[PATCH 2/7] cex: fix parse state leaks

* src/parse_simulation.c: Fix bug in parse_state_free.
Free new_root when simulate_reduction generates zero states.

* src/parse-simulation.c, src/parse-simulation.h: Create parse_state_list type.
(parse_state_list_append) New.
* src/parse-simulation.c, src/parse-simulation.h, src/counterexample.c:
Replace all uses of lists of parse states and appends to parse_state_lists with the new API.
---
 src/counterexample.c   | 16 +++++-----
 src/parse-simulation.c | 69 ++++++++++++++++++++++++------------------
 src/parse-simulation.h |  9 +++---
 3 files changed, 54 insertions(+), 40 deletions(-)

diff --git a/src/counterexample.c b/src/counterexample.c
index 83813162..7e9c5656 100644
--- a/src/counterexample.c
+++ b/src/counterexample.c
@@ -701,7 +701,8 @@ production_step (search_state *ss, int parser_state)
 {
   const state_item *other_si = parse_state_tail (ss->states[1 - parser_state]);
   symbol_number other_sym = item_number_as_symbol_number (*other_si->item);
-  gl_list_t prods = simulate_production (ss->states[parser_state], other_sym);
+  parse_state_list prods =
+    simulate_production (ss->states[parser_state], other_sym);
   int complexity = ss->complexity + PRODUCTION_COST;
 
   gl_list_iterator_t it = gl_list_iterator (prods);
@@ -751,7 +752,8 @@ reduction_step (search_state *ss, const item_number *conflict_item,
     }
 
   // FIXME: search_state *new_root = copy_search_state (ss);
-  gl_list_t reduced = simulate_reduction (ps, rule_len, symbol_set);
+  parse_state_list reduced =
+    simulate_reduction (ps, rule_len, symbol_set);
   gl_list_iterator_t it = gl_list_iterator (reduced);
   parse_state *reduced_ps;
   while (gl_list_iterator_next (&it, (const void **) &reduced_ps, NULL))
@@ -787,7 +789,7 @@ search_state_prepend (search_state *ss, symbol_number sym, bitset guide)
   if (prod1 != SI_PRODUCTION (si2src))
     {
       int prod_state = prod1 ? 0 : 1;
-      gl_list_t prev = parser_prepend (ss->states[prod_state]);
+      parse_state_list prev = parser_prepend (ss->states[prod_state]);
       gl_list_iterator_t iter = gl_list_iterator (prev);
       parse_state *ps = NULL;
       while (gl_list_iterator_next (&iter, (const void **)&ps, NULL))
@@ -813,8 +815,8 @@ search_state_prepend (search_state *ss, symbol_number sym, bitset guide)
   int complexity_cost = prod1 ? PRODUCTION_COST : UNSHIFT_COST;
   complexity_cost *= 2;
 
-  gl_list_t prev1 = parser_prepend (ss->states[0]);
-  gl_list_t prev2 = parser_prepend (ss->states[1]);
+  parse_state_list prev1 = parser_prepend (ss->states[0]);
+  parse_state_list prev2 = parser_prepend (ss->states[1]);
 
   // loop through each pair of possible prepend states and append search
   // states for each pair where the parser states correspond to the same
@@ -915,8 +917,8 @@ generate_next_states (search_state *ss, state_item *conflict1,
       if (*si1->item == *si2->item)
         {
           int complexity = ss->complexity + 2 * SHIFT_COST;
-          gl_list_t trans1 = simulate_transition (ps1);
-          gl_list_t trans2 = simulate_transition (ps2);
+          parse_state_list trans1 = simulate_transition (ps1);
+          parse_state_list trans2 = simulate_transition (ps2);
           gl_list_iterator_t it1 = gl_list_iterator (trans1);
           parse_state *tps1;
           while (gl_list_iterator_next (&it1, (const void **) &tps1, NULL))
diff --git a/src/parse-simulation.c b/src/parse-simulation.c
index 5648bd5a..6886593e 100644
--- a/src/parse-simulation.c
+++ b/src/parse-simulation.c
@@ -199,7 +199,8 @@ void
 free_parse_state (parse_state *original_ps)
 {
   bool free_contents = true;
-  for (parse_state *ps = original_ps; ps && free_contents; ps = ps->parent)
+  parse_state *parent_ps = NULL;
+  for (parse_state *ps = original_ps; ps && free_contents; ps = parent_ps)
     {
       --ps->reference_count;
       free_contents = (ps->reference_count == 1 && ps->free_contents_early)
@@ -213,11 +214,11 @@ free_parse_state (parse_state *original_ps)
           if (ps->derivs.contents)
             derivation_list_free (ps->derivs.contents);
         }
+      parent_ps = ps->parent;
       if (ps->reference_count <= 0)
         {
           free (ps);
           ++frees;
-          break;
         }
     }
 }
@@ -295,7 +296,7 @@ list_flatten_and_split (gl_list_t *list, gl_list_t *rets, int split, int n,
     }
 }
 
-static gl_list_t
+static parse_state_list
 parse_state_list_new (void)
 {
   return gl_list_create_empty (GL_LINKED_LIST, NULL, NULL,
@@ -303,6 +304,12 @@ parse_state_list_new (void)
                                true);
 }
 
+void parse_state_list_append (parse_state_list pl, parse_state *ps)
+{
+  parse_state_retain (ps);
+  gl_list_add_last (pl, ps);
+}
+
 // Emulates a reduction on a parse state by popping some amount of
 // derivations and state_items off of the parse_state and returning
 // the result in ret. Returns the derivation of what's popped.
@@ -389,7 +396,7 @@ parse_state_lists (parse_state *ps, gl_list_t *sitems,
  * nullable symbols whenever possible from the given state_item.
  */
 void
-nullable_closure (parse_state *ps, state_item *si, gl_list_t state_list)
+nullable_closure (parse_state *ps, state_item *si, parse_state_list state_list)
 {
   parse_state *current_ps = ps;
   state_item_number prev_sin = si - state_items;
@@ -405,8 +412,7 @@ nullable_closure (parse_state *ps, state_item *si, gl_list_t state_list)
       current_ps = copy_parse_state (false, current_ps);
       ps_si_append (current_ps, nsi);
       ps_derivs_append (current_ps, derivation_new_leaf (sp));
-      parse_state_retain (current_ps);
-      gl_list_add_last (state_list, current_ps);
+      parse_state_list_append (state_list, current_ps);
     }
 }
 
@@ -427,8 +433,7 @@ simulate_transition (parse_state *ps)
   parse_state *next_ps = copy_parse_state (false, ps);
   ps_si_append (next_ps, state_items + si_next);
   ps_derivs_append (next_ps, derivation_new_leaf (sym));
-  parse_state_retain (next_ps);
-  gl_list_add_last (result, next_ps);
+  parse_state_list_append (result, next_ps);
 
   nullable_closure (next_ps, state_items + si_next, result);
   return result;
@@ -473,8 +478,7 @@ simulate_production (parse_state *ps, symbol_number compat_sym)
             continue;
           parse_state *next_ps = copy_parse_state (false, ps);
           ps_si_append (next_ps, next);
-          parse_state_retain (next_ps);
-          gl_list_add_last (result, next_ps);
+          parse_state_list_append (result, next_ps);
           if (next_ps->depth >= 0)
             ++next_ps->depth;
           nullable_closure (next_ps, next, result);
@@ -512,8 +516,7 @@ simulate_reduction (parse_state *ps, int rule_len, bitset symbol_set)
     {
       state_item *tail = (state_item *) new_root->state_items.tail_elt;
       ps_si_append (new_root, state_items + si_trans[tail - state_items]);
-      parse_state_retain (new_root);
-      gl_list_add_last (result, new_root);
+      parse_state_list_append (result, new_root);
     }
   else
     {
@@ -521,22 +524,31 @@ simulate_reduction (parse_state *ps, int rule_len, bitset symbol_set)
       // with possible source state-items.
       const state_item *head = ps->state_items.head_elt;
       gl_list_t prev = lssi_reverse_production (head, symbol_set);
-      gl_list_iterator_t it = gl_list_iterator (prev);
-      state_item *psis;
-      while (gl_list_iterator_next (&it, (const void **) &psis, NULL))
+      // TODO: better understand what causes this case.
+      if (gl_list_size (prev) == 0)
+        {
+          // new_root needs to have an RC of 1 to be freed correctly here.
+          parse_state_retain (new_root);
+          free_parse_state (new_root);
+        }
+      else
         {
-          //Prepend the result from the reverse production
-          parse_state *copy = copy_parse_state (true, new_root);
-          ps_si_prepend (copy, psis);
-
-          // Append the left hand side to the end of the parser state
-          copy = copy_parse_state (false, copy);
-          struct si_chunk *sis = &copy->state_items;
-          const state_item *tail = sis->tail_elt;
-          ps_si_append (copy, state_items + si_trans[tail - state_items]);
-          parse_state_retain (copy);
-          gl_list_add_last (result, copy);
-          nullable_closure (copy, (state_item *) sis->tail_elt, result);
+          gl_list_iterator_t it = gl_list_iterator (prev);
+          state_item *psis;
+          while (gl_list_iterator_next (&it, (const void **) &psis, NULL))
+            {
+              //Prepend the result from the reverse production
+              parse_state *copy = copy_parse_state (true, new_root);
+              ps_si_prepend (copy, psis);
+
+              // Append the left hand side to the end of the parser state
+              copy = copy_parse_state (false, copy);
+              struct si_chunk *sis = &copy->state_items;
+              const state_item *tail = sis->tail_elt;
+              ps_si_append (copy, state_items + si_trans[tail - state_items]);
+              parse_state_list_append (result, copy);
+              nullable_closure (copy, (state_item *) sis->tail_elt, result);
+            }
         }
       gl_list_free (prev);
     }
@@ -556,11 +568,10 @@ parser_prepend (parse_state *ps)
   BITSET_FOR_EACH (biter, prev, sin, 0)
   {
     parse_state *copy = copy_parse_state (true, ps);
-    parse_state_retain (copy);
     ps_si_prepend (copy, state_items + sin);
     if (SI_TRANSITION (head))
       ps_derivs_prepend (copy, derivation_new_leaf (prepend_sym));
-    gl_list_add_last (result, copy);
+    parse_state_list_append (result, copy);
   }
   return result;
 }
diff --git a/src/parse-simulation.h b/src/parse-simulation.h
index a912f012..ae9410f6 100644
--- a/src/parse-simulation.h
+++ b/src/parse-simulation.h
@@ -72,6 +72,7 @@
  */
 
 typedef struct parse_state parse_state;
+typedef gl_list_t parse_state_list;
 
 parse_state *new_parse_state (const state_item *conflict);
 
@@ -110,22 +111,22 @@ void parse_state_lists (parse_state *ps, gl_list_t *state_items,
 /* Look at the tail state-item of the parse state and transition on the symbol
  * after its dot. The symbol gets added to derivs, and the resulting state-item
  * is appended to state-items. */
-gl_list_t simulate_transition (parse_state *ps);
+parse_state_list simulate_transition (parse_state *ps);
 
 /* Look at all of the productions for the non-terminal following the dot in the tail
  * state-item. Appends to state-items each production state-item which may start with
  * compat_sym. */
-gl_list_t simulate_production (parse_state *ps, symbol_number compat_sym);
+parse_state_list simulate_production (parse_state *ps, symbol_number compat_sym);
 
 /* Removes the last rule_len state-items along with their derivations. A new state-item is
  * appended representing the goto after the reduction. A derivation for the non-terminal that
  * was just reduced is appended which consists of the list of derivations that were just removed. */
-gl_list_t simulate_reduction (parse_state *ps, int rule_len,
+parse_state_list simulate_reduction (parse_state *ps, int rule_len,
                               bitset symbol_set);
 
 /* Generate states with a state-item prepended for each state-item that has a
  * transition or production step to ps's head. */
-gl_list_t parser_prepend (parse_state *ps);
+parse_state_list parser_prepend (parse_state *ps);
 
 void print_parse_state (parse_state *ps);
 
-- 
2.20.1 (Apple Git-117)