lists: fix various issues with the use of gnulib's list

First, we should avoid code such as

    gl_list_iterator_t it = gl_list_iterator (deriv->children);
    derivation *child = NULL;
    while (gl_list_iterator_next (&it, (const void **) &child, NULL))
      {
        derivation_print (child, f);

because of -Wstrict-aliasing (whose job is to catch type-punning
issues).  See https://lists.gnu.org/r/bug-bison/2020-05/msg00039.html.

Rather we need

    gl_list_iterator_t it = gl_list_iterator (deriv->children);
    const void **p = NULL;
    while (gl_list_iterator_next (&it, &p, NULL))
      {
        derivation *child = (derivation *) p;
        derivation_print (child, f);

Second, list iterators actually have destructors.  Even though they
are noop in the case of linked-lists, we should use them.

Let's address both issues with typed wrappers (such as
derivation_list_next) that take care of both issues, and besides allow
to scope the iterators within the loop:

    derivation *child;
    for (gl_list_iterator_t it = gl_list_iterator (deriv->children);
         derivation_list_next (&it, &child);
         )
      {
        derivation_print (child, f);

* src/derivation.h, src/derivation.c (derivation_list_next): New.
Use it where appropriate.
* src/counterexample.c (search_state_list_next): New.
Use it where appropriate.
* src/parse-simulation.h, src/parse-simulation.c
* src/state-item.h (state_item_list_next): New.
Use it where appropriate.

src/counterexample.c

@@ -334,9 +334,9 @@ complete_diverging_example (symbol_number conflict_sym,
               lookahead_required = false;
               derivation_list next_derivs =
                 expand_to_conflict (nsi, conflict_sym);
-              gl_list_iterator_t it = gl_list_iterator (next_derivs);
               derivation *d = NULL;
-              while (gl_list_iterator_next (&it, (const void **) &d, NULL))
+              for (gl_list_iterator_t it = gl_list_iterator (next_derivs);
+                   derivation_list_next (&it, &d);)
                 derivation_list_append (result, d);
               i += gl_list_size (next_derivs) - 1;
               derivation_list_free (next_derivs);
@@ -469,9 +469,10 @@ nonunifying_shift_path (gl_list_t reduce_path, state_item *shift_conflict)
   if (trace_flag & trace_cex)
     {
       fputs ("SHIFT ITEM PATH:\n", stderr);
-      gl_list_iterator_t it = gl_list_iterator (result);
       state_item *sip = NULL;
-      while (gl_list_iterator_next (&it, (const void **) &sip, NULL))
+      for (gl_list_iterator_t it = gl_list_iterator (result);
+           state_item_list_next (&it, &sip);
+           )
         print_state_item (sip, stderr);
     }
   return result;
@@ -574,6 +575,18 @@ search_state_print (search_state *ss)
   putc ('\n', stderr);
 }
 
+static inline bool
+search_state_list_next (gl_list_iterator_t *it, search_state **ss)
+{
+  const void *p = NULL;
+  bool res = gl_list_iterator_next (it, &p, NULL);
+  if (res)
+    *ss = (search_state*) p;
+  else
+    gl_list_iterator_free (it);
+  return res;
+}
+
 /*
  * When a search state is copied, this is used to
  * directly set one of the parse states
@@ -712,9 +725,10 @@ production_step (search_state *ss, int parser_state)
     simulate_production (ss->states[parser_state], other_sym);
   int complexity = ss->complexity + PRODUCTION_COST;
 
-  gl_list_iterator_t it = gl_list_iterator (prods);
   parse_state *ps = NULL;
-  while (gl_list_iterator_next (&it, (const void **) &ps, NULL))
+  for (gl_list_iterator_t it = gl_list_iterator (prods);
+       parse_state_list_next (&it, &ps);
+       )
     {
       search_state *copy = copy_search_state (ss);
       ss_set_parse_state (copy, parser_state, ps);
@@ -761,9 +775,10 @@ reduction_step (search_state *ss, const item_number *conflict_item,
   // FIXME: search_state *new_root = copy_search_state (ss);
   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))
+  parse_state *reduced_ps = NULL;
+  for (gl_list_iterator_t it = gl_list_iterator (reduced);
+       parse_state_list_next (&it, &reduced_ps);
+       )
     {
       search_state *copy = copy_search_state (ss);
       ss_set_parse_state (copy, parser_state, reduced_ps);
@@ -797,9 +812,10 @@ search_state_prepend (search_state *ss, symbol_number sym, bitset guide)
     {
       int prod_state = prod1 ? 0 : 1;
       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))
+      for (gl_list_iterator_t iter = gl_list_iterator (prev);
+           parse_state_list_next (&iter, &ps);
+           )
         {
           const state_item *psi = parse_state_head (ps);
           bool guided = bitset_test (guide, psi->state->number);
@@ -828,18 +844,20 @@ search_state_prepend (search_state *ss, symbol_number sym, bitset guide)
   // loop through each pair of possible prepend states and append search
   // states for each pair where the parser states correspond to the same
   // parsed input.
-  gl_list_iterator_t iter1 = gl_list_iterator (prev1);
-  parse_state *ps1;
-  while (gl_list_iterator_next (&iter1, (const void **)&ps1, NULL))
+  parse_state *ps1 = NULL;
+  for (gl_list_iterator_t iter1 = gl_list_iterator (prev1);
+       parse_state_list_next (&iter1, &ps1);
+       )
     {
       const state_item *psi1 = parse_state_head (ps1);
       bool guided1 = bitset_test (guide, psi1->state->number);
       if (!guided1 && !EXTENDED_SEARCH)
         continue;
 
-      gl_list_iterator_t iter2 = gl_list_iterator (prev2);
-      parse_state *ps2;
-      while (gl_list_iterator_next (&iter2, (const void **)&ps2, NULL))
+      parse_state *ps2 = NULL;
+      for (gl_list_iterator_t iter2 = gl_list_iterator (prev2);
+           parse_state_list_next (&iter2, &ps2);
+           )
         {
           const state_item *psi2 = parse_state_head (ps2);
 
@@ -926,16 +944,15 @@ generate_next_states (search_state *ss, state_item *conflict1,
           int complexity = ss->complexity + 2 * SHIFT_COST;
           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))
-            {
-              gl_list_iterator_t it2 = gl_list_iterator (trans2);
-              parse_state *tps2;
-              while (gl_list_iterator_next
-                     (&it2, (const void **) &tps2, NULL))
-                ssb_append (new_search_state (tps1, tps2, complexity));
-            }
+          parse_state *tps1 = NULL;
+          parse_state *tps2 = NULL;
+          for (gl_list_iterator_t it1 = gl_list_iterator (trans1);
+               parse_state_list_next (&it1, &tps1);
+               )
+            for (gl_list_iterator_t it2 = gl_list_iterator (trans2);
+                 parse_state_list_next (&it2, &tps2);
+                 )
+              ssb_append (new_search_state (tps1, tps2, complexity));
           gl_list_free (trans1);
           gl_list_free (trans2);
         }
@@ -958,43 +975,48 @@ generate_next_states (search_state *ss, state_item *conflict1,
       int len2 = rhe2 - rhs2;
       int size2 = parse_state_length (ps2);
       bool ready2 = si2reduce && len2 < size2;
-      // If there is a path ready for reduction
-      // without being prepended further, reduce.
-      if (ready1)
+      // If there is a path ready for reduction without being
+      // prepended further, reduce.
+      if (ready1 && ready2)
         {
           gl_list_t reduced1 = reduction_step (ss, conflict1->item, 0, len1);
-          gl_list_iterator_t iter = gl_list_iterator (reduced1);
+          gl_list_add_last (reduced1, ss);
           search_state *red1 = NULL;
-          if (ready2)
+          for (gl_list_iterator_t iter = gl_list_iterator (reduced1);
+               search_state_list_next (&iter, &red1);
+               )
             {
-              gl_list_add_last (reduced1, ss);
-              while (gl_list_iterator_next
-                     (&iter, (const void **) &red1, NULL))
-                {
-                  gl_list_t reduced2 =
-                    reduction_step (red1, conflict2->item, 1, len2);
-                  gl_list_iterator_t iter2 = gl_list_iterator (reduced2);
-                  search_state *red2;
-                  while (gl_list_iterator_next
-                         (&iter2, (const void **) &red2, NULL))
-                    ssb_append (red2);
-                  // avoid duplicates
-                  if (red1 != ss)
-                    ssb_append (red1);
-                  gl_list_free (reduced2);
-                }
+              gl_list_t reduced2 =
+                reduction_step (red1, conflict2->item, 1, len2);
+              search_state *red2 = NULL;
+              for (gl_list_iterator_t iter2 = gl_list_iterator (reduced2);
+                   search_state_list_next (&iter2, &red2);
+                   )
+                ssb_append (red2);
+              // Avoid duplicates.
+              if (red1 != ss)
+                ssb_append (red1);
+              gl_list_free (reduced2);
             }
-          else
-            while (gl_list_iterator_next (&iter, (const void **) &red1, NULL))
-              ssb_append (red1);
+          gl_list_free (reduced1);
+        }
+      else if (ready1)
+        {
+          gl_list_t reduced1 = reduction_step (ss, conflict1->item, 0, len1);
+          search_state *red1 = NULL;
+          for (gl_list_iterator_t iter = gl_list_iterator (reduced1);
+               search_state_list_next (&iter, &red1);
+               )
+            ssb_append (red1);
           gl_list_free (reduced1);
         }
       else if (ready2)
         {
           gl_list_t reduced2 = reduction_step (ss, conflict2->item, 1, len2);
-          gl_list_iterator_t iter2 = gl_list_iterator (reduced2);
-          search_state *red2;
-          while (gl_list_iterator_next (&iter2, (const void **) &red2, NULL))
+          search_state *red2 = NULL;
+          for (gl_list_iterator_t iter2 = gl_list_iterator (reduced2);
+               search_state_list_next (&iter2, &red2);
+               )
             ssb_append (red2);
           gl_list_free (reduced2);
         }
@@ -1046,9 +1068,11 @@ unifying_example (state_item_number itm1,
   while (gl_list_size (ssb_queue) > 0)
     {
       const search_state_bundle *ssb = gl_list_get_at (ssb_queue, 0);
-      gl_list_iterator_t it = gl_list_iterator (ssb->states);
+
       search_state *ss = NULL;
-      while (gl_list_iterator_next (&it, (const void **) &ss, NULL))
+      for (gl_list_iterator_t it = gl_list_iterator (ssb->states);
+           search_state_list_next (&it, &ss);
+           )
         {
           if (trace_flag & trace_cex)
             search_state_print (ss);
@@ -1157,19 +1181,21 @@ counterexample_report (state_item_number itm1, state_item_number itm2,
   // Compute the shortest lookahead-sensitive path and associated sets of
   // parser states.
   gl_list_t shortest_path = shortest_path_from_start (itm1, next_sym);
-  bool reduceProdReached = false;
+  bool reduce_prod_reached = false;
   const rule *reduce_rule = item_rule (state_items[itm1].item);
 
   bitset_zero (scp_set);
   bitset_zero (rpp_set);
-  gl_list_iterator_t it = gl_list_iterator (shortest_path);
+
   state_item *si = NULL;
-  while (gl_list_iterator_next (&it, (const void **) &si, NULL))
+  for (gl_list_iterator_t it = gl_list_iterator (shortest_path);
+       state_item_list_next (&it, &si);
+       )
     {
       bitset_set (scp_set, si->state->number);
-      reduceProdReached = reduceProdReached
+      reduce_prod_reached = reduce_prod_reached
                           || item_rule (si->item) == reduce_rule;
-      if (reduceProdReached)
+      if (reduce_prod_reached)
         bitset_set (rpp_set, si->state->number);
     }
   time_t t = time (NULL);

src/derivation.c

@@ -55,9 +55,10 @@ derivation_list_prepend (derivation_list dl, derivation *d)
 
 void derivation_list_free (derivation_list dl)
 {
-  gl_list_iterator_t it = gl_list_iterator (dl);
-  derivation *d;
-  while (gl_list_iterator_next (&it, (const void **) &d, NULL))
+  derivation *d = NULL;
+  for (gl_list_iterator_t it = gl_list_iterator (dl);
+       derivation_list_next (&it, &d);
+       )
     if (d != &d_dot)
       derivation_free (d);
   gl_list_free (dl);
@@ -94,9 +95,10 @@ derivation_free (derivation *d)
         {
           if (deriv->children)
             {
-              gl_list_iterator_t it = gl_list_iterator (deriv->children);
-              derivation *child;
-              while (gl_list_iterator_next (&it, (const void **) &child, NULL))
+              derivation *child = NULL;
+              for (gl_list_iterator_t it = gl_list_iterator (deriv->children);
+                   derivation_list_next (&it, &child);
+                   )
                 if (child != &d_dot)
                   gl_list_add_last (free_queue, child);
               gl_list_free (deriv->children);
@@ -114,9 +116,10 @@ derivation_size (const derivation *deriv)
   if (!deriv->children)
     return 1;
   int size = 1;
-  gl_list_iterator_t it = gl_list_iterator (deriv->children);
-  derivation *child;
-  while (gl_list_iterator_next (&it, (const void **) &child, NULL))
+  derivation *child = NULL;
+  for (gl_list_iterator_t it = gl_list_iterator (deriv->children);
+       derivation_list_next (&it, &child);
+       )
     size += derivation_size (child);
   return size;
 }
@@ -136,10 +139,12 @@ derivation_print (const derivation *deriv, FILE *f)
       fprintf (f, " %s", sym->tag);
       return;
     }
-  gl_list_iterator_t it = gl_list_iterator (deriv->children);
-  derivation *child;
+
   fprintf (f, " %s ::=[", sym->tag);
-  while (gl_list_iterator_next (&it, (const void **) &child, NULL))
+  derivation *child;
+  for (gl_list_iterator_t it = gl_list_iterator (deriv->children);
+       derivation_list_next (&it, &child);
+       )
     {
       derivation_print (child, f);
       fputs (" ", f);
@@ -162,10 +167,11 @@ derivation_print_leaves (const derivation *deriv, FILE *f)
       return;
     }
 
-  gl_list_iterator_t it = gl_list_iterator (deriv->children);
   const char *sep = "";
   derivation *child;
-  while (gl_list_iterator_next (&it, (const void **) &child, NULL))
+  for (gl_list_iterator_t it = gl_list_iterator (deriv->children);
+       derivation_list_next (&it, &child);
+       )
     {
       fputs (sep, f);
       sep = "  ";

src/derivation.h

@@ -37,6 +37,18 @@ static inline derivation_list derivation_list_new (void)
   return gl_list_create_empty (GL_LINKED_LIST, NULL, NULL, NULL, true);
 }
 
+static inline bool
+derivation_list_next (gl_list_iterator_t *it, derivation **d)
+{
+  const void *p = NULL;
+  bool res = gl_list_iterator_next (it, &p, NULL);
+  if (res)
+    *d = (derivation *) p;
+  else
+    gl_list_iterator_free (it);
+  return res;
+}
+
 void derivation_list_append (derivation_list dl, derivation *d);
 void derivation_list_prepend (derivation_list dl, derivation *d);
 void derivation_list_free (derivation_list dl);

src/parse-simulation.c

@@ -253,10 +253,12 @@ parse_state_completed_steps (const parse_state *ps, int *shifts, int *production
 
   gl_list_t sis = root_ps->state_items.contents;
   int count = 0;
-  gl_list_iterator_t it = gl_list_iterator (sis);
+
   state_item *last = NULL;
   state_item *next = NULL;
-  while (gl_list_iterator_next (&it, (const void **) &next, NULL))
+  for (gl_list_iterator_t it = gl_list_iterator (sis);
+       state_item_list_next (&it, &next);
+       )
     {
       if (last && last->state == next->state)
         ++count;
@@ -285,22 +287,24 @@ list_flatten_and_split (gl_list_t *list, gl_list_t *rets, int split, int n,
   int ret_array = 0;
   for (int i = 0; i < n; ++i)
     {
+      const void *p = NULL;
       gl_list_iterator_t it = gl_list_iterator (list[i]);
-      gl_list_t l;
-      while (gl_list_iterator_next (&it, (const void **) &l, NULL))
-        {
-          if (!l)
-            continue;
-          gl_list_iterator_t it2 = gl_list_iterator (l);
-          void *si;
-          while (gl_list_iterator_next (&it2, (const void **) &si, NULL))
-            {
-              if (ret_index++ == split)
-                ++ret_array;
-              if (rets[ret_array])
-                append_fn (rets[ret_array], si);
-            }
-        }
+      while (gl_list_iterator_next (&it, &p, NULL))
+        if (p)
+          {
+            gl_list_t l = (gl_list_t) p;
+            const void *si = NULL;
+            gl_list_iterator_t it2 = gl_list_iterator (l);
+            while (gl_list_iterator_next (&it2, &si, NULL))
+              {
+                if (ret_index++ == split)
+                  ++ret_array;
+                if (rets[ret_array])
+                  append_fn (rets[ret_array], si);
+              }
+            gl_list_iterator_free (&it2);
+          }
+      gl_list_iterator_free (&it);
     }
 }
 
@@ -540,11 +544,12 @@ simulate_reduction (parse_state *ps, int rule_len, bitset symbol_set)
         }
       else
         {
-          gl_list_iterator_t it = gl_list_iterator (prev);
-          state_item *psis;
-          while (gl_list_iterator_next (&it, (const void **) &psis, NULL))
+          state_item *psis = NULL;
+          for (gl_list_iterator_t it = gl_list_iterator (prev);
+               state_item_list_next (&it, &psis);
+               )
             {
-              //Prepend the result from the reverse production
+              // Prepend the result from the reverse production.
               parse_state *copy = copy_parse_state (true, new_root);
               ps_si_prepend (copy, psis);
 

src/parse-simulation.h

@@ -74,6 +74,18 @@
 typedef struct parse_state parse_state;
 typedef gl_list_t parse_state_list;
 
+static inline bool
+parse_state_list_next (gl_list_iterator_t *it, parse_state **ps)
+{
+  const void *p = NULL;
+  bool res = gl_list_iterator_next (it, &p, NULL);
+  if (res)
+    *ps = (parse_state *) p;
+  else
+    gl_list_iterator_free (it);
+  return res;
+}
+
 parse_state *new_parse_state (const state_item *conflict);
 
 size_t parse_state_hasher (const parse_state *ps, size_t max);

src/state-item.h

@@ -92,4 +92,17 @@ void state_items_free (void);
 
 bool production_allowed (const state_item *si, const state_item *next);
 
+static inline bool
+state_item_list_next (gl_list_iterator_t *it, state_item **si)
+{
+  const void *p = NULL;
+  bool res = gl_list_iterator_next (it, &p, NULL);
+  if (res)
+    *si = (state_item *) p;
+  else
+    gl_list_iterator_free (it);
+  return res;
+}
+
+
 #endif /* STATE_ITEM_H */