X-Git-Url: https://git.saurik.com/bison.git/blobdiff_plain/8efe435c059af57671105fd8671ba97bb8474264..d0ee410565c9d7bc876af42583ee092568f44fa8:/src/reader.c?ds=inline

diff --git a/src/reader.c b/src/reader.c
index f66a7607..7758c772 100644
--- a/src/reader.c
+++ b/src/reader.c
@@ -1,178 +1,158 @@
-/* Input parser for bison
-   Copyright (C) 1984, 1986, 1989, 1992, 1998, 2000, 2001, 2002
-   Free Software Foundation, Inc.
+/* Input parser for Bison
+
+   Copyright (C) 1984, 1986, 1989, 1992, 1998, 2000, 2001, 2002, 2003,
+   2005, 2006, 2007 Free Software Foundation, Inc.
 
    This file is part of Bison, the GNU Compiler Compiler.
 
-   Bison is free software; you can redistribute it and/or modify
+   This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
-   the Free Software Foundation; either version 2, or (at your option)
-   any later version.
+   the Free Software Foundation, either version 3 of the License, or
+   (at your option) any later version.
 
-   Bison is distributed in the hope that it will be useful,
+   This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.
 
    You should have received a copy of the GNU General Public License
-   along with Bison; see the file COPYING.  If not, write to
-   the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
-   Boston, MA 02111-1307, USA.  */
-
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
 
+#include <config.h>
 #include "system.h"
-#include "quotearg.h"
-#include "quote.h"
-#include "getargs.h"
-#include "files.h"
-#include "symtab.h"
-#include "options.h"
-#include "gram.h"
+
+#include <quotearg.h>
+
 #include "complain.h"
-#include "output.h"
-#include "reader.h"
 #include "conflicts.h"
+#include "files.h"
+#include "getargs.h"
+#include "gram.h"
 #include "muscle_tab.h"
+#include "reader.h"
+#include "symlist.h"
+#include "symtab.h"
+#include "scan-gram.h"
+#include "scan-code.h"
+
+static void check_and_convert_grammar (void);
 
-int lineno;
 static symbol_list *grammar = NULL;
-static int start_flag = 0;
+static bool start_flag = false;
+merger_list *merge_functions;
 
-/* Nonzero if %union has been seen.  */
-int typed = 0;
+/* Was %union seen?  */
+bool union_seen = false;
 
-static symbol_list *
-symbol_list_new (symbol_t *sym, location_t location)
-{
-  symbol_list *res = XMALLOC (symbol_list, 1);
-  res->next = NULL;
-  res->sym = sym;
-  res->location = location;
-  res->action = NULL;
-  res->ruleprec = NULL;
-  return res;
-}
+/* Was a tag seen?  */
+bool tag_seen = false;
 
+/* Should rules have a default precedence?  */
+bool default_prec = true;
 
-/*--------------------------------------------------------------.
-| Get the data type (alternative in the union) of the value for |
-| symbol N in rule RULE.                                        |
-`--------------------------------------------------------------*/
-
-char *
-get_type_name (int n, symbol_list *rule)
-{
-  int i;
-  symbol_list *rp;
-
-  if (n < 0)
-    {
-      complain (_("invalid $ value"));
-      return NULL;
-    }
-
-  rp = rule;
-  i = 0;
-
-  while (i < n)
-    {
-      rp = rp->next;
-      if (rp == NULL || rp->sym == NULL)
-	{
-	  complain (_("invalid $ value"));
-	  return NULL;
-	}
-      ++i;
-    }
-
-  return rp->sym->type_name;
-}
-
-
 /*-----------------------.
 | Set the start symbol.  |
 `-----------------------*/
 
 void
-grammar_start_symbol_set (symbol_t *s, location_t l)
+grammar_start_symbol_set (symbol *sym, location loc)
 {
   if (start_flag)
-    complain (_("multiple %s declarations"), "%start");
+    complain_at (loc, _("multiple %s declarations"), "%start");
   else
     {
-      start_flag = 1;
-      startsymbol = s;
-      startsymbol_location = l;
+      start_flag = true;
+      startsymbol = sym;
+      startsymbol_location = loc;
     }
 }
 
+
 
-/*----------------------------------------------------------------.
-| There are two prologues: one before %union, one after.  Augment |
-| the current one.                                                |
-`----------------------------------------------------------------*/
+/*------------------------------------------------------------------------.
+| Return the merger index for a merging function named NAME.  Records the |
+| function, if new, in MERGER_LIST.                                       |
+`------------------------------------------------------------------------*/
 
-void
-prologue_augment (const char *prologue, location_t location)
+static int
+get_merge_function (uniqstr name)
 {
-  struct obstack *oout =
-    !typed ? &pre_prologue_obstack : &post_prologue_obstack;
-
-  if (!no_lines_flag)
+  merger_list *syms;
+  merger_list head;
+  int n;
+
+  if (! glr_parser)
+    return 0;
+
+  head.next = merge_functions;
+  for (syms = &head, n = 1; syms->next; syms = syms->next, n += 1)
+    if (UNIQSTR_EQ (name, syms->next->name))
+      break;
+  if (syms->next == NULL)
     {
-      obstack_fgrow2 (oout, muscle_find ("linef"),
-		      location.first_line,
-		      quotearg_style (c_quoting_style,
-				      muscle_find ("filename")));
+      syms->next = xmalloc (sizeof syms->next[0]);
+      syms->next->name = uniqstr_new (name);
+      /* After all symbol type declarations have been parsed, packgram invokes
+	 record_merge_function_type to set the type.  */
+      syms->next->type = NULL;
+      syms->next->next = NULL;
+      merge_functions = head.next;
     }
-  obstack_sgrow (oout, prologue);
+  return n;
 }
 
+/*-------------------------------------------------------------------------.
+| For the existing merging function with index MERGER, record the result   |
+| type as TYPE as required by the lhs of the rule whose %merge declaration |
+| is at DECLARATION_LOC.                                                   |
+`-------------------------------------------------------------------------*/
 
+static void
+record_merge_function_type (int merger, uniqstr type, location declaration_loc)
+{
+  int merger_find;
+  merger_list *merge_function;
 
+  if (merger <= 0)
+    return;
 
-/*----------------------.
-| Handle the epilogue.  |
-`----------------------*/
+  if (type == NULL)
+    type = uniqstr_new ("");
 
-void
-epilogue_set (const char *epilogue, location_t location)
-{
-  if (!no_lines_flag)
+  merger_find = 1;
+  for (merge_function = merge_functions;
+       merge_function != NULL && merger_find != merger;
+       merge_function = merge_function->next)
+    merger_find += 1;
+  aver (merge_function != NULL && merger_find == merger);
+  if (merge_function->type != NULL && !UNIQSTR_EQ (merge_function->type, type))
     {
-      obstack_fgrow2 (&muscle_obstack, muscle_find ("linef"),
-		      location.first_line,
-		      quotearg_style (c_quoting_style,
-				      muscle_find ("filename")));
+      complain_at (declaration_loc,
+		   _("result type clash on merge function `%s': <%s> != <%s>"),
+		   merge_function->name, type, merge_function->type);
+      complain_at (merge_function->type_declaration_location,
+		   _("previous declaration"));
     }
-  obstack_sgrow (&muscle_obstack, epilogue);
-  obstack_1grow (&muscle_obstack, 0);
-  muscle_insert ("epilogue", obstack_finish (&muscle_obstack));
+  merge_function->type = uniqstr_new (type);
+  merge_function->type_declaration_location = declaration_loc;
 }
 
+/*--------------------------------------.
+| Free all merge-function definitions.	|
+`--------------------------------------*/
 
-
-
-/*-------------------------------------------------------------------.
-| Generate a dummy symbol, a nonterminal, whose name cannot conflict |
-| with the user's names.                                             |
-`-------------------------------------------------------------------*/
-
-static symbol_t *
-gensym (void)
+void
+free_merger_functions (void)
 {
-  /* Incremented for each generated symbol */
-  static int gensym_count = 0;
-  static char buf[256];
-
-  symbol_t *sym;
-
-  sprintf (buf, "@%d", ++gensym_count);
-  sym = getsym (buf);
-  sym->class = nterm_sym;
-  sym->number = nvars++;
-  return sym;
+  merger_list *L0 = merge_functions;
+  while (L0)
+    {
+      merger_list *L1 = L0->next;
+      free (L0);
+      L0 = L1;
+    }
 }
+
 
 /*-------------------------------------------------------------------.
 | Parse the input grammar into a one symbol_list structure.  Each    |
@@ -183,23 +163,16 @@ gensym (void)
 |                                                                    |
 | All actions are copied out, labelled by the rule number they apply |
 | to.                                                                |
-|                                                                    |
-| Bison used to allow some %directives in the rules sections, but    |
-| this is no longer consider appropriate: (i) the documented grammar |
-| doesn't claim it, (ii), it would promote bad style, (iii), error   |
-| recovery for %directives consists in skipping the junk until a `%' |
-| is seen and helrp synchronizing.  This scheme is definitely wrong  |
-| in the rules section.                                              |
 `-------------------------------------------------------------------*/
 
 /* The (currently) last symbol of GRAMMAR. */
-symbol_list *grammar_end = NULL;
+static symbol_list *grammar_end = NULL;
 
-/* Append S to the GRAMMAR. */
-void
-grammar_symbol_append (symbol_t *symbol, location_t location)
+/* Append SYM to the grammar.  */
+static void
+grammar_symbol_append (symbol *sym, location loc)
 {
-  symbol_list *p = symbol_list_new (symbol, location);
+  symbol_list *p = symbol_list_sym_new (sym, loc);
 
   if (grammar_end)
     grammar_end->next = p;
@@ -207,13 +180,18 @@ grammar_symbol_append (symbol_t *symbol, location_t location)
     grammar = p;
 
   grammar_end = p;
+
+  /* A null SYM stands for an end of rule; it is not an actual
+     part of it.  */
+  if (sym)
+    ++nritems;
 }
 
 /* The rule currently being defined, and the previous rule.
    CURRENT_RULE points to the first LHS of the current rule, while
    PREVIOUS_RULE_END points to the *end* of the previous rule (NULL).  */
-symbol_list *current_rule = NULL;
-symbol_list *previous_rule_end = NULL;
+static symbol_list *current_rule = NULL;
+static symbol_list *previous_rule_end = NULL;
 
 
 /*----------------------------------------------.
@@ -221,25 +199,15 @@ symbol_list *previous_rule_end = NULL;
 `----------------------------------------------*/
 
 void
-grammar_rule_begin (symbol_t *lhs, location_t location)
+grammar_current_rule_begin (symbol *lhs, location loc)
 {
-  if (!start_flag)
-    {
-      startsymbol = lhs;
-      startsymbol_location = location;
-      start_flag = 1;
-    }
-
   /* Start a new rule and record its lhs.  */
   ++nrules;
-  ++nritems;
-
   previous_rule_end = grammar_end;
-  grammar_symbol_append (lhs, location);
+  grammar_symbol_append (lhs, loc);
   current_rule = grammar_end;
 
   /* Mark the rule's lhs as a nonterminal if not already so.  */
-
   if (lhs->class == unknown_sym)
     {
       lhs->class = nterm_sym;
@@ -247,39 +215,83 @@ grammar_rule_begin (symbol_t *lhs, location_t location)
       ++nvars;
     }
   else if (lhs->class == token_sym)
-    complain (_("rule given for %s, which is a token"), lhs->tag);
+    complain_at (loc, _("rule given for %s, which is a token"), lhs->tag);
 }
 
-/* Check that the last rule (CURRENT_RULE) is properly defined.  For
-   instance, there should be no type clash on the default action.  */
+
+/*----------------------------------------------------------------------.
+| A symbol should be used if either:                                    |
+|   1. It has a destructor.                                             |
+|   2. --warnings=midrule-values and the symbol is a mid-rule symbol    |
+|      (i.e., the generated LHS replacing a mid-rule action) that was   |
+|      assigned to or used, as in "exp: { $$ = 1; } { $$ = $1; }".      |
+`----------------------------------------------------------------------*/
+
+static bool
+symbol_should_be_used (symbol_list const *s)
+{
+  if (symbol_destructor_get (s->content.sym)->code)
+    return true;
+  if (warnings_flag & warnings_midrule_values)
+    return ((s->midrule && s->midrule->action_props.is_value_used)
+	    || (s->midrule_parent_rule
+		&& symbol_list_n_get (s->midrule_parent_rule,
+				      s->midrule_parent_rhs_index)
+                     ->action_props.is_value_used));
+  return false;
+}
+
+/*----------------------------------------------------------------.
+| Check that the rule R is properly defined.  For instance, there |
+| should be no type clash on the default action.                  |
+`----------------------------------------------------------------*/
 
 static void
-grammar_current_rule_check (void)
+grammar_rule_check (const symbol_list *r)
 {
-  symbol_t *lhs = current_rule->sym;
-  symbol_t *first_rhs = current_rule->next->sym;
+  /* Type check.
 
-  /* If there is an action, then there is nothing we can do: the user
-     is allowed to shoot in her foot.  */
-  if (current_rule->action)
-    return;
+     If there is an action, then there is nothing we can do: the user
+     is allowed to shoot herself in the foot.
 
-  /* If $$ is being set in default way, report if any type mismatch.
-     */
-  if (first_rhs)
+     Don't worry about the default action if $$ is untyped, since $$'s
+     value can't be used.  */
+  if (!r->action_props.code && r->content.sym->type_name)
     {
-      const char *lhs_type = lhs->type_name       ? lhs->type_name       : "";
-      const char *rhs_type = first_rhs->type_name ? first_rhs->type_name : "";
-      if (strcmp (lhs_type, rhs_type))
-	complain (_("type clash (`%s' `%s') on default action"),
-		  lhs_type, rhs_type);
-    }
-  /* Warn if there is no default for $$ but we need one.  */
-  else
-    {
-      if (lhs->type_name)
-	complain (_("empty rule for typed nonterminal, and no action"));
+      symbol *first_rhs = r->next->content.sym;
+      /* If $$ is being set in default way, report if any type mismatch.  */
+      if (first_rhs)
+	{
+	  char const *lhs_type = r->content.sym->type_name;
+	  const char *rhs_type =
+	    first_rhs->type_name ? first_rhs->type_name : "";
+	  if (!UNIQSTR_EQ (lhs_type, rhs_type))
+	    warn_at (r->location,
+		     _("type clash on default action: <%s> != <%s>"),
+		     lhs_type, rhs_type);
+	}
+      /* Warn if there is no default for $$ but we need one.  */
+      else
+	warn_at (r->location,
+		 _("empty rule for typed nonterminal, and no action"));
     }
+
+  /* Check that symbol values that should be used are in fact used.  */
+  {
+    symbol_list const *l = r;
+    int n = 0;
+    for (; l && l->content.sym; l = l->next, ++n)
+      if (! (l->action_props.is_value_used
+	     || !symbol_should_be_used (l)
+	     /* The default action, $$ = $1, `uses' both.  */
+	     || (!r->action_props.code && (n == 0 || n == 1))))
+	{
+	  if (n)
+	    warn_at (r->location, _("unused value: $%d"), n);
+	  else
+	    warn_at (r->location, _("unset value: $$"));
+	}
+  }
 }
 
 
@@ -288,12 +300,11 @@ grammar_current_rule_check (void)
 `-------------------------------------*/
 
 void
-grammar_rule_end (location_t location)
+grammar_current_rule_end (location loc)
 {
   /* Put an empty link in the list to mark the end of this rule  */
   grammar_symbol_append (NULL, grammar_end->location);
-  current_rule->location = location;
-  grammar_current_rule_check ();
+  current_rule->location = loc;
 }
 
 
@@ -313,9 +324,9 @@ grammar_midrule_action (void)
 
   /* Make a DUMMY nonterminal, whose location is that of the midrule
      action.  Create the MIDRULE.  */
-  symbol_t *dummy = gensym ();
-  location_t dummy_location = current_rule->action_location;
-  symbol_list *midrule = symbol_list_new (dummy, dummy_location);
+  location dummy_location = current_rule->action_props.location;
+  symbol *dummy = dummy_symbol_get (dummy_location);
+  symbol_list *midrule = symbol_list_sym_new (dummy, dummy_location);
 
   /* Make a new rule, whose body is empty, before the current one, so
      that the action just read can belong to it.  */
@@ -323,9 +334,11 @@ grammar_midrule_action (void)
   ++nritems;
   /* Attach its location and actions to that of the DUMMY.  */
   midrule->location = dummy_location;
-  midrule->action = current_rule->action;
-  midrule->action_location = dummy_location;
-  current_rule->action = NULL;
+  code_props_rule_action_init (&midrule->action_props,
+                               current_rule->action_props.code,
+                               current_rule->action_props.location,
+                               midrule);
+  code_props_none_init (&current_rule->action_props);
 
   if (previous_rule_end)
     previous_rule_end->next = midrule;
@@ -333,49 +346,80 @@ grammar_midrule_action (void)
     grammar = midrule;
 
   /* End the dummy's rule.  */
-  previous_rule_end = symbol_list_new (NULL, dummy_location);
-  previous_rule_end->next = current_rule;
+  midrule->next = symbol_list_sym_new (NULL, dummy_location);
+  midrule->next->next = current_rule;
 
-  midrule->next = previous_rule_end;
+  previous_rule_end = midrule->next;
 
   /* Insert the dummy nonterminal replacing the midrule action into
-     the current rule.  */
+     the current rule.  Bind it to its dedicated rule.  */
   grammar_current_rule_symbol_append (dummy, dummy_location);
+  grammar_end->midrule = midrule;
+  midrule->midrule_parent_rule = current_rule;
+  midrule->midrule_parent_rhs_index = symbol_list_length (current_rule->next);
 }
 
 /* Set the precedence symbol of the current rule to PRECSYM. */
 
 void
-grammar_current_rule_prec_set (symbol_t *precsym)
+grammar_current_rule_prec_set (symbol *precsym, location loc)
 {
+  symbol_class_set (precsym, token_sym, loc, false);
   if (current_rule->ruleprec)
-    complain (_("two @prec's in a row"));
+    complain_at (loc, _("only one %s allowed per rule"), "%prec");
   current_rule->ruleprec = precsym;
 }
 
-/* Attach a SYMBOL to the current rule.  If needed, move the previous
-   action as a mid-rule action.  */
+/* Attach dynamic precedence DPREC to the current rule. */
 
 void
-grammar_current_rule_symbol_append (symbol_t *symbol, location_t location)
+grammar_current_rule_dprec_set (int dprec, location loc)
 {
-  if (current_rule->action)
-    grammar_midrule_action ();
-  ++nritems;
-  grammar_symbol_append (symbol, location);
+  if (! glr_parser)
+    warn_at (loc, _("%s affects only GLR parsers"), "%dprec");
+  if (dprec <= 0)
+    complain_at (loc, _("%s must be followed by positive number"), "%dprec");
+  else if (current_rule->dprec != 0)
+    complain_at (loc, _("only one %s allowed per rule"), "%dprec");
+  current_rule->dprec = dprec;
 }
 
+/* Attach a merge function NAME with argument type TYPE to current
+   rule. */
 
-/* Attach an ACTION to the current rule.  If needed, move the previous
+void
+grammar_current_rule_merge_set (uniqstr name, location loc)
+{
+  if (! glr_parser)
+    warn_at (loc, _("%s affects only GLR parsers"), "%merge");
+  if (current_rule->merger != 0)
+    complain_at (loc, _("only one %s allowed per rule"), "%merge");
+  current_rule->merger = get_merge_function (name);
+  current_rule->merger_declaration_location = loc;
+}
+
+/* Attach SYM to the current rule.  If needed, move the previous
    action as a mid-rule action.  */
 
 void
-grammar_current_rule_action_append (const char *action, location_t location)
+grammar_current_rule_symbol_append (symbol *sym, location loc)
+{
+  if (current_rule->action_props.code)
+    grammar_midrule_action ();
+  grammar_symbol_append (sym, loc);
+}
+
+/* Attach an ACTION to the current rule.  */
+
+void
+grammar_current_rule_action_append (const char *action, location loc)
 {
-  if (current_rule->action)
+  if (current_rule->action_props.code)
     grammar_midrule_action ();
-  current_rule->action = action;
-  current_rule->action_location = location;
+  /* After all symbol declarations have been parsed, packgram invokes
+     code_props_translate_code.  */
+  code_props_rule_action_init (&current_rule->action_props, action, loc,
+                               current_rule);
 }
 
 
@@ -387,41 +431,69 @@ grammar_current_rule_action_append (const char *action, location_t location)
 static void
 packgram (void)
 {
-  unsigned int itemno;
-  int ruleno;
-  symbol_list *p;
+  unsigned int itemno = 0;
+  rule_number ruleno = 0;
+  symbol_list *p = grammar;
+
+  ritem = xnmalloc (nritems + 1, sizeof *ritem);
 
-  ritem = XCALLOC (item_number_t, nritems);
-  rules = XCALLOC (rule_t, nrules) - 1;
+  /* This sentinel is used by build_relations in gram.c.  */
+  *ritem++ = 0;
 
-  itemno = 0;
-  ruleno = 1;
+  rules = xnmalloc (nrules, sizeof *rules);
 
-  p = grammar;
   while (p)
     {
-      symbol_t *ruleprec = p->ruleprec;
+      int rule_length = 0;
+      symbol *ruleprec = p->ruleprec;
+      record_merge_function_type (p->merger, p->content.sym->type_name,
+				  p->merger_declaration_location);
       rules[ruleno].user_number = ruleno;
       rules[ruleno].number = ruleno;
-      rules[ruleno].lhs = p->sym;
+      rules[ruleno].lhs = p->content.sym;
       rules[ruleno].rhs = ritem + itemno;
+      rules[ruleno].prec = NULL;
+      rules[ruleno].dprec = p->dprec;
+      rules[ruleno].merger = p->merger;
+      rules[ruleno].precsym = NULL;
       rules[ruleno].location = p->location;
-      rules[ruleno].useful = TRUE;
-      rules[ruleno].action = p->action;
-      rules[ruleno].action_location = p->action_location;
-
-      p = p->next;
-      while (p && p->sym)
+      rules[ruleno].useful = true;
+      rules[ruleno].action = p->action_props.code;
+      rules[ruleno].action_location = p->action_props.location;
+
+      /* If the midrule's $$ is set or its $n is used, remove the `$' from the
+	 symbol name so that it's a user-defined symbol so that the default
+	 %destructor and %printer apply.  */
+      if (p->midrule_parent_rule
+          && (p->action_props.is_value_used
+	      || symbol_list_n_get (p->midrule_parent_rule,
+				    p->midrule_parent_rhs_index)
+                   ->action_props.is_value_used))
+	p->content.sym->tag += 1;
+
+      /* Don't check the generated rule 0.  It has no action, so some rhs
+	 symbols may appear unused, but the parsing algorithm ensures that
+	 %destructor's are invoked appropriately.  */
+      if (p != grammar)
+	grammar_rule_check (p);
+
+      for (p = p->next; p && p->content.sym; p = p->next)
 	{
-	  /* item_number_t = symbol_number_t.
+	  ++rule_length;
+
+	  /* Don't allow rule_length == INT_MAX, since that might
+	     cause confusion with strtol if INT_MAX == LONG_MAX.  */
+	  if (rule_length == INT_MAX)
+	      fatal_at (rules[ruleno].location, _("rule is too long"));
+
+	  /* item_number = symbol_number.
 	     But the former needs to contain more: negative rule numbers. */
-	  ritem[itemno++] = symbol_number_as_item_number (p->sym->number);
+	  ritem[itemno++] =
+            symbol_number_as_item_number (p->content.sym->number);
 	  /* A rule gets by default the precedence and associativity
-	     of the last token in it.  */
-	  if (p->sym->class == token_sym)
-	    rules[ruleno].prec = p->sym;
-	  if (p)
-	    p = p->next;
+	     of its last token.  */
+	  if (p->content.sym->class == token_sym && default_prec)
+	    rules[ruleno].prec = p->content.sym;
 	}
 
       /* If this rule has a %prec,
@@ -431,16 +503,19 @@ packgram (void)
 	  rules[ruleno].precsym = ruleprec;
 	  rules[ruleno].prec = ruleprec;
 	}
-      ritem[itemno++] = -ruleno;
+      /* An item ends by the rule number (negated).  */
+      ritem[itemno++] = rule_number_as_item_number (ruleno);
+      aver (itemno < ITEM_NUMBER_MAX);
       ++ruleno;
+      aver (ruleno < RULE_NUMBER_MAX);
 
       if (p)
 	p = p->next;
     }
 
-  assert (itemno == nritems);
+  aver (itemno == nritems);
 
-  if (trace_flag)
+  if (trace_flag & trace_sets)
     ritem_print (stderr);
 }
 
@@ -454,88 +529,124 @@ packgram (void)
 void
 reader (void)
 {
-  gram_control_t gram_control;
-  lineno = 1;
-
   /* Initialize the symbol table.  */
   symbols_new ();
 
-  /* Construct the axiom symbol. */
-  axiom = getsym ("$axiom");
-  axiom->class = nterm_sym;
-  axiom->number = nvars++;
+  /* Construct the accept symbol. */
+  accept = symbol_get ("$accept", empty_location);
+  accept->class = nterm_sym;
+  accept->number = nvars++;
 
   /* Construct the error token */
-  errtoken = getsym ("error");
+  errtoken = symbol_get ("error", empty_location);
   errtoken->class = token_sym;
   errtoken->number = ntokens++;
 
   /* Construct a token that represents all undefined literal tokens.
      It is always token number 2.  */
-  undeftoken = getsym ("$undefined.");
+  undeftoken = symbol_get ("$undefined", empty_location);
   undeftoken->class = token_sym;
   undeftoken->number = ntokens++;
 
-  /* Initialize the obstacks. */
-  obstack_init (&pre_prologue_obstack);
-  obstack_init (&post_prologue_obstack);
+  gram_in = xfopen (grammar_file, "r");
+
+  gram__flex_debug = trace_flag & trace_scan;
+  gram_debug = trace_flag & trace_parse;
+  gram_scanner_initialize ();
+  gram_parse ();
 
-  finput = xfopen (infile, "r");
-  gram_in = finput;
+  if (! complaint_issued)
+    check_and_convert_grammar ();
+
+  xfclose (gram_in);
+}
 
-  gram_debug = !!getenv ("parse");
-  gram__flex_debug = !!getenv ("scan");
-  scanner_initialize ();
-  gram_parse (&gram_control);
 
-  /* Grammar has been read.  Do some checking */
+/*-------------------------------------------------------------.
+| Check the grammar that has just been read, and convert it to |
+| internal form.					       |
+`-------------------------------------------------------------*/
+
+static void
+check_and_convert_grammar (void)
+{
+  /* Grammar has been read.  Do some checking.  */
   if (nrules == 0)
     fatal (_("no rules in the input grammar"));
 
   /* Report any undefined symbols and consider them nonterminals.  */
   symbols_check_defined ();
 
-  /* If the user did not define her EOFTOKEN, do it now. */
-  if (!eoftoken)
+  /* If the user did not define her ENDTOKEN, do it now. */
+  if (!endtoken)
     {
-      eoftoken = getsym ("$");
-      eoftoken->class = token_sym;
-      eoftoken->number = 0;
+      endtoken = symbol_get ("$end", empty_location);
+      endtoken->class = token_sym;
+      endtoken->number = 0;
       /* Value specified by POSIX.  */
-      eoftoken->user_token_number = 0;
+      endtoken->user_token_number = 0;
+    }
+
+  /* Find the start symbol if no %start.  */
+  if (!start_flag)
+    {
+      symbol_list *node;
+      for (node = grammar;
+           node != NULL && symbol_is_dummy (node->content.sym);
+           node = node->next)
+        {
+          for (node = node->next;
+               node != NULL && node->content.sym != NULL;
+               node = node->next)
+            ;
+        }
+      aver (node != NULL);
+      grammar_start_symbol_set (node->content.sym,
+                                node->content.sym->location);
     }
 
-  /* Insert the initial rule, which line is that of the first rule
+  /* Insert the initial rule, whose line is that of the first rule
      (not that of the start symbol):
 
-     axiom: %start EOF.  */
+     accept: %start EOF.  */
   {
-    symbol_list *p = symbol_list_new (axiom, empty_location);
+    symbol_list *p = symbol_list_sym_new (accept, empty_location);
     p->location = grammar->location;
-    p->next = symbol_list_new (startsymbol, empty_location);
-    p->next->next = symbol_list_new (eoftoken, empty_location);
-    p->next->next->next = symbol_list_new (NULL, empty_location);
+    p->next = symbol_list_sym_new (startsymbol, empty_location);
+    p->next->next = symbol_list_sym_new (endtoken, empty_location);
+    p->next->next->next = symbol_list_sym_new (NULL, empty_location);
     p->next->next->next->next = grammar;
     nrules += 1;
     nritems += 3;
     grammar = p;
   }
 
-  if (nsyms > SHRT_MAX)
-    fatal (_("too many symbols (tokens plus nonterminals); maximum %d"),
-          SHRT_MAX);
-
-  assert (nsyms == ntokens + nvars);
-
-  xfclose (finput);
+  aver (nsyms <= SYMBOL_NUMBER_MAXIMUM && nsyms == ntokens + nvars);
 
   /* Assign the symbols their symbol numbers.  Write #defines for the
      token symbols into FDEFINES if requested.  */
   symbols_pack ();
 
+  /* Scan rule actions after invoking symbol_check_alias_consistency (in
+     symbols_pack above) so that token types are set correctly before the rule
+     action type checking.
+
+     Before invoking grammar_rule_check (in packgram below) on any rule, make
+     sure all actions have already been scanned in order to set `used' flags.
+     Otherwise, checking that a midrule's $$ should be set will not always work
+     properly because the check must forward-reference the midrule's parent
+     rule.  For the same reason, all the `used' flags must be set before
+     checking whether to remove `$' from any midrule symbol name (also in
+     packgram).  */
+  {
+    symbol_list *sym;
+    for (sym = grammar; sym; sym = sym->next)
+      code_props_translate_code (&sym->action_props);
+  }
+
   /* Convert the grammar into the format described in gram.h.  */
   packgram ();
 
   /* The grammar as a symbol_list is no longer needed. */
-  LIST_FREE (symbol_list, grammar);
+  symbol_list_free (grammar);
 }