src/reader.c

   1 /* Input parser for bison
   2    Copyright (C) 1984, 1986, 1989, 1992, 1998, 2000, 2001, 2002
   3    Free Software Foundation, Inc.
   4
   5    This file is part of Bison, the GNU Compiler Compiler.
   6
   7    Bison is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 2, or (at your option)
  10    any later version.
  11
  12    Bison is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with Bison; see the file COPYING.  If not, write to
  19    the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  20    Boston, MA 02111-1307, USA.  */
  21
  22
  23 #include "system.h"
  24 #include "quotearg.h"
  25 #include "quote.h"
  26 #include "getargs.h"
  27 #include "files.h"
  28 #include "symtab.h"
  29 #include "options.h"
  30 #include "gram.h"
  31 #include "complain.h"
  32 #include "output.h"
  33 #include "reader.h"
  34 #include "conflicts.h"
  35 #include "muscle_tab.h"
  36
  37 int lineno;
  38 static symbol_list *grammar = NULL;
  39 static int start_flag = 0;
  40
  41 /* Nonzero if %union has been seen.  */
  42 int typed = 0;
  43
  44 static symbol_list *
  45 symbol_list_new (symbol_t *sym)
  46 {
  47   symbol_list *res = XMALLOC (symbol_list, 1);
  48   res->next = NULL;
  49   res->sym = sym;
  50   res->line = lineno;
  51   res->action = NULL;
  52   res->action_line = 0;
  53   res->ruleprec = NULL;
  54   return res;
  55 }
  56
  57 \f
  58 /*--------------------------------------------------------------.
  59 | Get the data type (alternative in the union) of the value for |
  60 | symbol N in rule RULE.                                        |
  61 `--------------------------------------------------------------*/
  62
  63 char *
  64 get_type_name (int n, symbol_list *rule)
  65 {
  66   int i;
  67   symbol_list *rp;
  68
  69   if (n < 0)
  70     {
  71       complain (_("invalid $ value"));
  72       return NULL;
  73     }
  74
  75   rp = rule;
  76   i = 0;
  77
  78   while (i < n)
  79     {
  80       rp = rp->next;
  81       if (rp == NULL || rp->sym == NULL)
  82         {
  83           complain (_("invalid $ value"));
  84           return NULL;
  85         }
  86       ++i;
  87     }
  88
  89   return rp->sym->type_name;
  90 }
  91
  92
  93 /*-----------------------.
  94 | Set the start symbol.  |
  95 `-----------------------*/
  96
  97 void
  98 grammar_start_symbol_set (symbol_t *s)
  99 {
 100   if (start_flag)
 101     complain (_("multiple %s declarations"), "%start");
 102   else
 103     {
 104       start_flag = 1;
 105       startsymbol = s;
 106     }
 107 }
 108
 109
 110 /*----------------------------------------------------------------.
 111 | There are two prologues: one before %union, one after.  Augment |
 112 | the current one.                                                |
 113 `----------------------------------------------------------------*/
 114
 115 void
 116 prologue_augment (const char *prologue, location_t location)
 117 {
 118   struct obstack *oout =
 119     !typed ? &pre_prologue_obstack : &post_prologue_obstack;
 120
 121   if (!no_lines_flag)
 122     {
 123       obstack_fgrow2 (oout, muscle_find ("linef"),
 124                       location.first_line,
 125                       quotearg_style (c_quoting_style,
 126                                       muscle_find ("filename")));
 127     }
 128   obstack_sgrow (oout, prologue);
 129 }
 130
 131
 132
 133
 134 /*----------------------.
 135 | Handle the epilogue.  |
 136 `----------------------*/
 137
 138 void
 139 epilogue_set (const char *epilogue, location_t location)
 140 {
 141   if (!no_lines_flag)
 142     {
 143       obstack_fgrow2 (&muscle_obstack, muscle_find ("linef"),
 144                       location.first_line,
 145                       quotearg_style (c_quoting_style,
 146                                       muscle_find ("filename")));
 147     }
 148   obstack_sgrow (&muscle_obstack, epilogue);
 149   obstack_1grow (&muscle_obstack, 0);
 150   muscle_insert ("epilogue", obstack_finish (&muscle_obstack));
 151 }
 152
 153
 154 \f
 155
 156 /*-------------------------------------------------------------------.
 157 | Generate a dummy symbol, a nonterminal, whose name cannot conflict |
 158 | with the user's names.                                             |
 159 `-------------------------------------------------------------------*/
 160
 161 static symbol_t *
 162 gensym (void)
 163 {
 164   /* Incremented for each generated symbol */
 165   static int gensym_count = 0;
 166   static char buf[256];
 167
 168   symbol_t *sym;
 169
 170   sprintf (buf, "@%d", ++gensym_count);
 171   sym = getsym (buf);
 172   sym->class = nterm_sym;
 173   sym->number = nvars++;
 174   return sym;
 175 }
 176 \f
 177 /*-------------------------------------------------------------------.
 178 | Parse the input grammar into a one symbol_list structure.  Each    |
 179 | rule is represented by a sequence of symbols: the left hand side   |
 180 | followed by the contents of the right hand side, followed by a     |
 181 | null pointer instead of a symbol to terminate the rule.  The next  |
 182 | symbol is the lhs of the following rule.                           |
 183 |                                                                    |
 184 | All actions are copied out, labelled by the rule number they apply |
 185 | to.                                                                |
 186 |                                                                    |
 187 | Bison used to allow some %directives in the rules sections, but    |
 188 | this is no longer consider appropriate: (i) the documented grammar |
 189 | doesn't claim it, (ii), it would promote bad style, (iii), error   |
 190 | recovery for %directives consists in skipping the junk until a `%' |
 191 | is seen and helrp synchronizing.  This scheme is definitely wrong  |
 192 | in the rules section.                                              |
 193 `-------------------------------------------------------------------*/
 194
 195 /* The (currently) last symbol of GRAMMAR. */
 196 symbol_list *grammar_end = NULL;
 197
 198 /* Append S to the GRAMMAR. */
 199 void
 200 grammar_symbol_append (symbol_t *s)
 201 {
 202   symbol_list *p = symbol_list_new (s);
 203
 204   if (grammar_end)
 205     grammar_end->next = p;
 206   else
 207     grammar = p;
 208
 209   grammar_end = p;
 210 }
 211
 212 /* The rule currently being defined, and the previous rule.  Point to
 213    the first symbol of each list: their lhs.  */
 214 symbol_list *current_rule = NULL;
 215 symbol_list *previous_rule = NULL;
 216
 217
 218 /* Create a new rule for LHS in to the GRAMMAR. */
 219
 220 void
 221 grammar_rule_begin (symbol_t *lhs)
 222 {
 223   if (!start_flag)
 224     {
 225       startsymbol = lhs;
 226       start_flag = 1;
 227     }
 228
 229   /* Start a new rule and record its lhs.  */
 230   ++nrules;
 231   ++nritems;
 232
 233   previous_rule = grammar_end;
 234   grammar_symbol_append (lhs);
 235   current_rule = grammar_end;
 236
 237   /* Mark the rule's lhs as a nonterminal if not already so.  */
 238
 239   if (lhs->class == unknown_sym)
 240     {
 241       lhs->class = nterm_sym;
 242       lhs->number = nvars;
 243       ++nvars;
 244     }
 245   else if (lhs->class == token_sym)
 246     complain (_("rule given for %s, which is a token"), lhs->tag);
 247 }
 248
 249 /* Check that the last rule (CURRENT_RULE) is properly defined.  For
 250    instance, there should be no type clash on the default action.  */
 251
 252 static void
 253 grammar_current_rule_check (void)
 254 {
 255   symbol_t *lhs = current_rule->sym;
 256   symbol_t *first_rhs = current_rule->next->sym;
 257
 258   /* If there is an action, then there is nothing we can do: the user
 259      is allowed to shoot in her foot.  */
 260   if (current_rule->action)
 261     return;
 262
 263   /* If $$ is being set in default way, report if any type mismatch.
 264      */
 265   if (first_rhs)
 266     {
 267       const char *lhs_type = lhs->type_name       ? lhs->type_name       : "";
 268       const char *rhs_type = first_rhs->type_name ? first_rhs->type_name : "";
 269       if (strcmp (lhs_type, rhs_type))
 270         complain (_("type clash (`%s' `%s') on default action"),
 271                   lhs_type, rhs_type);
 272     }
 273   /* Warn if there is no default for $$ but we need one.  */
 274   else
 275     {
 276       if (lhs->type_name)
 277         complain (_("empty rule for typed nonterminal, and no action"));
 278     }
 279 }
 280
 281
 282 /* End the currently being grown rule. */
 283
 284 void
 285 grammar_rule_end (void)
 286 {
 287   /* Put an empty link in the list to mark the end of this rule  */
 288   grammar_symbol_append (NULL);
 289   grammar_current_rule_check ();
 290 }
 291
 292
 293 /* The previous action turns out the be a mid-rule action.  Attach it
 294    to the current rule, i.e., create a dummy symbol, attach it this
 295    mid-rule action, and append this dummy nonterminal to the current
 296    rule.  */
 297
 298 void
 299 grammar_midrule_action (void)
 300 {
 301   /* Since the action was written out with this rule's number, we must
 302      give the new rule this number by inserting the new rule before
 303      it.  */
 304
 305   /* Make a dummy nonterminal, a gensym.  */
 306   symbol_t *sdummy = gensym ();
 307   symbol_list *midrule_action = symbol_list_new (sdummy);
 308
 309   /* Make a new rule, whose body is empty, before the current one, so
 310      that the action just read can belong to it.  */
 311   ++nrules;
 312   ++nritems;
 313   /* Attach its lineno to that of the host rule.  */
 314   midrule_action->line = current_rule->line;
 315   /* Move the action from the host rule to this one.  */
 316   midrule_action->action = current_rule->action;
 317   midrule_action->action_line = current_rule->action_line;
 318   current_rule->action = NULL;
 319
 320   if (previous_rule)
 321     previous_rule->next = midrule_action;
 322   else
 323     grammar = midrule_action;
 324
 325   /* End of the rule. */
 326   previous_rule = symbol_list_new (NULL);
 327   previous_rule->next = current_rule;
 328
 329   midrule_action->next = previous_rule;
 330
 331   /* Insert the dummy generated by that rule into this rule.  */
 332   ++nritems;
 333   grammar_symbol_append (sdummy);
 334 }
 335
 336 /* Set the precedence symbol of the current rule to PRECSYM. */
 337
 338 void
 339 grammar_current_rule_prec_set (symbol_t *precsym)
 340 {
 341   if (current_rule->ruleprec)
 342     complain (_("two @prec's in a row"));
 343   current_rule->ruleprec = precsym;
 344 }
 345
 346 /* Attach a SYMBOL to the current rule.  If needed, move the previous
 347    action as a mid-rule action.  */
 348
 349 void
 350 grammar_current_rule_symbol_append (symbol_t *symbol)
 351 {
 352   if (current_rule->action)
 353     grammar_midrule_action ();
 354   ++nritems;
 355   grammar_symbol_append (symbol);
 356 }
 357
 358
 359 /* Attach an ACTION to the current rule.  If needed, move the previous
 360    action as a mid-rule action.  */
 361
 362 void
 363 grammar_current_rule_action_append (const char *action, int action_line)
 364 {
 365   if (current_rule->action)
 366     grammar_midrule_action ();
 367   current_rule->action = action;
 368   current_rule->action_line = action_line;
 369 }
 370
 371 \f
 372 /*---------------------------------------------------------------.
 373 | Convert the rules into the representation using RRHS, RLHS and |
 374 | RITEM.                                                         |
 375 `---------------------------------------------------------------*/
 376
 377 static void
 378 packgram (void)
 379 {
 380   unsigned int itemno;
 381   int ruleno;
 382   symbol_list *p;
 383
 384   ritem = XCALLOC (item_number_t, nritems);
 385   rules = XCALLOC (rule_t, nrules) - 1;
 386
 387   itemno = 0;
 388   ruleno = 1;
 389
 390   p = grammar;
 391   while (p)
 392     {
 393       symbol_t *ruleprec = p->ruleprec;
 394       rules[ruleno].user_number = ruleno;
 395       rules[ruleno].number = ruleno;
 396       rules[ruleno].lhs = p->sym;
 397       rules[ruleno].rhs = ritem + itemno;
 398       rules[ruleno].line = p->line;
 399       rules[ruleno].useful = TRUE;
 400       rules[ruleno].action = p->action;
 401       rules[ruleno].action_line = p->action_line;
 402
 403       p = p->next;
 404       while (p && p->sym)
 405         {
 406           /* item_number_t = symbol_number_t.
 407              But the former needs to contain more: negative rule numbers. */
 408           ritem[itemno++] = symbol_number_as_item_number (p->sym->number);
 409           /* A rule gets by default the precedence and associativity
 410              of the last token in it.  */
 411           if (p->sym->class == token_sym)
 412             rules[ruleno].prec = p->sym;
 413           if (p)
 414             p = p->next;
 415         }
 416
 417       /* If this rule has a %prec,
 418          the specified symbol's precedence replaces the default.  */
 419       if (ruleprec)
 420         {
 421           rules[ruleno].precsym = ruleprec;
 422           rules[ruleno].prec = ruleprec;
 423         }
 424       ritem[itemno++] = -ruleno;
 425       ++ruleno;
 426
 427       if (p)
 428         p = p->next;
 429     }
 430
 431   assert (itemno == nritems);
 432
 433   if (trace_flag)
 434     ritem_print (stderr);
 435 }
 436 \f
 437 /*------------------------------------------------------------------.
 438 | Read in the grammar specification and record it in the format     |
 439 | described in gram.h.  All actions are copied into ACTION_OBSTACK, |
 440 | in each case forming the body of a C function (YYACTION) which    |
 441 | contains a switch statement to decide which action to execute.    |
 442 `------------------------------------------------------------------*/
 443
 444 void
 445 reader (void)
 446 {
 447   gram_control_t gram_control;
 448   lineno = 1;
 449
 450   /* Initialize the symbol table.  */
 451   symbols_new ();
 452
 453   /* Construct the axiom symbol. */
 454   axiom = getsym ("$axiom");
 455   axiom->class = nterm_sym;
 456   axiom->number = nvars++;
 457
 458   /* Construct the error token */
 459   errtoken = getsym ("error");
 460   errtoken->class = token_sym;
 461   errtoken->number = ntokens++;
 462
 463   /* Construct a token that represents all undefined literal tokens.
 464      It is always token number 2.  */
 465   undeftoken = getsym ("$undefined.");
 466   undeftoken->class = token_sym;
 467   undeftoken->number = ntokens++;
 468
 469   /* Initialize the obstacks. */
 470   obstack_init (&pre_prologue_obstack);
 471   obstack_init (&post_prologue_obstack);
 472
 473   finput = xfopen (infile, "r");
 474   gram_in = finput;
 475
 476   gram_debug = !!getenv ("parse");
 477   gram__flex_debug = !!getenv ("scan");
 478   scanner_initialize ();
 479   gram_parse (&gram_control);
 480
 481   /* Grammar has been read.  Do some checking */
 482   if (nrules == 0)
 483     fatal (_("no rules in the input grammar"));
 484
 485   /* Report any undefined symbols and consider them nonterminals.  */
 486   symbols_check_defined ();
 487
 488   /* If the user did not define her EOFTOKEN, do it now. */
 489   if (!eoftoken)
 490     {
 491       eoftoken = getsym ("$");
 492       eoftoken->class = token_sym;
 493       eoftoken->number = 0;
 494       /* Value specified by POSIX.  */
 495       eoftoken->user_token_number = 0;
 496     }
 497
 498   /* Insert the initial rule, which line is that of the first rule
 499      (not that of the start symbol):
 500
 501      axiom: %start EOF.  */
 502   {
 503     symbol_list *p = symbol_list_new (axiom);
 504     p->line = grammar->line;
 505     p->next = symbol_list_new (startsymbol);
 506     p->next->next = symbol_list_new (eoftoken);
 507     p->next->next->next = symbol_list_new (NULL);
 508     p->next->next->next->next = grammar;
 509     nrules += 1;
 510     nritems += 3;
 511     grammar = p;
 512   }
 513
 514   if (nsyms > SHRT_MAX)
 515     fatal (_("too many symbols (tokens plus nonterminals); maximum %d"),
 516           SHRT_MAX);
 517
 518   assert (nsyms == ntokens + nvars);
 519
 520   xfclose (finput);
 521
 522   /* Assign the symbols their symbol numbers.  Write #defines for the
 523      token symbols into FDEFINES if requested.  */
 524   symbols_pack ();
 525
 526   /* Convert the grammar into the format described in gram.h.  */
 527   packgram ();
 528
 529   /* The grammar as a symbol_list is no longer needed. */
 530   LIST_FREE (symbol_list, grammar);
 531 }