From c55bfa2c6e816824f8928bde3717d94fc2ec8491 Mon Sep 17 00:00:00 2001
From: Mark Thom <markjordanthom@gmail.com>
Date: Sun, 13 Mar 2022 10:48:03 -0600
Subject: [PATCH] throw errors on cycles in sort/2 and keysort/2 (#1350 and
 #1351)

---
 src/heap_print.rs             | 2 +-
 src/machine/machine_errors.rs | 8 ++++----
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/src/heap_print.rs b/src/heap_print.rs
index 18d2d427..5380133f 100644
--- a/src/heap_print.rs
+++ b/src/heap_print.rs
@@ -1193,7 +1193,7 @@ impl<'a, Outputter: HCValueOutputter> HCPrinter<'a, Outputter> {
                         self.state_stack.push(TokenOrRedirect::Atom(atom!("...")));
                         self.state_stack.push(TokenOrRedirect::HeadTailSeparator);
                     } else if end_cell != empty_list_as_cell!() {
-                        if value.get_tag() != HeapCellValueTag::CStr {
+                        if end_h != h+1 && value.get_tag() != HeapCellValueTag::CStr {
                             self.iter.pop_stack();
                             self.iter.push_stack(h+1);
                         }
diff --git a/src/machine/machine_errors.rs b/src/machine/machine_errors.rs
index 889eb7ee..ced4c1af 100644
--- a/src/machine/machine_errors.rs
+++ b/src/machine/machine_errors.rs
@@ -792,7 +792,7 @@ impl MachineState {
                 let err = self.instantiation_error();
                 return Err(self.error_form(err, stub_gen()))
             }
-            CycleSearchResult::NotList(..) => {
+            CycleSearchResult::NotList(..) | CycleSearchResult::Cyclic(_) => {
                 let err = self.type_error(ValidType::List, list);
                 return Err(self.error_form(err, stub_gen()));
             }
@@ -800,7 +800,7 @@ impl MachineState {
         };
 
         match BrentAlgState::detect_cycles(&self.heap, sorted) {
-            CycleSearchResult::NotList(..) if !sorted.is_var() => {
+            CycleSearchResult::NotList(..) | CycleSearchResult::Cyclic(_) if !sorted.is_var() => {
                 let err = self.type_error(ValidType::List, sorted);
                 Err(self.error_form(err, stub_gen()))
             }
@@ -812,7 +812,7 @@ impl MachineState {
         let stub_gen = || functor_stub(atom!("keysort"), 2);
 
         match BrentAlgState::detect_cycles(&self.heap, list) {
-            CycleSearchResult::NotList(..) if !list.is_var() => {
+            CycleSearchResult::NotList(..) | CycleSearchResult::Cyclic(_) if !list.is_var() => {
                 let err = self.type_error(ValidType::List, list);
                 Err(self.error_form(err, stub_gen()))
             }
@@ -878,7 +878,7 @@ impl MachineState {
                 let err = self.instantiation_error();
                 Err(self.error_form(err, stub_gen()))
             }
-            CycleSearchResult::NotList(..) => {
+            CycleSearchResult::NotList(..) | CycleSearchResult::Cyclic(_) => {
                 let err = self.type_error(ValidType::List, pairs);
                 Err(self.error_form(err, stub_gen()))
             }
-- 
2.54.0