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   struct obstack el_obstack;
 142   obstack_init (&el_obstack);
 143
 144   if (!no_lines_flag)
 145     {
 146       obstack_fgrow2 (&el_obstack, muscle_find ("linef"),
 147                       location.first_line,
 148                       quotearg_style (c_quoting_style,
 149                                       muscle_find ("filename")));
 150     }
 151   obstack_sgrow (&el_obstack, epilogue);
 152   obstack_1grow (&el_obstack, 0);
 153   muscle_insert ("epilogue", obstack_finish (&el_obstack));
 154 }
 155
 156
 157 \f
 158
 159 /*-------------------------------------------------------------------.
 160 | Generate a dummy symbol, a nonterminal, whose name cannot conflict |
 161 | with the user's names.                                             |
 162 `-------------------------------------------------------------------*/
 163
 164 static symbol_t *
 165 gensym (void)
 166 {
 167   /* Incremented for each generated symbol */
 168   static int gensym_count = 0;
 169   static char buf[256];
 170
 171   symbol_t *sym;
 172
 173   sprintf (buf, "@%d", ++gensym_count);
 174   sym = getsym (buf);
 175   sym->class = nterm_sym;
 176   sym->number = nvars++;
 177   return sym;
 178 }
 179 \f
 180 /*-------------------------------------------------------------------.
 181 | Parse the input grammar into a one symbol_list structure.  Each    |
 182 | rule is represented by a sequence of symbols: the left hand side   |
 183 | followed by the contents of the right hand side, followed by a     |
 184 | null pointer instead of a symbol to terminate the rule.  The next  |
 185 | symbol is the lhs of the following rule.                           |
 186 |                                                                    |
 187 | All actions are copied out, labelled by the rule number they apply |
 188 | to.                                                                |
 189 |                                                                    |
 190 | Bison used to allow some %directives in the rules sections, but    |
 191 | this is no longer consider appropriate: (i) the documented grammar |
 192 | doesn't claim it, (ii), it would promote bad style, (iii), error   |
 193 | recovery for %directives consists in skipping the junk until a `%' |
 194 | is seen and helrp synchronizing.  This scheme is definitely wrong  |
 195 | in the rules section.                                              |
 196 `-------------------------------------------------------------------*/
 197
 198 /* The (currently) last symbol of GRAMMAR. */
 199 symbol_list *grammar_end = NULL;
 200
 201 /* Append S to the GRAMMAR. */
 202 void
 203 grammar_symbol_append (symbol_t *s)
 204 {
 205   symbol_list *p = symbol_list_new (s);
 206
 207   if (grammar_end)
 208     grammar_end->next = p;
 209   else
 210     grammar = p;
 211
 212   grammar_end = p;
 213 }
 214
 215 /* The rule currently being defined, and the previous rule.  Point to
 216    the first symbol of each list: their lhs.  */
 217 symbol_list *current_rule = NULL;
 218 symbol_list *previous_rule = NULL;
 219
 220
 221 /* Create a new rule for LHS in to the GRAMMAR. */
 222
 223 void
 224 grammar_rule_begin (symbol_t *lhs)
 225 {
 226   if (!start_flag)
 227     {
 228       startsymbol = lhs;
 229       start_flag = 1;
 230     }
 231
 232   /* Start a new rule and record its lhs.  */
 233   ++nrules;
 234   ++nritems;
 235
 236   previous_rule = grammar_end;
 237   grammar_symbol_append (lhs);
 238   current_rule = grammar_end;
 239
 240   /* Mark the rule's lhs as a nonterminal if not already so.  */
 241
 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 (_("rule given for %s, which is a token"), lhs->tag);
 250 }
 251
 252 /* Check that the last rule (CURRENT_RULE) is properly defined.  For
 253    instance, there should be no type clash on the default action.  */
 254
 255 static void
 256 grammar_current_rule_check (void)
 257 {
 258   symbol_t *lhs = current_rule->sym;
 259   symbol_t *first_rhs = current_rule->next->sym;
 260
 261   /* If there is an action, then there is nothing we can do: the user
 262      is allowed to shoot in her foot.  */
 263   if (current_rule->action)
 264     return;
 265
 266   /* If $$ is being set in default way, report if any type mismatch.
 267      */
 268   if (first_rhs)
 269     {
 270       const char *lhs_type = lhs->type_name       ? lhs->type_name       : "";
 271       const char *rhs_type = first_rhs->type_name ? first_rhs->type_name : "";
 272       if (strcmp (lhs_type, rhs_type))
 273         complain (_("type clash (`%s' `%s') on default action"),
 274                   lhs_type, rhs_type);
 275     }
 276   /* Warn if there is no default for $$ but we need one.  */
 277   else
 278     {
 279       if (lhs->type_name)
 280         complain (_("empty rule for typed nonterminal, and no action"));
 281     }
 282 }
 283
 284
 285 /* End the currently being grown rule. */
 286
 287 void
 288 grammar_rule_end (void)
 289 {
 290   /* Put an empty link in the list to mark the end of this rule  */
 291   grammar_symbol_append (NULL);
 292   grammar_current_rule_check ();
 293 }
 294
 295
 296 /* The previous action turns out the be a mid-rule action.  Attach it
 297    to the current rule, i.e., create a dummy symbol, attach it this
 298    mid-rule action, and append this dummy nonterminal to the current
 299    rule.  */
 300
 301 void
 302 grammar_midrule_action (void)
 303 {
 304   /* Since the action was written out with this rule's number, we must
 305      give the new rule this number by inserting the new rule before
 306      it.  */
 307
 308   /* Make a dummy nonterminal, a gensym.  */
 309   symbol_t *sdummy = gensym ();
 310   symbol_list *midrule_action = symbol_list_new (sdummy);
 311
 312   /* Make a new rule, whose body is empty, before the current one, so
 313      that the action just read can belong to it.  */
 314   ++nrules;
 315   ++nritems;
 316   /* Attach its lineno to that of the host rule.  */
 317   midrule_action->line = current_rule->line;
 318   /* Move the action from the host rule to this one.  */
 319   midrule_action->action = current_rule->action;
 320   midrule_action->action_line = current_rule->action_line;
 321   current_rule->action = NULL;
 322
 323   if (previous_rule)
 324     previous_rule->next = midrule_action;
 325   else
 326     grammar = midrule_action;
 327
 328   /* End of the rule. */
 329   previous_rule = symbol_list_new (NULL);
 330   previous_rule->next = current_rule;
 331
 332   midrule_action->next = previous_rule;
 333
 334   /* Insert the dummy generated by that rule into this rule.  */
 335   ++nritems;
 336   grammar_symbol_append (sdummy);
 337 }
 338
 339 /* Set the precedence symbol of the current rule to PRECSYM. */
 340
 341 void
 342 grammar_current_rule_prec_set (symbol_t *precsym)
 343 {
 344   if (current_rule->ruleprec)
 345     complain (_("two @prec's in a row"));
 346   current_rule->ruleprec = precsym;
 347 }
 348
 349 /* Attach a SYMBOL to the current rule.  If needed, move the previous
 350    action as a mid-rule action.  */
 351
 352 void
 353 grammar_current_rule_symbol_append (symbol_t *symbol)
 354 {
 355   if (current_rule->action)
 356     grammar_midrule_action ();
 357   ++nritems;
 358   grammar_symbol_append (symbol);
 359 }
 360
 361
 362 /* Attach an ACTION to the current rule.  If needed, move the previous
 363    action as a mid-rule action.  */
 364
 365 void
 366 grammar_current_rule_action_append (const char *action, int action_line)
 367 {
 368   if (current_rule->action)
 369     grammar_midrule_action ();
 370   current_rule->action = action;
 371   current_rule->action_line = action_line;
 372 }
 373
 374 \f
 375 /*---------------------------------------------------------------.
 376 | Convert the rules into the representation using RRHS, RLHS and |
 377 | RITEM.                                                         |
 378 `---------------------------------------------------------------*/
 379
 380 static void
 381 packgram (void)
 382 {
 383   unsigned int itemno;
 384   int ruleno;
 385   symbol_list *p;
 386
 387   ritem = XCALLOC (item_number_t, nritems);
 388   rules = XCALLOC (rule_t, nrules) - 1;
 389
 390   itemno = 0;
 391   ruleno = 1;
 392
 393   p = grammar;
 394   while (p)
 395     {
 396       symbol_t *ruleprec = p->ruleprec;
 397       rules[ruleno].user_number = ruleno;
 398       rules[ruleno].number = ruleno;
 399       rules[ruleno].lhs = p->sym;
 400       rules[ruleno].rhs = ritem + itemno;
 401       rules[ruleno].line = p->line;
 402       rules[ruleno].useful = TRUE;
 403       rules[ruleno].action = p->action;
 404       rules[ruleno].action_line = p->action_line;
 405
 406       p = p->next;
 407       while (p && p->sym)
 408         {
 409           /* item_number_t = symbol_number_t.
 410              But the former needs to contain more: negative rule numbers. */
 411           ritem[itemno++] = symbol_number_as_item_number (p->sym->number);
 412           /* A rule gets by default the precedence and associativity
 413              of the last token in it.  */
 414           if (p->sym->class == token_sym)
 415             rules[ruleno].prec = p->sym;
 416           if (p)
 417             p = p->next;
 418         }
 419
 420       /* If this rule has a %prec,
 421          the specified symbol's precedence replaces the default.  */
 422       if (ruleprec)
 423         {
 424           rules[ruleno].precsym = ruleprec;
 425           rules[ruleno].prec = ruleprec;
 426         }
 427       ritem[itemno++] = -ruleno;
 428       ++ruleno;
 429
 430       if (p)
 431         p = p->next;
 432     }
 433
 434   assert (itemno == nritems);
 435
 436   if (trace_flag)
 437     ritem_print (stderr);
 438 }
 439 \f
 440 /*------------------------------------------------------------------.
 441 | Read in the grammar specification and record it in the format     |
 442 | described in gram.h.  All actions are copied into ACTION_OBSTACK, |
 443 | in each case forming the body of a C function (YYACTION) which    |
 444 | contains a switch statement to decide which action to execute.    |
 445 `------------------------------------------------------------------*/
 446
 447 void
 448 reader (void)
 449 {
 450   gram_control_t gram_control;
 451   lineno = 1;
 452
 453   /* Initialize the muscle obstack.  */
 454   obstack_init (&muscle_obstack);
 455
 456   /* Initialize the symbol table.  */
 457   symbols_new ();
 458
 459   /* Construct the axiom symbol. */
 460   axiom = getsym ("$axiom");
 461   axiom->class = nterm_sym;
 462   axiom->number = nvars++;
 463
 464   /* Construct the error token */
 465   errtoken = getsym ("error");
 466   errtoken->class = token_sym;
 467   errtoken->number = ntokens++;
 468
 469   /* Construct a token that represents all undefined literal tokens.
 470      It is always token number 2.  */
 471   undeftoken = getsym ("$undefined.");
 472   undeftoken->class = token_sym;
 473   undeftoken->number = ntokens++;
 474
 475   /* Initialize the obstacks. */
 476   obstack_init (&action_obstack);
 477   obstack_init (&output_obstack);
 478   obstack_init (&pre_prologue_obstack);
 479   obstack_init (&post_prologue_obstack);
 480
 481   finput = xfopen (infile, "r");
 482   gram_in = finput;
 483
 484   gram_debug = !!getenv ("parse");
 485   gram__flex_debug = !!getenv ("scan");
 486   scanner_initialize ();
 487   gram_parse (&gram_control);
 488
 489   /* Grammar has been read.  Do some checking */
 490   if (nrules == 0)
 491     fatal (_("no rules in the input grammar"));
 492
 493   /* Report any undefined symbols and consider them nonterminals.  */
 494   symbols_check_defined ();
 495
 496   /* If the user did not define her EOFTOKEN, do it now. */
 497   if (!eoftoken)
 498     {
 499       eoftoken = getsym ("$");
 500       eoftoken->class = token_sym;
 501       eoftoken->number = 0;
 502       /* Value specified by POSIX.  */
 503       eoftoken->user_token_number = 0;
 504     }
 505
 506   /* Insert the initial rule, which line is that of the first rule
 507      (not that of the start symbol):
 508
 509      axiom: %start EOF.  */
 510   {
 511     symbol_list *p = symbol_list_new (axiom);
 512     p->line = grammar->line;
 513     p->next = symbol_list_new (startsymbol);
 514     p->next->next = symbol_list_new (eoftoken);
 515     p->next->next->next = symbol_list_new (NULL);
 516     p->next->next->next->next = grammar;
 517     nrules += 1;
 518     nritems += 3;
 519     grammar = p;
 520   }
 521
 522   if (nsyms > SHRT_MAX)
 523     fatal (_("too many symbols (tokens plus nonterminals); maximum %d"),
 524           SHRT_MAX);
 525
 526   assert (nsyms == ntokens + nvars);
 527
 528   xfclose (finput);
 529
 530   /* Assign the symbols their symbol numbers.  Write #defines for the
 531      token symbols into FDEFINES if requested.  */
 532   symbols_pack ();
 533
 534   /* Convert the grammar into the format described in gram.h.  */
 535   packgram ();
 536
 537   /* The grammar as a symbol_list is no longer needed. */
 538   LIST_FREE (symbol_list, grammar);
 539 }