X-Git-Url: https://git.saurik.com/bison.git/blobdiff_plain/76290368d48b584808a120dfbd415be93aef04f6..3209eb1c4c5de8dd812e65da27df00c548f476fe:/src/reader.c

diff --git a/src/reader.c b/src/reader.c
index ce23f48c..f2e12c6b 100644
--- a/src/reader.c
+++ b/src/reader.c
@@ -1,42 +1,41 @@
 /* Input parser for Bison
 
-   Copyright (C) 1984, 1986, 1989, 1992, 1998, 2000, 2001, 2002, 2003,
-   2005, 2006 Free Software Foundation, Inc.
+   Copyright (C) 1984, 1986, 1989, 1992, 1998, 2000-2003, 2005-2007,
+   2009-2015 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 "muscle-tab.h"
 #include "reader.h"
 #include "symlist.h"
 #include "symtab.h"
 #include "scan-gram.h"
 #include "scan-code.h"
 
+static void prepare_percent_define_front_end_variables (void);
 static void check_and_convert_grammar (void);
 
 static symbol_list *grammar = NULL;
@@ -60,7 +59,7 @@ void
 grammar_start_symbol_set (symbol *sym, location loc)
 {
   if (start_flag)
-    complain_at (loc, _("multiple %s declarations"), "%start");
+    complain (&loc, complaint, _("multiple %s declarations"), "%start");
   else
     {
       start_flag = true;
@@ -69,27 +68,6 @@ grammar_start_symbol_set (symbol *sym, location loc)
     }
 }
 
-
-/*---------------------------------------------------------------------.
-| There are two prologues: one before the first %union and one after.  |
-| Augment the one specified by POST.                                   |
-`---------------------------------------------------------------------*/
-
-void
-prologue_augment (const char *prologue, location loc, bool post)
-{
-  struct obstack *oout =
-    !post ? &pre_prologue_obstack : &post_prologue_obstack;
-
-  obstack_fgrow1 (oout, "]b4_syncline(%d, [[", loc.start.line);
-  /* FIXME: Protection of M4 characters missing here.  See
-     output.c:escaped_output.  */
-  MUSCLE_OBSTACK_SGROW (oout,
-			quotearg_style (c_quoting_style, loc.start.file));
-  obstack_sgrow (oout, "]])[\n");
-  obstack_sgrow (oout, prologue);
-}
-
 
 
 /*------------------------------------------------------------------------.
@@ -116,7 +94,7 @@ get_merge_function (uniqstr name)
       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.  */
+         record_merge_function_type to set the type.  */
       syms->next->type = NULL;
       syms->next->next = NULL;
       merge_functions = head.next;
@@ -150,18 +128,23 @@ record_merge_function_type (int merger, uniqstr type, location declaration_loc)
   aver (merge_function != NULL && merger_find == merger);
   if (merge_function->type != NULL && !UNIQSTR_EQ (merge_function->type, type))
     {
-      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"));
+      unsigned indent = 0;
+      complain_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_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
@@ -192,7 +175,7 @@ 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_sym_new (sym, loc);
@@ -208,8 +191,27 @@ grammar_symbol_append (symbol *sym, location loc)
      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 (&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).  */
@@ -222,12 +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)
 {
+  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.  */
@@ -238,35 +247,32 @@ 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 (&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. --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; }".      |
+|   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)
+symbol_should_be_used (symbol_list const *s, bool *midrule_warning)
 {
-  if (code_props_code_get (symbol_destructor_get (s->content.sym)))
+  if (symbol_code_props_get (s->content.sym, destructor)->code)
     return true;
-  if (warnings_flag & warnings_midrule_values)
+  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)))
     {
-      if (s->midrule && code_props_is_value_used (s->midrule->action_props))
-        return true;
-      if (s->midrule_parent_rule)
-        {
-          symbol_list *rhs_node =
-            symbol_list_n_get (s->midrule_parent_rule,
-                               s->midrule_parent_rhs_index);
-          if (code_props_is_value_used (rhs_node->action_props))
-            return true;
-        }
+      *midrule_warning = true;
+      return true;
     }
   return false;
 }
@@ -286,24 +292,24 @@ 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 (!code_props_code_get (r->action_props) && r->content.sym->type_name)
+  if (!r->action_props.code && r->content.sym->type_name)
     {
       symbol *first_rhs = r->next->content.sym;
       /* If $$ is being set in default way, report if any type mismatch.  */
       if (first_rhs)
-	{
-	  char const *lhs_type = r->content.sym->type_name;
-	  const char *rhs_type =
-	    first_rhs->type_name ? first_rhs->type_name : "";
-	  if (!UNIQSTR_EQ (lhs_type, rhs_type))
-	    warn_at (r->location,
-		     _("type clash on default action: <%s> != <%s>"),
-		     lhs_type, rhs_type);
-	}
+        {
+          char const *lhs_type = r->content.sym->type_name;
+          const char *rhs_type =
+            first_rhs->type_name ? first_rhs->type_name : "";
+          if (!UNIQSTR_EQ (lhs_type, rhs_type))
+            complain (&r->location, Wother,
+                      _("type clash on default action: <%s> != <%s>"),
+                      lhs_type, rhs_type);
+        }
       /* Warn if there is no default for $$ but we need one.  */
       else
-	warn_at (r->location,
-		 _("empty rule for typed nonterminal, and no action"));
+        complain (&r->location, Wother,
+                  _("empty rule for typed nonterminal, and no action"));
     }
 
   /* Check that symbol values that should be used are in fact used.  */
@@ -311,18 +317,42 @@ grammar_rule_check (const symbol_list *r)
     symbol_list const *l = r;
     int n = 0;
     for (; l && l->content.sym; l = l->next, ++n)
-      if (! (code_props_is_value_used (l->action_props)
-	     || !symbol_should_be_used (l)
-	     /* The default action, $$ = $1, `uses' both.  */
-	     || (!code_props_code_get (r->action_props)
-                 && (n == 0 || n == 1))))
-	{
-	  if (n)
-	    warn_at (r->location, _("unused value: $%d"), n);
-	  else
-	    warn_at (r->location, _("unset value: $$"));
-	}
+      {
+        bool midrule_warning = false;
+        if (!l->action_props.is_value_used
+            && symbol_should_be_used (l, &midrule_warning)
+            /* The default action, $$ = $1, 'uses' both.  */
+            && (r->action_props.code || (n != 0 && n != 1)))
+          {
+            warnings warn_flag = midrule_warning ? Wmidrule_values : Wother;
+            if (n)
+              complain (&l->location, warn_flag, _("unused value: $%d"), n);
+            else
+              complain (&l->location, warn_flag, _("unset value: $$"));
+          }
+      }
   }
+
+  /* Check that %empty => empty rule.  */
+  if (r->percent_empty_loc.start.file
+      && r->next && r->next->content.sym)
+    complain (&r->percent_empty_loc, complaint,
+              _("%%empty on non-empty rule"));
+
+  /* Check that empty rule => %empty.  */
+  if (!(r->next && r->next->content.sym)
+      && !r->midrule_parent_rule
+      && !r->percent_empty_loc.start.file)
+    complain (&r->location, Wempty_rule, _("empty rule without %%empty"));
+
+  /* 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 (&r->location, Wother,
+              _("token for %%prec is not defined: %s"), r->ruleprec->tag);
 }
 
 
@@ -355,22 +385,24 @@ grammar_midrule_action (void)
 
   /* Make a DUMMY nonterminal, whose location is that of the midrule
      action.  Create the MIDRULE.  */
-  location dummy_location =
-    code_props_location_get (current_rule->action_props);
+  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);
 
+  /* 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.  */
   ++nrules;
   ++nritems;
   /* Attach its location and actions to that of the DUMMY.  */
   midrule->location = dummy_location;
-  code_props_rule_action_init (
-    &midrule->action_props,
-    code_props_code_get (current_rule->action_props),
-    code_props_location_get (current_rule->action_props),
-    midrule);
+  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)
@@ -386,7 +418,8 @@ grammar_midrule_action (void)
 
   /* Insert the dummy nonterminal replacing the midrule action into
      the current rule.  Bind it to its dedicated rule.  */
-  grammar_current_rule_symbol_append (dummy, dummy_location);
+  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);
@@ -397,9 +430,38 @@ 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");
-  current_rule->ruleprec = precsym;
+    duplicate_directive ("%prec",
+                         current_rule->ruleprec->location, loc);
+  else
+    current_rule->ruleprec = precsym;
+}
+
+/* Set %empty for the current rule. */
+
+void
+grammar_current_rule_empty_set (location loc)
+{
+  /* If %empty is used and -Wno-empty-rule is not, then enable
+     -Wempty-rule.  */
+  if (warning_is_unset (Wempty_rule))
+    warning_argmatch ("empty-rule", 0, 0);
+  if (current_rule->percent_empty_loc.start.file)
+    duplicate_directive ("%empty",
+                         current_rule->percent_empty_loc, loc);
+  else
+    current_rule->percent_empty_loc = loc;
 }
 
 /* Attach dynamic precedence DPREC to the current rule. */
@@ -408,12 +470,19 @@ void
 grammar_current_rule_dprec_set (int dprec, location loc)
 {
   if (! glr_parser)
-    warn_at (loc, _("%s affects only GLR parsers"), "%dprec");
+    complain (&loc, Wother, _("%s affects only GLR parsers"),
+              "%dprec");
   if (dprec <= 0)
-    complain_at (loc, _("%s must be followed by positive number"), "%dprec");
+    complain (&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");
-  current_rule->dprec = dprec;
+    duplicate_directive ("%dprec",
+                         current_rule->dprec_location, loc);
+  else
+    {
+      current_rule->dprec = dprec;
+      current_rule->dprec_location = loc;
+    }
 }
 
 /* Attach a merge function NAME with argument type TYPE to current
@@ -423,35 +492,47 @@ void
 grammar_current_rule_merge_set (uniqstr name, location loc)
 {
   if (! glr_parser)
-    warn_at (loc, _("%s affects only GLR parsers"), "%merge");
+    complain (&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->merger_declaration_location = loc;
+    duplicate_directive ("%merge",
+                         current_rule->merger_declaration_location, loc);
+  else
+    {
+      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 (code_props_code_get (current_rule->action_props))
+  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.  */
 
 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 (code_props_code_get (current_rule->action_props))
+  if (current_rule->action_props.code)
     grammar_midrule_action ();
   /* 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);
+                               current_rule, name, is_predicate);
 }
 
 
@@ -465,7 +546,7 @@ packgram (void)
 {
   unsigned int itemno = 0;
   rule_number ruleno = 0;
-  symbol_list *p = grammar;
+  symbol_list *p;
 
   ritem = xnmalloc (nritems + 1, sizeof *ritem);
 
@@ -474,26 +555,11 @@ packgram (void)
 
   rules = xnmalloc (nrules, sizeof *rules);
 
-  /* Before invoking grammar_rule_check on any rule, make sure all actions have
-     already been scanned in order to set `used' flags.  Otherwise, checking
-     that a midrule's $$ should be set will not always work properly because
-     the check must forward-reference the midrule's parent rule.  For the same
-     reason, all the `used' flags must be set before checking whether to remove
-     `$' from any midrule symbol name.  */
-  while (p)
-    {
-      code_props_translate_code (&p->action_props);
-      if (p)
-	p = p->next;
-    }
-
-  p = grammar;
-  while (p)
+  for (p = grammar; p; p = p->next)
     {
-      int rule_length = 0;
       symbol *ruleprec = p->ruleprec;
       record_merge_function_type (p->merger, p->content.sym->type_name,
-				  p->merger_declaration_location);
+                                  p->merger_declaration_location);
       rules[ruleno].user_number = ruleno;
       rules[ruleno].number = ruleno;
       rules[ruleno].lhs = p->content.sym;
@@ -504,62 +570,60 @@ packgram (void)
       rules[ruleno].precsym = NULL;
       rules[ruleno].location = p->location;
       rules[ruleno].useful = true;
-      rules[ruleno].action = code_props_code_get (p->action_props);
-      if (rules[ruleno].action)
-        rules[ruleno].action_location =
-          code_props_location_get (p->action_props);
-
-      /* If the midrule's $$ 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.  */
+      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
-          && (code_props_is_value_used (p->action_props)
-	      || code_props_is_value_used (
-		   symbol_list_n_get (
-		     p->midrule_parent_rule,
-		     p->midrule_parent_rhs_index)->action_props)))
-	p->content.sym->tag += 1;
+          && (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.  */
+         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)
-	      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->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;
-	}
+        grammar_rule_check (p);
+
+      {
+        size_t rule_length = 0;
+        for (p = p->next; 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 (&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;
     }
 
   aver (itemno == nritems);
@@ -597,27 +661,53 @@ 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;
   gram_scanner_initialize ();
   gram_parse ();
+  prepare_percent_define_front_end_variables ();
 
-  if (! complaint_issued)
+  if (complaint_status  < status_complaint)
     check_and_convert_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-state", "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-reduction", "most");
+    else
+      muscle_percent_define_default ("lr.default-reduction", "accepting");
+    free (lr_type);
+  }
+
+  /* Check %define front-end variables.  */
+  {
+    static char const * const values[] = {
+      "lr.type", "lalr", "ielr", "canonical-lr", NULL,
+      "lr.default-reduction", "most", "consistent", "accepting", NULL,
+      NULL
+    };
+    muscle_percent_define_check_values (values);
+  }
+}
+
 
 /*-------------------------------------------------------------.
 | Check the grammar that has just been read, and convert it to |
-| internal form.					       |
+| internal form.                                               |
 `-------------------------------------------------------------*/
 
 static void
@@ -625,10 +715,7 @@ 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 ();
+    complain (NULL, fatal, _("no rules in the input grammar"));
 
   /* If the user did not define her ENDTOKEN, do it now. */
   if (!endtoken)
@@ -640,6 +727,9 @@ check_and_convert_grammar (void)
       endtoken->user_token_number = 0;
     }
 
+  /* Report any undefined symbols and consider them nonterminals.  */
+  symbols_check_defined ();
+
   /* Find the start symbol if no %start.  */
   if (!start_flag)
     {
@@ -661,7 +751,7 @@ check_and_convert_grammar (void)
   /* Insert the initial rule, whose line is that of the first rule
      (not that of the start symbol):
 
-     accept: %start EOF.  */
+     $accept: %start $end.  */
   {
     symbol_list *p = symbol_list_sym_new (accept, empty_location);
     p->location = grammar->location;
@@ -674,12 +764,30 @@ check_and_convert_grammar (void)
     grammar = p;
   }
 
-  aver (nsyms <= SYMBOL_NUMBER_MAXIMUM && nsyms == ntokens + nvars);
+  aver (nsyms <= SYMBOL_NUMBER_MAXIMUM);
+  aver (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 ();