DJGPP spicific: NULL pointer fix

[bison.git] / src / reader.c

/* Input parser for bison
   Copyright 1984, 1986, 1989, 1992, 1998, 2000, 2001
   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
   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.

   Bison 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.  */


#include "system.h"
#include "obstack.h"
#include "quotearg.h"
#include "quote.h"
#include "getargs.h"
#include "files.h"
#include "symtab.h"
#include "lex.h"
#include "gram.h"
#include "complain.h"
#include "output.h"
#include "reader.h"
#include "conflicts.h"

typedef struct symbol_list
{
  struct symbol_list *next;
  bucket *sym;
  int line;
  bucket *ruleprec;
}
symbol_list;

int lineno;
char **tags;
short *user_toknums;
static symbol_list *grammar;
static int start_flag;
static bucket *startval;

/* Nonzero if components of semantic values are used, implying
   they must be unions.  */
static int value_components_used;

/* Nonzero if %union has been seen.  */
static int typed;

/* Incremented for each %left, %right or %nonassoc seen */
static int lastprec;

static bucket *errtoken;
static bucket *undeftoken;


static symbol_list *
symbol_list_new (bucket *sym)
{
  symbol_list *res = XMALLOC (symbol_list, 1);
  res->next = NULL;
  res->sym = sym;
  res->line = lineno;
  res->ruleprec = NULL;
  return res;
}

\f

/*===================\
| Low level lexing.  |
\===================*/

static void
skip_to_char (int target)
{
  int c;
  if (target == '\n')
    complain (_("   Skipping to next \\n"));
  else
    complain (_("   Skipping to next %c"), target);

  do
    c = skip_white_space ();
  while (c != target && c != EOF);
  if (c != EOF)
    ungetc (c, finput);
}


/*---------------------------------------------------------.
| Read a signed integer from STREAM and return its value.  |
`---------------------------------------------------------*/

static inline int
read_signed_integer (FILE *stream)
{
  int c = getc (stream);
  int sign = 1;
  int n = 0;

  if (c == '-')
    {
      c = getc (stream);
      sign = -1;
    }

  while (isdigit (c))
    {
      n = 10 * n + (c - '0');
      c = getc (stream);
    }

  ungetc (c, stream);

  return sign * n;
}
\f
/*--------------------------------------------------------------.
| Get the data type (alternative in the union) of the value for |
| symbol N in rule RULE.                                        |
`--------------------------------------------------------------*/

static char *
get_type_name (int n, symbol_list *rule)
{
  int i;
  symbol_list *rp;

  if (n < 0)
    {
      complain (_("invalid $ value"));
      return NULL;
    }

  rp = rule;
  i = 0;

  while (i < n)
    {
      rp = rp->next;
      if (rp == NULL || rp->sym == NULL)
        {
          complain (_("invalid $ value"));
          return NULL;
        }
      i++;
    }

  return rp->sym->type_name;
}
\f
/*------------------------------------------------------------.
| Dump the string from FIN to OOUT if non null.  MATCH is the |
| delimiter of the string (either ' or ").                    |
`------------------------------------------------------------*/

static inline void
copy_string (FILE *fin, struct obstack *oout, int match)
{
  int c;

  obstack_1grow (oout, match);

  c = getc (fin);

  while (c != match)
    {
      if (c == EOF)
        fatal (_("unterminated string at end of file"));
      if (c == '\n')
        {
          complain (_("unterminated string"));
          ungetc (c, fin);
          c = match;            /* invent terminator */
          continue;
        }

      obstack_1grow (oout, c);

      if (c == '\\')
        {
          c = getc (fin);
          if (c == EOF)
            fatal (_("unterminated string at end of file"));
          obstack_1grow (oout, c);

          if (c == '\n')
            lineno++;
        }

      c = getc (fin);
    }

  obstack_1grow (oout, c);
}


/*-----------------------------------------------------------------.
| Dump the wannabee comment from IN to OUT1 and OUT2 (which can be |
| NULL).  In fact we just saw a `/', which might or might not be a |
| comment.  In any case, copy what we saw.                         |
|                                                                  |
| OUT2 might be NULL.                                              |
`-----------------------------------------------------------------*/

static inline void
copy_comment2 (FILE *fin, struct obstack *oout1, struct obstack *oout2)
{
  int cplus_comment;
  int ended;
  int c;

  /* We read a `/', output it. */
  obstack_1grow (oout1, '/');
  if (oout2)
    obstack_1grow (oout2, '/');

  switch ((c = getc (fin)))
    {
    case '/':
      cplus_comment = 1;
      break;
    case '*':
      cplus_comment = 0;
      break;
    default:
      ungetc (c, fin);
      return;
    }

  obstack_1grow (oout1, c);
  if (oout2)
    obstack_1grow (oout2, c);
  c = getc (fin);

  ended = 0;
  while (!ended)
    {
      if (!cplus_comment && c == '*')
        {
          while (c == '*')
            {
              obstack_1grow (oout1, c);
              if (oout2)
                obstack_1grow (oout2, c);
              c = getc (fin);
            }

          if (c == '/')
            {
              obstack_1grow (oout1, c);
              if (oout2)
                obstack_1grow (oout2, c);
              ended = 1;
            }
        }
      else if (c == '\n')
        {
          lineno++;
          obstack_1grow (oout1, c);
          if (oout2)
            obstack_1grow (oout2, c);
          if (cplus_comment)
            ended = 1;
          else
            c = getc (fin);
        }
      else if (c == EOF)
        fatal (_("unterminated comment"));
      else
        {
          obstack_1grow (oout1, c);
          if (oout2)
            obstack_1grow (oout2, c);
          c = getc (fin);
        }
    }
}


/*-------------------------------------------------------------------.
| Dump the comment (actually the current string starting with a `/') |
| from FIN to OOUT.                                                  |
`-------------------------------------------------------------------*/

static inline void
copy_comment (FILE *fin, struct obstack *oout)
{
  copy_comment2 (fin, oout, NULL);
}


/*-----------------------------------------------------------------.
| FIN is pointing to a location (i.e., a `@').  Output to OOUT a   |
| reference to this location. STACK_OFFSET is the number of values |
| in the current rule so far, which says where to find `@0' with   |
| respect to the top of the stack.                                 |
`-----------------------------------------------------------------*/

static inline void
copy_at (FILE *fin, struct obstack *oout,
         struct symbol_list *rule, int stack_offset)
{
  symbol_list *rp;
  int c;

  c = getc (fin);
  if (c == '$')
    {
      obstack_sgrow (oout, "yyloc");
      locations_flag = 1;
    }
  else if (isdigit (c) || c == '-')
    {
      int n, i;

      ungetc (c, fin);
      n = read_signed_integer (fin);

      rp = rule;
      i = 0;

      while (i < n)
        {
          rp = rp->next;
          if (rp == NULL)
            {
              complain (_("invalid @ value"));
              return;
            }
          i++;
        }

      obstack_fgrow1 (oout, "yylsp[%d]", n - stack_offset);
      locations_flag = 1;
    }
  else
    {
      char buf[] = "@c";
      buf[1] = c;
      complain (_("%s is invalid"), quote (buf));
    }
}


/*-------------------------------------------------------------------.
| FIN is pointing to a wannabee semantic value (i.e., a `$').        |
|                                                                    |
| Possible inputs: $[<TYPENAME>]($|integer)                          |
|                                                                    |
| Output to OOUT a reference to this semantic value. STACK_OFFSET is |
| the number of values in the current rule so far, which says where  |
| to find `$0' with respect to the top of the stack.                 |
`-------------------------------------------------------------------*/

static inline void
copy_dollar (FILE *fin, struct obstack *oout,
             symbol_list *rule, int stack_offset)
{
  int c = getc (fin);
  const char *type_name = NULL;

  /* Get the type name if explicit. */
  if (c == '<')
    {
      read_type_name (fin);
      type_name = token_buffer;
      value_components_used = 1;
      c = getc (fin);
    }

  if (c == '$')
    {
      obstack_sgrow (oout, "yyval");

      if (!type_name)
        type_name = get_type_name (0, rule);
      if (type_name)
        obstack_fgrow1 (oout, ".%s", type_name);
      if (!type_name && typed)
        complain (_("$$ of `%s' has no declared type"),
                  rule->sym->tag);
    }
  else if (isdigit (c) || c == '-')
    {
      int n;
      ungetc (c, fin);
      n = read_signed_integer (fin);

      if (!type_name && n > 0)
        type_name = get_type_name (n, rule);

      obstack_fgrow1 (oout, "yyvsp[%d]", n - stack_offset);

      if (type_name)
        obstack_fgrow1 (oout, ".%s", type_name);
      if (!type_name && typed)
        complain (_("$%d of `%s' has no declared type"),
                  n, rule->sym->tag);
    }
  else
    {
      char buf[] = "$c";
      buf[1] = c;
      complain (_("%s is invalid"), quote (buf));
    }
}
\f
/*-------------------------------------------------------------------.
| Copy the contents of a `%{ ... %}' into the definitions file.  The |
| `%{' has already been read.  Return after reading the `%}'.        |
`-------------------------------------------------------------------*/

static void
copy_definition (void)
{
  int c;
  /* -1 while reading a character if prev char was %. */
  int after_percent;

  if (!no_lines_flag)
    obstack_fgrow2 (&attrs_obstack, "#line %d %s\n",
                    lineno, quotearg_style (c_quoting_style, infile));

  after_percent = 0;

  c = getc (finput);

  for (;;)
    {
      switch (c)
        {
        case '\n':
          obstack_1grow (&attrs_obstack, c);
          lineno++;
          break;

        case '%':
          after_percent = -1;
          break;

        case '\'':
        case '"':
          copy_string (finput, &attrs_obstack, c);
          break;

        case '/':
          copy_comment (finput, &attrs_obstack);
          break;

        case EOF:
          fatal ("%s", _("unterminated `%{' definition"));

        default:
          obstack_1grow (&attrs_obstack, c);
        }

      c = getc (finput);

      if (after_percent)
        {
          if (c == '}')
            return;
          obstack_1grow (&attrs_obstack, '%');
        }
      after_percent = 0;
    }
}


/*-------------------------------------------------------------------.
| Parse what comes after %token or %nterm.  For %token, WHAT_IS is   |
| token_sym and WHAT_IS_NOT is nterm_sym.  For %nterm, the arguments |
| are reversed.                                                      |
`-------------------------------------------------------------------*/

static void
parse_token_decl (symbol_class what_is, symbol_class what_is_not)
{
  token_t token = tok_undef;
  char *typename = NULL;

  /* The symbol being defined.  */
  struct bucket *symbol = NULL;

  /* After `%token' and `%nterm', any number of symbols maybe be
     defined.  */
  for (;;)
    {
      int tmp_char = ungetc (skip_white_space (), finput);

      /* `%' (for instance from `%token', or from `%%' etc.) is the
         only valid means to end this declaration.  */
      if (tmp_char == '%')
        return;
      if (tmp_char == EOF)
        fatal (_("Premature EOF after %s"), token_buffer);

      token = lex ();
      if (token == tok_comma)
        {
          symbol = NULL;
          continue;
        }
      if (token == tok_typename)
        {
          typename = xstrdup (token_buffer);
          value_components_used = 1;
          symbol = NULL;
        }
      else if (token == tok_identifier && *symval->tag == '\"' && symbol)
        {
          if (symval->alias)
            warn (_("symbol `%s' used more than once as a literal string"),
                  symval->tag);
          else if (symbol->alias)
            warn (_("symbol `%s' given more than one literal string"),
                  symbol->tag);
          else
            {
              symval->class = token_sym;
              symval->type_name = typename;
              symval->user_token_number = symbol->user_token_number;
              symbol->user_token_number = SALIAS;
              symval->alias = symbol;
              symbol->alias = symval;
              /* symbol and symval combined are only one symbol */
              nsyms--;
            }
          symbol = NULL;
        }
      else if (token == tok_identifier)
        {
          int oldclass = symval->class;
          symbol = symval;

          if (symbol->class == what_is_not)
            complain (_("symbol %s redefined"), symbol->tag);
          symbol->class = what_is;
          if (what_is == nterm_sym && oldclass != nterm_sym)
            symbol->value = nvars++;

          if (typename)
            {
              if (symbol->type_name == NULL)
                symbol->type_name = typename;
              else if (strcmp (typename, symbol->type_name) != 0)
                complain (_("type redeclaration for %s"), symbol->tag);
            }
        }
      else if (symbol && token == tok_number)
        {
          symbol->user_token_number = numval;
        }
      else
        {
          complain (_("`%s' is invalid in %s"),
                    token_buffer,
                    (what_is == token_sym) ? "%token" : "%nterm");
          skip_to_char ('%');
        }
    }

}


/*------------------------------.
| Parse what comes after %start |
`------------------------------*/

static void
parse_start_decl (void)
{
  if (start_flag)
    complain (_("multiple %s declarations"), "%start");
  if (lex () != tok_identifier)
    complain (_("invalid %s declaration"), "%start");
  else
    {
      start_flag = 1;
      startval = symval;
    }
}

/*-----------------------------------------------------------.
| read in a %type declaration and record its information for |
| get_type_name to access                                    |
`-----------------------------------------------------------*/

static void
parse_type_decl (void)
{
  char *name;

  if (lex () != tok_typename)
    {
      complain ("%s", _("%type declaration has no <typename>"));
      skip_to_char ('%');
      return;
    }

  name = xstrdup (token_buffer);

  for (;;)
    {
      token_t t;
      int tmp_char = ungetc (skip_white_space (), finput);

      if (tmp_char == '%')
        return;
      if (tmp_char == EOF)
        fatal (_("Premature EOF after %s"), token_buffer);

      t = lex ();

      switch (t)
        {

        case tok_comma:
        case tok_semicolon:
          break;

        case tok_identifier:
          if (symval->type_name == NULL)
            symval->type_name = name;
          else if (strcmp (name, symval->type_name) != 0)
            complain (_("type redeclaration for %s"), symval->tag);

          break;

        default:
          complain (_("invalid %%type declaration due to item: %s"),
                    token_buffer);
          skip_to_char ('%');
        }
    }
}



/*----------------------------------------------------------------.
| Read in a %left, %right or %nonassoc declaration and record its |
| information.                                                    |
`----------------------------------------------------------------*/

static void
parse_assoc_decl (associativity assoc)
{
  char *name = NULL;
  int prev = 0;

  lastprec++;                   /* Assign a new precedence level, never 0.  */

  for (;;)
    {
      token_t t;
      int tmp_char = ungetc (skip_white_space (), finput);

      if (tmp_char == '%')
        return;
      if (tmp_char == EOF)
        fatal (_("Premature EOF after %s"), token_buffer);

      t = lex ();

      switch (t)
        {
        case tok_typename:
          name = xstrdup (token_buffer);
          break;

        case tok_comma:
          break;

        case tok_identifier:
          if (symval->prec != 0)
            complain (_("redefining precedence of %s"), symval->tag);
          symval->prec = lastprec;
          symval->assoc = assoc;
          if (symval->class == nterm_sym)
            complain (_("symbol %s redefined"), symval->tag);
          symval->class = token_sym;
          if (name)
            {                   /* record the type, if one is specified */
              if (symval->type_name == NULL)
                symval->type_name = name;
              else if (strcmp (name, symval->type_name) != 0)
                complain (_("type redeclaration for %s"), symval->tag);
            }
          break;

        case tok_number:
          if (prev == tok_identifier)
            {
              symval->user_token_number = numval;
            }
          else
            {
              complain (_
                        ("invalid text (%s) - number should be after identifier"),
token_buffer);
              skip_to_char ('%');
            }
          break;

        case tok_semicolon:
          return;

        default:
          complain (_("unexpected item: %s"), token_buffer);
          skip_to_char ('%');
        }

      prev = t;
    }
}



/*--------------------------------------------------------------.
| Copy the union declaration into ATTRS_OBSTACK (and fdefines), |
| where it is made into the definition of YYSTYPE, the type of  |
| elements of the parser value stack.                           |
`--------------------------------------------------------------*/

static void
parse_union_decl (void)
{
  int c;
  int count = 0;
  const char *prologue = "\
#ifndef YYSTYPE\n\
typedef union";
  const char *epilogue = "\
 yystype;\n\
# define YYSTYPE yystype\n\
#endif\n";

  if (typed)
    complain (_("multiple %s declarations"), "%union");

  typed = 1;

  if (!no_lines_flag)
    obstack_fgrow2 (&attrs_obstack, "\n#line %d %s\n",
                    lineno, quotearg_style (c_quoting_style, infile));
  else
    obstack_1grow (&attrs_obstack, '\n');

  obstack_sgrow (&attrs_obstack, prologue);
  if (defines_flag)
    obstack_sgrow (&defines_obstack, prologue);

  c = getc (finput);

  while (c != EOF)
    {

      /* If C contains '/', it is output by copy_comment ().  */
      if (c != '/')
        {
          obstack_1grow (&attrs_obstack, c);
          if (defines_flag)
            obstack_1grow (&defines_obstack, c);
        }

      switch (c)
        {
        case '\n':
          lineno++;
          break;

        case '/':
          copy_comment2 (finput, &defines_obstack, &attrs_obstack);
          break;

        case '{':
          count++;
          break;

        case '}':
          if (count == 0)
            complain (_("unmatched %s"), "`}'");
          count--;
          if (count <= 0)
            {
              obstack_sgrow (&attrs_obstack, epilogue);
              if (defines_flag)
                obstack_sgrow (&defines_obstack, epilogue);
              /* JF don't choke on trailing semi */
              c = skip_white_space ();
              if (c != ';')
                ungetc (c, finput);
              return;
            }
        }

      c = getc (finput);
    }
}


/*-------------------------------------------------------.
| Parse the declaration %expect N which says to expect N |
| shift-reduce conflicts.                                |
`-------------------------------------------------------*/

static void
parse_expect_decl (void)
{
  int c = skip_white_space ();
  ungetc (c, finput);

  if (!isdigit (c))
    complain (_("argument of %%expect is not an integer"));
  else
    expected_conflicts = read_signed_integer (finput);
}


/*-------------------------------------------------------------------.
| Parse what comes after %thong.  the full syntax is                 |
|                                                                    |
|                %thong <type> token number literal                  |
|                                                                    |
| the <type> or number may be omitted.  The number specifies the     |
| user_token_number.                                                 |
|                                                                    |
| Two symbols are entered in the table, one for the token symbol and |
| one for the literal.  Both are given the <type>, if any, from the  |
| declaration.  The ->user_token_number of the first is SALIAS and   |
| the ->user_token_number of the second is set to the number, if     |
| any, from the declaration.  The two symbols are linked via         |
| pointers in their ->alias fields.                                  |
|                                                                    |
| During OUTPUT_DEFINES_TABLE, the symbol is reported thereafter,    |
| only the literal string is retained it is the literal string that  |
| is output to yytname                                               |
`-------------------------------------------------------------------*/

static void
parse_thong_decl (void)
{
  token_t token;
  struct bucket *symbol;
  char *typename = 0;
  int usrtoknum = SUNDEF;

  token = lex ();               /* fetch typename or first token */
  if (token == tok_typename)
    {
      typename = xstrdup (token_buffer);
      value_components_used = 1;
      token = lex ();           /* fetch first token */
    }

  /* process first token */

  if (token != tok_identifier)
    {
      complain (_("unrecognized item %s, expected an identifier"),
                token_buffer);
      skip_to_char ('%');
      return;
    }
  symval->class = token_sym;
  symval->type_name = typename;
  symval->user_token_number = SALIAS;
  symbol = symval;

  token = lex ();               /* get number or literal string */

  if (token == tok_number)
    {
      usrtoknum = numval;
      token = lex ();           /* okay, did number, now get literal */
    }

  /* process literal string token */

  if (token != tok_identifier || *symval->tag != '\"')
    {
      complain (_("expected string constant instead of %s"), token_buffer);
      skip_to_char ('%');
      return;
    }
  symval->class = token_sym;
  symval->type_name = typename;
  symval->user_token_number = usrtoknum;

  symval->alias = symbol;
  symbol->alias = symval;

  /* symbol and symval combined are only one symbol.  */
  nsyms--;
}


/*------------------------------------------------------------------.
| Parse a double quoted parameter. It was used for                  |
| %{source,header}_extension.  For the moment, It is not used since |
| extension features have been removed.                             |
`------------------------------------------------------------------*/

#if 0

static const char *
parse_dquoted_param (const char *from)
{
  char buff[32];
  int c;
  int i;

  c = skip_white_space ();

  if (c != '"')
    {
      ungetc (c, finput);
      complain (_("invalid %s declaration"), from);
      return NULL;
    }

  c = getc (finput);
  for (i = 0; (c >= '!') && (c <= '~'); i++)
    {
      if (c == '"')
        break;

      if (c == '\\')
        {
          c = getc (finput);
          if ((c < '!') && (c > '~'))
            break;
        }

      buff[i] = c;
      c = getc (finput);
    }
  buff[i] = '\0';

  if (c != '"')
    {
      ungetc (c, finput);
      complain (_("invalid %s declaration"), from);
      return NULL;
    }

  return xstrdup (buff);
}

#endif


/*----------------------------------------------------------------.
| Read from finput until `%%' is seen.  Discard the `%%'.  Handle |
| any `%' declarations, and copy the contents of any `%{ ... %}'  |
| groups to ATTRS_OBSTACK.                                        |
`----------------------------------------------------------------*/

static void
read_declarations (void)
{
  for (;;)
    {
      int c = skip_white_space ();

      if (c == '%')
        {
          token_t tok = parse_percent_token ();

          switch (tok)
            {
            case tok_two_percents:
              return;

            case tok_percent_left_curly:
              copy_definition ();
              break;

            case tok_token:
              parse_token_decl (token_sym, nterm_sym);
              break;

            case tok_nterm:
              parse_token_decl (nterm_sym, token_sym);
              break;

            case tok_type:
              parse_type_decl ();
              break;

            case tok_start:
              parse_start_decl ();
              break;

            case tok_union:
              parse_union_decl ();
              break;

            case tok_expect:
              parse_expect_decl ();
              break;

            case tok_thong:
              parse_thong_decl ();
              break;

            case tok_left:
              parse_assoc_decl (left_assoc);
              break;

            case tok_right:
              parse_assoc_decl (right_assoc);
              break;

            case tok_nonassoc:
              parse_assoc_decl (non_assoc);
              break;

            case tok_noop:
              break;

            case tok_stropt:
            case tok_intopt:
            case tok_obsolete:
              abort ();
              break;

            case tok_illegal:
            default:
              complain (_("unrecognized: %s"), token_buffer);
              skip_to_char ('%');
            }
        }
      else if (c == EOF)
        fatal (_("no input grammar"));
      else
        {
          char buf[] = "c";
          buf[0] = c;
          complain (_("unknown character: %s"), quote (buf));
          skip_to_char ('%');
        }
    }
}
\f
/*-------------------------------------------------------------------.
| Assuming that a `{' has just been seen, copy everything up to the  |
| matching `}' into the actions file.  STACK_OFFSET is the number of |
| values in the current rule so far, which says where to find `$0'   |
| with respect to the top of the stack.                              |
`-------------------------------------------------------------------*/

static void
copy_action (symbol_list *rule, int stack_offset)
{
  int c;
  int count;
  char buf[4096];

  /* offset is always 0 if parser has already popped the stack pointer */
  if (semantic_parser)
    stack_offset = 0;

  sprintf (buf, "\ncase %d:\n", nrules);
  obstack_grow (&action_obstack, buf, strlen (buf));

  if (!no_lines_flag)
    {
      sprintf (buf, "#line %d %s\n",
               lineno, quotearg_style (c_quoting_style, infile));
      obstack_grow (&action_obstack, buf, strlen (buf));
    }
  obstack_1grow (&action_obstack, '{');

  count = 1;
  c = getc (finput);

  while (count > 0)
    {
      while (c != '}')
        {
          switch (c)
            {
            case '\n':
              obstack_1grow (&action_obstack, c);
              lineno++;
              break;

            case '{':
              obstack_1grow (&action_obstack, c);
              count++;
              break;

            case '\'':
            case '"':
              copy_string (finput, &action_obstack, c);
              break;

            case '/':
              copy_comment (finput, &action_obstack);
              break;

            case '$':
              copy_dollar (finput, &action_obstack,
                           rule, stack_offset);
              break;

            case '@':
              copy_at (finput, &action_obstack,
                       rule, stack_offset);
              break;

            case EOF:
              fatal (_("unmatched %s"), "`{'");

            default:
              obstack_1grow (&action_obstack, c);
            }

          c = getc (finput);
        }

      /* above loop exits when c is '}' */

      if (--count)
        {
          obstack_1grow (&action_obstack, c);
          c = getc (finput);
        }
    }

  /* As a Bison extension, add the ending semicolon.  Since some Yacc
     don't do that, help people using bison as a Yacc finding their
     missing semicolons.  */
  if (yacc_flag)
    obstack_sgrow (&action_obstack, "}\n    break;");
  else
    obstack_sgrow (&action_obstack, ";\n    break;}");
}
\f
/*-------------------------------------------------------------------.
| After `%guard' is seen in the input file, copy the actual guard    |
| into the guards file.  If the guard is followed by an action, copy |
| that into the actions file.  STACK_OFFSET is the number of values  |
| in the current rule so far, which says where to find `$0' with     |
| respect to the top of the stack, for the simple parser in which    |
| the stack is not popped until after the guard is run.              |
`-------------------------------------------------------------------*/

static void
copy_guard (symbol_list *rule, int stack_offset)
{
  int c;
  int count;
  int brace_flag = 0;

  /* offset is always 0 if parser has already popped the stack pointer */
  if (semantic_parser)
    stack_offset = 0;

  obstack_fgrow1 (&guard_obstack, "\ncase %d:\n", nrules);
  if (!no_lines_flag)
    obstack_fgrow2 (&guard_obstack, "#line %d %s\n",
                    lineno, quotearg_style (c_quoting_style, infile));
  obstack_1grow (&guard_obstack, '{');

  count = 0;
  c = getc (finput);

  while (brace_flag ? (count > 0) : (c != ';'))
    {
      switch (c)
        {
        case '\n':
          obstack_1grow (&guard_obstack, c);
          lineno++;
          break;

        case '{':
          obstack_1grow (&guard_obstack, c);
          brace_flag = 1;
          count++;
          break;

        case '}':
          obstack_1grow (&guard_obstack, c);
          if (count > 0)
            count--;
          else
            {
              complain (_("unmatched %s"), "`}'");
              c = getc (finput);        /* skip it */
            }
          break;

        case '\'':
        case '"':
          copy_string (finput, &guard_obstack, c);
          break;

        case '/':
          copy_comment (finput, &guard_obstack);
          break;

        case '$':
          copy_dollar (finput, &guard_obstack, rule, stack_offset);
          break;

        case '@':
          copy_at (finput, &guard_obstack, rule, stack_offset);
          break;

        case EOF:
          fatal ("%s", _("unterminated %guard clause"));

        default:
          obstack_1grow (&guard_obstack, c);
        }

      if (c != '}' || count != 0)
        c = getc (finput);
    }

  c = skip_white_space ();

  obstack_sgrow (&guard_obstack, ";\n    break;}");
  if (c == '{')
    copy_action (rule, stack_offset);
  else if (c == '=')
    {
      c = getc (finput);        /* why not skip_white_space -wjh */
      if (c == '{')
        copy_action (rule, stack_offset);
    }
  else
    ungetc (c, finput);
}
\f

/*-------------------------------------------------------------------.
| Generate a dummy symbol, a nonterminal, whose name cannot conflict |
| with the user's names.                                             |
`-------------------------------------------------------------------*/

static bucket *
gensym (void)
{
  /* Incremented for each generated symbol */
  static int gensym_count = 0;
  static char buf[256];

  bucket *sym;

  sprintf (buf, "@%d", ++gensym_count);
  token_buffer = buf;
  sym = getsym (token_buffer);
  sym->class = nterm_sym;
  sym->value = nvars++;
  return sym;
}

#if 0
/*------------------------------------------------------------------.
| read in a %type declaration and record its information for        |
| get_type_name to access.  This is unused.  It is only called from |
| the #if 0 part of readgram                                        |
`------------------------------------------------------------------*/

static int
get_type (void)
{
  int k;
  token_t token;
  char *name;

  token = lex ();

  if (token != tok_typename)
    {
      complain (_("invalid %s declaration"), "%type");
      return t;
    }

  name = xstrdup (token_buffer);

  for (;;)
    {
      token = lex ();

      switch (token)
        {
        case tok_semicolon:
          return lex ();

        case tok_comma:
          break;

        case tok_identifier:
          if (symval->type_name == NULL)
            symval->type_name = name;
          else if (strcmp (name, symval->type_name) != 0)
            complain (_("type redeclaration for %s"), symval->tag);

          break;

        default:
          return token;
        }
    }
}

#endif
\f
/*------------------------------------------------------------------.
| Parse the input grammar into a one symbol_list structure.  Each   |
| rule is represented by a sequence of symbols: the left hand side  |
| followed by the contents of the right hand side, followed by a    |
| null pointer instead of a symbol to terminate the rule.  The next |
| symbol is the lhs of the following rule.                          |
|                                                                   |
| All guards and actions are copied out to the appropriate files,   |
| labelled by the rule number they apply to.                        |
`------------------------------------------------------------------*/

static void
readgram (void)
{
  token_t t;
  bucket *lhs = NULL;
  symbol_list *p;
  symbol_list *p1;
  bucket *bp;

  /* Points to first symbol_list of current rule. its symbol is the
     lhs of the rule.  */
  symbol_list *crule;
  /* Points to the symbol_list preceding crule.  */
  symbol_list *crule1;

  p1 = NULL;

  t = lex ();

  while (t != tok_two_percents && t != tok_eof)
    {
      if (t == tok_identifier || t == tok_bar)
        {
          int action_flag = 0;
          /* Number of symbols in rhs of this rule so far */
          int rulelength = 0;
          int xactions = 0;     /* JF for error checking */
          bucket *first_rhs = 0;

          if (t == tok_identifier)
            {
              lhs = symval;

              if (!start_flag)
                {
                  startval = lhs;
                  start_flag = 1;
                }

              t = lex ();
              if (t != tok_colon)
                {
                  complain (_("ill-formed rule: initial symbol not followed by colon"));
                  unlex (t);
                }
            }

          if (nrules == 0 && t == tok_bar)
            {
              complain (_("grammar starts with vertical bar"));
              lhs = symval;     /* BOGUS: use a random symval */
            }
          /* start a new rule and record its lhs.  */

          nrules++;
          nitems++;

          p = symbol_list_new (lhs);

          crule1 = p1;
          if (p1)
            p1->next = p;
          else
            grammar = p;

          p1 = p;
          crule = p;

          /* mark the rule's lhs as a nonterminal if not already so.  */

          if (lhs->class == unknown_sym)
            {
              lhs->class = nterm_sym;
              lhs->value = nvars;
              nvars++;
            }
          else if (lhs->class == token_sym)
            complain (_("rule given for %s, which is a token"), lhs->tag);

          /* read the rhs of the rule.  */

          for (;;)
            {
              t = lex ();
              if (t == tok_prec)
                {
                  t = lex ();
                  crule->ruleprec = symval;
                  t = lex ();
                }

              if (!(t == tok_identifier || t == tok_left_curly))
                break;

              /* If next token is an identifier, see if a colon follows it.
                 If one does, exit this rule now.  */
              if (t == tok_identifier)
                {
                  bucket *ssave;
                  token_t t1;

                  ssave = symval;
                  t1 = lex ();
                  unlex (t1);
                  symval = ssave;
                  if (t1 == tok_colon)
                    break;

                  if (!first_rhs)       /* JF */
                    first_rhs = symval;
                  /* Not followed by colon =>
                     process as part of this rule's rhs.  */
                }

              /* If we just passed an action, that action was in the middle
                 of a rule, so make a dummy rule to reduce it to a
                 non-terminal.  */
              if (action_flag)
                {
                  /* Since the action was written out with this rule's
                     number, we must give the new rule this number by
                     inserting the new rule before it.  */

                  /* Make a dummy nonterminal, a gensym.  */
                  bucket *sdummy = gensym ();

                  /* Make a new rule, whose body is empty, before the
                     current one, so that the action just read can
                     belong to it.  */
                  nrules++;
                  nitems++;
                  p = symbol_list_new (sdummy);
                  /* Attach its lineno to that of the host rule. */
                  p->line = crule->line;
                  if (crule1)
                    crule1->next = p;
                  else
                    grammar = p;
                  /* End of the rule. */
                  crule1 = symbol_list_new (NULL);
                  crule1->next = crule;

                  p->next = crule1;

                  /* Insert the dummy generated by that rule into this
                     rule.  */
                  nitems++;
                  p = symbol_list_new (sdummy);
                  p1->next = p;
                  p1 = p;

                  action_flag = 0;
                }

              if (t == tok_identifier)
                {
                  nitems++;
                  p = symbol_list_new (symval);
                  p1->next = p;
                  p1 = p;
                }
              else              /* handle an action.  */
                {
                  copy_action (crule, rulelength);
                  action_flag = 1;
                  xactions++;   /* JF */
                }
              rulelength++;
            }                   /* end of  read rhs of rule */

          /* Put an empty link in the list to mark the end of this rule  */
          p = symbol_list_new (NULL);
          p1->next = p;
          p1 = p;

          if (t == tok_prec)
            {
              complain (_("two @prec's in a row"));
              t = lex ();
              crule->ruleprec = symval;
              t = lex ();
            }
          if (t == tok_guard)
            {
              if (!semantic_parser)
                complain (_("%%guard present but %%semantic_parser not specified"));

              copy_guard (crule, rulelength);
              t = lex ();
            }
          else if (t == tok_left_curly)
            {
              /* This case never occurs -wjh */
              if (action_flag)
                complain (_("two actions at end of one rule"));
              copy_action (crule, rulelength);
              action_flag = 1;
              xactions++;       /* -wjh */
              t = lex ();
            }
          /* If $$ is being set in default way, report if any type
             mismatch.  */
          else if (!xactions
                   && first_rhs && lhs->type_name != first_rhs->type_name)
            {
              if (lhs->type_name == 0
                  || first_rhs->type_name == 0
                  || strcmp (lhs->type_name, first_rhs->type_name))
                complain (_("type clash (`%s' `%s') on default action"),
                          lhs->type_name ? lhs->type_name : "",
                          first_rhs->type_name ? first_rhs->type_name : "");
            }
          /* Warn if there is no default for $$ but we need one.  */
          else if (!xactions && !first_rhs && lhs->type_name != 0)
            complain (_("empty rule for typed nonterminal, and no action"));
          if (t == tok_semicolon)
            t = lex ();
        }
#if 0
      /* these things can appear as alternatives to rules.  */
/* NO, they cannot.
        a) none of the documentation allows them
        b) most of them scan forward until finding a next %
                thus they may swallow lots of intervening rules
*/
      else if (t == tok_token)
        {
          parse_token_decl (token_sym, nterm_sym);
          t = lex ();
        }
      else if (t == tok_nterm)
        {
          parse_token_decl (nterm_sym, token_sym);
          t = lex ();
        }
      else if (t == tok_type)
        {
          t = get_type ();
        }
      else if (t == tok_union)
        {
          parse_union_decl ();
          t = lex ();
        }
      else if (t == tok_expect)
        {
          parse_expect_decl ();
          t = lex ();
        }
      else if (t == tok_start)
        {
          parse_start_decl ();
          t = lex ();
        }
#endif

      else
        {
          complain (_("invalid input: %s"), quote (token_buffer));
          t = lex ();
        }
    }

  /* grammar has been read.  Do some checking */

  if (nsyms > MAXSHORT)
    fatal (_("too many symbols (tokens plus nonterminals); maximum %d"),
           MAXSHORT);
  if (nrules == 0)
    fatal (_("no rules in the input grammar"));

  /* JF put out same default YYSTYPE as YACC does */
  if (typed == 0
      && !value_components_used)
    {
      /* We used to use `unsigned long' as YYSTYPE on MSDOS,
         but it seems better to be consistent.
         Most programs should declare their own type anyway.  */
      obstack_sgrow (&attrs_obstack,
                           "#ifndef YYSTYPE\n#define YYSTYPE int\n#endif\n");
      if (defines_flag)
        obstack_sgrow (&defines_obstack, "\
# ifndef YYSTYPE\n\
#  define YYSTYPE int\n\
# endif\n");
    }

  /* Report any undefined symbols and consider them nonterminals.  */

  for (bp = firstsymbol; bp; bp = bp->next)
    if (bp->class == unknown_sym)
      {
        complain (_
                  ("symbol %s is used, but is not defined as a token and has no rules"),
                  bp->tag);
        bp->class = nterm_sym;
        bp->value = nvars++;
      }

  ntokens = nsyms - nvars;
}
\f
/*--------------------------------------------------------------.
| For named tokens, but not literal ones, define the name.  The |
| value is the user token number.                               |
`--------------------------------------------------------------*/

static void
output_token_defines (struct obstack *oout)
{
  bucket *bp;
  char *cp, *symbol;
  char c;

  for (bp = firstsymbol; bp; bp = bp->next)
    {
      symbol = bp->tag;         /* get symbol */

      if (bp->value >= ntokens)
        continue;
      if (bp->user_token_number == SALIAS)
        continue;
      if ('\'' == *symbol)
        continue;               /* skip literal character */
      if (bp == errtoken)
        continue;               /* skip error token */
      if ('\"' == *symbol)
        {
          /* use literal string only if given a symbol with an alias */
          if (bp->alias)
            symbol = bp->alias->tag;
          else
            continue;
        }

      /* Don't #define nonliteral tokens whose names contain periods.  */
      cp = symbol;
      while ((c = *cp++) && c != '.');
      if (c != '\0')
        continue;

      obstack_fgrow2 (oout, "# define\t%s\t%d\n",
                      symbol, bp->user_token_number);
      if (semantic_parser)
        /* FIXME: This is certainly dead wrong, and should be just as
           above. --akim.  */
        obstack_fgrow2 (oout, "# define\tT%s\t%d\n", symbol, bp->value);
    }

  obstack_1grow (oout, '\n');
}


/*--------------------.
| Output the header.  |
`--------------------*/

static void
symbols_output (void)
{
  if (defines_flag)
    {
      output_token_defines (&defines_obstack);

      if (!pure_parser)
        {
          if (spec_name_prefix)
            obstack_fgrow1 (&defines_obstack, "\nextern YYSTYPE %slval;\n",
                            spec_name_prefix);
          else
            obstack_sgrow (&defines_obstack,
                                 "\nextern YYSTYPE yylval;\n");
        }

      if (semantic_parser)
        {
          int i;

          for (i = ntokens; i < nsyms; i++)
            {
              /* don't make these for dummy nonterminals made by gensym.  */
              if (*tags[i] != '@')
                obstack_fgrow2 (&defines_obstack,
                                "# define\tNT%s\t%d\n", tags[i], i);
            }
#if 0
          /* `fdefines' is now a temporary file, so we need to copy its
             contents in `done', so we can't close it here.  */
          fclose (fdefines);
          fdefines = NULL;
#endif
        }
    }
}


/*------------------------------------------------------------------.
| Set TOKEN_TRANSLATIONS.  Check that no two symbols share the same |
| number.                                                           |
`------------------------------------------------------------------*/

static void
token_translations_init (void)
{
  bucket *bp = NULL;
  int i;

  token_translations = XCALLOC (short, max_user_token_number + 1);

  /* Initialize all entries for literal tokens to 2, the internal
     token number for $undefined., which represents all invalid
     inputs.  */
  for (i = 0; i <= max_user_token_number; i++)
    token_translations[i] = 2;

  for (bp = firstsymbol; bp; bp = bp->next)
    {
      /* Non-terminal? */
      if (bp->value >= ntokens)
        continue;
      /* A token string alias? */
      if (bp->user_token_number == SALIAS)
        continue;

      assert (bp->user_token_number != SUNDEF);

      /* A token which translation has already been set? */
      if (token_translations[bp->user_token_number] != 2)
        complain (_("tokens %s and %s both assigned number %d"),
                  tags[token_translations[bp->user_token_number]],
                  bp->tag, bp->user_token_number);
      token_translations[bp->user_token_number] = bp->value;
    }
}


/*------------------------------------------------------------------.
| Assign symbol numbers, and write definition of token names into   |
| FDEFINES.  Set up vectors TAGS and SPREC of names and precedences |
| of symbols.                                                       |
`------------------------------------------------------------------*/

static void
packsymbols (void)
{
  bucket *bp = NULL;
  int tokno = 1;
  int last_user_token_number;
  static char DOLLAR[] = "$";

  tags = XCALLOC (char *, nsyms + 1);
  user_toknums = XCALLOC (short, nsyms + 1);

  sprec = XCALLOC (short, nsyms);
  sassoc = XCALLOC (short, nsyms);

  /* The EOF token. */
  tags[0] = DOLLAR;
  user_toknums[0] = 0;

  max_user_token_number = 256;
  last_user_token_number = 256;

  for (bp = firstsymbol; bp; bp = bp->next)
    {
      if (bp->class == nterm_sym)
        {
          bp->value += ntokens;
        }
      else if (bp->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 (bp->value == 0)
            bp->value = bp->alias->value = tokno++;

          if (bp->prec != bp->alias->prec)
            {
              if (bp->prec != 0 && bp->alias->prec != 0
                  && bp->user_token_number == SALIAS)
                complain (_("conflicting precedences for %s and %s"),
                          bp->tag, bp->alias->tag);
              if (bp->prec != 0)
                bp->alias->prec = bp->prec;
              else
                bp->prec = bp->alias->prec;
            }

          if (bp->assoc != bp->alias->assoc)
            {
              if (bp->assoc != 0 && bp->alias->assoc != 0
                  && bp->user_token_number == SALIAS)
                complain (_("conflicting assoc values for %s and %s"),
                          bp->tag, bp->alias->tag);
              if (bp->assoc != 0)
                bp->alias->assoc = bp->assoc;
              else
                bp->assoc = bp->alias->assoc;
            }

          if (bp->user_token_number == SALIAS)
            continue;           /* do not do processing below for SALIASs */

        }
      else                      /* bp->class == token_sym */
        {
          bp->value = tokno++;
        }

      if (bp->class == token_sym)
        {
          if (bp->user_token_number == SUNDEF)
            bp->user_token_number = ++last_user_token_number;
          if (bp->user_token_number > max_user_token_number)
            max_user_token_number = bp->user_token_number;
        }

      tags[bp->value] = bp->tag;
      user_toknums[bp->value] = bp->user_token_number;
      sprec[bp->value] = bp->prec;
      sassoc[bp->value] = bp->assoc;
    }

  token_translations_init ();

  error_token_number = errtoken->value;

  if (!no_parser_flag)
    output_token_defines (&table_obstack);

  if (startval->class == unknown_sym)
    fatal (_("the start symbol %s is undefined"), startval->tag);
  else if (startval->class == token_sym)
    fatal (_("the start symbol %s is a token"), startval->tag);

  start_symbol = startval->value;
}


/*---------------------------------------------------------------.
| Convert the rules into the representation using RRHS, RLHS and |
| RITEMS.                                                        |
`---------------------------------------------------------------*/

static void
packgram (void)
{
  int itemno;
  int ruleno;
  symbol_list *p;

  ritem = XCALLOC (short, nitems + 1);
  rule_table = XCALLOC (rule_t, nrules) - 1;

  itemno = 0;
  ruleno = 1;

  p = grammar;
  while (p)
    {
      bucket *ruleprec = p->ruleprec;
      rule_table[ruleno].lhs = p->sym->value;
      rule_table[ruleno].rhs = itemno;
      rule_table[ruleno].line = p->line;
      rule_table[ruleno].useful = TRUE;

      p = p->next;
      while (p && p->sym)
        {
          ritem[itemno++] = p->sym->value;
          /* A rule gets by default the precedence and associativity
             of the last token in it.  */
          if (p->sym->class == token_sym)
            {
              rule_table[ruleno].prec = p->sym->prec;
              rule_table[ruleno].assoc = p->sym->assoc;
            }
          if (p)
            p = p->next;
        }

      /* If this rule has a %prec,
         the specified symbol's precedence replaces the default.  */
      if (ruleprec)
        {
          rule_table[ruleno].prec = ruleprec->prec;
          rule_table[ruleno].assoc = ruleprec->assoc;
          rule_table[ruleno].precsym = ruleprec->value;
        }

      ritem[itemno++] = -ruleno;
      ruleno++;

      if (p)
        p = p->next;
    }

  ritem[itemno] = 0;

  if (trace_flag)
    ritem_print (stderr);
}
\f
/*-------------------------------------------------------------------.
| Read in the grammar specification and record it in the format      |
| described in gram.h.  All guards are copied into the GUARD_OBSTACK |
| and all actions into ACTION_OBSTACK, in each case forming the body |
| of a C function (YYGUARD or YYACTION) which contains a switch      |
| statement to decide which guard or action to execute.              |
`-------------------------------------------------------------------*/

void
reader (void)
{
  start_flag = 0;
  startval = NULL;              /* start symbol not specified yet. */

  nsyms = 1;
  nvars = 0;
  nrules = 0;
  nitems = 0;

  typed = 0;
  lastprec = 0;

  semantic_parser = 0;
  pure_parser = 0;

  grammar = NULL;

  lex_init ();
  lineno = 1;

  /* Initialize the symbol table.  */
  tabinit ();
  /* Construct the error token */
  errtoken = getsym ("error");
  errtoken->class = token_sym;
  errtoken->user_token_number = 256;    /* Value specified by POSIX.  */
  /* Construct a token that represents all undefined literal tokens.
     It is always token number 2.  */
  undeftoken = getsym ("$undefined.");
  undeftoken->class = token_sym;
  undeftoken->user_token_number = 2;

  /* Read the declaration section.  Copy %{ ... %} groups to
     TABLE_OBSTACK and FDEFINES file.  Also notice any %token, %left,
     etc. found there.  */
  obstack_fgrow3 (&table_obstack, "\
/* %s, made from %s\n\
   by GNU bison %s.  */\n\
\n",
                  no_parser_flag ? "Bison-generated parse tables" : "A Bison parser",
                  infile, VERSION);

  obstack_sgrow (&table_obstack,
                       "#define YYBISON 1  /* Identify Bison output.  */\n\n");
  read_declarations ();
  /* Start writing the guard and action files, if they are needed.  */
  output_headers ();
  /* Read in the grammar, build grammar in list form.  Write out
     guards and actions.  */
  readgram ();
  /* Now we know whether we need the line-number stack.  If we do,
     write its type into the .tab.h file.  */
  if (defines_flag)
    reader_output_yylsp (&defines_obstack);
  /* Write closing delimiters for actions and guards.  */
  output_trailers ();
  if (locations_flag)
    obstack_sgrow (&table_obstack, "#define YYLSP_NEEDED 1\n\n");
  /* Assign the symbols their symbol numbers.  Write #defines for the
     token symbols into FDEFINES if requested.  */
  packsymbols ();
  /* Convert the grammar into the format described in gram.h.  */
  packgram ();
  /* Output the headers. */
  symbols_output ();
}


/*------------------------------------------------------------------.
| Define YYLTYPE.  Cannot be in the skeleton since we might have to |
| output it in the headers if --defines is used.                    |
`------------------------------------------------------------------*/

void
reader_output_yylsp (struct obstack *oout)
{
  if (locations_flag)
    obstack_sgrow (oout, "\
\n\
#ifndef YYLTYPE\n\
typedef struct yyltype\n\
{\n\
  int first_line;\n\
  int first_column;\n\
\n\
  int last_line;\n\
  int last_column;\n\
} yyltype;\n\
\n\
# define YYLTYPE yyltype\n\
#endif\n\
\n");
}