From: Mark Thom <markjordanthom@gmail.com>
Date: Sat, 2 Feb 2019 19:45:50 +0000 (-0700)
Subject: record perm vars only while resident stack frame is still up
X-Git-Tag: v0.8.110~280
X-Git-Url: https://git.sagredo.dev/?a=commitdiff_plain;h=a28c8934f3b7a29cdaab5d32e351dcb05db6bbff;p=scryer-prolog.git

record perm vars only while resident stack frame is still up
---

diff --git a/src/prolog/machine/mod.rs b/src/prolog/machine/mod.rs
index a13cd773..c4ada3f1 100644
--- a/src/prolog/machine/mod.rs
+++ b/src/prolog/machine/mod.rs
@@ -592,13 +592,14 @@ impl MachineState {
     {
         for (var, var_data) in alloc_locs {
             match var_data {
-                &VarData::Perm(p) if p > 0 => {
-                    let e = self.e;
-                    let r = var_data.as_reg_type().reg_num();
-                    let addr = self.and_stack[e][r].clone();
+                &VarData::Perm(p) if p > 0 =>
+                    if !heap_locs.contains_key(var) {
+                        let e = self.e;
+                        let r = var_data.as_reg_type().reg_num(); // crashes here.
+                        let addr = self.and_stack[e][r].clone();
 
-                    heap_locs.insert(var.clone(), addr);
-                },
+                        heap_locs.insert(var.clone(), addr);
+                    },
                 &VarData::Temp(cn, _, _) if cn == chunk_num => {
                     let r = var_data.as_reg_type();