Have Bison grammars parsed by a Bison grammar.

[bison.git] / src / reader.c

/* Input parser for bison
   Copyright (C) 1984, 1986, 1989, 1992, 1998, 2000, 2001, 2002
   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 "quotearg.h"
#include "quote.h"
#include "getargs.h"
#include "files.h"
#include "symtab.h"
#include "options.h"
#include "gram.h"
#include "complain.h"
#include "output.h"
#include "reader.h"
#include "conflicts.h"
#include "muscle_tab.h"

int lineno;
static symbol_list *grammar = NULL;
static int start_flag = 0;

/* Nonzero if %union has been seen.  */
int typed = 0;

static symbol_list *
symbol_list_new (symbol_t *sym)
{
  symbol_list *res = XMALLOC (symbol_list, 1);
  res->next = NULL;
  res->sym = sym;
  res->line = lineno;
  res->action = NULL;
  res->action_line = 0;
  res->ruleprec = NULL;
  return res;
}

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

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;
}


/*-----------------------.
| Set the start symbol.  |
`-----------------------*/

void
grammar_start_symbol_set (symbol_t *s)
{
  if (start_flag)
    complain (_("multiple %s declarations"), "%start");
  else
    {
      start_flag = 1;
      startsymbol = s;
    }
}


/*----------------------------------------------------------------.
| There are two prologues: one before %union, one after.  Augment |
| the current one.                                                |
`----------------------------------------------------------------*/

void
prologue_augment (const char *prologue, int location)
{
  struct obstack *oout =
    !typed ? &pre_prologue_obstack : &post_prologue_obstack;

  if (!no_lines_flag)
    {
      obstack_fgrow2 (oout, muscle_find ("linef"),
		      location, quotearg_style (c_quoting_style,
						muscle_find ("filename")));
    }
  obstack_sgrow (oout, prologue);
}




/*----------------------.
| Handle the epilogue.  |
`----------------------*/

void
epilogue_set (const char *epilogue, int location)
{
  struct obstack el_obstack;
  obstack_init (&el_obstack);

  if (!no_lines_flag)
    {
      obstack_fgrow2 (&el_obstack, muscle_find ("linef"),
		      location, quotearg_style (c_quoting_style,
						muscle_find ("filename")));
    }
  obstack_sgrow (&el_obstack, epilogue);
  obstack_1grow (&el_obstack, 0);
  muscle_insert ("epilogue", obstack_finish (&el_obstack));
}


\f

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

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

  symbol_t *sym;

  sprintf (buf, "@%d", ++gensym_count);
  sym = getsym (buf);
  sym->class = nterm_sym;
  sym->number = nvars++;
  return sym;
}
\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 actions are copied out, labelled by the rule number they apply |
| to.                                                                |
|                                                                    |
| Bison used to allow some %directives in the rules sections, but    |
| this is no longer consider appropriate: (i) the documented grammar |
| doesn't claim it, (ii), it would promote bad style, (iii), error   |
| recovery for %directives consists in skipping the junk until a `%' |
| is seen and helrp synchronizing.  This scheme is definitely wrong  |
| in the rules section.                                              |
`-------------------------------------------------------------------*/

/* The (currently) last symbol of GRAMMAR. */
symbol_list *grammar_end = NULL;

/* Append S to the GRAMMAR. */
void
grammar_symbol_append (symbol_t *s)
{
  symbol_list *p = symbol_list_new (s);

  if (grammar_end)
    grammar_end->next = p;
  else
    grammar = p;

  grammar_end = p;
}

/* The rule currently being defined, and the previous rule.  Point to
   the first symbol of each list: their lhs.  */
symbol_list *current_rule = NULL;
symbol_list *previous_rule = NULL;


/* Create a new rule for LHS in to the GRAMMAR. */

void
grammar_rule_begin (symbol_t *lhs)
{
  if (!start_flag)
    {
      startsymbol = lhs;
      start_flag = 1;
    }

  /* Start a new rule and record its lhs.  */
  ++nrules;
  ++nritems;

  previous_rule = grammar_end;
  grammar_symbol_append (lhs);
  current_rule = grammar_end;

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

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

/* Check that the last rule (CURRENT_RULE) is properly defined.  For
   instance, there should be no type clash on the default action.  */

static void
grammar_current_rule_check (void)
{
  symbol_t *lhs = current_rule->sym;
  symbol_t *first_rhs = current_rule->next->sym;

  /* If there is an action, then there is nothing we can do: the user
     is allowed to shoot in her foot.  */
  if (current_rule->action)
    return;

  /* If $$ is being set in default way, report if any type mismatch.
     */
  if (first_rhs)
    {
      const char *lhs_type = lhs->type_name       ? lhs->type_name       : "";
      const char *rhs_type = first_rhs->type_name ? first_rhs->type_name : "";
      if (strcmp (lhs_type, rhs_type))
	complain (_("type clash (`%s' `%s') on default action"),
		  lhs_type, rhs_type);
    }
  /* Warn if there is no default for $$ but we need one.  */
  else
    {
      if (lhs->type_name)
	complain (_("empty rule for typed nonterminal, and no action"));
    }
}


/* End the currently being grown rule. */

void
grammar_rule_end (void)
{
  /* Put an empty link in the list to mark the end of this rule  */
  grammar_symbol_append (NULL);
  grammar_current_rule_check ();
}


/* The previous action turns out the be a mid-rule action.  Attach it
   to the current rule, i.e., create a dummy symbol, attach it this
   mid-rule action, and append this dummy nonterminal to the current
   rule.  */

void
grammar_midrule_action (void)
{
  /* 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.  */
  symbol_t *sdummy = gensym ();
  symbol_list *midrule_action = symbol_list_new (sdummy);

  /* Make a new rule, whose body is empty, before the current one, so
     that the action just read can belong to it.  */
  ++nrules;
  ++nritems;
  /* Attach its lineno to that of the host rule.  */
  midrule_action->line = current_rule->line;
  /* Move the action from the host rule to this one.  */
  midrule_action->action = current_rule->action;
  midrule_action->action_line = current_rule->action_line;
  current_rule->action = NULL;

  if (previous_rule)
    previous_rule->next = midrule_action;
  else
    grammar = midrule_action;

  /* End of the rule. */
  previous_rule = symbol_list_new (NULL);
  previous_rule->next = current_rule;

  midrule_action->next = previous_rule;

  /* Insert the dummy generated by that rule into this rule.  */
  ++nritems;
  grammar_symbol_append (sdummy);
}

/* Set the precedence symbol of the current rule to PRECSYM. */

void
grammar_current_rule_prec_set (symbol_t *precsym)
{
  if (current_rule->ruleprec)
    complain (_("two @prec's in a row"));
  current_rule->ruleprec = precsym;
}

/* Attach a SYMBOL to the current rule.  If needed, move the previous
   action as a mid-rule action.  */

void
grammar_current_rule_symbol_append (symbol_t *symbol)
{
  if (current_rule->action)
    grammar_midrule_action ();
  ++nritems;
  grammar_symbol_append (symbol);
}


/* Attach an ACTION to the current rule.  If needed, move the previous
   action as a mid-rule action.  */

void
grammar_current_rule_action_append (const char *action, int action_line)
{
  if (current_rule->action)
    grammar_midrule_action ();
  current_rule->action = action;
  current_rule->action_line = action_line;
}

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

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

  ritem = XCALLOC (item_number_t, nritems);
  rules = XCALLOC (rule_t, nrules) - 1;

  itemno = 0;
  ruleno = 1;

  p = grammar;
  while (p)
    {
      symbol_t *ruleprec = p->ruleprec;
      rules[ruleno].user_number = ruleno;
      rules[ruleno].number = ruleno;
      rules[ruleno].lhs = p->sym;
      rules[ruleno].rhs = ritem + itemno;
      rules[ruleno].line = p->line;
      rules[ruleno].useful = TRUE;
      rules[ruleno].action = p->action;
      rules[ruleno].action_line = p->action_line;

      p = p->next;
      while (p && p->sym)
	{
	  /* item_number_t = symbol_number_t.
	     But the former needs to contain more: negative rule numbers. */
	  ritem[itemno++] = symbol_number_as_item_number (p->sym->number);
	  /* A rule gets by default the precedence and associativity
	     of the last token in it.  */
	  if (p->sym->class == token_sym)
	    rules[ruleno].prec = p->sym;
	  if (p)
	    p = p->next;
	}

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

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

  assert (itemno == nritems);

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

void
reader (void)
{
  gram_control_t gram_control;
  lineno = 1;

  /* Initialize the muscle obstack.  */
  obstack_init (&muscle_obstack);

  /* Initialize the symbol table.  */
  symbols_new ();

  /* Construct the axiom symbol. */
  axiom = getsym ("$axiom");
  axiom->class = nterm_sym;
  axiom->number = nvars++;

  /* Construct the error token */
  errtoken = getsym ("error");
  errtoken->class = token_sym;
  errtoken->number = ntokens++;

  /* Construct a token that represents all undefined literal tokens.
     It is always token number 2.  */
  undeftoken = getsym ("$undefined.");
  undeftoken->class = token_sym;
  undeftoken->number = ntokens++;

  /* Initialize the obstacks. */
  obstack_init (&action_obstack);
  obstack_init (&output_obstack);
  obstack_init (&pre_prologue_obstack);
  obstack_init (&post_prologue_obstack);

  finput = xfopen (infile, "r");
  gram_in = finput;

  gram_debug = !!getenv ("parse");
  gram__flex_debug = !!getenv ("scan");
  gram_parse (&gram_control);

  /* Grammar has been read.  Do some checking */
  if (nrules == 0)
    fatal (_("no rules in the input grammar"));

  /* Report any undefined symbols and consider them nonterminals.  */
  symbols_check_defined ();

  /* If the user did not define her EOFTOKEN, do it now. */
  if (!eoftoken)
    {
      eoftoken = getsym ("$");
      eoftoken->class = token_sym;
      eoftoken->number = 0;
      /* Value specified by POSIX.  */
      eoftoken->user_token_number = 0;
    }

  /* Insert the initial rule, which line is that of the first rule
     (not that of the start symbol):

     axiom: %start EOF.  */
  {
    symbol_list *p = symbol_list_new (axiom);
    p->line = grammar->line;
    p->next = symbol_list_new (startsymbol);
    p->next->next = symbol_list_new (eoftoken);
    p->next->next->next = symbol_list_new (NULL);
    p->next->next->next->next = grammar;
    nrules += 1;
    nritems += 3;
    grammar = p;
  }

  if (nsyms > SHRT_MAX)
    fatal (_("too many symbols (tokens plus nonterminals); maximum %d"),
          SHRT_MAX);

  assert (nsyms == ntokens + nvars);

  xfclose (finput);

  /* Assign the symbols their symbol numbers.  Write #defines for the
     token symbols into FDEFINES if requested.  */
  symbols_pack ();

  /* Convert the grammar into the format described in gram.h.  */
  packgram ();

  /* The grammar as a symbol_list is no longer needed. */
  LIST_FREE (symbol_list, grammar);
}