X-Git-Url: https://git.saurik.com/bison.git/blobdiff_plain/da2a7671e11663b9ad941aa3e1f3014d6ad950cb..468455e12b995d4b44a648cb47b749ead4453bae:/src/symtab.c

diff --git a/src/symtab.c b/src/symtab.c
index c0368f71..002f6e37 100644
--- a/src/symtab.c
+++ b/src/symtab.c
@@ -1,35 +1,39 @@
 /* Symbol table manager for Bison.
 
-   Copyright (C) 1984, 1989, 2000, 2001, 2002, 2004 Free Software
+   Copyright (C) 1984, 1989, 2000-2002, 2004-2012 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., 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 <hash.h>
-#include <quotearg.h>
 
 #include "complain.h"
 #include "gram.h"
 #include "symtab.h"
 
+/*-------------------------------------------------------------------.
+| Symbols sorted by tag.  Allocated by the first invocation of       |
+| symbols_do, after which no more symbols should be created.         |
+`-------------------------------------------------------------------*/
+
+static symbol **symbols_sorted = NULL;
+
 /*------------------------.
 | Distinguished symbols.  |
 `------------------------*/
@@ -41,6 +45,15 @@ symbol *accept = NULL;
 symbol *startsymbol = NULL;
 location startsymbol_location;
 
+/*---------------------------------------.
+| Default %destructor's and %printer's.  |
+`---------------------------------------*/
+
+static code_props default_tagged_destructor = CODE_PROPS_NONE_INIT;
+static code_props default_tagless_destructor = CODE_PROPS_NONE_INIT;
+static code_props default_tagged_printer = CODE_PROPS_NONE_INIT;
+static code_props default_tagless_printer = CODE_PROPS_NONE_INIT;
+
 /*---------------------------------.
 | Create a new symbol, named TAG.  |
 `---------------------------------*/
@@ -51,12 +64,19 @@ symbol_new (uniqstr tag, location loc)
   symbol *res = xmalloc (sizeof *res);
 
   uniqstr_assert (tag);
+
+  /* If the tag is not a string (starts with a double quote), check
+     that it is valid for Yacc. */
+  if (tag[0] != '\"' && tag[0] != '\'' && mbschr (tag, '-'))
+    yacc_at (loc, _("POSIX Yacc forbids dashes in symbol names: %s"),
+             tag);
+
   res->tag = tag;
   res->location = loc;
 
   res->type_name = NULL;
-  res->destructor = NULL;
-  res->printer = NULL;
+  code_props_none_init (&res->destructor);
+  code_props_none_init (&res->printer);
 
   res->number = NUMBER_UNDEFINED;
   res->prec = 0;
@@ -65,11 +85,61 @@ symbol_new (uniqstr tag, location loc)
 
   res->alias = NULL;
   res->class = unknown_sym;
+  res->declared = false;
 
+  if (nsyms == SYMBOL_NUMBER_MAXIMUM)
+    fatal (_("too many symbols in input grammar (limit is %d)"),
+	   SYMBOL_NUMBER_MAXIMUM);
   nsyms++;
   return res;
 }
 
+/*----------------------------------------.
+| Create a new semantic type, named TAG.  |
+`----------------------------------------*/
+
+static semantic_type *
+semantic_type_new (uniqstr tag)
+{
+  semantic_type *res = xmalloc (sizeof *res);
+
+  uniqstr_assert (tag);
+  res->tag = tag;
+  code_props_none_init (&res->destructor);
+  code_props_none_init (&res->printer);
+
+  return res;
+}
+
+
+/*-----------------.
+| Print a symbol.  |
+`-----------------*/
+
+#define SYMBOL_ATTR_PRINT(Attr)				\
+  if (s->Attr)						\
+    fprintf (f, " %s { %s }", #Attr, s->Attr)
+
+#define SYMBOL_CODE_PRINT(Attr)                         \
+  if (s->Attr.code)                                     \
+    fprintf (f, " %s { %s }", #Attr, s->Attr.code)
+
+void
+symbol_print (symbol *s, FILE *f)
+{
+  if (s)
+    {
+      fprintf (f, "\"%s\"", s->tag);
+      SYMBOL_ATTR_PRINT (type_name);
+      SYMBOL_CODE_PRINT (destructor);
+      SYMBOL_CODE_PRINT (printer);
+    }
+  else
+    fprintf (f, "<NULL>");
+}
+
+#undef SYMBOL_ATTR_PRINT
+#undef SYMBOL_CODE_PRINT
 
 /*------------------------------------------------------------------.
 | Complain that S's WHAT is redeclared at SECOND, and was first set |
@@ -77,12 +147,22 @@ symbol_new (uniqstr tag, location loc)
 `------------------------------------------------------------------*/
 
 static void
-redeclaration (symbol* s, const char *what, location first, location second)
+symbol_redeclaration (symbol *s, const char *what, location first,
+                      location second)
 {
   complain_at (second, _("%s redeclaration for %s"), what, s->tag);
-  complain_at (first, _("first declaration"));
+  complain_at (first, _("previous declaration"));
 }
 
+static void
+semantic_type_redeclaration (semantic_type *s, const char *what, location first,
+                             location second)
+{
+  complain_at (second, _("%s redeclaration for <%s>"), what, s->tag);
+  complain_at (first, _("previous declaration"));
+}
+
+
 
 /*-----------------------------------------------------------------.
 | Set the TYPE_NAME associated with SYM.  Does nothing if passed 0 |
@@ -95,47 +175,123 @@ symbol_type_set (symbol *sym, uniqstr type_name, location loc)
   if (type_name)
     {
       if (sym->type_name)
-	redeclaration (sym, "%type", sym->type_location, loc);
+	symbol_redeclaration (sym, "%type", sym->type_location, loc);
       uniqstr_assert (type_name);
       sym->type_name = type_name;
       sym->type_location = loc;
     }
 }
 
+/*-----------------------------------------.
+| Set the DESTRUCTOR associated with SYM.  |
+`-----------------------------------------*/
 
-/*------------------------------------------------------------------.
-| Set the DESTRUCTOR associated with SYM.  Do nothing if passed 0.  |
-`------------------------------------------------------------------*/
+void
+symbol_destructor_set (symbol *sym, code_props const *destructor)
+{
+  if (sym->destructor.code)
+    symbol_redeclaration (sym, "%destructor", sym->destructor.location,
+                          destructor->location);
+  sym->destructor = *destructor;
+}
+
+/*------------------------------------------.
+| Set the DESTRUCTOR associated with TYPE.  |
+`------------------------------------------*/
 
 void
-symbol_destructor_set (symbol *sym, char *destructor, location loc)
+semantic_type_destructor_set (semantic_type *type,
+                              code_props const *destructor)
 {
-  if (destructor)
+  if (type->destructor.code)
+    semantic_type_redeclaration (type, "%destructor",
+                                 type->destructor.location,
+                                 destructor->location);
+  type->destructor = *destructor;
+}
+
+/*---------------------------------------.
+| Get the computed %destructor for SYM.  |
+`---------------------------------------*/
+
+code_props const *
+symbol_destructor_get (symbol const *sym)
+{
+  /* Per-symbol %destructor.  */
+  if (sym->destructor.code)
+    return &sym->destructor;
+
+  /* Per-type %destructor.  */
+  if (sym->type_name)
     {
-      if (sym->destructor)
-	redeclaration (sym, "%destructor", sym->destructor_location, loc);
-      sym->destructor = destructor;
-      sym->destructor_location = loc;
+      code_props const *destructor =
+        &semantic_type_get (sym->type_name)->destructor;
+      if (destructor->code)
+        return destructor;
     }
+
+  /* Apply default %destructor's only to user-defined symbols.  */
+  if (sym->tag[0] == '$' || sym == errtoken)
+    return &code_props_none;
+
+  if (sym->type_name)
+    return &default_tagged_destructor;
+  return &default_tagless_destructor;
 }
 
+/*--------------------------------------.
+| Set the PRINTER associated with SYM.  |
+`--------------------------------------*/
 
-/*---------------------------------------------------------------.
-| Set the PRINTER associated with SYM.  Do nothing if passed 0.  |
-`---------------------------------------------------------------*/
+void
+symbol_printer_set (symbol *sym, code_props const *printer)
+{
+  if (sym->printer.code)
+    symbol_redeclaration (sym, "%printer",
+                          sym->printer.location, printer->location);
+  sym->printer = *printer;
+}
+
+/*---------------------------------------.
+| Set the PRINTER associated with TYPE.  |
+`---------------------------------------*/
 
 void
-symbol_printer_set (symbol *sym, char *printer, location loc)
+semantic_type_printer_set (semantic_type *type, code_props const *printer)
+{
+  if (type->printer.code)
+    semantic_type_redeclaration (type, "%printer",
+                                 type->printer.location, printer->location);
+  type->printer = *printer;
+}
+
+/*------------------------------------.
+| Get the computed %printer for SYM.  |
+`------------------------------------*/
+
+code_props const *
+symbol_printer_get (symbol const *sym)
 {
-  if (printer)
+  /* Per-symbol %printer.  */
+  if (sym->printer.code)
+    return &sym->printer;
+
+  /* Per-type %printer.  */
+  if (sym->type_name)
     {
-      if (sym->printer)
-	redeclaration (sym, "%printer", sym->destructor_location, loc);
-      sym->printer = printer;
-      sym->printer_location = loc;
+      code_props const *printer = &semantic_type_get (sym->type_name)->printer;
+      if (printer->code)
+        return printer;
     }
-}
 
+  /* Apply the default %printer only to user-defined symbols.  */
+  if (sym->tag[0] == '$' || sym == errtoken)
+    return &code_props_none;
+
+  if (sym->type_name)
+    return &default_tagged_printer;
+  return &default_tagless_printer;
+}
 
 /*-----------------------------------------------------------------.
 | Set the PRECEDENCE associated with SYM.  Does nothing if invoked |
@@ -148,14 +304,15 @@ symbol_precedence_set (symbol *sym, int prec, assoc a, location loc)
   if (a != undef_assoc)
     {
       if (sym->prec != 0)
-	redeclaration (sym, assoc_to_string (a), sym->prec_location, loc);
+	symbol_redeclaration (sym, assoc_to_string (a), sym->prec_location,
+                              loc);
       sym->prec = prec;
       sym->assoc = a;
       sym->prec_location = loc;
     }
 
   /* Only terminals have a precedence. */
-  symbol_class_set (sym, token_sym, loc);
+  symbol_class_set (sym, token_sym, loc, false);
 }
 
 
@@ -164,10 +321,13 @@ symbol_precedence_set (symbol *sym, int prec, assoc a, location loc)
 `------------------------------------*/
 
 void
-symbol_class_set (symbol *sym, symbol_class class, location loc)
+symbol_class_set (symbol *sym, symbol_class class, location loc, bool declaring)
 {
   if (sym->class != unknown_sym && sym->class != class)
-    complain_at (loc, _("symbol %s redefined"), sym->tag);
+    {
+      complain_at (loc, _("symbol %s redefined"), sym->tag);
+      sym->declared = false;
+    }
 
   if (class == nterm_sym && sym->class != nterm_sym)
     sym->number = nvars++;
@@ -175,6 +335,13 @@ symbol_class_set (symbol *sym, symbol_class class, location loc)
     sym->number = ntokens++;
 
   sym->class = class;
+
+  if (declaring)
+    {
+      if (sym->declared)
+	warn_at (loc, _("symbol %s redeclared"), sym->tag);
+      sym->declared = true;
+    }
 }
 
 
@@ -185,22 +352,26 @@ symbol_class_set (symbol *sym, symbol_class class, location loc)
 void
 symbol_user_token_number_set (symbol *sym, int user_token_number, location loc)
 {
-  if (sym->class != token_sym)
-    abort ();
+  int *user_token_numberp;
 
-  if (sym->user_token_number != USER_NUMBER_UNDEFINED
-      && sym->user_token_number != user_token_number)
+  if (sym->user_token_number != USER_NUMBER_HAS_STRING_ALIAS)
+    user_token_numberp = &sym->user_token_number;
+  else
+    user_token_numberp = &sym->alias->user_token_number;
+  if (*user_token_numberp != USER_NUMBER_UNDEFINED
+      && *user_token_numberp != user_token_number)
     complain_at (loc, _("redefining user token number of %s"), sym->tag);
 
-  sym->user_token_number = user_token_number;
+  *user_token_numberp = user_token_number;
   /* User defined $end token? */
   if (user_token_number == 0)
     {
       endtoken = sym;
-      endtoken->number = 0;
       /* It is always mapped to 0, so it was already counted in
 	 NTOKENS.  */
-      --ntokens;
+      if (endtoken->number != NUMBER_UNDEFINED)
+        --ntokens;
+      endtoken->number = 0;
     }
 }
 
@@ -233,34 +404,24 @@ symbol_check_defined_processor (void *sym, void *null ATTRIBUTE_UNUSED)
 }
 
 
-/*------------------------------------------------------------------.
-| Declare the new symbol SYM.  Make it an alias of SYMVAL, and type |
-| SYMVAL with SYM's type.                                           |
-`------------------------------------------------------------------*/
-
 void
-symbol_make_alias (symbol *sym, symbol *symval, location loc)
+symbol_make_alias (symbol *sym, symbol *str, location loc)
 {
-  if (symval->alias)
-    warn_at (loc, _("symbol `%s' used more than once as a literal string"),
-	     symval->tag);
+  if (str->alias)
+    warn_at (loc, _("symbol %s used more than once as a literal string"),
+             str->tag);
   else if (sym->alias)
-    warn_at (loc, _("symbol `%s' given more than one literal string"),
-	     sym->tag);
+    warn_at (loc, _("symbol %s given more than one literal string"),
+             sym->tag);
   else
     {
-      symval->class = token_sym;
-      symval->user_token_number = sym->user_token_number;
-      sym->user_token_number = USER_NUMBER_ALIAS;
-      symval->alias = sym;
-      sym->alias = symval;
-      /* sym and symval combined are only one symbol.  */
-      nsyms--;
-      ntokens--;
-      if (ntokens != sym->number && ntokens != symval->number)
-	abort ();
-      sym->number = symval->number =
-	(symval->number < sym->number) ? symval->number : sym->number;
+      str->class = token_sym;
+      str->user_token_number = sym->user_token_number;
+      sym->user_token_number = USER_NUMBER_HAS_STRING_ALIAS;
+      str->alias = sym;
+      sym->alias = str;
+      str->number = sym->number;
+      symbol_type_set (str, sym->type_name, loc);
     }
 }
 
@@ -273,48 +434,47 @@ symbol_make_alias (symbol *sym, symbol *symval, location loc)
 static inline void
 symbol_check_alias_consistency (symbol *this)
 {
-  symbol *alias = this;
-  symbol *orig  = this->alias;
+  symbol *sym = this;
+  symbol *str = this->alias;
 
-  /* Check only those that _are_ the aliases.  */
-  if (!(this->alias && this->user_token_number == USER_NUMBER_ALIAS))
+  /* Check only the symbol in the symbol-string pair.  */
+  if (!(this->alias
+        && this->user_token_number == USER_NUMBER_HAS_STRING_ALIAS))
     return;
 
-  if (orig->type_name || alias->type_name)
+  if (str->type_name != sym->type_name)
     {
-      if (orig->type_name)
-	symbol_type_set (alias, orig->type_name, orig->type_location);
+      if (str->type_name)
+	symbol_type_set (sym, str->type_name, str->type_location);
       else
-	symbol_type_set (orig, alias->type_name, alias->type_location);
+	symbol_type_set (str, sym->type_name, sym->type_location);
     }
 
 
-  if (orig->destructor || alias->destructor)
+  if (str->destructor.code || sym->destructor.code)
     {
-      if (orig->destructor)
-	symbol_destructor_set (alias, orig->destructor,
-			       orig->destructor_location);
+      if (str->destructor.code)
+	symbol_destructor_set (sym, &str->destructor);
       else
-	symbol_destructor_set (orig, alias->destructor,
-			       alias->destructor_location);
+	symbol_destructor_set (str, &sym->destructor);
     }
 
-  if (orig->printer || alias->printer)
+  if (str->printer.code || sym->printer.code)
     {
-      if (orig->printer)
-	symbol_printer_set (alias, orig->printer, orig->printer_location);
+      if (str->printer.code)
+	symbol_printer_set (sym, &str->printer);
       else
-	symbol_printer_set (orig, alias->printer, alias->printer_location);
+	symbol_printer_set (str, &sym->printer);
     }
 
-  if (alias->prec || orig->prec)
+  if (sym->prec || str->prec)
     {
-      if (orig->prec)
-	symbol_precedence_set (alias, orig->prec, orig->assoc,
-			       orig->prec_location);
+      if (str->prec)
+	symbol_precedence_set (sym, str->prec, str->assoc,
+			       str->prec_location);
       else
-	symbol_precedence_set (orig, alias->prec, alias->assoc,
-			       alias->prec_location);
+	symbol_precedence_set (str, sym->prec, sym->assoc,
+			       sym->prec_location);
     }
 }
 
@@ -335,35 +495,11 @@ symbol_check_alias_consistency_processor (void *this,
 static inline bool
 symbol_pack (symbol *this)
 {
+  aver (this->number != NUMBER_UNDEFINED);
   if (this->class == nterm_sym)
-    {
-      this->number += ntokens;
-    }
-  else if (this->alias)
-    {
-      /* This symbol and its alias are a single token defn.
-	 Allocate a tokno, and assign to both check agreement of
-	 prec and assoc fields and make both the same */
-      if (this->number == NUMBER_UNDEFINED)
-	{
-	  if (this == endtoken || this->alias == endtoken)
-	    this->number = this->alias->number = 0;
-	  else
-	    {
-	      if (this->alias->number == NUMBER_UNDEFINED)
-		abort ();
-	      this->number = this->alias->number;
-	    }
-	}
-      /* Do not do processing below for USER_NUMBER_ALIASes.  */
-      if (this->user_token_number == USER_NUMBER_ALIAS)
-	return true;
-    }
-  else /* this->class == token_sym */
-    {
-      if (this->number == NUMBER_UNDEFINED)
-	abort ();
-    }
+    this->number += ntokens;
+  else if (this->user_token_number == USER_NUMBER_HAS_STRING_ALIAS)
+    return true;
 
   symbols[this->number] = this;
   return true;
@@ -376,7 +512,26 @@ symbol_pack_processor (void *this, void *null ATTRIBUTE_UNUSED)
 }
 
 
+static void
+user_token_number_redeclaration (int num, symbol *first, symbol *second)
+{
+  /* User token numbers are not assigned during the parsing, but in a
+     second step, via a traversal of the symbol table sorted on tag.
 
+     However, error messages make more sense if we keep the first
+     declaration first.  */
+  if (location_cmp (first->location, second->location) > 0)
+    {
+      symbol* tmp = first;
+      first = second;
+      second = tmp;
+    }
+  complain_at (second->location,
+               _("user token number %d redeclaration for %s"),
+               num, second->tag);
+  complain_at (first->location, _("previous declaration for %s"),
+               first->tag);
+}
 
 /*--------------------------------------------------.
 | Put THIS in TOKEN_TRANSLATIONS if it is a token.  |
@@ -387,14 +542,14 @@ symbol_translation (symbol *this)
 {
   /* Non-terminal? */
   if (this->class == token_sym
-      && this->user_token_number != USER_NUMBER_ALIAS)
+      && this->user_token_number != USER_NUMBER_HAS_STRING_ALIAS)
     {
       /* A token which translation has already been set? */
       if (token_translations[this->user_token_number] != undeftoken->number)
-	complain_at (this->location,
-		     _("tokens %s and %s both assigned number %d"),
-		     symbols[token_translations[this->user_token_number]]->tag,
-		     this->tag, this->user_token_number);
+	user_token_number_redeclaration
+          (this->user_token_number,
+           symbols[token_translations[this->user_token_number]],
+           this);
 
       token_translations[this->user_token_number] = this->number;
     }
@@ -409,14 +564,15 @@ symbol_translation_processor (void *this, void *null ATTRIBUTE_UNUSED)
 }
 
 
-/*----------------------.
-| A symbol hash table.  |
-`----------------------*/
+/*---------------------------------------.
+| Symbol and semantic type hash tables.  |
+`---------------------------------------*/
 
-/* Initial capacity of symbols hash table.  */
+/* Initial capacity of symbol and semantic type hash table.  */
 #define HT_INITIAL_CAPACITY 257
 
 static struct hash_table *symbol_table = NULL;
+static struct hash_table *semantic_type_table = NULL;
 
 static inline bool
 hash_compare_symbol (const symbol *m1, const symbol *m2)
@@ -425,12 +581,25 @@ hash_compare_symbol (const symbol *m1, const symbol *m2)
   return UNIQSTR_EQ (m1->tag, m2->tag);
 }
 
+static inline bool
+hash_compare_semantic_type (const semantic_type *m1, const semantic_type *m2)
+{
+  /* Since names are unique, we can compare the pointers themselves.  */
+  return UNIQSTR_EQ (m1->tag, m2->tag);
+}
+
 static bool
 hash_symbol_comparator (void const *m1, void const *m2)
 {
   return hash_compare_symbol (m1, m2);
 }
 
+static bool
+hash_semantic_type_comparator (void const *m1, void const *m2)
+{
+  return hash_compare_semantic_type (m1, m2);
+}
+
 static inline size_t
 hash_symbol (const symbol *m, size_t tablesize)
 {
@@ -438,12 +607,24 @@ hash_symbol (const symbol *m, size_t tablesize)
   return ((uintptr_t) m->tag) % tablesize;
 }
 
+static inline size_t
+hash_semantic_type (const semantic_type *m, size_t tablesize)
+{
+  /* Since names are unique, we can hash the pointer itself.  */
+  return ((uintptr_t) m->tag) % tablesize;
+}
+
 static size_t
 hash_symbol_hasher (void const *m, size_t tablesize)
 {
   return hash_symbol (m, tablesize);
 }
 
+static size_t
+hash_semantic_type_hasher (void const *m, size_t tablesize)
+{
+  return hash_semantic_type (m, tablesize);
+}
 
 /*-------------------------------.
 | Create the symbol hash table.  |
@@ -457,6 +638,11 @@ symbols_new (void)
 				  hash_symbol_hasher,
 				  hash_symbol_comparator,
 				  free);
+  semantic_type_table = hash_initialize (HT_INITIAL_CAPACITY,
+				         NULL,
+				         hash_semantic_type_hasher,
+				         hash_semantic_type_comparator,
+				         free);
 }
 
 
@@ -466,26 +652,75 @@ symbols_new (void)
 `----------------------------------------------------------------*/
 
 symbol *
-symbol_get (const char *key, location loc)
+symbol_from_uniqstr (const uniqstr key, location loc)
 {
   symbol probe;
   symbol *entry;
 
-  /* Keep the symbol in a printable form.  */
-  key = uniqstr_new (quotearg_style (escape_quoting_style, key));
   probe.tag = key;
   entry = hash_lookup (symbol_table, &probe);
 
   if (!entry)
     {
       /* First insertion in the hash. */
+      aver (!symbols_sorted);
       entry = symbol_new (key, loc);
-      hash_insert (symbol_table, entry);
+      if (!hash_insert (symbol_table, entry))
+        xalloc_die ();
     }
   return entry;
 }
 
 
+/*-----------------------------------------------------------------------.
+| Find the semantic type named KEY, and return it.  If it does not exist |
+| yet, create it.                                                        |
+`-----------------------------------------------------------------------*/
+
+semantic_type *
+semantic_type_from_uniqstr (const uniqstr key)
+{
+  semantic_type probe;
+  semantic_type *entry;
+
+  probe.tag = key;
+  entry = hash_lookup (semantic_type_table, &probe);
+
+  if (!entry)
+    {
+      /* First insertion in the hash. */
+      entry = semantic_type_new (key);
+      if (!hash_insert (semantic_type_table, entry))
+        xalloc_die ();
+    }
+  return entry;
+}
+
+
+/*----------------------------------------------------------------.
+| Find the symbol named KEY, and return it.  If it does not exist |
+| yet, create it.                                                 |
+`----------------------------------------------------------------*/
+
+symbol *
+symbol_get (const char *key, location loc)
+{
+  return symbol_from_uniqstr (uniqstr_new (key), loc);
+}
+
+
+/*-----------------------------------------------------------------------.
+| Find the semantic type named KEY, and return it.  If it does not exist |
+| yet, create it.                                                        |
+`-----------------------------------------------------------------------*/
+
+semantic_type *
+semantic_type_get (const char *key)
+{
+  return semantic_type_from_uniqstr (uniqstr_new (key));
+}
+
+
 /*------------------------------------------------------------------.
 | Generate a dummy nonterminal, whose name cannot conflict with the |
 | user's names.                                                     |
@@ -500,13 +735,18 @@ dummy_symbol_get (location loc)
 
   symbol *sym;
 
-  sprintf (buf, "@%d", ++dummy_count);
+  sprintf (buf, "$@%d", ++dummy_count);
   sym = symbol_get (buf, loc);
   sym->class = nterm_sym;
   sym->number = nvars++;
   return sym;
 }
 
+bool
+symbol_is_dummy (const symbol *sym)
+{
+  return sym->tag[0] == '@' || (sym->tag[0] == '$' && sym->tag[1] == '@');
+}
 
 /*-------------------.
 | Free the symbols.  |
@@ -516,7 +756,9 @@ void
 symbols_free (void)
 {
   hash_free (symbol_table);
+  hash_free (semantic_type_table);
   free (symbols);
+  free (symbols_sorted);
 }
 
 
@@ -525,13 +767,36 @@ symbols_free (void)
 | terminals.                                                     |
 `---------------------------------------------------------------*/
 
+static int
+symbols_cmp (symbol const *a, symbol const *b)
+{
+  return strcmp (a->tag, b->tag);
+}
+
+static int
+symbols_cmp_qsort (void const *a, void const *b)
+{
+  return symbols_cmp (*(symbol * const *)a, *(symbol * const *)b);
+}
+
 static void
 symbols_do (Hash_processor processor, void *processor_data)
 {
-  hash_do_for_each (symbol_table, processor, processor_data);
+  size_t count = hash_get_n_entries (symbol_table);
+  if (!symbols_sorted)
+    {
+      symbols_sorted = xnmalloc (count, sizeof *symbols_sorted);
+      hash_get_entries (symbol_table, (void**)symbols_sorted, count);
+      qsort (symbols_sorted, count, sizeof *symbols_sorted,
+             symbols_cmp_qsort);
+    }
+  {
+    size_t i;
+    for (i = 0; i < count; ++i)
+      processor (symbols_sorted[i], processor_data);
+  }
 }
 
-
 /*--------------------------------------------------------------.
 | Check that all the symbols are defined.  Report any undefined |
 | symbols and consider them nonterminals.                       |
@@ -607,11 +872,35 @@ symbols_token_translations_init (void)
 void
 symbols_pack (void)
 {
-  symbols = xcalloc (nsyms, sizeof *symbols);
-
   symbols_do (symbol_check_alias_consistency_processor, NULL);
+
+  symbols = xcalloc (nsyms, sizeof *symbols);
   symbols_do (symbol_pack_processor, NULL);
 
+  /* Aliases leave empty slots in symbols, so remove them.  */
+  {
+    int writei;
+    int readi;
+    int nsyms_old = nsyms;
+    for (writei = 0, readi = 0; readi < nsyms_old; readi += 1)
+      {
+        if (symbols[readi] == NULL)
+          {
+            nsyms -= 1;
+            ntokens -= 1;
+          }
+        else
+          {
+            symbols[writei] = symbols[readi];
+            symbols[writei]->number = writei;
+            if (symbols[writei]->alias)
+              symbols[writei]->alias->number = writei;
+            writei += 1;
+          }
+      }
+  }
+  symbols = xnrealloc (symbols, nsyms, sizeof *symbols);
+
   symbols_token_translations_init ();
 
   if (startsymbol->class == unknown_sym)
@@ -623,3 +912,60 @@ symbols_pack (void)
 	      _("the start symbol %s is a token"),
 	      startsymbol->tag);
 }
+
+
+/*--------------------------------------------------.
+| Set default tagged/tagless %destructor/%printer.  |
+`--------------------------------------------------*/
+
+void
+default_tagged_destructor_set (code_props const *destructor)
+{
+  if (default_tagged_destructor.code)
+    {
+      complain_at (destructor->location,
+                   _("redeclaration for default tagged %%destructor"));
+      complain_at (default_tagged_destructor.location,
+		   _("previous declaration"));
+    }
+  default_tagged_destructor = *destructor;
+}
+
+void
+default_tagless_destructor_set (code_props const *destructor)
+{
+  if (default_tagless_destructor.code)
+    {
+      complain_at (destructor->location,
+                   _("redeclaration for default tagless %%destructor"));
+      complain_at (default_tagless_destructor.location,
+		   _("previous declaration"));
+    }
+  default_tagless_destructor = *destructor;
+}
+
+void
+default_tagged_printer_set (code_props const *printer)
+{
+  if (default_tagged_printer.code)
+    {
+      complain_at (printer->location,
+                   _("redeclaration for default tagged %%printer"));
+      complain_at (default_tagged_printer.location,
+		   _("previous declaration"));
+    }
+  default_tagged_printer = *printer;
+}
+
+void
+default_tagless_printer_set (code_props const *printer)
+{
+  if (default_tagless_printer.code)
+    {
+      complain_at (printer->location,
+                   _("redeclaration for default tagless %%printer"));
+      complain_at (default_tagless_printer.location,
+		   _("previous declaration"));
+    }
+  default_tagless_printer = *printer;
+}