Permit int->ptr->int roundtrip

src/eval_context.rs

@@ -1438,6 +1438,7 @@ impl<'a, 'tcx> EvalContext<'a, 'tcx> {
                     panic!("Failed to access local: {:?}", err);
                 }
                 Ok(Value::ByRef(ptr)) => {
+                    write!(msg, " by ref:").unwrap();
                     allocs.push(ptr.alloc_id);
                 }
                 Ok(Value::ByVal(val)) => {

src/memory.rs

@@ -605,7 +605,7 @@ impl<'a, 'tcx> Memory<'a, 'tcx> {
         if size == 0 {
             return Ok(&[]);
         }
-        if self.relocations(ptr, size)?.count() != 0 {
+        if self.has_non_int_relocations(ptr, size)? {
             return Err(EvalError::ReadPointerAsBytes);
         }
         self.check_defined(ptr, size)?;
@@ -703,7 +703,7 @@ impl<'a, 'tcx> Memory<'a, 'tcx> {
         let offset = ptr.offset as usize;
         match alloc.bytes[offset..].iter().position(|&c| c == 0) {
             Some(size) => {
-                if self.relocations(ptr, (size + 1) as u64)?.count() != 0 {
+                if self.has_non_int_relocations(ptr, (size + 1) as u64)? {
                     return Err(EvalError::ReadPointerAsBytes);
                 }
                 self.check_defined(ptr, (size + 1) as u64)?;
@@ -887,6 +887,12 @@ impl<'a, 'tcx> Memory<'a, 'tcx> {
         Ok(self.get(ptr.alloc_id)?.relocations.range(start..end))
     }
 
+    fn has_non_int_relocations(&self, ptr: Pointer, size: u64)
+        -> EvalResult<'tcx, bool>
+    {
+        Ok(self.relocations(ptr, size)?.any(|(_, &alloc_id)| alloc_id != NEVER_ALLOC_ID))
+    }
+
     fn clear_relocations(&mut self, ptr: Pointer, size: u64) -> EvalResult<'tcx> {
         // Find all relocations overlapping the given range.
         let keys: Vec<_> = self.relocations(ptr, size)?.map(|(&k, _)| k).collect();

tests/run-pass/ptr_int_casts.rs

@@ -0,0 +1,16 @@
+// fn eq_ref<T>(x: &T, y: &T) -> bool {
+//     x as *const _ == y as *const _
+// }
+
+fn main() {
+    // int-ptr-int
+    assert_eq!(1 as *const i32 as usize, 1);
+
+    // TODO
+//     {   // ptr-int-ptr
+//         let x = 13;
+//         let y = &x as *const _ as usize;
+//         let y = y as *const _;
+//         assert!(eq_ref(&x, unsafe { &*y }));
+//     }
+}