X-Git-Url: https://git.saurik.com/bison.git/blobdiff_plain/8f3596a6337cf30a3641967d450d1c9d77861edc..595284e9d0277517bac8f3fc7bcdd529d97aa6f9:/src/reader.c

diff --git a/src/reader.c b/src/reader.c
index f02e132f..f658e64e 100644
--- a/src/reader.c
+++ b/src/reader.c
@@ -1,50 +1,52 @@
 /* Input parser for Bison
 
-   Copyright (C) 1984, 1986, 1989, 1992, 1998, 2000, 2001, 2002, 2003,
-   2005 Free Software Foundation, Inc.
+   Copyright (C) 1984, 1986, 1989, 1992, 1998, 2000-2003, 2005-2007,
+   2009-2012 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., 51 Franklin Street, Fifth Floor,
-   Boston, MA 02110-1301, 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 "complain.h"
 #include "conflicts.h"
 #include "files.h"
 #include "getargs.h"
 #include "gram.h"
-#include "muscle_tab.h"
-#include "output.h"
+#include "muscle-tab.h"
 #include "reader.h"
 #include "symlist.h"
 #include "symtab.h"
+#include "scan-gram.h"
+#include "scan-code.h"
 
-static void grammar_midrule_action (void);
-static void grammar_symbol_append (symbol *sym, location loc);
+static void prepare_percent_define_front_end_variables (void);
+static void check_and_convert_grammar (void);
 
 static symbol_list *grammar = NULL;
 static bool start_flag = false;
 merger_list *merge_functions;
 
 /* Was %union seen?  */
-bool typed = false;
+bool union_seen = false;
+
+/* Was a tag seen?  */
+bool tag_seen = false;
 
 /* Should rules have a default precedence?  */
 bool default_prec = true;
@@ -57,7 +59,7 @@ void
 grammar_start_symbol_set (symbol *sym, location loc)
 {
   if (start_flag)
-    complain_at (loc, _("multiple %s declarations"), "%start");
+    complain_at (loc, complaint, _("multiple %s declarations"), "%start");
   else
     {
       start_flag = true;
@@ -66,35 +68,15 @@ grammar_start_symbol_set (symbol *sym, location loc)
     }
 }
 
-
-/*----------------------------------------------------------------.
-| There are two prologues: one before %union, one after.  Augment |
-| the current one.                                                |
-`----------------------------------------------------------------*/
-
-void
-prologue_augment (const char *prologue, location loc)
-{
-  struct obstack *oout =
-    !typed ? &pre_prologue_obstack : &post_prologue_obstack;
-
-  obstack_fgrow1 (oout, "]b4_syncline(%d, [[", loc.start.line);
-  MUSCLE_OBSTACK_SGROW (oout,
-			quotearg_style (c_quoting_style, loc.start.file));
-  obstack_sgrow (oout, "]])[\n");
-  obstack_sgrow (oout, prologue);
-}
-
 
 
-/*-------------------------------------------------------------------.
-| Return the merger index for a merging function named NAME, whose   |
-| arguments have type TYPE.  Records the function, if new, in        |
-| MERGER_LIST.							     |
-`-------------------------------------------------------------------*/
+/*------------------------------------------------------------------------.
+| Return the merger index for a merging function named NAME.  Records the |
+| function, if new, in MERGER_LIST.                                       |
+`------------------------------------------------------------------------*/
 
 static int
-get_merge_function (uniqstr name, uniqstr type, location loc)
+get_merge_function (uniqstr name)
 {
   merger_list *syms;
   merger_list head;
@@ -103,9 +85,6 @@ get_merge_function (uniqstr name, uniqstr type, location loc)
   if (! glr_parser)
     return 0;
 
-  if (type == NULL)
-    type = uniqstr_new ("");
-
   head.next = merge_functions;
   for (syms = &head, n = 1; syms->next; syms = syms->next, n += 1)
     if (UNIQSTR_EQ (name, syms->next->name))
@@ -114,18 +93,58 @@ get_merge_function (uniqstr name, uniqstr type, location loc)
     {
       syms->next = xmalloc (sizeof syms->next[0]);
       syms->next->name = uniqstr_new (name);
-      syms->next->type = uniqstr_new (type);
+      /* 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;
     }
-  else if (!UNIQSTR_EQ (type, syms->next->type))
-    warn_at (loc, _("result type clash on merge function %s: <%s> != <%s>"),
-	     name, type, syms->next->type);
   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;
+
+  if (type == NULL)
+    type = uniqstr_new ("");
+
+  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))
+    {
+      unsigned indent = 0;
+      complain_at_indent (declaration_loc, complaint, &indent,
+                          _("result type clash on merge function %s: "
+                            "<%s> != <%s>"),
+                          quote (merge_function->name), type,
+                          merge_function->type);
+      indent += SUB_INDENT;
+      complain_at_indent (merge_function->type_declaration_location, complaint,
+                          &indent,
+                          _("previous declaration"));
+    }
+  merge_function->type = uniqstr_new (type);
+  merge_function->type_declaration_location = declaration_loc;
+}
+
 /*--------------------------------------.
-| Free all merge-function definitions.	|
+| Free all merge-function definitions.  |
 `--------------------------------------*/
 
 void
@@ -156,10 +175,10 @@ free_merger_functions (void)
 static symbol_list *grammar_end = NULL;
 
 /* Append SYM to the grammar.  */
-static void
+static symbol_list *
 grammar_symbol_append (symbol *sym, location loc)
 {
-  symbol_list *p = symbol_list_new (sym, loc);
+  symbol_list *p = symbol_list_sym_new (sym, loc);
 
   if (grammar_end)
     grammar_end->next = p;
@@ -168,16 +187,35 @@ grammar_symbol_append (symbol *sym, location loc)
 
   grammar_end = p;
 
-  /* SYM = 0 stands for an end of rule, it is not an actual
+  /* A null SYM stands for an end of rule; it is not an actual
      part of it.  */
   if (sym)
     ++nritems;
+
+  return p;
 }
 
+static void
+assign_named_ref (symbol_list *p, named_ref *name)
+{
+  symbol *sym = p->content.sym;
+
+  if (name->id == sym->tag)
+    {
+      complain_at (name->loc, Wother,
+                   _("duplicated symbol name for %s ignored"),
+                   quote (sym->tag));
+      named_ref_free (name);
+    }
+  else
+    p->named_ref = name;
+}
+
+
 /* 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;
+static symbol_list *current_rule = NULL;
 static symbol_list *previous_rule_end = NULL;
 
 
@@ -186,19 +224,19 @@ static symbol_list *previous_rule_end = NULL;
 `----------------------------------------------*/
 
 void
-grammar_current_rule_begin (symbol *lhs, location loc)
+grammar_current_rule_begin (symbol *lhs, location loc,
+                            named_ref *lhs_name)
 {
-  if (!start_flag)
-    {
-      startsymbol = lhs;
-      startsymbol_location = loc;
-      start_flag = true;
-    }
+  symbol_list* p;
 
   /* Start a new rule and record its lhs.  */
   ++nrules;
   previous_rule_end = grammar_end;
-  grammar_symbol_append (lhs, loc);
+
+  p = grammar_symbol_append (lhs, loc);
+  if (lhs_name)
+    assign_named_ref (p, named_ref_copy (lhs_name));
+
   current_rule = grammar_end;
 
   /* Mark the rule's lhs as a nonterminal if not already so.  */
@@ -209,10 +247,36 @@ grammar_current_rule_begin (symbol *lhs, location loc)
       ++nvars;
     }
   else if (lhs->class == token_sym)
-    complain_at (loc, _("rule given for %s, which is a token"), lhs->tag);
+    complain_at (loc, complaint, _("rule given for %s, which is a token"),
+                 lhs->tag);
 }
 
 
+/*----------------------------------------------------------------------.
+| A symbol should be used if either:                                    |
+|   1. It has a destructor.                                             |
+|   2. 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, bool *midrule_warning)
+{
+  if (symbol_code_props_get (s->content.sym, destructor)->code)
+    return true;
+  if ((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))
+    {
+      *midrule_warning = true;
+      return true;
+    }
+  return false;
+}
+
 /*----------------------------------------------------------------.
 | Check that the rule R is properly defined.  For instance, there |
 | should be no type clash on the default action.                  |
@@ -228,40 +292,55 @@ grammar_rule_check (const symbol_list *r)
 
      Don't worry about the default action if $$ is untyped, since $$'s
      value can't be used.  */
-  if (!r->action && r->sym->type_name)
+  if (!r->action_props.code && r->content.sym->type_name)
     {
-      symbol *first_rhs = r->next->sym;
+      symbol *first_rhs = r->next->content.sym;
       /* If $$ is being set in default way, report if any type mismatch.  */
       if (first_rhs)
-	{
-	  char const *lhs_type = r->sym->type_name;
-	  const char *rhs_type =
-	    first_rhs->type_name ? first_rhs->type_name : "";
-	  if (!UNIQSTR_EQ (lhs_type, rhs_type))
-	    warn_at (r->location,
-		     _("type clash on default action: <%s> != <%s>"),
-		     lhs_type, rhs_type);
-	}
+        {
+          char const *lhs_type = r->content.sym->type_name;
+          const char *rhs_type =
+            first_rhs->type_name ? first_rhs->type_name : "";
+          if (!UNIQSTR_EQ (lhs_type, rhs_type))
+            complain_at (r->location, Wother,
+                         _("type clash on default action: <%s> != <%s>"),
+                         lhs_type, rhs_type);
+        }
       /* Warn if there is no default for $$ but we need one.  */
       else
-	warn_at (r->location,
-		 _("empty rule for typed nonterminal, and no action"));
+        complain_at (r->location, Wother,
+                     _("empty rule for typed nonterminal, and no action"));
     }
-  
-  /* Check that typed symbol values are used.  */
+
+  /* Check that symbol values that should be used are in fact used.  */
   {
-    symbol_list *l = r;
+    symbol_list const *l = r;
     int n = 0;
-    for (; l && l->sym; l = l->next, ++n)
-      if (! (l->used
-	     || !l->sym->type_name
-	     /* The default action, $$ = $1, `uses' both.  */
-	     || !r->action && (n == 0 || n == 1)))
-	if (n)
-	  warn_at (r->location, _("unused value: $%d"), n);
-	else
-	  warn_at (r->location, _("unset value: $$"));
+    for (; l && l->content.sym; l = l->next, ++n)
+      {
+        bool midrule_warning = false;
+        if (!l->action_props.is_value_used
+            && symbol_should_be_used (l, &midrule_warning)
+            /* The default action, $$ = $1, `uses' both.  */
+            && (r->action_props.code || (n != 0 && n != 1)))
+          {
+            warnings warn_flag = midrule_warning ? Wmidrule_values : Wother;
+            if (n)
+              complain_at (r->location, warn_flag, _("unused value: $%d"), n);
+            else
+              complain_at (r->location, warn_flag, _("unset value: $$"));
+          }
+      }
   }
+
+  /* See comments in grammar_current_rule_prec_set for how POSIX
+     mandates this complaint.  It's only for identifiers, so skip
+     it for char literals and strings, which are always tokens.  */
+  if (r->ruleprec
+      && r->ruleprec->tag[0] != '\'' && r->ruleprec->tag[0] != '"'
+      && r->ruleprec->status != declared && !r->ruleprec->prec)
+    complain_at (r->location, Wother,
+                 _("token for %%prec is not defined: %s"), r->ruleprec->tag);
 }
 
 
@@ -275,7 +354,6 @@ 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 = loc;
-  grammar_rule_check (current_rule);
 }
 
 
@@ -286,7 +364,7 @@ grammar_current_rule_end (location loc)
 | rule.                                                              |
 `-------------------------------------------------------------------*/
 
-static void
+void
 grammar_midrule_action (void)
 {
   /* Since the action was written out with this rule's number, we must
@@ -295,9 +373,12 @@ grammar_midrule_action (void)
 
   /* Make a DUMMY nonterminal, whose location is that of the midrule
      action.  Create the MIDRULE.  */
-  location dummy_location = current_rule->action_location;
+  location dummy_location = current_rule->action_props.location;
   symbol *dummy = dummy_symbol_get (dummy_location);
-  symbol_list *midrule = symbol_list_new (dummy, dummy_location);
+  symbol_list *midrule = symbol_list_sym_new (dummy, dummy_location);
+
+  /* Remember named_ref of previous action. */
+  named_ref *action_name = current_rule->action_props.named_ref;
 
   /* Make a new rule, whose body is empty, before the current one, so
      that the action just read can belong to it.  */
@@ -305,9 +386,12 @@ 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, 0,
+                               current_rule->action_props.is_predicate);
+  code_props_none_init (&current_rule->action_props);
 
   if (previous_rule_end)
     previous_rule_end->next = midrule;
@@ -315,14 +399,18 @@ 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.  */
-  grammar_current_rule_symbol_append (dummy, dummy_location);
+     the current rule.  Bind it to its dedicated rule.  */
+  grammar_current_rule_symbol_append (dummy, dummy_location,
+                                      action_name);
+  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. */
@@ -330,8 +418,19 @@ grammar_midrule_action (void)
 void
 grammar_current_rule_prec_set (symbol *precsym, location loc)
 {
+  /* POSIX says that any identifier is a nonterminal if it does not
+     appear on the LHS of a grammar rule and is not defined by %token
+     or by one of the directives that assigns precedence to a token.  We
+     ignore this here because the only kind of identifier that POSIX
+     allows to follow a %prec is a token and because assuming it's a
+     token now can produce more logical error messages.  Nevertheless,
+     grammar_rule_check does obey what we believe is the real intent of
+     POSIX here: that an error be reported for any identifier that
+     appears after %prec but that is not defined separately as a
+     token.  */
+  symbol_class_set (precsym, token_sym, loc, false);
   if (current_rule->ruleprec)
-    complain_at (loc, _("only one %s allowed per rule"), "%prec");
+    complain_at (loc, complaint, _("only one %s allowed per rule"), "%prec");
   current_rule->ruleprec = precsym;
 }
 
@@ -341,11 +440,13 @@ void
 grammar_current_rule_dprec_set (int dprec, location loc)
 {
   if (! glr_parser)
-    warn_at (loc, _("%s affects only GLR parsers"), "%dprec");
+    complain_at (loc, Wother, _("%s affects only GLR parsers"),
+                 "%dprec");
   if (dprec <= 0)
-    complain_at (loc, _("%s must be followed by positive number"), "%dprec");
+    complain_at (loc, complaint, _("%s must be followed by positive number"),
+                 "%dprec");
   else if (current_rule->dprec != 0)
-    complain_at (loc, _("only one %s allowed per rule"), "%dprec");
+    complain_at (loc, complaint, _("only one %s allowed per rule"), "%dprec");
   current_rule->dprec = dprec;
 }
 
@@ -356,34 +457,43 @@ void
 grammar_current_rule_merge_set (uniqstr name, location loc)
 {
   if (! glr_parser)
-    warn_at (loc, _("%s affects only GLR parsers"), "%merge");
+    complain_at (loc, Wother, _("%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->sym->type_name, loc);
+    complain_at (loc, complaint, _("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_symbol_append (symbol *sym, location loc)
+grammar_current_rule_symbol_append (symbol *sym, location loc,
+                                    named_ref *name)
 {
-  if (current_rule->action)
+  symbol_list *p;
+  if (current_rule->action_props.code)
     grammar_midrule_action ();
-  grammar_symbol_append (sym, loc);
+  p = grammar_symbol_append (sym, loc);
+  if (name)
+    assign_named_ref(p, name);
+  if (sym->status == undeclared || sym->status == used)
+    sym->status = needed;
 }
 
-/* Attach an ACTION to the current rule.  If needed, move the previous
-   action as a mid-rule action.  */
+/* Attach an ACTION to the current rule.  */
 
 void
-grammar_current_rule_action_append (const char *action, location loc)
+grammar_current_rule_action_append (const char *action, location loc,
+                                    named_ref *name, bool is_predicate)
 {
-  if (current_rule->action)
+  if (current_rule->action_props.code)
     grammar_midrule_action ();
-  current_rule->action = action;
-  current_rule->action_location = loc;
+  /* 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, name, is_predicate);
 }
 
 
@@ -399,15 +509,22 @@ packgram (void)
   rule_number ruleno = 0;
   symbol_list *p = grammar;
 
-  ritem = xnmalloc (nritems, sizeof *ritem);
+  ritem = xnmalloc (nritems + 1, sizeof *ritem);
+
+  /* This sentinel is used by build_relations in gram.c.  */
+  *ritem++ = 0;
+
   rules = xnmalloc (nrules, sizeof *rules);
 
   while (p)
     {
+      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;
@@ -415,39 +532,63 @@ packgram (void)
       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)
-	{
-	  /* item_number = symbol_number.
-	     But the former needs to contain more: negative rule numbers. */
-	  ritem[itemno++] = symbol_number_as_item_number (p->sym->number);
-	  /* A rule gets by default the precedence and associativity
-	     of the last token in it.  */
-	  if (p->sym->class == token_sym && default_prec)
-	    rules[ruleno].prec = p->sym;
-	  if (p)
-	    p = p->next;
-	}
+      rules[ruleno].action = p->action_props.code;
+      rules[ruleno].action_location = p->action_props.location;
+      rules[ruleno].is_predicate = p->action_props.is_predicate;
+
+      /* 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)
+        {
+          ++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)
+            complain_at (rules[ruleno].location, fatal, _("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->content.sym->number);
+          /* A rule gets by default the precedence and associativity
+             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,
          the specified symbol's precedence replaces the default.  */
       if (ruleprec)
-	{
-	  rules[ruleno].precsym = ruleprec;
-	  rules[ruleno].prec = ruleprec;
-	}
+        {
+          rules[ruleno].precsym = ruleprec;
+          rules[ruleno].prec = ruleprec;
+        }
+      /* 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;
+        p = p->next;
     }
 
-  if (itemno != nritems)
-    abort ();
+  aver (itemno == nritems);
 
   if (trace_flag & trace_sets)
     ritem_print (stderr);
@@ -482,28 +623,61 @@ reader (void)
   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;
-  scanner_initialize ();
+  gram_scanner_initialize ();
   gram_parse ();
+  prepare_percent_define_front_end_variables ();
 
-  /* If something went wrong during the parsing, don't try to
-     continue.  */
-  if (complaint_issued)
-    return;
+  if (! complaint_issued)
+    check_and_convert_grammar ();
 
-  /* Grammar has been read.  Do some checking */
-  if (nrules == 0)
-    fatal (_("no rules in the input grammar"));
+  xfclose (gram_in);
+}
+
+static void
+prepare_percent_define_front_end_variables (void)
+{
+  /* Set %define front-end variable defaults.  */
+  muscle_percent_define_default ("lr.keep-unreachable-states", "false");
+  {
+    char *lr_type;
+    /* IELR would be a better default, but LALR is historically the
+       default.  */
+    muscle_percent_define_default ("lr.type", "lalr");
+    lr_type = muscle_percent_define_get ("lr.type");
+    if (STRNEQ (lr_type, "canonical-lr"))
+      muscle_percent_define_default ("lr.default-reductions", "most");
+    else
+      muscle_percent_define_default ("lr.default-reductions", "accepting");
+    free (lr_type);
+  }
+
+  /* Check %define front-end variables.  */
+  {
+    static char const * const values[] = {
+      "lr.type", "lalr", "ielr", "canonical-lr", NULL,
+      "lr.default-reductions", "most", "consistent", "accepting", NULL,
+      NULL
+    };
+    muscle_percent_define_check_values (values);
+  }
+}
 
-  /* Report any undefined symbols and consider them nonterminals.  */
-  symbols_check_defined ();
+
+/*-------------------------------------------------------------.
+| 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)
+    complain (fatal, _("no rules in the input grammar"));
 
   /* If the user did not define her ENDTOKEN, do it now. */
   if (!endtoken)
@@ -515,34 +689,69 @@ reader (void)
       endtoken->user_token_number = 0;
     }
 
-  /* Insert the initial rule, which line is that of the first rule
+  /* Report any undefined symbols and consider them nonterminals.  */
+  symbols_check_defined ();
+
+  /* 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, whose line is that of the first rule
      (not that of the start symbol):
 
      accept: %start EOF.  */
   {
-    symbol_list *p = symbol_list_new (accept, 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 (endtoken, 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 <= SYMBOL_NUMBER_MAXIMUM && nsyms == ntokens + nvars))
-    abort ();
-
-  xfclose (gram_in);
+  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);
 }