cex: display the rule numbers

From

    Example: "if" expr "then" "if" expr "then" stmt • "else" stmt
    Shift derivation
      if_stmt
      ↳ "if" expr "then" stmt
                         ↳ if_stmt
                           ↳ "if" expr "then" stmt • "else" stmt
    Reduce derivation
      if_stmt
      ↳ "if" expr "then" stmt                        "else" stmt
                         ↳ if_stmt
                           ↳ "if" expr "then" stmt •

to

    Example: "if" expr "then" "if" expr "then" stmt • "else" stmt
    Shift derivation
      if_stmt
      ↳ 3: "if" expr "then" stmt
                            ↳ 2: if_stmt
                                 ↳ 4: "if" expr "then" stmt • "else" stmt
    Example: "if" expr "then" "if" expr "then" stmt • "else" stmt
    Reduce derivation
      if_stmt
      ↳ 4: "if" expr "then" stmt                              "else" stmt
                            ↳ 2: if_stmt
                                 ↳ 3: "if" expr "then" stmt •

* src/state-item.h, src/state-item.c (state_item_rule): New.
* src/derivation.h, src/derivation.c (struct derivation): Add a rule
member.
Adjust dependencies.
* src/counterexample.c, src/parse-simulation.c: Pass the rule to
derivation_new.
* src/derivation.c (fprintf_if): New.
(derivation_width, derivation_print_tree_impl): Take the rule number
into account.

* tests/conflicts.at, tests/counterexample.at, tests/diagnostics.at,
* tests/report.at: Adjust.

* doc/bison.texi: Adjust.

src/counterexample.c

@@ -288,7 +288,8 @@ expand_to_conflict (state_item_number start, symbol_number conflict_sym)
             derivation_list_append (result, derivation_new_leaf (*i));
           symbol_number lhs =
             rules[item_number_as_rule_number (*i)].lhs->number;
-          derivation *deriv = derivation_new (lhs, result);
+          derivation *deriv = derivation_new (lhs, result,
+                                              state_item_rule (si));
           result = derivation_list_new ();
           derivation_list_append (result, deriv);
         }
@@ -422,7 +423,7 @@ complete_diverging_example (symbol_number conflict_sym,
             derivation_list_prepend (result, derivation_new_leaf (*i));
         }
       // completing the derivation
-      derivation *new_deriv = derivation_new (r->lhs->number, result);
+      derivation *new_deriv = derivation_new (r->lhs->number, result, r);
       result = derivation_list_new ();
       derivation_list_append (result, new_deriv);
     }

src/derivation.c

@@ -25,6 +25,7 @@
 #include <c-ctype.h>
 #include <gl_linked_list.h>
 #include <mbswidth.h>
+#include <vasnprintf.h>
 
 #include "system.h"
 #include "complain.h"
@@ -34,13 +35,15 @@ struct derivation
   symbol_number sym;
   derivation_list children;
   int reference_count;
+  // The rule SYM -> CHILDREN.
+  const rule *rule;
   // Color assigned for styling.  Guarantees that the derivation is
   // always displayed with the same color, independently of the order
   // in which the derivations are traversed.
   int color;
 };
 
-static derivation d_dot = { -1, NULL, -1, -1 };
+static derivation d_dot = { -1, NULL, -1, NULL, -1 };
 
 derivation *
 derivation_dot (void)
@@ -74,12 +77,14 @@ void derivation_list_free (derivation_list dl)
 }
 
 derivation *
-derivation_new (symbol_number sym, derivation_list children)
+derivation_new (symbol_number sym, derivation_list children,
+                const rule *r)
 {
   derivation *res = xmalloc (sizeof *res);
   res->sym = sym;
   res->children = children;
   res->reference_count = 0;
+  res->rule = r;
   res->color = -1;
   return res;
 }
@@ -205,6 +210,23 @@ fputs_if (bool cond, FILE *out, int *padding, const char *s)
   return res;
 }
 
+static int
+fprintf_if (bool cond, FILE *out, int *padding, const char *fmt, ...)
+{
+  char buf[256];
+  size_t len = sizeof (buf);
+  va_list args;
+  va_start (args, fmt);
+  char *cp = vasnprintf (buf, &len, fmt, args);
+  va_end (args);
+  if (!cp)
+    xalloc_die ();
+  int res = fputs_if (cond, out, padding, cp);
+  if (cp != buf)
+    free (cp);
+  return res;
+}
+
 // The width taken to report this derivation recursively down to its
 // leaves.
 static int
@@ -217,6 +239,7 @@ derivation_width (const derivation *deriv)
 
       // Arrow and space.
       int children_width = down_arrow_width;
+      children_width += snprintf (NULL, 0, "%d: ", deriv->rule->number);
       if (gl_list_size (deriv->children) == 0)
         // Empty rhs.
         children_width += empty_width;
@@ -281,6 +304,7 @@ derivation_print_tree_impl (const derivation *deriv, FILE *out,
       else
         {
           res += fputs_if (depth == 1, out, padding, down_arrow);
+          res += fprintf_if (depth == 1, out, padding, "%d: ", deriv->rule->number);
           if (gl_list_size (deriv->children) == 0)
             // Empty rhs.
             res += fputs_if (depth == 1, out, padding, empty);

src/derivation.h

@@ -54,11 +54,14 @@ 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);
 
-derivation *derivation_new (symbol_number sym, derivation_list children);
+// rule_num is the number of the rule SYM -> CHILDREN.
+derivation *
+derivation_new (symbol_number sym, derivation_list children,
+                const rule *r);
 
 static inline derivation *derivation_new_leaf (symbol_number sym)
 {
-  return derivation_new (sym, NULL);
+  return derivation_new (sym, NULL, NULL);
 }
 
 // Number of symbols.

src/parse-simulation.c

@@ -421,7 +421,9 @@ nullable_closure (parse_state *ps, state_item *si, parse_state_list state_list)
       state_item *nsi = &state_items[sin];
       current_ps = copy_parse_state (false, current_ps);
       ps_si_append (current_ps, nsi);
-      ps_derivs_append (current_ps, derivation_new (sp, derivation_list_new ()));
+      ps_derivs_append (current_ps,
+                        derivation_new (sp, derivation_list_new (),
+                                        state_item_rule (nsi)));
       parse_state_list_append (state_list, current_ps);
     }
 }
@@ -516,7 +518,7 @@ simulate_reduction (parse_state *ps, int rule_len, bitset symbol_set)
   state_item *si = (state_item *) ps->state_items.tail_elt;
   const rule *r = item_rule (si->item);
   symbol_number lhs = r->lhs->number;
-  derivation *deriv = derivation_new (lhs, popped_derivs);
+  derivation *deriv = derivation_new (lhs, popped_derivs, state_item_rule (si));
   --new_root->depth;
   ps_derivs_append (new_root, deriv);
 

src/state-item.c

@@ -482,6 +482,12 @@ state_item_print (const state_item *si, FILE *out, const char *prefix)
   putc ('\n', out);
 }
 
+const rule*
+state_item_rule (const state_item *si)
+{
+  return item_rule (si->item);
+}
+
 /**
  * Report the state_item graph
  */

src/state-item.h

@@ -93,6 +93,7 @@ void state_items_init (void);
 void state_items_free (void);
 
 void state_item_print (const state_item *si, FILE *out, const char *prefix);
+const rule *state_item_rule (const state_item *si);
 
 bool production_allowed (const state_item *si, const state_item *next);