointer);

src/memory.rs

@@ -284,6 +284,10 @@ impl Memory {
         Ok(())
     }
 
+    pub fn read_bytes(&self, ptr: Pointer, size: usize) -> EvalResult<&[u8]> {
+        self.get_bytes(ptr, size)
+    }
+
     pub fn write_bytes(&mut self, ptr: Pointer, src: &[u8]) -> EvalResult<()> {
         let bytes = try!(self.get_bytes_mut(ptr, src.len()));
         bytes.clone_from_slice(src);