do not deref AttrVar binding in redo_attr_var_binding (#2059)

2023-09-28 15:25:57 -06:00
parent 40d3345cd5
commit 11cd42379b
1 changed files with 3 additions and 1 deletions
--- a/src/machine/system_calls.rs
+++ b/src/machine/system_calls.rs
@@ -5659,7 +5659,9 @@ impl Machine {
    }
    #[inline(always)]
    pub(crate) fn redo_attr_var_binding(&mut self) {
-        let var = self.deref_register(1);
+        // registers[1] MUST NOT be dereferenced here. the original
+        // AttrVar binding site must be preserved.
+        let var = self.machine_st.registers[1];
        let value = self.deref_register(2);

        debug_assert_eq!(HeapCellValueTag::AttrVar, var.get_tag());