src/reader.c

   1 /* Input parser for Bison
   2
   3    Copyright (C) 1984, 1986, 1989, 1992, 1998, 2000, 2001, 2002, 2003,
   4    2005, 2006, 2007, 2009 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 #include <quotearg.h>
  26
  27 #include "complain.h"
  28 #include "conflicts.h"
  29 #include "files.h"
  30 #include "getargs.h"
  31 #include "gram.h"
  32 #include "muscle-tab.h"
  33 #include "reader.h"
  34 #include "symlist.h"
  35 #include "symtab.h"
  36 #include "scan-gram.h"
  37 #include "scan-code.h"
  38
  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       complain_at (declaration_loc,
 132                    _("result type clash on merge function `%s': <%s> != <%s>"),
 133                    merge_function->name, type, merge_function->type);
 134       complain_at (merge_function->type_declaration_location,
 135                    _("previous declaration"));
 136     }
 137   merge_function->type = uniqstr_new (type);
 138   merge_function->type_declaration_location = declaration_loc;
 139 }
 140
 141 /*--------------------------------------.
 142 | Free all merge-function definitions.  |
 143 `--------------------------------------*/
 144
 145 void
 146 free_merger_functions (void)
 147 {
 148   merger_list *L0 = merge_functions;
 149   while (L0)
 150     {
 151       merger_list *L1 = L0->next;
 152       free (L0);
 153       L0 = L1;
 154     }
 155 }
 156
 157 \f
 158 /*-------------------------------------------------------------------.
 159 | Parse the input grammar into a one symbol_list structure.  Each    |
 160 | rule is represented by a sequence of symbols: the left hand side   |
 161 | followed by the contents of the right hand side, followed by a     |
 162 | null pointer instead of a symbol to terminate the rule.  The next  |
 163 | symbol is the lhs of the following rule.                           |
 164 |                                                                    |
 165 | All actions are copied out, labelled by the rule number they apply |
 166 | to.                                                                |
 167 `-------------------------------------------------------------------*/
 168
 169 /* The (currently) last symbol of GRAMMAR. */
 170 static symbol_list *grammar_end = NULL;
 171
 172 /* Append SYM to the grammar.  */
 173 static symbol_list *
 174 grammar_symbol_append (symbol *sym, location loc)
 175 {
 176   symbol_list *p = symbol_list_sym_new (sym, loc);
 177
 178   if (grammar_end)
 179     grammar_end->next = p;
 180   else
 181     grammar = p;
 182
 183   grammar_end = p;
 184
 185   /* A null SYM stands for an end of rule; it is not an actual
 186      part of it.  */
 187   if (sym)
 188     ++nritems;
 189
 190   return p;
 191 }
 192
 193 /* The rule currently being defined, and the previous rule.
 194    CURRENT_RULE points to the first LHS of the current rule, while
 195    PREVIOUS_RULE_END points to the *end* of the previous rule (NULL).  */
 196 static symbol_list *current_rule = NULL;
 197 static symbol_list *previous_rule_end = NULL;
 198
 199
 200 /*----------------------------------------------.
 201 | Create a new rule for LHS in to the GRAMMAR.  |
 202 `----------------------------------------------*/
 203
 204 void
 205 grammar_current_rule_begin (symbol *lhs, location loc,
 206                             named_ref *lhs_named_ref)
 207 {
 208   symbol_list* p;
 209
 210   /* Start a new rule and record its lhs.  */
 211   ++nrules;
 212   previous_rule_end = grammar_end;
 213
 214   p = grammar_symbol_append (lhs, loc);
 215   if (lhs_named_ref)
 216     {
 217       if (lhs_named_ref->id == lhs->tag)
 218         {
 219           warn_at (lhs_named_ref->loc,
 220                    _("duplicated symbol name for %s ignored"),
 221                    quote (lhs->tag));
 222           named_ref_free (lhs_named_ref);
 223         }
 224       else
 225         p->named_ref = lhs_named_ref;
 226     }
 227
 228   current_rule = grammar_end;
 229
 230   /* Mark the rule's lhs as a nonterminal if not already so.  */
 231   if (lhs->class == unknown_sym)
 232     {
 233       lhs->class = nterm_sym;
 234       lhs->number = nvars;
 235       ++nvars;
 236     }
 237   else if (lhs->class == token_sym)
 238     complain_at (loc, _("rule given for %s, which is a token"), lhs->tag);
 239 }
 240
 241
 242 /*----------------------------------------------------------------------.
 243 | A symbol should be used if either:                                    |
 244 |   1. It has a destructor.                                             |
 245 |   2. --warnings=midrule-values and the symbol is a mid-rule symbol    |
 246 |      (i.e., the generated LHS replacing a mid-rule action) that was   |
 247 |      assigned to or used, as in "exp: { $$ = 1; } { $$ = $1; }".      |
 248 `----------------------------------------------------------------------*/
 249
 250 static bool
 251 symbol_should_be_used (symbol_list const *s)
 252 {
 253   if (symbol_destructor_get (s->content.sym)->code)
 254     return true;
 255   if (warnings_flag & warnings_midrule_values)
 256     return ((s->midrule && s->midrule->action_props.is_value_used)
 257             || (s->midrule_parent_rule
 258                 && symbol_list_n_get (s->midrule_parent_rule,
 259                                       s->midrule_parent_rhs_index)
 260                      ->action_props.is_value_used));
 261   return false;
 262 }
 263
 264 /*----------------------------------------------------------------.
 265 | Check that the rule R is properly defined.  For instance, there |
 266 | should be no type clash on the default action.                  |
 267 `----------------------------------------------------------------*/
 268
 269 static void
 270 grammar_rule_check (const symbol_list *r)
 271 {
 272   /* Type check.
 273
 274      If there is an action, then there is nothing we can do: the user
 275      is allowed to shoot herself in the foot.
 276
 277      Don't worry about the default action if $$ is untyped, since $$'s
 278      value can't be used.  */
 279   if (!r->action_props.code && r->content.sym->type_name)
 280     {
 281       symbol *first_rhs = r->next->content.sym;
 282       /* If $$ is being set in default way, report if any type mismatch.  */
 283       if (first_rhs)
 284         {
 285           char const *lhs_type = r->content.sym->type_name;
 286           const char *rhs_type =
 287             first_rhs->type_name ? first_rhs->type_name : "";
 288           if (!UNIQSTR_EQ (lhs_type, rhs_type))
 289             warn_at (r->location,
 290                      _("type clash on default action: <%s> != <%s>"),
 291                      lhs_type, rhs_type);
 292         }
 293       /* Warn if there is no default for $$ but we need one.  */
 294       else
 295         warn_at (r->location,
 296                  _("empty rule for typed nonterminal, and no action"));
 297     }
 298
 299   /* Check that symbol values that should be used are in fact used.  */
 300   {
 301     symbol_list const *l = r;
 302     int n = 0;
 303     for (; l && l->content.sym; l = l->next, ++n)
 304       if (! (l->action_props.is_value_used
 305              || !symbol_should_be_used (l)
 306              /* The default action, $$ = $1, `uses' both.  */
 307              || (!r->action_props.code && (n == 0 || n == 1))))
 308         {
 309           if (n)
 310             warn_at (r->location, _("unused value: $%d"), n);
 311           else
 312             warn_at (r->location, _("unset value: $$"));
 313         }
 314   }
 315 }
 316
 317
 318 /*-------------------------------------.
 319 | End the currently being grown rule.  |
 320 `-------------------------------------*/
 321
 322 void
 323 grammar_current_rule_end (location loc)
 324 {
 325   /* Put an empty link in the list to mark the end of this rule  */
 326   grammar_symbol_append (NULL, grammar_end->location);
 327   current_rule->location = loc;
 328 }
 329
 330
 331 /*-------------------------------------------------------------------.
 332 | The previous action turns out the be a mid-rule action.  Attach it |
 333 | to the current rule, i.e., create a dummy symbol, attach it this   |
 334 | mid-rule action, and append this dummy nonterminal to the current  |
 335 | rule.                                                              |
 336 `-------------------------------------------------------------------*/
 337
 338 void
 339 grammar_midrule_action (void)
 340 {
 341   /* Since the action was written out with this rule's number, we must
 342      give the new rule this number by inserting the new rule before
 343      it.  */
 344
 345   /* Make a DUMMY nonterminal, whose location is that of the midrule
 346      action.  Create the MIDRULE.  */
 347   location dummy_location = current_rule->action_props.location;
 348   symbol *dummy = dummy_symbol_get (dummy_location);
 349   symbol_list *midrule = symbol_list_sym_new (dummy, dummy_location);
 350
 351   /* Remember named_ref of previous action */
 352   named_ref *named_ref = current_rule->action_props.named_ref;
 353
 354   /* Make a new rule, whose body is empty, before the current one, so
 355      that the action just read can belong to it.  */
 356   ++nrules;
 357   ++nritems;
 358   /* Attach its location and actions to that of the DUMMY.  */
 359   midrule->location = dummy_location;
 360   code_props_rule_action_init (&midrule->action_props,
 361                                current_rule->action_props.code,
 362                                current_rule->action_props.location,
 363                                midrule, 0);
 364   code_props_none_init (&current_rule->action_props);
 365
 366   if (previous_rule_end)
 367     previous_rule_end->next = midrule;
 368   else
 369     grammar = midrule;
 370
 371   /* End the dummy's rule.  */
 372   midrule->next = symbol_list_sym_new (NULL, dummy_location);
 373   midrule->next->next = current_rule;
 374
 375   previous_rule_end = midrule->next;
 376
 377   /* Insert the dummy nonterminal replacing the midrule action into
 378      the current rule.  Bind it to its dedicated rule.  */
 379   grammar_current_rule_symbol_append (dummy, dummy_location, named_ref);
 380   grammar_end->midrule = midrule;
 381   midrule->midrule_parent_rule = current_rule;
 382   midrule->midrule_parent_rhs_index = symbol_list_length (current_rule->next);
 383 }
 384
 385 /* Set the precedence symbol of the current rule to PRECSYM. */
 386
 387 void
 388 grammar_current_rule_prec_set (symbol *precsym, location loc)
 389 {
 390   symbol_class_set (precsym, token_sym, loc, false);
 391   if (current_rule->ruleprec)
 392     complain_at (loc, _("only one %s allowed per rule"), "%prec");
 393   current_rule->ruleprec = precsym;
 394 }
 395
 396 /* Attach dynamic precedence DPREC to the current rule. */
 397
 398 void
 399 grammar_current_rule_dprec_set (int dprec, location loc)
 400 {
 401   if (! glr_parser)
 402     warn_at (loc, _("%s affects only GLR parsers"), "%dprec");
 403   if (dprec <= 0)
 404     complain_at (loc, _("%s must be followed by positive number"), "%dprec");
 405   else if (current_rule->dprec != 0)
 406     complain_at (loc, _("only one %s allowed per rule"), "%dprec");
 407   current_rule->dprec = dprec;
 408 }
 409
 410 /* Attach a merge function NAME with argument type TYPE to current
 411    rule. */
 412
 413 void
 414 grammar_current_rule_merge_set (uniqstr name, location loc)
 415 {
 416   if (! glr_parser)
 417     warn_at (loc, _("%s affects only GLR parsers"), "%merge");
 418   if (current_rule->merger != 0)
 419     complain_at (loc, _("only one %s allowed per rule"), "%merge");
 420   current_rule->merger = get_merge_function (name);
 421   current_rule->merger_declaration_location = loc;
 422 }
 423
 424 /* Attach SYM to the current rule.  If needed, move the previous
 425    action as a mid-rule action.  */
 426
 427 void
 428 grammar_current_rule_symbol_append (symbol *sym, location loc,
 429                                     named_ref *named_ref)
 430 {
 431   symbol_list *p;
 432   if (current_rule->action_props.code)
 433     grammar_midrule_action ();
 434   p = grammar_symbol_append (sym, loc);
 435
 436   if (named_ref)
 437     {
 438        if (named_ref->id == sym->tag)
 439         {
 440           warn_at (named_ref->loc,
 441                    _("duplicated symbol name for %s ignored"),
 442                    quote (sym->tag));
 443           named_ref_free (named_ref);
 444         }
 445        else
 446          p->named_ref = named_ref;
 447     }
 448 }
 449
 450 /* Attach an ACTION to the current rule.  */
 451
 452 void
 453 grammar_current_rule_action_append (const char *action, location loc,
 454                                     named_ref *named_ref)
 455 {
 456   if (current_rule->action_props.code)
 457     grammar_midrule_action ();
 458   /* After all symbol declarations have been parsed, packgram invokes
 459      code_props_translate_code.  */
 460   code_props_rule_action_init (&current_rule->action_props, action, loc,
 461                                current_rule, named_ref);
 462 }
 463
 464 \f
 465 /*---------------------------------------------------------------.
 466 | Convert the rules into the representation using RRHS, RLHS and |
 467 | RITEM.                                                         |
 468 `---------------------------------------------------------------*/
 469
 470 static void
 471 packgram (void)
 472 {
 473   unsigned int itemno = 0;
 474   rule_number ruleno = 0;
 475   symbol_list *p = grammar;
 476
 477   ritem = xnmalloc (nritems + 1, sizeof *ritem);
 478
 479   /* This sentinel is used by build_relations in gram.c.  */
 480   *ritem++ = 0;
 481
 482   rules = xnmalloc (nrules, sizeof *rules);
 483
 484   while (p)
 485     {
 486       int rule_length = 0;
 487       symbol *ruleprec = p->ruleprec;
 488       record_merge_function_type (p->merger, p->content.sym->type_name,
 489                                   p->merger_declaration_location);
 490       rules[ruleno].user_number = ruleno;
 491       rules[ruleno].number = ruleno;
 492       rules[ruleno].lhs = p->content.sym;
 493       rules[ruleno].rhs = ritem + itemno;
 494       rules[ruleno].prec = NULL;
 495       rules[ruleno].dprec = p->dprec;
 496       rules[ruleno].merger = p->merger;
 497       rules[ruleno].precsym = NULL;
 498       rules[ruleno].location = p->location;
 499       rules[ruleno].useful = true;
 500       rules[ruleno].action = p->action_props.code;
 501       rules[ruleno].action_location = p->action_props.location;
 502
 503       /* If the midrule's $$ is set or its $n is used, remove the `$' from the
 504          symbol name so that it's a user-defined symbol so that the default
 505          %destructor and %printer apply.  */
 506       if (p->midrule_parent_rule
 507           && (p->action_props.is_value_used
 508               || symbol_list_n_get (p->midrule_parent_rule,
 509                                     p->midrule_parent_rhs_index)
 510                    ->action_props.is_value_used))
 511         p->content.sym->tag += 1;
 512
 513       /* Don't check the generated rule 0.  It has no action, so some rhs
 514          symbols may appear unused, but the parsing algorithm ensures that
 515          %destructor's are invoked appropriately.  */
 516       if (p != grammar)
 517         grammar_rule_check (p);
 518
 519       for (p = p->next; p && p->content.sym; p = p->next)
 520         {
 521           ++rule_length;
 522
 523           /* Don't allow rule_length == INT_MAX, since that might
 524              cause confusion with strtol if INT_MAX == LONG_MAX.  */
 525           if (rule_length == INT_MAX)
 526               fatal_at (rules[ruleno].location, _("rule is too long"));
 527
 528           /* item_number = symbol_number.
 529              But the former needs to contain more: negative rule numbers. */
 530           ritem[itemno++] =
 531             symbol_number_as_item_number (p->content.sym->number);
 532           /* A rule gets by default the precedence and associativity
 533              of its last token.  */
 534           if (p->content.sym->class == token_sym && default_prec)
 535             rules[ruleno].prec = p->content.sym;
 536         }
 537
 538       /* If this rule has a %prec,
 539          the specified symbol's precedence replaces the default.  */
 540       if (ruleprec)
 541         {
 542           rules[ruleno].precsym = ruleprec;
 543           rules[ruleno].prec = ruleprec;
 544         }
 545       /* An item ends by the rule number (negated).  */
 546       ritem[itemno++] = rule_number_as_item_number (ruleno);
 547       aver (itemno < ITEM_NUMBER_MAX);
 548       ++ruleno;
 549       aver (ruleno < RULE_NUMBER_MAX);
 550
 551       if (p)
 552         p = p->next;
 553     }
 554
 555   aver (itemno == nritems);
 556
 557   if (trace_flag & trace_sets)
 558     ritem_print (stderr);
 559 }
 560 \f
 561 /*------------------------------------------------------------------.
 562 | Read in the grammar specification and record it in the format     |
 563 | described in gram.h.  All actions are copied into ACTION_OBSTACK, |
 564 | in each case forming the body of a C function (YYACTION) which    |
 565 | contains a switch statement to decide which action to execute.    |
 566 `------------------------------------------------------------------*/
 567
 568 void
 569 reader (void)
 570 {
 571   /* Initialize the symbol table.  */
 572   symbols_new ();
 573
 574   /* Construct the accept symbol. */
 575   accept = symbol_get ("$accept", empty_location);
 576   accept->class = nterm_sym;
 577   accept->number = nvars++;
 578
 579   /* Construct the error token */
 580   errtoken = symbol_get ("error", empty_location);
 581   errtoken->class = token_sym;
 582   errtoken->number = ntokens++;
 583
 584   /* Construct a token that represents all undefined literal tokens.
 585      It is always token number 2.  */
 586   undeftoken = symbol_get ("$undefined", empty_location);
 587   undeftoken->class = token_sym;
 588   undeftoken->number = ntokens++;
 589
 590   gram_in = xfopen (grammar_file, "r");
 591
 592   gram__flex_debug = trace_flag & trace_scan;
 593   gram_debug = trace_flag & trace_parse;
 594   gram_scanner_initialize ();
 595   gram_parse ();
 596
 597   /* Set front-end %define variable defaults.  */
 598   muscle_percent_define_default ("lr.keep-unreachable-states", "false");
 599   {
 600     char *lr_type;
 601     /* IELR would be a better default, but LALR is historically the
 602        default.  */
 603     muscle_percent_define_default ("lr.type", "LALR");
 604     lr_type = muscle_percent_define_get ("lr.type");
 605     if (0 != strcmp (lr_type, "canonical LR"))
 606       muscle_percent_define_default ("lr.default-reductions", "all");
 607     else
 608       muscle_percent_define_default ("lr.default-reductions", "accepting");
 609     free (lr_type);
 610   }
 611
 612   /* Check front-end %define variables.  */
 613   {
 614     static char const * const values[] = {
 615       "lr.type", "LALR", "IELR", "canonical LR", NULL,
 616       "lr.default-reductions", "all", "consistent", "accepting", NULL,
 617       NULL
 618     };
 619     muscle_percent_define_check_values (values);
 620   }
 621
 622   if (! complaint_issued)
 623     check_and_convert_grammar ();
 624
 625   xfclose (gram_in);
 626 }
 627
 628
 629 /*-------------------------------------------------------------.
 630 | Check the grammar that has just been read, and convert it to |
 631 | internal form.                                               |
 632 `-------------------------------------------------------------*/
 633
 634 static void
 635 check_and_convert_grammar (void)
 636 {
 637   /* Grammar has been read.  Do some checking.  */
 638   if (nrules == 0)
 639     fatal (_("no rules in the input grammar"));
 640
 641   /* Report any undefined symbols and consider them nonterminals.  */
 642   symbols_check_defined ();
 643
 644   /* If the user did not define her ENDTOKEN, do it now. */
 645   if (!endtoken)
 646     {
 647       endtoken = symbol_get ("$end", empty_location);
 648       endtoken->class = token_sym;
 649       endtoken->number = 0;
 650       /* Value specified by POSIX.  */
 651       endtoken->user_token_number = 0;
 652     }
 653
 654   /* Find the start symbol if no %start.  */
 655   if (!start_flag)
 656     {
 657       symbol_list *node;
 658       for (node = grammar;
 659            node != NULL && symbol_is_dummy (node->content.sym);
 660            node = node->next)
 661         {
 662           for (node = node->next;
 663                node != NULL && node->content.sym != NULL;
 664                node = node->next)
 665             ;
 666         }
 667       aver (node != NULL);
 668       grammar_start_symbol_set (node->content.sym,
 669                                 node->content.sym->location);
 670     }
 671
 672   /* Insert the initial rule, whose line is that of the first rule
 673      (not that of the start symbol):
 674
 675      accept: %start EOF.  */
 676   {
 677     symbol_list *p = symbol_list_sym_new (accept, empty_location);
 678     p->location = grammar->location;
 679     p->next = symbol_list_sym_new (startsymbol, empty_location);
 680     p->next->next = symbol_list_sym_new (endtoken, empty_location);
 681     p->next->next->next = symbol_list_sym_new (NULL, empty_location);
 682     p->next->next->next->next = grammar;
 683     nrules += 1;
 684     nritems += 3;
 685     grammar = p;
 686   }
 687
 688   aver (nsyms <= SYMBOL_NUMBER_MAXIMUM && nsyms == ntokens + nvars);
 689
 690   /* Assign the symbols their symbol numbers.  Write #defines for the
 691      token symbols into FDEFINES if requested.  */
 692   symbols_pack ();
 693
 694   /* Scan rule actions after invoking symbol_check_alias_consistency (in
 695      symbols_pack above) so that token types are set correctly before the rule
 696      action type checking.
 697
 698      Before invoking grammar_rule_check (in packgram below) on any rule, make
 699      sure all actions have already been scanned in order to set `used' flags.
 700      Otherwise, checking that a midrule's $$ should be set will not always work
 701      properly because the check must forward-reference the midrule's parent
 702      rule.  For the same reason, all the `used' flags must be set before
 703      checking whether to remove `$' from any midrule symbol name (also in
 704      packgram).  */
 705   {
 706     symbol_list *sym;
 707     for (sym = grammar; sym; sym = sym->next)
 708       code_props_translate_code (&sym->action_props);
 709   }
 710
 711   /* Convert the grammar into the format described in gram.h.  */
 712   packgram ();
 713
 714   /* The grammar as a symbol_list is no longer needed. */
 715   symbol_list_free (grammar);
 716 }