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, int 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, quotearg_style (c_quoting_style,
 125                                                 muscle_find ("filename")));
 126     }
 127   obstack_sgrow (oout, prologue);
 128 }
 129
 130
 131
 132
 133 /*----------------------.
 134 | Handle the epilogue.  |
 135 `----------------------*/
 136
 137 void
 138 epilogue_set (const char *epilogue, int location)
 139 {
 140   struct obstack el_obstack;
 141   obstack_init (&el_obstack);
 142
 143   if (!no_lines_flag)
 144     {
 145       obstack_fgrow2 (&el_obstack, muscle_find ("linef"),
 146                       location, quotearg_style (c_quoting_style,
 147                                                 muscle_find ("filename")));
 148     }
 149   obstack_sgrow (&el_obstack, epilogue);
 150   obstack_1grow (&el_obstack, 0);
 151   muscle_insert ("epilogue", obstack_finish (&el_obstack));
 152 }
 153
 154
 155 \f
 156
 157 /*-------------------------------------------------------------------.
 158 | Generate a dummy symbol, a nonterminal, whose name cannot conflict |
 159 | with the user's names.                                             |
 160 `-------------------------------------------------------------------*/
 161
 162 static symbol_t *
 163 gensym (void)
 164 {
 165   /* Incremented for each generated symbol */
 166   static int gensym_count = 0;
 167   static char buf[256];
 168
 169   symbol_t *sym;
 170
 171   sprintf (buf, "@%d", ++gensym_count);
 172   sym = getsym (buf);
 173   sym->class = nterm_sym;
 174   sym->number = nvars++;
 175   return sym;
 176 }
 177 \f
 178 /*-------------------------------------------------------------------.
 179 | Parse the input grammar into a one symbol_list structure.  Each    |
 180 | rule is represented by a sequence of symbols: the left hand side   |
 181 | followed by the contents of the right hand side, followed by a     |
 182 | null pointer instead of a symbol to terminate the rule.  The next  |
 183 | symbol is the lhs of the following rule.                           |
 184 |                                                                    |
 185 | All actions are copied out, labelled by the rule number they apply |
 186 | to.                                                                |
 187 |                                                                    |
 188 | Bison used to allow some %directives in the rules sections, but    |
 189 | this is no longer consider appropriate: (i) the documented grammar |
 190 | doesn't claim it, (ii), it would promote bad style, (iii), error   |
 191 | recovery for %directives consists in skipping the junk until a `%' |
 192 | is seen and helrp synchronizing.  This scheme is definitely wrong  |
 193 | in the rules section.                                              |
 194 `-------------------------------------------------------------------*/
 195
 196 /* The (currently) last symbol of GRAMMAR. */
 197 symbol_list *grammar_end = NULL;
 198
 199 /* Append S to the GRAMMAR. */
 200 void
 201 grammar_symbol_append (symbol_t *s)
 202 {
 203   symbol_list *p = symbol_list_new (s);
 204
 205   if (grammar_end)
 206     grammar_end->next = p;
 207   else
 208     grammar = p;
 209
 210   grammar_end = p;
 211 }
 212
 213 /* The rule currently being defined, and the previous rule.  Point to
 214    the first symbol of each list: their lhs.  */
 215 symbol_list *current_rule = NULL;
 216 symbol_list *previous_rule = NULL;
 217
 218
 219 /* Create a new rule for LHS in to the GRAMMAR. */
 220
 221 void
 222 grammar_rule_begin (symbol_t *lhs)
 223 {
 224   if (!start_flag)
 225     {
 226       startsymbol = lhs;
 227       start_flag = 1;
 228     }
 229
 230   /* Start a new rule and record its lhs.  */
 231   ++nrules;
 232   ++nritems;
 233
 234   previous_rule = grammar_end;
 235   grammar_symbol_append (lhs);
 236   current_rule = grammar_end;
 237
 238   /* Mark the rule's lhs as a nonterminal if not already so.  */
 239
 240   if (lhs->class == unknown_sym)
 241     {
 242       lhs->class = nterm_sym;
 243       lhs->number = nvars;
 244       ++nvars;
 245     }
 246   else if (lhs->class == token_sym)
 247     complain (_("rule given for %s, which is a token"), lhs->tag);
 248 }
 249
 250 /* Check that the last rule (CURRENT_RULE) is properly defined.  For
 251    instance, there should be no type clash on the default action.  */
 252
 253 static void
 254 grammar_current_rule_check (void)
 255 {
 256   symbol_t *lhs = current_rule->sym;
 257   symbol_t *first_rhs = current_rule->next->sym;
 258
 259   /* If there is an action, then there is nothing we can do: the user
 260      is allowed to shoot in her foot.  */
 261   if (current_rule->action)
 262     return;
 263
 264   /* If $$ is being set in default way, report if any type mismatch.
 265      */
 266   if (first_rhs)
 267     {
 268       const char *lhs_type = lhs->type_name       ? lhs->type_name       : "";
 269       const char *rhs_type = first_rhs->type_name ? first_rhs->type_name : "";
 270       if (strcmp (lhs_type, rhs_type))
 271         complain (_("type clash (`%s' `%s') on default action"),
 272                   lhs_type, rhs_type);
 273     }
 274   /* Warn if there is no default for $$ but we need one.  */
 275   else
 276     {
 277       if (lhs->type_name)
 278         complain (_("empty rule for typed nonterminal, and no action"));
 279     }
 280 }
 281
 282
 283 /* End the currently being grown rule. */
 284
 285 void
 286 grammar_rule_end (void)
 287 {
 288   /* Put an empty link in the list to mark the end of this rule  */
 289   grammar_symbol_append (NULL);
 290   grammar_current_rule_check ();
 291 }
 292
 293
 294 /* The previous action turns out the be a mid-rule action.  Attach it
 295    to the current rule, i.e., create a dummy symbol, attach it this
 296    mid-rule action, and append this dummy nonterminal to the current
 297    rule.  */
 298
 299 void
 300 grammar_midrule_action (void)
 301 {
 302   /* Since the action was written out with this rule's number, we must
 303      give the new rule this number by inserting the new rule before
 304      it.  */
 305
 306   /* Make a dummy nonterminal, a gensym.  */
 307   symbol_t *sdummy = gensym ();
 308   symbol_list *midrule_action = symbol_list_new (sdummy);
 309
 310   /* Make a new rule, whose body is empty, before the current one, so
 311      that the action just read can belong to it.  */
 312   ++nrules;
 313   ++nritems;
 314   /* Attach its lineno to that of the host rule.  */
 315   midrule_action->line = current_rule->line;
 316   /* Move the action from the host rule to this one.  */
 317   midrule_action->action = current_rule->action;
 318   midrule_action->action_line = current_rule->action_line;
 319   current_rule->action = NULL;
 320
 321   if (previous_rule)
 322     previous_rule->next = midrule_action;
 323   else
 324     grammar = midrule_action;
 325
 326   /* End of the rule. */
 327   previous_rule = symbol_list_new (NULL);
 328   previous_rule->next = current_rule;
 329
 330   midrule_action->next = previous_rule;
 331
 332   /* Insert the dummy generated by that rule into this rule.  */
 333   ++nritems;
 334   grammar_symbol_append (sdummy);
 335 }
 336
 337 /* Set the precedence symbol of the current rule to PRECSYM. */
 338
 339 void
 340 grammar_current_rule_prec_set (symbol_t *precsym)
 341 {
 342   if (current_rule->ruleprec)
 343     complain (_("two @prec's in a row"));
 344   current_rule->ruleprec = precsym;
 345 }
 346
 347 /* Attach a SYMBOL to the current rule.  If needed, move the previous
 348    action as a mid-rule action.  */
 349
 350 void
 351 grammar_current_rule_symbol_append (symbol_t *symbol)
 352 {
 353   if (current_rule->action)
 354     grammar_midrule_action ();
 355   ++nritems;
 356   grammar_symbol_append (symbol);
 357 }
 358
 359
 360 /* Attach an ACTION to the current rule.  If needed, move the previous
 361    action as a mid-rule action.  */
 362
 363 void
 364 grammar_current_rule_action_append (const char *action, int action_line)
 365 {
 366   if (current_rule->action)
 367     grammar_midrule_action ();
 368   current_rule->action = action;
 369   current_rule->action_line = action_line;
 370 }
 371
 372 \f
 373 /*---------------------------------------------------------------.
 374 | Convert the rules into the representation using RRHS, RLHS and |
 375 | RITEM.                                                         |
 376 `---------------------------------------------------------------*/
 377
 378 static void
 379 packgram (void)
 380 {
 381   unsigned int itemno;
 382   int ruleno;
 383   symbol_list *p;
 384
 385   ritem = XCALLOC (item_number_t, nritems);
 386   rules = XCALLOC (rule_t, nrules) - 1;
 387
 388   itemno = 0;
 389   ruleno = 1;
 390
 391   p = grammar;
 392   while (p)
 393     {
 394       symbol_t *ruleprec = p->ruleprec;
 395       rules[ruleno].user_number = ruleno;
 396       rules[ruleno].number = ruleno;
 397       rules[ruleno].lhs = p->sym;
 398       rules[ruleno].rhs = ritem + itemno;
 399       rules[ruleno].line = p->line;
 400       rules[ruleno].useful = TRUE;
 401       rules[ruleno].action = p->action;
 402       rules[ruleno].action_line = p->action_line;
 403
 404       p = p->next;
 405       while (p && p->sym)
 406         {
 407           /* item_number_t = symbol_number_t.
 408              But the former needs to contain more: negative rule numbers. */
 409           ritem[itemno++] = symbol_number_as_item_number (p->sym->number);
 410           /* A rule gets by default the precedence and associativity
 411              of the last token in it.  */
 412           if (p->sym->class == token_sym)
 413             rules[ruleno].prec = p->sym;
 414           if (p)
 415             p = p->next;
 416         }
 417
 418       /* If this rule has a %prec,
 419          the specified symbol's precedence replaces the default.  */
 420       if (ruleprec)
 421         {
 422           rules[ruleno].precsym = ruleprec;
 423           rules[ruleno].prec = ruleprec;
 424         }
 425       ritem[itemno++] = -ruleno;
 426       ++ruleno;
 427
 428       if (p)
 429         p = p->next;
 430     }
 431
 432   assert (itemno == nritems);
 433
 434   if (trace_flag)
 435     ritem_print (stderr);
 436 }
 437 \f
 438 /*------------------------------------------------------------------.
 439 | Read in the grammar specification and record it in the format     |
 440 | described in gram.h.  All actions are copied into ACTION_OBSTACK, |
 441 | in each case forming the body of a C function (YYACTION) which    |
 442 | contains a switch statement to decide which action to execute.    |
 443 `------------------------------------------------------------------*/
 444
 445 void
 446 reader (void)
 447 {
 448   gram_control_t gram_control;
 449   lineno = 1;
 450
 451   /* Initialize the muscle obstack.  */
 452   obstack_init (&muscle_obstack);
 453
 454   /* Initialize the symbol table.  */
 455   symbols_new ();
 456
 457   /* Construct the axiom symbol. */
 458   axiom = getsym ("$axiom");
 459   axiom->class = nterm_sym;
 460   axiom->number = nvars++;
 461
 462   /* Construct the error token */
 463   errtoken = getsym ("error");
 464   errtoken->class = token_sym;
 465   errtoken->number = ntokens++;
 466
 467   /* Construct a token that represents all undefined literal tokens.
 468      It is always token number 2.  */
 469   undeftoken = getsym ("$undefined.");
 470   undeftoken->class = token_sym;
 471   undeftoken->number = ntokens++;
 472
 473   /* Initialize the obstacks. */
 474   obstack_init (&action_obstack);
 475   obstack_init (&output_obstack);
 476   obstack_init (&pre_prologue_obstack);
 477   obstack_init (&post_prologue_obstack);
 478
 479   finput = xfopen (infile, "r");
 480   gram_in = finput;
 481
 482   gram_debug = !!getenv ("parse");
 483   gram__flex_debug = !!getenv ("scan");
 484   scanner_initialize ();
 485   gram_parse (&gram_control);
 486
 487   /* Grammar has been read.  Do some checking */
 488   if (nrules == 0)
 489     fatal (_("no rules in the input grammar"));
 490
 491   /* Report any undefined symbols and consider them nonterminals.  */
 492   symbols_check_defined ();
 493
 494   /* If the user did not define her EOFTOKEN, do it now. */
 495   if (!eoftoken)
 496     {
 497       eoftoken = getsym ("$");
 498       eoftoken->class = token_sym;
 499       eoftoken->number = 0;
 500       /* Value specified by POSIX.  */
 501       eoftoken->user_token_number = 0;
 502     }
 503
 504   /* Insert the initial rule, which line is that of the first rule
 505      (not that of the start symbol):
 506
 507      axiom: %start EOF.  */
 508   {
 509     symbol_list *p = symbol_list_new (axiom);
 510     p->line = grammar->line;
 511     p->next = symbol_list_new (startsymbol);
 512     p->next->next = symbol_list_new (eoftoken);
 513     p->next->next->next = symbol_list_new (NULL);
 514     p->next->next->next->next = grammar;
 515     nrules += 1;
 516     nritems += 3;
 517     grammar = p;
 518   }
 519
 520   if (nsyms > SHRT_MAX)
 521     fatal (_("too many symbols (tokens plus nonterminals); maximum %d"),
 522           SHRT_MAX);
 523
 524   assert (nsyms == ntokens + nvars);
 525
 526   xfclose (finput);
 527
 528   /* Assign the symbols their symbol numbers.  Write #defines for the
 529      token symbols into FDEFINES if requested.  */
 530   symbols_pack ();
 531
 532   /* Convert the grammar into the format described in gram.h.  */
 533   packgram ();
 534
 535   /* The grammar as a symbol_list is no longer needed. */
 536   LIST_FREE (symbol_list, grammar);
 537 }