src/reader.c

   1 /* Input parser for Bison
   2
   3    Copyright (C) 1984, 1986, 1989, 1992, 1998, 2000-2003, 2005-2007,
   4    2009-2012 Free Software Foundation, Inc.
   5
   6    This file is part of Bison, the GNU Compiler Compiler.
   7
   8    This program is free software: you can redistribute it and/or modify
   9    it under the terms of the GNU General Public License as published by
  10    the Free Software Foundation, either version 3 of the License, or
  11    (at your option) any later version.
  12
  13    This program is distributed in the hope that it will be useful,
  14    but WITHOUT ANY WARRANTY; without even the implied warranty of
  15    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16    GNU General Public License for more details.
  17
  18    You should have received a copy of the GNU General Public License
  19    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  20
  21 #include <config.h>
  22 #include "system.h"
  23
  24 #include <quote.h>
  25
  26 #include "complain.h"
  27 #include "conflicts.h"
  28 #include "files.h"
  29 #include "getargs.h"
  30 #include "gram.h"
  31 #include "muscle-tab.h"
  32 #include "reader.h"
  33 #include "symlist.h"
  34 #include "symtab.h"
  35 #include "scan-gram.h"
  36 #include "scan-code.h"
  37
  38 static void prepare_percent_define_front_end_variables (void);
  39 static void check_and_convert_grammar (void);
  40
  41 static symbol_list *grammar = NULL;
  42 static bool start_flag = false;
  43 merger_list *merge_functions;
  44
  45 /* Was %union seen?  */
  46 bool union_seen = false;
  47
  48 /* Was a tag seen?  */
  49 bool tag_seen = false;
  50
  51 /* Should rules have a default precedence?  */
  52 bool default_prec = true;
  53 \f
  54 /*-----------------------.
  55 | Set the start symbol.  |
  56 `-----------------------*/
  57
  58 void
  59 grammar_start_symbol_set (symbol *sym, location loc)
  60 {
  61   if (start_flag)
  62     complain_at (loc, _("multiple %s declarations"), "%start");
  63   else
  64     {
  65       start_flag = true;
  66       startsymbol = sym;
  67       startsymbol_location = loc;
  68     }
  69 }
  70
  71 \f
  72
  73 /*------------------------------------------------------------------------.
  74 | Return the merger index for a merging function named NAME.  Records the |
  75 | function, if new, in MERGER_LIST.                                       |
  76 `------------------------------------------------------------------------*/
  77
  78 static int
  79 get_merge_function (uniqstr name)
  80 {
  81   merger_list *syms;
  82   merger_list head;
  83   int n;
  84
  85   if (! glr_parser)
  86     return 0;
  87
  88   head.next = merge_functions;
  89   for (syms = &head, n = 1; syms->next; syms = syms->next, n += 1)
  90     if (UNIQSTR_EQ (name, syms->next->name))
  91       break;
  92   if (syms->next == NULL)
  93     {
  94       syms->next = xmalloc (sizeof syms->next[0]);
  95       syms->next->name = uniqstr_new (name);
  96       /* After all symbol type declarations have been parsed, packgram invokes
  97          record_merge_function_type to set the type.  */
  98       syms->next->type = NULL;
  99       syms->next->next = NULL;
 100       merge_functions = head.next;
 101     }
 102   return n;
 103 }
 104
 105 /*-------------------------------------------------------------------------.
 106 | For the existing merging function with index MERGER, record the result   |
 107 | type as TYPE as required by the lhs of the rule whose %merge declaration |
 108 | is at DECLARATION_LOC.                                                   |
 109 `-------------------------------------------------------------------------*/
 110
 111 static void
 112 record_merge_function_type (int merger, uniqstr type, location declaration_loc)
 113 {
 114   int merger_find;
 115   merger_list *merge_function;
 116
 117   if (merger <= 0)
 118     return;
 119
 120   if (type == NULL)
 121     type = uniqstr_new ("");
 122
 123   merger_find = 1;
 124   for (merge_function = merge_functions;
 125        merge_function != NULL && merger_find != merger;
 126        merge_function = merge_function->next)
 127     merger_find += 1;
 128   aver (merge_function != NULL && merger_find == merger);
 129   if (merge_function->type != NULL && !UNIQSTR_EQ (merge_function->type, type))
 130     {
 131       unsigned indent = 0;
 132       complain_at_indent (declaration_loc, &indent,
 133                           _("result type clash on merge function %s: "
 134                             "<%s> != <%s>"),
 135                           quote (merge_function->name), type,
 136                           merge_function->type);
 137       indent += SUB_INDENT;
 138       complain_at_indent (merge_function->type_declaration_location, &indent,
 139                           _("previous declaration"));
 140    }
 141   merge_function->type = uniqstr_new (type);
 142   merge_function->type_declaration_location = declaration_loc;
 143 }
 144
 145 /*--------------------------------------.
 146 | Free all merge-function definitions.  |
 147 `--------------------------------------*/
 148
 149 void
 150 free_merger_functions (void)
 151 {
 152   merger_list *L0 = merge_functions;
 153   while (L0)
 154     {
 155       merger_list *L1 = L0->next;
 156       free (L0);
 157       L0 = L1;
 158     }
 159 }
 160
 161 \f
 162 /*-------------------------------------------------------------------.
 163 | Parse the input grammar into a one symbol_list structure.  Each    |
 164 | rule is represented by a sequence of symbols: the left hand side   |
 165 | followed by the contents of the right hand side, followed by a     |
 166 | null pointer instead of a symbol to terminate the rule.  The next  |
 167 | symbol is the lhs of the following rule.                           |
 168 |                                                                    |
 169 | All actions are copied out, labelled by the rule number they apply |
 170 | to.                                                                |
 171 `-------------------------------------------------------------------*/
 172
 173 /* The (currently) last symbol of GRAMMAR. */
 174 static symbol_list *grammar_end = NULL;
 175
 176 /* Append SYM to the grammar.  */
 177 static symbol_list *
 178 grammar_symbol_append (symbol *sym, location loc)
 179 {
 180   symbol_list *p = symbol_list_sym_new (sym, loc);
 181
 182   if (grammar_end)
 183     grammar_end->next = p;
 184   else
 185     grammar = p;
 186
 187   grammar_end = p;
 188
 189   /* A null SYM stands for an end of rule; it is not an actual
 190      part of it.  */
 191   if (sym)
 192     ++nritems;
 193
 194   return p;
 195 }
 196
 197 static void
 198 assign_named_ref (symbol_list *p, named_ref *name)
 199 {
 200   symbol *sym = p->content.sym;
 201
 202   if (name->id == sym->tag)
 203     {
 204       warn_at (name->loc,
 205                _("duplicated symbol name for %s ignored"),
 206                quote (sym->tag));
 207       named_ref_free (name);
 208     }
 209   else
 210     p->named_ref = name;
 211 }
 212
 213
 214 /* The rule currently being defined, and the previous rule.
 215    CURRENT_RULE points to the first LHS of the current rule, while
 216    PREVIOUS_RULE_END points to the *end* of the previous rule (NULL).  */
 217 static symbol_list *current_rule = NULL;
 218 static symbol_list *previous_rule_end = NULL;
 219
 220
 221 /*----------------------------------------------.
 222 | Create a new rule for LHS in to the GRAMMAR.  |
 223 `----------------------------------------------*/
 224
 225 void
 226 grammar_current_rule_begin (symbol *lhs, location loc,
 227                             named_ref *lhs_name)
 228 {
 229   symbol_list* p;
 230
 231   /* Start a new rule and record its lhs.  */
 232   ++nrules;
 233   previous_rule_end = grammar_end;
 234
 235   p = grammar_symbol_append (lhs, loc);
 236   if (lhs_name)
 237     assign_named_ref (p, named_ref_copy (lhs_name));
 238
 239   current_rule = grammar_end;
 240
 241   /* Mark the rule's lhs as a nonterminal if not already so.  */
 242   if (lhs->class == unknown_sym)
 243     {
 244       lhs->class = nterm_sym;
 245       lhs->number = nvars;
 246       ++nvars;
 247     }
 248   else if (lhs->class == token_sym)
 249     complain_at (loc, _("rule given for %s, which is a token"), lhs->tag);
 250 }
 251
 252
 253 /*----------------------------------------------------------------------.
 254 | A symbol should be used if either:                                    |
 255 |   1. It has a destructor.                                             |
 256 |   2. The symbol is a mid-rule symbol (i.e., the generated LHS         |
 257 |      replacing a mid-rule action) that was assigned to or used, as in |
 258 |      "exp: { $$ = 1; } { $$ = $1; }".                                 |
 259 `----------------------------------------------------------------------*/
 260
 261 static bool
 262 symbol_should_be_used (symbol_list const *s, bool *midrule_warning)
 263 {
 264   if (symbol_destructor_get (s->content.sym)->code)
 265     return true;
 266   if ((s->midrule && s->midrule->action_props.is_value_used)
 267       || (s->midrule_parent_rule
 268           && symbol_list_n_get (s->midrule_parent_rule,
 269                                 s->midrule_parent_rhs_index)
 270                ->action_props.is_value_used))
 271     {
 272       *midrule_warning = true;
 273       return true;
 274     }
 275   return false;
 276 }
 277
 278 /*----------------------------------------------------------------.
 279 | Check that the rule R is properly defined.  For instance, there |
 280 | should be no type clash on the default action.                  |
 281 `----------------------------------------------------------------*/
 282
 283 static void
 284 grammar_rule_check (const symbol_list *r)
 285 {
 286   /* Type check.
 287
 288      If there is an action, then there is nothing we can do: the user
 289      is allowed to shoot herself in the foot.
 290
 291      Don't worry about the default action if $$ is untyped, since $$'s
 292      value can't be used.  */
 293   if (!r->action_props.code && r->content.sym->type_name)
 294     {
 295       symbol *first_rhs = r->next->content.sym;
 296       /* If $$ is being set in default way, report if any type mismatch.  */
 297       if (first_rhs)
 298         {
 299           char const *lhs_type = r->content.sym->type_name;
 300           const char *rhs_type =
 301             first_rhs->type_name ? first_rhs->type_name : "";
 302           if (!UNIQSTR_EQ (lhs_type, rhs_type))
 303             warn_at (r->location,
 304                      _("type clash on default action: <%s> != <%s>"),
 305                      lhs_type, rhs_type);
 306         }
 307       /* Warn if there is no default for $$ but we need one.  */
 308       else
 309         warn_at (r->location,
 310                  _("empty rule for typed nonterminal, and no action"));
 311     }
 312
 313   /* Check that symbol values that should be used are in fact used.  */
 314   {
 315     symbol_list const *l = r;
 316     int n = 0;
 317     for (; l && l->content.sym; l = l->next, ++n)
 318       {
 319         bool midrule_warning = false;
 320         if (!l->action_props.is_value_used
 321             && symbol_should_be_used (l, &midrule_warning)
 322             /* The default action, $$ = $1, `uses' both.  */
 323             && (r->action_props.code || (n != 0 && n != 1)))
 324           {
 325             void (*warn_at_ptr)(location, char const*, ...) =
 326               midrule_warning ? midrule_value_at : warn_at;
 327             if (n)
 328               warn_at_ptr (l->location, _("unused value: $%d"), n);
 329             else
 330               warn_at_ptr (l->location, _("unset value: $$"));
 331           }
 332       }
 333   }
 334
 335   /* See comments in grammar_current_rule_prec_set for how POSIX
 336      mandates this complaint.  It's only for identifiers, so skip
 337      it for char literals and strings, which are always tokens.  */
 338   if (r->ruleprec
 339       && r->ruleprec->tag[0] != '\'' && r->ruleprec->tag[0] != '"'
 340       && !r->ruleprec->declared && !r->ruleprec->prec)
 341     warn_at (r->location, _("token for %%prec is not defined: %s"),
 342              r->ruleprec->tag);
 343 }
 344
 345
 346 /*-------------------------------------.
 347 | End the currently being grown rule.  |
 348 `-------------------------------------*/
 349
 350 void
 351 grammar_current_rule_end (location loc)
 352 {
 353   /* Put an empty link in the list to mark the end of this rule  */
 354   grammar_symbol_append (NULL, grammar_end->location);
 355   current_rule->location = loc;
 356 }
 357
 358
 359 /*-------------------------------------------------------------------.
 360 | The previous action turns out the be a mid-rule action.  Attach it |
 361 | to the current rule, i.e., create a dummy symbol, attach it this   |
 362 | mid-rule action, and append this dummy nonterminal to the current  |
 363 | rule.                                                              |
 364 `-------------------------------------------------------------------*/
 365
 366 void
 367 grammar_midrule_action (void)
 368 {
 369   /* Since the action was written out with this rule's number, we must
 370      give the new rule this number by inserting the new rule before
 371      it.  */
 372
 373   /* Make a DUMMY nonterminal, whose location is that of the midrule
 374      action.  Create the MIDRULE.  */
 375   location dummy_location = current_rule->action_props.location;
 376   symbol *dummy = dummy_symbol_get (dummy_location);
 377   symbol_list *midrule = symbol_list_sym_new (dummy, dummy_location);
 378
 379   /* Remember named_ref of previous action. */
 380   named_ref *action_name = current_rule->action_props.named_ref;
 381
 382   /* Make a new rule, whose body is empty, before the current one, so
 383      that the action just read can belong to it.  */
 384   ++nrules;
 385   ++nritems;
 386   /* Attach its location and actions to that of the DUMMY.  */
 387   midrule->location = dummy_location;
 388   code_props_rule_action_init (&midrule->action_props,
 389                                current_rule->action_props.code,
 390                                current_rule->action_props.location,
 391                                midrule, 0);
 392   code_props_none_init (&current_rule->action_props);
 393
 394   if (previous_rule_end)
 395     previous_rule_end->next = midrule;
 396   else
 397     grammar = midrule;
 398
 399   /* End the dummy's rule.  */
 400   midrule->next = symbol_list_sym_new (NULL, dummy_location);
 401   midrule->next->next = current_rule;
 402
 403   previous_rule_end = midrule->next;
 404
 405   /* Insert the dummy nonterminal replacing the midrule action into
 406      the current rule.  Bind it to its dedicated rule.  */
 407   grammar_current_rule_symbol_append (dummy, dummy_location,
 408                                       action_name);
 409   grammar_end->midrule = midrule;
 410   midrule->midrule_parent_rule = current_rule;
 411   midrule->midrule_parent_rhs_index = symbol_list_length (current_rule->next);
 412 }
 413
 414 /* Set the precedence symbol of the current rule to PRECSYM. */
 415
 416 void
 417 grammar_current_rule_prec_set (symbol *precsym, location loc)
 418 {
 419   /* POSIX says that any identifier is a nonterminal if it does not
 420      appear on the LHS of a grammar rule and is not defined by %token
 421      or by one of the directives that assigns precedence to a token.  We
 422      ignore this here because the only kind of identifier that POSIX
 423      allows to follow a %prec is a token and because assuming it's a
 424      token now can produce more logical error messages.  Nevertheless,
 425      grammar_rule_check does obey what we believe is the real intent of
 426      POSIX here: that an error be reported for any identifier that
 427      appears after %prec but that is not defined separately as a
 428      token.  */
 429   symbol_class_set (precsym, token_sym, loc, false);
 430   if (current_rule->ruleprec)
 431     complain_at (loc, _("only one %s allowed per rule"), "%prec");
 432   current_rule->ruleprec = precsym;
 433 }
 434
 435 /* Attach dynamic precedence DPREC to the current rule. */
 436
 437 void
 438 grammar_current_rule_dprec_set (int dprec, location loc)
 439 {
 440   if (! glr_parser)
 441     warn_at (loc, _("%s affects only GLR parsers"), "%dprec");
 442   if (dprec <= 0)
 443     complain_at (loc, _("%s must be followed by positive number"), "%dprec");
 444   else if (current_rule->dprec != 0)
 445     complain_at (loc, _("only one %s allowed per rule"), "%dprec");
 446   current_rule->dprec = dprec;
 447 }
 448
 449 /* Attach a merge function NAME with argument type TYPE to current
 450    rule. */
 451
 452 void
 453 grammar_current_rule_merge_set (uniqstr name, location loc)
 454 {
 455   if (! glr_parser)
 456     warn_at (loc, _("%s affects only GLR parsers"), "%merge");
 457   if (current_rule->merger != 0)
 458     complain_at (loc, _("only one %s allowed per rule"), "%merge");
 459   current_rule->merger = get_merge_function (name);
 460   current_rule->merger_declaration_location = loc;
 461 }
 462
 463 /* Attach SYM to the current rule.  If needed, move the previous
 464    action as a mid-rule action.  */
 465
 466 void
 467 grammar_current_rule_symbol_append (symbol *sym, location loc,
 468                                     named_ref *name)
 469 {
 470   symbol_list *p;
 471   if (current_rule->action_props.code)
 472     grammar_midrule_action ();
 473   p = grammar_symbol_append (sym, loc);
 474   if (name)
 475     assign_named_ref(p, name);
 476 }
 477
 478 /* Attach an ACTION to the current rule.  */
 479
 480 void
 481 grammar_current_rule_action_append (const char *action, location loc,
 482                                     named_ref *name)
 483 {
 484   if (current_rule->action_props.code)
 485     grammar_midrule_action ();
 486   /* After all symbol declarations have been parsed, packgram invokes
 487      code_props_translate_code.  */
 488   code_props_rule_action_init (&current_rule->action_props, action, loc,
 489                                current_rule, name);
 490 }
 491
 492 \f
 493 /*---------------------------------------------------------------.
 494 | Convert the rules into the representation using RRHS, RLHS and |
 495 | RITEM.                                                         |
 496 `---------------------------------------------------------------*/
 497
 498 static void
 499 packgram (void)
 500 {
 501   unsigned int itemno = 0;
 502   rule_number ruleno = 0;
 503   symbol_list *p = grammar;
 504
 505   ritem = xnmalloc (nritems + 1, sizeof *ritem);
 506
 507   /* This sentinel is used by build_relations in gram.c.  */
 508   *ritem++ = 0;
 509
 510   rules = xnmalloc (nrules, sizeof *rules);
 511
 512   while (p)
 513     {
 514       int rule_length = 0;
 515       symbol *ruleprec = p->ruleprec;
 516       record_merge_function_type (p->merger, p->content.sym->type_name,
 517                                   p->merger_declaration_location);
 518       rules[ruleno].user_number = ruleno;
 519       rules[ruleno].number = ruleno;
 520       rules[ruleno].lhs = p->content.sym;
 521       rules[ruleno].rhs = ritem + itemno;
 522       rules[ruleno].prec = NULL;
 523       rules[ruleno].dprec = p->dprec;
 524       rules[ruleno].merger = p->merger;
 525       rules[ruleno].precsym = NULL;
 526       rules[ruleno].location = p->location;
 527       rules[ruleno].useful = true;
 528       rules[ruleno].action = p->action_props.code;
 529       rules[ruleno].action_location = p->action_props.location;
 530
 531       /* If the midrule's $$ is set or its $n is used, remove the `$' from the
 532          symbol name so that it's a user-defined symbol so that the default
 533          %destructor and %printer apply.  */
 534       if (p->midrule_parent_rule
 535           && (p->action_props.is_value_used
 536               || symbol_list_n_get (p->midrule_parent_rule,
 537                                     p->midrule_parent_rhs_index)
 538                    ->action_props.is_value_used))
 539         p->content.sym->tag += 1;
 540
 541       /* Don't check the generated rule 0.  It has no action, so some rhs
 542          symbols may appear unused, but the parsing algorithm ensures that
 543          %destructor's are invoked appropriately.  */
 544       if (p != grammar)
 545         grammar_rule_check (p);
 546
 547       for (p = p->next; p && p->content.sym; p = p->next)
 548         {
 549           ++rule_length;
 550
 551           /* Don't allow rule_length == INT_MAX, since that might
 552              cause confusion with strtol if INT_MAX == LONG_MAX.  */
 553           if (rule_length == INT_MAX)
 554               fatal_at (rules[ruleno].location, _("rule is too long"));
 555
 556           /* item_number = symbol_number.
 557              But the former needs to contain more: negative rule numbers. */
 558           ritem[itemno++] =
 559             symbol_number_as_item_number (p->content.sym->number);
 560           /* A rule gets by default the precedence and associativity
 561              of its last token.  */
 562           if (p->content.sym->class == token_sym && default_prec)
 563             rules[ruleno].prec = p->content.sym;
 564         }
 565
 566       /* If this rule has a %prec,
 567          the specified symbol's precedence replaces the default.  */
 568       if (ruleprec)
 569         {
 570           rules[ruleno].precsym = ruleprec;
 571           rules[ruleno].prec = ruleprec;
 572         }
 573       /* An item ends by the rule number (negated).  */
 574       ritem[itemno++] = rule_number_as_item_number (ruleno);
 575       aver (itemno < ITEM_NUMBER_MAX);
 576       ++ruleno;
 577       aver (ruleno < RULE_NUMBER_MAX);
 578
 579       if (p)
 580         p = p->next;
 581     }
 582
 583   aver (itemno == nritems);
 584
 585   if (trace_flag & trace_sets)
 586     ritem_print (stderr);
 587 }
 588 \f
 589 /*------------------------------------------------------------------.
 590 | Read in the grammar specification and record it in the format     |
 591 | described in gram.h.  All actions are copied into ACTION_OBSTACK, |
 592 | in each case forming the body of a C function (YYACTION) which    |
 593 | contains a switch statement to decide which action to execute.    |
 594 `------------------------------------------------------------------*/
 595
 596 void
 597 reader (void)
 598 {
 599   /* Initialize the symbol table.  */
 600   symbols_new ();
 601
 602   /* Construct the accept symbol. */
 603   accept = symbol_get ("$accept", empty_location);
 604   accept->class = nterm_sym;
 605   accept->number = nvars++;
 606
 607   /* Construct the error token */
 608   errtoken = symbol_get ("error", empty_location);
 609   errtoken->class = token_sym;
 610   errtoken->number = ntokens++;
 611
 612   /* Construct a token that represents all undefined literal tokens.
 613      It is always token number 2.  */
 614   undeftoken = symbol_get ("$undefined", empty_location);
 615   undeftoken->class = token_sym;
 616   undeftoken->number = ntokens++;
 617
 618   gram_in = xfopen (grammar_file, "r");
 619
 620   gram__flex_debug = trace_flag & trace_scan;
 621   gram_debug = trace_flag & trace_parse;
 622   gram_scanner_initialize ();
 623   gram_parse ();
 624   prepare_percent_define_front_end_variables ();
 625
 626   if (! complaint_issued)
 627     check_and_convert_grammar ();
 628
 629   xfclose (gram_in);
 630 }
 631
 632 static void
 633 prepare_percent_define_front_end_variables (void)
 634 {
 635   /* Set %define front-end variable defaults.  */
 636   muscle_percent_define_default ("lr.keep-unreachable-states", "false");
 637   {
 638     char *lr_type;
 639     /* IELR would be a better default, but LALR is historically the
 640        default.  */
 641     muscle_percent_define_default ("lr.type", "lalr");
 642     lr_type = muscle_percent_define_get ("lr.type");
 643     if (0 != strcmp (lr_type, "canonical-lr"))
 644       muscle_percent_define_default ("lr.default-reductions", "most");
 645     else
 646       muscle_percent_define_default ("lr.default-reductions", "accepting");
 647     free (lr_type);
 648   }
 649
 650   /* Check %define front-end variables.  */
 651   {
 652     static char const * const values[] = {
 653       "lr.type", "lalr", "ielr", "canonical-lr", NULL,
 654       "lr.default-reductions", "most", "consistent", "accepting", NULL,
 655       NULL
 656     };
 657     muscle_percent_define_check_values (values);
 658   }
 659 }
 660
 661
 662 /*-------------------------------------------------------------.
 663 | Check the grammar that has just been read, and convert it to |
 664 | internal form.                                               |
 665 `-------------------------------------------------------------*/
 666
 667 static void
 668 check_and_convert_grammar (void)
 669 {
 670   /* Grammar has been read.  Do some checking.  */
 671   if (nrules == 0)
 672     fatal (_("no rules in the input grammar"));
 673
 674   /* If the user did not define her ENDTOKEN, do it now. */
 675   if (!endtoken)
 676     {
 677       endtoken = symbol_get ("$end", empty_location);
 678       endtoken->class = token_sym;
 679       endtoken->number = 0;
 680       /* Value specified by POSIX.  */
 681       endtoken->user_token_number = 0;
 682     }
 683
 684   /* Report any undefined symbols and consider them nonterminals.  */
 685   symbols_check_defined ();
 686
 687   /* Find the start symbol if no %start.  */
 688   if (!start_flag)
 689     {
 690       symbol_list *node;
 691       for (node = grammar;
 692            node != NULL && symbol_is_dummy (node->content.sym);
 693            node = node->next)
 694         {
 695           for (node = node->next;
 696                node != NULL && node->content.sym != NULL;
 697                node = node->next)
 698             ;
 699         }
 700       aver (node != NULL);
 701       grammar_start_symbol_set (node->content.sym,
 702                                 node->content.sym->location);
 703     }
 704
 705   /* Insert the initial rule, whose line is that of the first rule
 706      (not that of the start symbol):
 707
 708      accept: %start EOF.  */
 709   {
 710     symbol_list *p = symbol_list_sym_new (accept, empty_location);
 711     p->location = grammar->location;
 712     p->next = symbol_list_sym_new (startsymbol, empty_location);
 713     p->next->next = symbol_list_sym_new (endtoken, empty_location);
 714     p->next->next->next = symbol_list_sym_new (NULL, empty_location);
 715     p->next->next->next->next = grammar;
 716     nrules += 1;
 717     nritems += 3;
 718     grammar = p;
 719   }
 720
 721   aver (nsyms <= SYMBOL_NUMBER_MAXIMUM && nsyms == ntokens + nvars);
 722
 723   /* Assign the symbols their symbol numbers.  Write #defines for the
 724      token symbols into FDEFINES if requested.  */
 725   symbols_pack ();
 726
 727   /* Scan rule actions after invoking symbol_check_alias_consistency (in
 728      symbols_pack above) so that token types are set correctly before the rule
 729      action type checking.
 730
 731      Before invoking grammar_rule_check (in packgram below) on any rule, make
 732      sure all actions have already been scanned in order to set `used' flags.
 733      Otherwise, checking that a midrule's $$ should be set will not always work
 734      properly because the check must forward-reference the midrule's parent
 735      rule.  For the same reason, all the `used' flags must be set before
 736      checking whether to remove `$' from any midrule symbol name (also in
 737      packgram).  */
 738   {
 739     symbol_list *sym;
 740     for (sym = grammar; sym; sym = sym->next)
 741       code_props_translate_code (&sym->action_props);
 742   }
 743
 744   /* Convert the grammar into the format described in gram.h.  */
 745   packgram ();
 746
 747   /* The grammar as a symbol_list is no longer needed. */
 748   symbol_list_free (grammar);
 749 }