fix copy_term/3 infinite looping on cyclic terms

2019-12-03 22:01:38 -07:00
parent 33c60d3434
commit 738ea59e23
1 changed files with 5 additions and 0 deletions
--- a/src/prolog/machine/copier.rs
+++ b/src/prolog/machine/copier.rs
@@ -90,6 +90,11 @@ impl<T: CopierTarget> CopyTermState<T> {
            ra @ Addr::AttrVar(_) | ra @ Addr::HeapCell(..) | ra @ Addr::StackCell(..) => {
                if ra == rd {
                    self.reinstantiate_var(ra, threshold);
+
+                    if let AttrVarPolicy::StripAttributes = self.attr_var_policy {
+                        self.trail.push((Ref::HeapCell(addr), self.target[addr].clone()));
+                        self.target[addr] = HeapCellValue::Addr(Addr::HeapCell(threshold));
+                    }
                } else {
                    self.target[threshold] = HeapCellValue::Addr(ra);
                }