X-Git-Url: https://git.saurik.com/bison.git/blobdiff_plain/9e6688995eda7d08bc189537cde8d2a856d76bda..ccdc1577ef7fb32a5e30cb655337e7cd42b98987:/src/scan-code.l?ds=inline

diff --git a/src/scan-code.l b/src/scan-code.l
index 94a8eeb5..24ef5d92 100644
--- a/src/scan-code.l
+++ b/src/scan-code.l
@@ -1,12 +1,12 @@
 /* Bison Action Scanner                             -*- C -*-
 
-   Copyright (C) 2006 Free Software Foundation, Inc.
+   Copyright (C) 2006-2012 Free Software Foundation, Inc.
 
    This file is part of Bison, the GNU Compiler Compiler.
 
-   This program 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 of the License, or
+   the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.
 
    This program is distributed in the hope that it will be useful,
@@ -15,48 +15,54 @@
    GNU General Public License for more details.
 
    You should have received a copy of the GNU General Public License
-   along with this program; 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/>.  */
 
-%option debug nodefault nounput noyywrap never-interactive
+%option debug nodefault noinput nounput noyywrap never-interactive
 %option prefix="code_" outfile="lex.yy.c"
 
 %{
-#include <config.h>
-#include "system.h"
-
 /* Work around a bug in flex 2.5.31.  See Debian bug 333231
    <http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=333231>.  */
 #undef code_wrap
 #define code_wrap() 1
 
 #define FLEX_PREFIX(Id) code_ ## Id
-#include "complain.h"
-#include "flex-scanner.h"
-#include "reader.h"
-#include "getargs.h"
-#include <assert.h>
+#include <src/flex-scanner.h>
+
+#include <src/complain.h>
+#include <src/reader.h>
+#include <src/getargs.h>
+#include <src/muscle-tab.h>
+#include <src/scan-code.h>
+#include <src/symlist.h>
+
+#include <c-ctype.h>
 #include <get-errno.h>
 #include <quote.h>
 
-#include "scan-code.h"
-
 /* The current calling start condition: SC_RULE_ACTION or
    SC_SYMBOL_ACTION. */
-# define YY_DECL const char *code_lex (int sc_context)
+# define YY_DECL static char *code_lex (code_props *self, int sc_context)
 YY_DECL;
 
 #define YY_USER_ACTION  location_compute (loc, &loc->end, yytext, yyleng);
 
-static void handle_action_dollar (char *cp, location dollar_loc);
-static void handle_action_at (char *cp, location at_loc);
+static void handle_action_dollar (symbol_list *rule, char *cp,
+                                  location dollar_loc);
+static void handle_action_at (symbol_list *rule, char *cp, location at_loc);
+
+/* A string to be pushed to obstack after dollar/at has been handled. */
+static char *ref_tail_fields;
+
 static location the_location;
 static location *loc = &the_location;
 
-/* The rule being processed. */
-symbol_list *current_rule;
+/* A string representing the most recent translation.  */
+static char *last_string;
+
+/* True if an untyped $$ or $n was seen.  */
+static bool untyped_var_seen;
+
 %}
  /* C and C++ comments in code. */
 %x SC_COMMENT SC_LINE_COMMENT
@@ -70,29 +76,49 @@ symbol_list *current_rule;
 /* POSIX says that a tag must be both an id and a C union member, but
    historically almost any character is allowed in a tag.  We disallow
    NUL and newline, as this simplifies our implementation.  */
-tag	 [^\0\n>]+
+tag      [^\0\n>]+
 
 /* Zero or more instances of backslash-newline.  Following GCC, allow
    white space between the backslash and the newline.  */
-splice	 (\\[ \f\t\v]*\n)*
+splice   (\\[ \f\t\v]*\n)*
+
+/* C style identifier. Must start with letter. Will be used for
+   named symbol references. Shall be kept synchronized with
+   scan-gram.l "letter" and "id". */
+letter    [.abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_]
+id        {letter}({letter}|[-0-9])*
+ref      -?[0-9]+|{id}|"["{id}"]"|"$"
 
 %%
 
 %{
   /* Nesting level of the current code in braces.  */
-  int braces_level IF_LINT (= 0);
+  int braces_level = 0;
+
+  /* Whether a semicolon is probably needed.
+     The heuristic is that a semicolon is not needed after '{', '}', ';',
+     or a C preprocessor directive, and that whitespaces and comments
+     do not affect this flag.
+     Note that '{' does not need a semicolon because of '{}'.
+     A semicolon may be needed before a cpp direcive, but don't bother.  */
+  bool need_semicolon = false;
+
+  /* Whether in a C preprocessor directive.  Don't use a start condition
+     for this because, at the end of strings and comments, we still need
+     to know whether we're in a directive.  */
+  bool in_cpp = false;
 
   /* This scanner is special: it is invoked only once, henceforth
      is expected to return only once.  This initialization is
      therefore done once per action to translate. */
-  assert (sc_context == SC_SYMBOL_ACTION
-	  || sc_context == SC_RULE_ACTION
-	  || sc_context == INITIAL);
+  aver (sc_context == SC_SYMBOL_ACTION
+        || sc_context == SC_RULE_ACTION
+        || sc_context == INITIAL);
   BEGIN sc_context;
 %}
 
   /*------------------------------------------------------------.
-  | Scanning a C comment.  The initial `/ *' is already eaten.  |
+  | Scanning a C comment.  The initial '/ *' is already eaten.  |
   `------------------------------------------------------------*/
 
 <SC_COMMENT>
@@ -102,13 +128,13 @@ splice	 (\\[ \f\t\v]*\n)*
 
 
   /*--------------------------------------------------------------.
-  | Scanning a line comment.  The initial `//' is already eaten.  |
+  | Scanning a line comment.  The initial '//' is already eaten.  |
   `--------------------------------------------------------------*/
 
 <SC_LINE_COMMENT>
 {
-  "\n"		 STRING_GROW; BEGIN sc_context;
-  {splice}	 STRING_GROW;
+  "\n"           STRING_GROW; BEGIN sc_context;
+  {splice}       STRING_GROW;
 }
 
 
@@ -118,17 +144,17 @@ splice	 (\\[ \f\t\v]*\n)*
 
 <SC_CHARACTER,SC_STRING>
 {
-  {splice}|\\{splice}.	STRING_GROW;
+  {splice}|\\{splice}.  STRING_GROW;
 }
 
 <SC_CHARACTER>
 {
-  "'"		STRING_GROW; BEGIN sc_context;
+  "'"           STRING_GROW; BEGIN sc_context;
 }
 
 <SC_STRING>
 {
-  "\""		STRING_GROW; BEGIN sc_context;
+  "\""          STRING_GROW; BEGIN sc_context;
 }
 
 
@@ -136,10 +162,12 @@ splice	 (\\[ \f\t\v]*\n)*
   "'" {
     STRING_GROW;
     BEGIN SC_CHARACTER;
+    need_semicolon = true;
   }
   "\"" {
     STRING_GROW;
     BEGIN SC_STRING;
+    need_semicolon = true;
   }
   "/"{splice}"*" {
     STRING_GROW;
@@ -153,47 +181,99 @@ splice	 (\\[ \f\t\v]*\n)*
 
 <SC_RULE_ACTION>
 {
-  "$"("<"{tag}">")?(-?[0-9]+|"$")   handle_action_dollar (yytext, *loc);
-  "@"(-?[0-9]+|"$")		    handle_action_at (yytext, *loc);
-
+  "$"("<"{tag}">")?{ref}  {
+    ref_tail_fields = 0;
+    handle_action_dollar (self->rule, yytext, *loc);
+    if (ref_tail_fields) {
+      obstack_sgrow (&obstack_for_string, ref_tail_fields);
+    }
+    need_semicolon = true;
+  }
+  "@"{ref} {
+    ref_tail_fields = 0;
+    handle_action_at (self->rule, yytext, *loc);
+    if (ref_tail_fields) {
+      obstack_sgrow (&obstack_for_string, ref_tail_fields);
+    }
+    need_semicolon = true;
+  }
   "$"  {
-    warn_at (*loc, _("stray `$'"));
+    complain_at (*loc, Wother, _("stray '$'"));
     obstack_sgrow (&obstack_for_string, "$][");
+    need_semicolon = true;
   }
   "@"  {
-    warn_at (*loc, _("stray `@'"));
+    complain_at (*loc, Wother, _("stray '@'"));
     obstack_sgrow (&obstack_for_string, "@@");
+    need_semicolon = true;
+  }
+  "["  {
+    obstack_sgrow (&obstack_for_string, "@{");
+    need_semicolon = true;
+  }
+  "]"  {
+    obstack_sgrow (&obstack_for_string, "@}");
+    need_semicolon = true;
   }
 
-  "{"  STRING_GROW; ++braces_level;
+  ";"  STRING_GROW;                 need_semicolon = false;
+  "{"  STRING_GROW; ++braces_level; need_semicolon = false;
   "}"  {
-    bool outer_brace = --braces_level < 0;
+    bool outer_brace = --braces_level == 0;
 
-    /* As an undocumented Bison extension, append `;' before the last
+    /* As an undocumented Bison extension, append ';' before the last
        brace in braced code, so that the user code can omit trailing
-       `;'.  But do not append `;' if emulating Yacc, since Yacc does
-       not append one.
-
-       FIXME: Bison should warn if a semicolon seems to be necessary
-       here, and should omit the semicolon if it seems unnecessary
-       (e.g., after ';', '{', or '}', each followed by comments or
-       white space).  Such a warning shouldn't depend on --yacc; it
-       should depend on a new --pedantic option, which would cause
-       Bison to warn if it detects an extension to POSIX.  --pedantic
-       should also diagnose other Bison extensions like %yacc.
-       Perhaps there should also be a GCC-style --pedantic-errors
-       option, so that such warnings are diagnosed as errors.  */
-    if (outer_brace && ! yacc_flag)
-      obstack_1grow (&obstack_for_string, ';');
+       ';'.  But do not append ';' if emulating Yacc, since Yacc does
+       not append one.  */
+    if (outer_brace && !yacc_flag && language_prio == default_prio
+        && skeleton_prio == default_prio && need_semicolon && ! in_cpp)
+      {
+        complain_at (*loc, Wother,
+                     _("a ';' might be needed at the end of action code"));
+        complain_at (*loc, Wother,
+                     _("future versions of Bison will not add the ';'"));
+        obstack_1grow (&obstack_for_string, ';');
+      }
 
     STRING_GROW;
+    need_semicolon = false;
   }
+
+  /* Preprocessing directives should only be recognized at the beginning
+     of lines, allowing whitespace including comments, but in C/C++,
+     '#' can only be the start of preprocessor directives or within
+     '#define' directives anyway, so don't bother with begin of line.  */
+  "#"       STRING_GROW; in_cpp = true;
+
+  {splice}  STRING_GROW;
+  [\n\r]    STRING_GROW; if (in_cpp) in_cpp = need_semicolon = false;
+  [ \t\f]   STRING_GROW;
+
+  /* YYFAIL is undocumented and was formally deprecated in Bison
+     2.4.2.  */
+  YYFAIL {
+    STRING_GROW; need_semicolon = true;
+    complain_at (*loc, Wother,
+                 _("use of YYFAIL, which is deprecated and will be removed"));
+  }
+
+  /* The sole purpose of this is to make sure identifiers that merely
+     contain YYFAIL don't produce the above warning.  */
+  [A-Za-z_][0-9A-Za-z_]* STRING_GROW; need_semicolon = true;
+
+  . STRING_GROW; need_semicolon = true;
 }
 
 <SC_SYMBOL_ACTION>
 {
-  "$$"   obstack_sgrow (&obstack_for_string, "]b4_dollar_dollar[");
-  "@$"   obstack_sgrow (&obstack_for_string, "]b4_at_dollar[");
+  "$$" {
+    obstack_sgrow (&obstack_for_string, "]b4_dollar_dollar[");
+    self->is_value_used = true;
+  }
+  "@$" {
+    obstack_sgrow (&obstack_for_string, "]b4_at_dollar[");
+    muscle_percent_define_ensure("locations", the_location, true);
+  }
 }
 
 
@@ -203,26 +283,411 @@ splice	 (\\[ \f\t\v]*\n)*
 
 <*>
 {
-  \$	obstack_sgrow (&obstack_for_string, "$][");
-  \@	obstack_sgrow (&obstack_for_string, "@@");
-  \[	obstack_sgrow (&obstack_for_string, "@{");
-  \]	obstack_sgrow (&obstack_for_string, "@}");
+  \$    obstack_sgrow (&obstack_for_string, "$][");
+  \@    obstack_sgrow (&obstack_for_string, "@@");
+  \[    obstack_sgrow (&obstack_for_string, "@{");
+  \]    obstack_sgrow (&obstack_for_string, "@}");
 }
 
   /*-----------------------------------------------------.
   | By default, grow the string obstack with the input.  |
   `-----------------------------------------------------*/
 
-<*>.|\n	STRING_GROW;
+<*>.|\n STRING_GROW;
 
  /* End of processing. */
-<*><<EOF>>	 {
-                   obstack_1grow (&obstack_for_string, '\0');
-		   return obstack_finish (&obstack_for_string);
+<*><<EOF>>       {
+                   STRING_FINISH;
+                   return last_string;
                  }
 
 %%
 
+static inline bool
+is_dot_or_dash (char ch)
+{
+  return ch == '.' || ch == '-';
+}
+
+static inline bool
+contains_dot_or_dash (const char* p)
+{
+  for (; *p; ++p)
+    if (is_dot_or_dash (*p))
+      return true;
+  return false;
+}
+
+/* Defines a variant of a symbolic name resolution. */
+typedef struct
+{
+  /* Index in symbol list. */
+  unsigned symbol_index;
+
+  /* Matched symbol id and loc. */
+  uniqstr id;
+  location loc;
+
+  /* Hiding named reference. */
+  named_ref* hidden_by;
+
+  /* Error flags. May contain zero (no errors) or
+     a combination of VARIANT_* values. */
+  unsigned err;
+} variant;
+
+/* Set when the variant refers to a symbol hidden
+   by an explicit symbol reference. */
+#define VARIANT_HIDDEN (1 << 0)
+
+/* Set when the variant refers to a symbol containing
+   dots or dashes. Will require explicit bracketing. */
+#define VARIANT_BAD_BRACKETING (1 << 1)
+
+/* Set when the variant refers to a symbol which is
+   not visible from current midrule. */
+#define VARIANT_NOT_VISIBLE_FROM_MIDRULE (1 << 2)
+
+static variant *variant_table = 0;
+static unsigned variant_table_size = 0;
+static unsigned variant_count = 0;
+
+static variant *
+variant_table_grow (void)
+{
+  ++variant_count;
+  if (variant_count > variant_table_size)
+    {
+      while (variant_count > variant_table_size)
+        variant_table_size = 2 * variant_table_size + 3;
+      variant_table = xnrealloc (variant_table, variant_table_size,
+                                 sizeof *variant_table);
+    }
+  return &variant_table[variant_count - 1];
+}
+
+static void
+variant_table_free (void)
+{
+  free (variant_table);
+  variant_table = 0;
+  variant_table_size = variant_count = 0;
+}
+
+static char *
+find_prefix_end (const char *prefix, char *begin, char *end)
+{
+  char *ptr = begin;
+
+  for (; *prefix && ptr != end; ++prefix, ++ptr)
+    if (*prefix != *ptr)
+      return 0;
+
+  if (*prefix)
+    return 0;
+
+  return ptr;
+}
+
+static variant *
+variant_add (uniqstr id, location id_loc, unsigned symbol_index,
+             char *cp, char *cp_end, bool explicit_bracketing)
+{
+  char *prefix_end;
+
+  prefix_end = find_prefix_end (id, cp, cp_end);
+  if (prefix_end &&
+      (prefix_end == cp_end ||
+       (!explicit_bracketing && is_dot_or_dash (*prefix_end))))
+    {
+      variant *r = variant_table_grow ();
+      r->symbol_index = symbol_index;
+      r->id = id;
+      r->loc = id_loc;
+      r->hidden_by = NULL;
+      r->err = 0;
+      return r;
+    }
+  else
+    return NULL;
+}
+
+static const char *
+get_at_spec(unsigned symbol_index)
+{
+  static char at_buf[20];
+  if (symbol_index == 0)
+    strcpy (at_buf, "$$");
+  else
+    snprintf (at_buf, sizeof at_buf, "$%u", symbol_index);
+  return at_buf;
+}
+
+static void
+show_sub_messages (const char* cp, bool explicit_bracketing,
+                   int midrule_rhs_index, char dollar_or_at,
+                   bool is_warning, unsigned indent)
+{
+  unsigned i;
+
+  for (i = 0; i < variant_count; ++i)
+    {
+      const variant *var = &variant_table[i];
+      const char *at_spec = get_at_spec (var->symbol_index);
+
+      if (var->err == 0)
+        {
+          if (is_warning)
+            complain_at_indent (var->loc, Wother, &indent,
+                                _("refers to: %c%s at %s"), dollar_or_at,
+                                var->id, at_spec);
+          else
+            complain_at_indent (var->loc, complaint, &indent,
+                                _("refers to: %c%s at %s"), dollar_or_at,
+                                var->id, at_spec);
+        }
+      else
+        {
+          static struct obstack msg_buf;
+          const char *tail = explicit_bracketing ? "" :
+            cp + strlen (var->id);
+          const char *id = var->hidden_by ? var->hidden_by->id :
+            var->id;
+          location id_loc = var->hidden_by ? var->hidden_by->loc :
+            var->loc;
+
+          /* Create the explanation message. */
+          obstack_init (&msg_buf);
+
+          obstack_fgrow1 (&msg_buf, _("possibly meant: %c"), dollar_or_at);
+          if (contains_dot_or_dash (id))
+            obstack_fgrow1 (&msg_buf, "[%s]", id);
+          else
+            obstack_sgrow (&msg_buf, id);
+          obstack_sgrow (&msg_buf, tail);
+
+          if (var->err & VARIANT_HIDDEN)
+            {
+              obstack_fgrow1 (&msg_buf, _(", hiding %c"), dollar_or_at);
+              if (contains_dot_or_dash (var->id))
+                obstack_fgrow1 (&msg_buf, "[%s]", var->id);
+              else
+                obstack_sgrow (&msg_buf, var->id);
+              obstack_sgrow (&msg_buf, tail);
+            }
+
+          obstack_fgrow1 (&msg_buf, _(" at %s"), at_spec);
+
+          if (var->err & VARIANT_NOT_VISIBLE_FROM_MIDRULE)
+            {
+              const char *format =
+                _(", cannot be accessed from mid-rule action at $%d");
+              obstack_fgrow1 (&msg_buf, format, midrule_rhs_index);
+            }
+
+          obstack_1grow (&msg_buf, '\0');
+          if (is_warning)
+            complain_at_indent (id_loc, Wother, &indent, "%s",
+                                (char *) obstack_finish (&msg_buf));
+          else
+            complain_at_indent (id_loc, complaint, &indent, "%s",
+                                (char *) obstack_finish (&msg_buf));
+          obstack_free (&msg_buf, 0);
+        }
+    }
+}
+
+/* Returned from "parse_ref" when the reference
+   is inappropriate. */
+#define INVALID_REF (INT_MIN)
+
+/* Returned from "parse_ref" when the reference
+   points to LHS ($$) of the current rule or midrule. */
+#define LHS_REF (INT_MIN + 1)
+
+/* Sub-messages indent. */
+#define SUB_INDENT (4)
+
+/* Parse named or positional reference. In case of positional
+   references, can return negative values for $-n "deep" stack
+   accesses. */
+static long int
+parse_ref (char *cp, symbol_list *rule, int rule_length,
+           int midrule_rhs_index, char *text, location text_loc,
+           char dollar_or_at)
+{
+  symbol_list *l;
+  char *cp_end;
+  bool explicit_bracketing;
+  unsigned i;
+  unsigned valid_variants = 0;
+  unsigned valid_variant_index = 0;
+
+  if ('$' == *cp)
+    return LHS_REF;
+
+  if (c_isdigit (*cp) || (*cp == '-' && c_isdigit (* (cp + 1))))
+    {
+      long int num = strtol (cp, &cp, 10);
+      if (1 - INT_MAX + rule_length <= num && num <= rule_length)
+        return num;
+      else
+        {
+          complain_at (text_loc, complaint, _("integer out of range: %s"),
+                       quote (text));
+          return INVALID_REF;
+        }
+    }
+
+  if ('[' == *cp)
+    {
+      /* Ignore the brackets. */
+      char *p;
+      for (p = ++cp; *p != ']'; ++p)
+        continue;
+      cp_end = p;
+
+      explicit_bracketing = true;
+    }
+  else
+    {
+      /* Take all characters of the name. */
+      char* p;
+      for (p = cp; *p; ++p)
+        if (is_dot_or_dash (*p))
+          {
+            ref_tail_fields = p;
+            break;
+          }
+      for (p = cp; *p; ++p)
+        continue;
+      cp_end = p;
+
+      explicit_bracketing = false;
+    }
+
+  /* Add all relevant variants. */
+  {
+    unsigned symbol_index;
+    variant_count = 0;
+    for (symbol_index = 0, l = rule; !symbol_list_null (l);
+         ++symbol_index, l = l->next)
+      {
+        variant *var;
+        if (l->content_type != SYMLIST_SYMBOL)
+          continue;
+
+        var = variant_add (l->content.sym->tag, l->sym_loc,
+                           symbol_index, cp, cp_end, explicit_bracketing);
+        if (var && l->named_ref)
+          var->hidden_by = l->named_ref;
+
+        if (l->named_ref)
+          variant_add (l->named_ref->id, l->named_ref->loc,
+                       symbol_index, cp, cp_end, explicit_bracketing);
+      }
+  }
+
+  /* Check errors. */
+  for (i = 0; i < variant_count; ++i)
+    {
+      variant *var = &variant_table[i];
+      unsigned symbol_index = var->symbol_index;
+
+      /* Check visibility from mid-rule actions. */
+      if (midrule_rhs_index != 0
+          && (symbol_index == 0 || midrule_rhs_index < symbol_index))
+        var->err |= VARIANT_NOT_VISIBLE_FROM_MIDRULE;
+
+      /* Check correct bracketing. */
+      if (!explicit_bracketing && contains_dot_or_dash (var->id))
+        var->err |= VARIANT_BAD_BRACKETING;
+
+      /* Check using of hidden symbols. */
+      if (var->hidden_by)
+        var->err |= VARIANT_HIDDEN;
+
+      if (!var->err)
+        {
+          valid_variant_index = i;
+          ++valid_variants;
+        }
+    }
+
+  switch (valid_variants)
+    {
+    case 0:
+      {
+        unsigned len = (explicit_bracketing || !ref_tail_fields) ?
+          cp_end - cp : ref_tail_fields - cp;
+        unsigned indent = 0;
+
+        complain_at_indent (text_loc, complaint, &indent,
+                            _("invalid reference: %s"), quote (text));
+        indent += SUB_INDENT;
+        if (len == 0)
+          {
+            location sym_loc = text_loc;
+            sym_loc.start.column += 1;
+            sym_loc.end = sym_loc.start;
+            const char *format =
+              _("syntax error after '%c', expecting integer, letter,"
+                " '_', '[', or '$'");
+            complain_at_indent (sym_loc, complaint, &indent, format,
+                                dollar_or_at);
+          }
+        else if (midrule_rhs_index)
+          {
+            const char *format =
+              _("symbol not found in production before $%d: %.*s");
+            complain_at_indent (rule->location, complaint, &indent, format,
+                                midrule_rhs_index, len, cp);
+          }
+        else
+          {
+            const char *format =
+              _("symbol not found in production: %.*s");
+            complain_at_indent (rule->location, complaint, &indent, format,
+                                len, cp);
+          }
+
+        if (variant_count > 0)
+          show_sub_messages (cp, explicit_bracketing, midrule_rhs_index,
+                             dollar_or_at, false, indent);
+        return INVALID_REF;
+      }
+    case 1:
+      {
+        unsigned indent = 0;
+        if (variant_count > 1)
+          {
+            complain_at_indent (text_loc, Wother, &indent,
+                                _("misleading reference: %s"), quote (text));
+            show_sub_messages (cp, explicit_bracketing, midrule_rhs_index,
+                               dollar_or_at, true, indent + SUB_INDENT);
+          }
+        {
+          unsigned symbol_index =
+            variant_table[valid_variant_index].symbol_index;
+          return (symbol_index == midrule_rhs_index) ? LHS_REF : symbol_index;
+        }
+      }
+    case 2:
+    default:
+      {
+        unsigned indent = 0;
+        complain_at_indent (text_loc, complaint, &indent,
+                            _("ambiguous reference: %s"), quote (text));
+        show_sub_messages (cp, explicit_bracketing, midrule_rhs_index,
+                           dollar_or_at, false, indent + SUB_INDENT);
+        return INVALID_REF;
+      }
+    }
+
+  /* Not reachable. */
+  return INVALID_REF;
+}
+
 /* Keeps track of the maximum number of semantic values to the left of
    a handle (those referenced by $0, $-1, etc.) are required by the
    semantic actions of this grammar. */
@@ -230,7 +695,7 @@ int max_left_semantic_context = 0;
 
 
 /*------------------------------------------------------------------.
-| TEXT is pointing to a wannabee semantic value (i.e., a `$').      |
+| TEXT is pointing to a wannabee semantic value (i.e., a '$').      |
 |                                                                   |
 | Possible inputs: $[<TYPENAME>]($|integer)                         |
 |                                                                   |
@@ -238,92 +703,152 @@ int max_left_semantic_context = 0;
 `------------------------------------------------------------------*/
 
 static void
-handle_action_dollar (char *text, location dollar_loc)
+handle_action_dollar (symbol_list *rule, char *text, location dollar_loc)
 {
-  const char *type_name = NULL;
+  char const *type_name = NULL;
   char *cp = text + 1;
-  int rule_length = symbol_list_length (current_rule->next);
+  char *gt_ptr = 0;
+  symbol_list *effective_rule;
+  int effective_rule_length;
+  int n;
+
+  if (rule->midrule_parent_rule)
+    {
+      effective_rule = rule->midrule_parent_rule;
+      effective_rule_length = rule->midrule_parent_rhs_index - 1;
+    }
+  else
+    {
+      effective_rule = rule;
+      effective_rule_length = symbol_list_length (rule->next);
+    }
 
   /* Get the type name if explicit. */
   if (*cp == '<')
     {
       type_name = ++cp;
       while (*cp != '>')
-	++cp;
-      *cp = '\0';
+        ++cp;
+
+      /* The '>' symbol will be later replaced by '\0'. Original
+         'text' is needed for error messages. */
+      gt_ptr = cp;
       ++cp;
+      if (untyped_var_seen)
+        complain_at (dollar_loc, complaint,
+                  _("explicit type given in untyped grammar"));
+      tag_seen = true;
     }
 
-  if (*cp == '$')
+  n = parse_ref (cp, effective_rule, effective_rule_length,
+                 rule->midrule_parent_rhs_index, text, dollar_loc, '$');
+
+  if (gt_ptr)
+    *gt_ptr = '\0';
+
+  switch (n)
     {
+    case INVALID_REF:
+      break;
+
+    case LHS_REF:
       if (!type_name)
-	type_name = symbol_list_n_type_name_get (current_rule, dollar_loc, 0);
-      if (!type_name && typed)
-	complain_at (dollar_loc, _("$$ of `%s' has no declared type"),
-		     current_rule->sym->tag);
+        type_name = symbol_list_n_type_name_get (rule, dollar_loc, 0);
+
       if (!type_name)
-	type_name = "";
+        {
+          if (union_seen | tag_seen)
+            {
+              if (rule->midrule_parent_rule)
+                complain_at (dollar_loc, complaint,
+                             _("$$ for the midrule at $%d of %s"
+                               " has no declared type"),
+                             rule->midrule_parent_rhs_index,
+                             quote (effective_rule->content.sym->tag));
+              else
+                complain_at (dollar_loc, complaint,
+                             _("$$ of %s has no declared type"),
+                             quote (rule->content.sym->tag));
+            }
+          else
+            untyped_var_seen = true;
+          type_name = "";
+        }
+
       obstack_fgrow1 (&obstack_for_string,
-		      "]b4_lhs_value([%s])[", type_name);
-      current_rule->used = true;
-    }
-  else
-    {
-      long int num;
-      set_errno (0);
-      num = strtol (cp, 0, 10);
-      if (INT_MIN <= num && num <= rule_length && ! get_errno ())
-	{
-	  int n = num;
-	  if (1-n > max_left_semantic_context)
-	    max_left_semantic_context = 1-n;
-	  if (!type_name && n > 0)
-	    type_name =
-	      symbol_list_n_type_name_get (current_rule, dollar_loc, n);
-	  if (!type_name && typed)
-	    complain_at (dollar_loc, _("$%d of `%s' has no declared type"),
-			 n, current_rule->sym->tag);
-	  if (!type_name)
-	    type_name = "";
-	  obstack_fgrow3 (&obstack_for_string,
-			  "]b4_rhs_value(%d, %d, [%s])[",
-			  rule_length, n, type_name);
-	  symbol_list_n_used_set (current_rule, n, true);
-	}
-      else
-	complain_at (dollar_loc, _("integer out of range: %s"), quote (text));
+                      "]b4_lhs_value([%s])[", type_name);
+      rule->action_props.is_value_used = true;
+      break;
+
+    default:
+      if (max_left_semantic_context < 1 - n)
+        max_left_semantic_context = 1 - n;
+      if (!type_name && 0 < n)
+        type_name =
+          symbol_list_n_type_name_get (effective_rule, dollar_loc, n);
+      if (!type_name)
+        {
+          if (union_seen | tag_seen)
+            complain_at (dollar_loc, complaint,
+                         _("$%s of %s has no declared type"), cp,
+                         quote (effective_rule->content.sym->tag));
+          else
+            untyped_var_seen = true;
+          type_name = "";
+        }
+
+      obstack_fgrow3 (&obstack_for_string,
+                      "]b4_rhs_value(%d, %d, [%s])[",
+                      effective_rule_length, n, type_name);
+      if (n > 0)
+        symbol_list_n_get (effective_rule, n)->action_props.is_value_used =
+          true;
+      break;
     }
 }
 
 
 /*------------------------------------------------------.
-| TEXT is a location token (i.e., a `@...').  Output to |
+| TEXT is a location token (i.e., a '@...').  Output to |
 | OBSTACK_FOR_STRING a reference to this location.      |
 `------------------------------------------------------*/
 
 static void
-handle_action_at (char *text, location at_loc)
+handle_action_at (symbol_list *rule, char *text, location at_loc)
 {
   char *cp = text + 1;
-  int rule_length = symbol_list_length (current_rule->next);
-  locations_flag = true;
+  symbol_list *effective_rule;
+  int effective_rule_length;
+  int n;
 
-  if (*cp == '$')
-    obstack_sgrow (&obstack_for_string, "]b4_lhs_location[");
+  if (rule->midrule_parent_rule)
+    {
+      effective_rule = rule->midrule_parent_rule;
+      effective_rule_length = rule->midrule_parent_rhs_index - 1;
+    }
   else
     {
-      long int num;
-      set_errno (0);
-      num = strtol (cp, 0, 10);
-
-      if (INT_MIN <= num && num <= rule_length && ! get_errno ())
-	{
-	  int n = num;
-	  obstack_fgrow2 (&obstack_for_string, "]b4_rhs_location(%d, %d)[",
-			  rule_length, n);
-	}
-      else
-	complain_at (at_loc, _("integer out of range: %s"), quote (text));
+      effective_rule = rule;
+      effective_rule_length = symbol_list_length (rule->next);
+    }
+
+  muscle_percent_define_ensure("locations", at_loc, true);
+
+  n = parse_ref (cp, effective_rule, effective_rule_length,
+                       rule->midrule_parent_rhs_index, text, at_loc, '@');
+  switch (n)
+    {
+    case INVALID_REF:
+      break;
+
+    case LHS_REF:
+      obstack_sgrow (&obstack_for_string, "]b4_lhs_location[");
+      break;
+
+    default:
+      obstack_fgrow2 (&obstack_for_string, "]b4_rhs_location(%d, %d)[",
+                      effective_rule_length, n);
+      break;
     }
 }
 
@@ -332,59 +857,106 @@ handle_action_at (char *text, location at_loc)
 | Initialize the scanner.  |
 `-------------------------*/
 
-/* Translate the dollars and ats in \a a, whose location is l.
-   Depending on the \a sc_context (SC_RULE_ACTION, SC_SYMBOL_ACTION,
-   INITIAL), the processing is different.  */
+/* Translate the dollars and ats in \a self, in the context \a sc_context
+   (SC_RULE_ACTION, SC_SYMBOL_ACTION, INITIAL).  */
 
-static const char *
-translate_action (int sc_context, const char *a, location l)
+static char const *
+translate_action (code_props *self, int sc_context)
 {
-  const char *res;
+  char *res;
   static bool initialized = false;
   if (!initialized)
     {
       obstack_init (&obstack_for_string);
-      /* The initial buffer, never used. */
-      yy_delete_buffer (YY_CURRENT_BUFFER);
       yy_flex_debug = 0;
       initialized = true;
     }
 
-  loc->start = loc->end = l.start;
-  yy_switch_to_buffer (yy_scan_string (a));
-  res = code_lex (sc_context);
+  loc->start = loc->end = self->location.start;
+  yy_switch_to_buffer (yy_scan_string (self->code));
+  res = code_lex (self, sc_context);
   yy_delete_buffer (YY_CURRENT_BUFFER);
 
   return res;
 }
 
-const char *
-translate_rule_action (symbol_list *r, const char *a, location l)
+/*------------------------------------------------------------------------.
+| Implementation of the public interface as documented in "scan-code.h".  |
+`------------------------------------------------------------------------*/
+
+void
+code_props_none_init (code_props *self)
 {
-  current_rule = r;
-  return translate_action (SC_RULE_ACTION, a, l);
+  *self = code_props_none;
 }
 
-const char *
-translate_symbol_action (const char *a, location l)
+code_props const code_props_none = CODE_PROPS_NONE_INIT;
+
+void
+code_props_plain_init (code_props *self, char const *code,
+                       location code_loc)
+{
+  code_props_none_init (self);
+  self->kind = CODE_PROPS_PLAIN;
+  self->code = code;
+  self->location = code_loc;
+}
+
+void
+code_props_symbol_action_init (code_props *self, char const *code,
+                               location code_loc)
+{
+  code_props_none_init (self);
+  self->kind = CODE_PROPS_SYMBOL_ACTION;
+  self->code = code;
+  self->location = code_loc;
+}
+
+void
+code_props_rule_action_init (code_props *self, char const *code,
+                             location code_loc, symbol_list *rule,
+                             named_ref *name, bool is_predicate)
 {
-  return translate_action (SC_SYMBOL_ACTION, a, l);
+  code_props_none_init (self);
+  self->kind = CODE_PROPS_RULE_ACTION;
+  self->code = code;
+  self->location = code_loc;
+  self->rule = rule;
+  self->named_ref = name;
+  self->is_predicate = is_predicate;
 }
 
-const char *
-translate_code (const char *a, location l)
+void
+code_props_translate_code (code_props *self)
 {
-  return translate_action (INITIAL, a, l);
+  switch (self->kind)
+    {
+      case CODE_PROPS_NONE:
+        break;
+      case CODE_PROPS_PLAIN:
+        self->code = translate_action (self, INITIAL);
+        break;
+      case CODE_PROPS_SYMBOL_ACTION:
+        self->code = translate_action (self, SC_SYMBOL_ACTION);
+        break;
+      case CODE_PROPS_RULE_ACTION:
+        self->code = translate_action (self, SC_RULE_ACTION);
+        break;
+    }
 }
 
-/*-----------------------------------------------.
-| Free all the memory allocated to the scanner.  |
-`-----------------------------------------------*/
+void
+code_scanner_last_string_free (void)
+{
+  STRING_FREE;
+}
 
 void
 code_scanner_free (void)
 {
   obstack_free (&obstack_for_string, 0);
+  variant_table_free ();
+
   /* Reclaim Flex's buffers.  */
-  yy_delete_buffer (YY_CURRENT_BUFFER);
+  yylex_destroy ();
 }