gdb/parse.c

   1 /* Parse expressions for GDB.
   2    Copyright (C) 1986, 1989, 1990, 1991 Free Software Foundation, Inc.
   3    Modified from expread.y by the Department of Computer Science at the
   4    State University of New York at Buffalo, 1991.
   5
   6 This file is part of GDB.
   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 2 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, write to the Free Software
  20 Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.  */
  21
  22 /* Parse an expression from text in a string,
  23    and return the result as a  struct expression  pointer.
  24    That structure contains arithmetic operations in reverse polish,
  25    with constants represented by operations that are followed by special data.
  26    See expression.h for the details of the format.
  27    What is important here is that it can be built up sequentially
  28    during the process of parsing; the lower levels of the tree always
  29    come first in the result.  */
  30
  31 #include "defs.h"
  32 #include "symtab.h"
  33 #include "gdbtypes.h"
  34 #include "frame.h"
  35 #include "expression.h"
  36 #include "value.h"
  37 #include "command.h"
  38 #include "language.h"
  39 #include "parser-defs.h"
  40
  41 static void
  42 free_funcalls PARAMS ((void));
  43
  44 static void
  45 prefixify_expression PARAMS ((struct expression *));
  46
  47 static int
  48 length_of_subexp PARAMS ((struct expression *, int));
  49
  50 static void
  51 prefixify_subexp PARAMS ((struct expression *, struct expression *, int, int));
  52
  53 /* Data structure for saving values of arglist_len for function calls whose
  54    arguments contain other function calls.  */
  55
  56 struct funcall
  57   {
  58     struct funcall *next;
  59     int arglist_len;
  60   };
  61
  62 static struct funcall *funcall_chain;
  63
  64 /* Assign machine-independent names to certain registers
  65    (unless overridden by the REGISTER_NAMES table) */
  66
  67 #ifdef NO_STD_REGS
  68 unsigned num_std_regs = 0;
  69 struct std_regs std_regs[1];
  70 #else
  71 struct std_regs std_regs[] = {
  72
  73 #ifdef PC_REGNUM
  74         { "pc", PC_REGNUM },
  75 #endif
  76 #ifdef FP_REGNUM
  77         { "fp", FP_REGNUM },
  78 #endif
  79 #ifdef SP_REGNUM
  80         { "sp", SP_REGNUM },
  81 #endif
  82 #ifdef PS_REGNUM
  83         { "ps", PS_REGNUM },
  84 #endif
  85
  86 };
  87
  88 unsigned num_std_regs = (sizeof std_regs / sizeof std_regs[0]);
  89
  90 #endif
  91
  92
  93 /* Begin counting arguments for a function call,
  94    saving the data about any containing call.  */
  95
  96 void
  97 start_arglist ()
  98 {
  99   register struct funcall *new;
 100
 101   new = (struct funcall *) xmalloc (sizeof (struct funcall));
 102   new->next = funcall_chain;
 103   new->arglist_len = arglist_len;
 104   arglist_len = 0;
 105   funcall_chain = new;
 106 }
 107
 108 /* Return the number of arguments in a function call just terminated,
 109    and restore the data for the containing function call.  */
 110
 111 int
 112 end_arglist ()
 113 {
 114   register int val = arglist_len;
 115   register struct funcall *call = funcall_chain;
 116   funcall_chain = call->next;
 117   arglist_len = call->arglist_len;
 118   free ((PTR)call);
 119   return val;
 120 }
 121
 122 /* Free everything in the funcall chain.
 123    Used when there is an error inside parsing.  */
 124
 125 static void
 126 free_funcalls ()
 127 {
 128   register struct funcall *call, *next;
 129
 130   for (call = funcall_chain; call; call = next)
 131     {
 132       next = call->next;
 133       free ((PTR)call);
 134     }
 135 }
 136 \f
 137 /* This page contains the functions for adding data to the  struct expression
 138    being constructed.  */
 139
 140 /* Add one element to the end of the expression.  */
 141
 142 /* To avoid a bug in the Sun 4 compiler, we pass things that can fit into
 143    a register through here */
 144
 145 void
 146 write_exp_elt (expelt)
 147      union exp_element expelt;
 148 {
 149   if (expout_ptr >= expout_size)
 150     {
 151       expout_size *= 2;
 152       expout = (struct expression *)
 153         xrealloc ((char *) expout, sizeof (struct expression)
 154                   + EXP_ELEM_TO_BYTES (expout_size));
 155     }
 156   expout->elts[expout_ptr++] = expelt;
 157 }
 158
 159 void
 160 write_exp_elt_opcode (expelt)
 161      enum exp_opcode expelt;
 162 {
 163   union exp_element tmp;
 164
 165   tmp.opcode = expelt;
 166
 167   write_exp_elt (tmp);
 168 }
 169
 170 void
 171 write_exp_elt_sym (expelt)
 172      struct symbol *expelt;
 173 {
 174   union exp_element tmp;
 175
 176   tmp.symbol = expelt;
 177
 178   write_exp_elt (tmp);
 179 }
 180
 181 void
 182 write_exp_elt_block (b)
 183      struct block *b;
 184 {
 185   union exp_element tmp;
 186   tmp.block = b;
 187   write_exp_elt (tmp);
 188 }
 189
 190 void
 191 write_exp_elt_longcst (expelt)
 192      LONGEST expelt;
 193 {
 194   union exp_element tmp;
 195
 196   tmp.longconst = expelt;
 197
 198   write_exp_elt (tmp);
 199 }
 200
 201 void
 202 write_exp_elt_dblcst (expelt)
 203      double expelt;
 204 {
 205   union exp_element tmp;
 206
 207   tmp.doubleconst = expelt;
 208
 209   write_exp_elt (tmp);
 210 }
 211
 212 void
 213 write_exp_elt_type (expelt)
 214      struct type *expelt;
 215 {
 216   union exp_element tmp;
 217
 218   tmp.type = expelt;
 219
 220   write_exp_elt (tmp);
 221 }
 222
 223 void
 224 write_exp_elt_intern (expelt)
 225      struct internalvar *expelt;
 226 {
 227   union exp_element tmp;
 228
 229   tmp.internalvar = expelt;
 230
 231   write_exp_elt (tmp);
 232 }
 233
 234 /* Add a string constant to the end of the expression.
 235
 236    String constants are stored by first writing an expression element
 237    that contains the length of the string, then stuffing the string
 238    constant itself into however many expression elements are needed
 239    to hold it, and then writing another expression element that contains
 240    the length of the string.  I.E. an expression element at each end of
 241    the string records the string length, so you can skip over the
 242    expression elements containing the actual string bytes from either
 243    end of the string.  Note that this also allows gdb to handle
 244    strings with embedded null bytes, as is required for some languages.
 245
 246    Don't be fooled by the fact that the string is null byte terminated,
 247    this is strictly for the convenience of debugging gdb itself.  Gdb
 248    Gdb does not depend up the string being null terminated, since the
 249    actual length is recorded in expression elements at each end of the
 250    string.  The null byte is taken into consideration when computing how
 251    many expression elements are required to hold the string constant, of
 252    course. */
 253
 254
 255 void
 256 write_exp_string (str)
 257      struct stoken str;
 258 {
 259   register int len = str.length;
 260   register int lenelt;
 261   register char *strdata;
 262
 263   /* Compute the number of expression elements required to hold the string
 264      (including a null byte terminator), along with one expression element
 265      at each end to record the actual string length (not including the
 266      null byte terminator). */
 267
 268   lenelt = 2 + BYTES_TO_EXP_ELEM (len + 1);
 269
 270   /* Ensure that we have enough available expression elements to store
 271      everything. */
 272
 273   if ((expout_ptr + lenelt) >= expout_size)
 274     {
 275       expout_size = max (expout_size * 2, expout_ptr + lenelt + 10);
 276       expout = (struct expression *)
 277         xrealloc ((char *) expout, (sizeof (struct expression)
 278                                     + EXP_ELEM_TO_BYTES (expout_size)));
 279     }
 280
 281   /* Write the leading length expression element (which advances the current
 282      expression element index), then write the string constant followed by a
 283      terminating null byte, and then write the trailing length expression
 284      element. */
 285
 286   write_exp_elt_longcst ((LONGEST) len);
 287   strdata = (char *) &expout->elts[expout_ptr];
 288   memcpy (strdata, str.ptr, len);
 289   *(strdata + len) = '\0';
 290   expout_ptr += lenelt - 2;
 291   write_exp_elt_longcst ((LONGEST) len);
 292 }
 293
 294 /* Add a bitstring constant to the end of the expression.
 295
 296    Bitstring constants are stored by first writing an expression element
 297    that contains the length of the bitstring (in bits), then stuffing the
 298    bitstring constant itself into however many expression elements are
 299    needed to hold it, and then writing another expression element that
 300    contains the length of the bitstring.  I.E. an expression element at
 301    each end of the bitstring records the bitstring length, so you can skip
 302    over the expression elements containing the actual bitstring bytes from
 303    either end of the bitstring. */
 304
 305 void
 306 write_exp_bitstring (str)
 307      struct stoken str;
 308 {
 309   register int bits = str.length;       /* length in bits */
 310   register int len = (bits + HOST_CHAR_BIT - 1) / HOST_CHAR_BIT;
 311   register int lenelt;
 312   register char *strdata;
 313
 314   /* Compute the number of expression elements required to hold the bitstring,
 315      along with one expression element at each end to record the actual
 316      bitstring length in bits. */
 317
 318   lenelt = 2 + BYTES_TO_EXP_ELEM (len);
 319
 320   /* Ensure that we have enough available expression elements to store
 321      everything. */
 322
 323   if ((expout_ptr + lenelt) >= expout_size)
 324     {
 325       expout_size = max (expout_size * 2, expout_ptr + lenelt + 10);
 326       expout = (struct expression *)
 327         xrealloc ((char *) expout, (sizeof (struct expression)
 328                                     + EXP_ELEM_TO_BYTES (expout_size)));
 329     }
 330
 331   /* Write the leading length expression element (which advances the current
 332      expression element index), then write the bitstring constant, and then
 333      write the trailing length expression element. */
 334
 335   write_exp_elt_longcst ((LONGEST) bits);
 336   strdata = (char *) &expout->elts[expout_ptr];
 337   memcpy (strdata, str.ptr, len);
 338   expout_ptr += lenelt - 2;
 339   write_exp_elt_longcst ((LONGEST) bits);
 340 }
 341 \f
 342 /* Return a null-terminated temporary copy of the name
 343    of a string token.  */
 344
 345 char *
 346 copy_name (token)
 347      struct stoken token;
 348 {
 349   memcpy (namecopy, token.ptr, token.length);
 350   namecopy[token.length] = 0;
 351   return namecopy;
 352 }
 353 \f
 354 /* Reverse an expression from suffix form (in which it is constructed)
 355    to prefix form (in which we can conveniently print or execute it).  */
 356
 357 static void
 358 prefixify_expression (expr)
 359      register struct expression *expr;
 360 {
 361   register int len =
 362     sizeof (struct expression) + EXP_ELEM_TO_BYTES (expr->nelts);
 363   register struct expression *temp;
 364   register int inpos = expr->nelts, outpos = 0;
 365
 366   temp = (struct expression *) alloca (len);
 367
 368   /* Copy the original expression into temp.  */
 369   memcpy (temp, expr, len);
 370
 371   prefixify_subexp (temp, expr, inpos, outpos);
 372 }
 373
 374 /* Return the number of exp_elements in the subexpression of EXPR
 375    whose last exp_element is at index ENDPOS - 1 in EXPR.  */
 376
 377 static int
 378 length_of_subexp (expr, endpos)
 379      register struct expression *expr;
 380      register int endpos;
 381 {
 382   register int oplen = 1;
 383   register int args = 0;
 384   register int i;
 385
 386   if (endpos < 1)
 387     error ("?error in length_of_subexp");
 388
 389   i = (int) expr->elts[endpos - 1].opcode;
 390
 391   switch (i)
 392     {
 393       /* C++  */
 394     case OP_SCOPE:
 395       oplen = longest_to_int (expr->elts[endpos - 2].longconst);
 396       oplen = 5 + BYTES_TO_EXP_ELEM (oplen + 1);
 397       break;
 398
 399     case OP_LONG:
 400     case OP_DOUBLE:
 401     case OP_VAR_VALUE:
 402       oplen = 4;
 403       break;
 404
 405     case OP_TYPE:
 406     case OP_BOOL:
 407     case OP_LAST:
 408     case OP_REGISTER:
 409     case OP_INTERNALVAR:
 410       oplen = 3;
 411       break;
 412
 413     case OP_FUNCALL:
 414       oplen = 3;
 415       args = 1 + longest_to_int (expr->elts[endpos - 2].longconst);
 416       break;
 417
 418     case UNOP_MAX:
 419     case UNOP_MIN:
 420       oplen = 3;
 421       break;
 422
 423    case BINOP_VAL:
 424    case UNOP_CAST:
 425    case UNOP_MEMVAL:
 426       oplen = 3;
 427       args = 1;
 428       break;
 429
 430     case UNOP_ABS:
 431     case UNOP_CAP:
 432     case UNOP_CHR:
 433     case UNOP_FLOAT:
 434     case UNOP_HIGH:
 435     case UNOP_ODD:
 436     case UNOP_ORD:
 437     case UNOP_TRUNC:
 438       oplen = 1;
 439       args = 1;
 440       break;
 441
 442     case STRUCTOP_STRUCT:
 443     case STRUCTOP_PTR:
 444       args = 1;
 445       /* fall through */
 446     case OP_M2_STRING:
 447     case OP_STRING:
 448       oplen = longest_to_int (expr->elts[endpos - 2].longconst);
 449       oplen = 4 + BYTES_TO_EXP_ELEM (oplen + 1);
 450       break;
 451
 452     case OP_BITSTRING:
 453       oplen = longest_to_int (expr->elts[endpos - 2].longconst);
 454       oplen = (oplen + HOST_CHAR_BIT - 1) / HOST_CHAR_BIT;
 455       oplen = 4 + BYTES_TO_EXP_ELEM (oplen);
 456       break;
 457
 458     case OP_ARRAY:
 459       oplen = 4;
 460       args = longest_to_int (expr->elts[endpos - 2].longconst);
 461       args -= longest_to_int (expr->elts[endpos - 3].longconst);
 462       args += 1;
 463       break;
 464
 465     case TERNOP_COND:
 466       args = 3;
 467       break;
 468
 469       /* Modula-2 */
 470    case MULTI_SUBSCRIPT:
 471       oplen=3;
 472       args = 1 + longest_to_int (expr->elts[endpos- 2].longconst);
 473       break;
 474
 475     case BINOP_ASSIGN_MODIFY:
 476       oplen = 3;
 477       args = 2;
 478       break;
 479
 480       /* C++ */
 481     case OP_THIS:
 482       oplen = 2;
 483       break;
 484
 485     default:
 486       args = 1 + (i < (int) BINOP_END);
 487     }
 488
 489   while (args > 0)
 490     {
 491       oplen += length_of_subexp (expr, endpos - oplen);
 492       args--;
 493     }
 494
 495   return oplen;
 496 }
 497
 498 /* Copy the subexpression ending just before index INEND in INEXPR
 499    into OUTEXPR, starting at index OUTBEG.
 500    In the process, convert it from suffix to prefix form.  */
 501
 502 static void
 503 prefixify_subexp (inexpr, outexpr, inend, outbeg)
 504      register struct expression *inexpr;
 505      struct expression *outexpr;
 506      register int inend;
 507      int outbeg;
 508 {
 509   register int oplen = 1;
 510   register int args = 0;
 511   register int i;
 512   int *arglens;
 513   enum exp_opcode opcode;
 514
 515   /* Compute how long the last operation is (in OPLEN),
 516      and also how many preceding subexpressions serve as
 517      arguments for it (in ARGS).  */
 518
 519   opcode = inexpr->elts[inend - 1].opcode;
 520   switch (opcode)
 521     {
 522       /* C++  */
 523     case OP_SCOPE:
 524       oplen = longest_to_int (inexpr->elts[inend - 2].longconst);
 525       oplen = 5 + BYTES_TO_EXP_ELEM (oplen + 1);
 526       break;
 527
 528     case OP_LONG:
 529     case OP_DOUBLE:
 530     case OP_VAR_VALUE:
 531       oplen = 4;
 532       break;
 533
 534     case OP_TYPE:
 535     case OP_BOOL:
 536     case OP_LAST:
 537     case OP_REGISTER:
 538     case OP_INTERNALVAR:
 539       oplen = 3;
 540       break;
 541
 542     case OP_FUNCALL:
 543       oplen = 3;
 544       args = 1 + longest_to_int (inexpr->elts[inend - 2].longconst);
 545       break;
 546
 547     case UNOP_MIN:
 548     case UNOP_MAX:
 549       oplen = 3;
 550       break;
 551
 552     case UNOP_CAST:
 553     case UNOP_MEMVAL:
 554       oplen = 3;
 555       args = 1;
 556       break;
 557
 558     case UNOP_ABS:
 559     case UNOP_CAP:
 560     case UNOP_CHR:
 561     case UNOP_FLOAT:
 562     case UNOP_HIGH:
 563     case UNOP_ODD:
 564     case UNOP_ORD:
 565     case UNOP_TRUNC:
 566       oplen=1;
 567       args=1;
 568       break;
 569
 570     case STRUCTOP_STRUCT:
 571     case STRUCTOP_PTR:
 572       args = 1;
 573       /* fall through */
 574     case OP_M2_STRING:
 575     case OP_STRING:
 576       oplen = longest_to_int (inexpr->elts[inend - 2].longconst);
 577       oplen = 4 + BYTES_TO_EXP_ELEM (oplen + 1);
 578       break;
 579
 580     case OP_BITSTRING:
 581       oplen = longest_to_int (inexpr->elts[inend - 2].longconst);
 582       oplen = (oplen + HOST_CHAR_BIT - 1) / HOST_CHAR_BIT;
 583       oplen = 4 + BYTES_TO_EXP_ELEM (oplen);
 584       break;
 585
 586     case OP_ARRAY:
 587       oplen = 4;
 588       args = longest_to_int (inexpr->elts[inend - 2].longconst);
 589       args -= longest_to_int (inexpr->elts[inend - 3].longconst);
 590       args += 1;
 591       break;
 592
 593     case TERNOP_COND:
 594       args = 3;
 595       break;
 596
 597     case BINOP_ASSIGN_MODIFY:
 598       oplen = 3;
 599       args = 2;
 600       break;
 601
 602       /* Modula-2 */
 603    case MULTI_SUBSCRIPT:
 604       oplen=3;
 605       args = 1 + longest_to_int (inexpr->elts[inend - 2].longconst);
 606       break;
 607
 608       /* C++ */
 609     case OP_THIS:
 610       oplen = 2;
 611       break;
 612
 613     default:
 614       args = 1 + ((int) opcode < (int) BINOP_END);
 615     }
 616
 617   /* Copy the final operator itself, from the end of the input
 618      to the beginning of the output.  */
 619   inend -= oplen;
 620   memcpy (&outexpr->elts[outbeg], &inexpr->elts[inend],
 621           EXP_ELEM_TO_BYTES (oplen));
 622   outbeg += oplen;
 623
 624   /* Find the lengths of the arg subexpressions.  */
 625   arglens = (int *) alloca (args * sizeof (int));
 626   for (i = args - 1; i >= 0; i--)
 627     {
 628       oplen = length_of_subexp (inexpr, inend);
 629       arglens[i] = oplen;
 630       inend -= oplen;
 631     }
 632
 633   /* Now copy each subexpression, preserving the order of
 634      the subexpressions, but prefixifying each one.
 635      In this loop, inend starts at the beginning of
 636      the expression this level is working on
 637      and marches forward over the arguments.
 638      outbeg does similarly in the output.  */
 639   for (i = 0; i < args; i++)
 640     {
 641       oplen = arglens[i];
 642       inend += oplen;
 643       prefixify_subexp (inexpr, outexpr, inend, outbeg);
 644       outbeg += oplen;
 645     }
 646 }
 647 \f
 648 /* This page contains the two entry points to this file.  */
 649
 650 /* Read an expression from the string *STRINGPTR points to,
 651    parse it, and return a pointer to a  struct expression  that we malloc.
 652    Use block BLOCK as the lexical context for variable names;
 653    if BLOCK is zero, use the block of the selected stack frame.
 654    Meanwhile, advance *STRINGPTR to point after the expression,
 655    at the first nonwhite character that is not part of the expression
 656    (possibly a null character).
 657
 658    If COMMA is nonzero, stop if a comma is reached.  */
 659
 660 struct expression *
 661 parse_exp_1 (stringptr, block, comma)
 662      char **stringptr;
 663      struct block *block;
 664      int comma;
 665 {
 666   struct cleanup *old_chain;
 667
 668   lexptr = *stringptr;
 669
 670   paren_depth = 0;
 671   type_stack_depth = 0;
 672
 673   comma_terminates = comma;
 674
 675   if (lexptr == 0 || *lexptr == 0)
 676     error_no_arg ("expression to compute");
 677
 678   old_chain = make_cleanup (free_funcalls, 0);
 679   funcall_chain = 0;
 680
 681   expression_context_block = block ? block : get_selected_block ();
 682
 683   namecopy = (char *) alloca (strlen (lexptr) + 1);
 684   expout_size = 10;
 685   expout_ptr = 0;
 686   expout = (struct expression *)
 687     xmalloc (sizeof (struct expression) + EXP_ELEM_TO_BYTES (expout_size));
 688   expout->language_defn = current_language;
 689   make_cleanup (free_current_contents, &expout);
 690
 691   if (current_language->la_parser ())
 692     current_language->la_error (NULL);
 693
 694   discard_cleanups (old_chain);
 695
 696   /* Record the actual number of expression elements, and then
 697      reallocate the expression memory so that we free up any
 698      excess elements. */
 699
 700   expout->nelts = expout_ptr;
 701   expout = (struct expression *)
 702     xrealloc ((char *) expout,
 703               sizeof (struct expression) + EXP_ELEM_TO_BYTES (expout_ptr));;
 704
 705   /* Convert expression from postfix form as generated by yacc
 706      parser, to a prefix form. */
 707
 708   DUMP_EXPRESSION (expout, stdout, "before conversion to prefix form");
 709   prefixify_expression (expout);
 710   DUMP_EXPRESSION (expout, stdout, "after conversion to prefix form");
 711
 712   *stringptr = lexptr;
 713   return expout;
 714 }
 715
 716 /* Parse STRING as an expression, and complain if this fails
 717    to use up all of the contents of STRING.  */
 718
 719 struct expression *
 720 parse_expression (string)
 721      char *string;
 722 {
 723   register struct expression *exp;
 724   exp = parse_exp_1 (&string, 0, 0);
 725   if (*string)
 726     error ("Junk after end of expression.");
 727   return exp;
 728 }
 729
 730 void
 731 push_type (tp)
 732      enum type_pieces tp;
 733 {
 734   if (type_stack_depth == type_stack_size)
 735     {
 736       type_stack_size *= 2;
 737       type_stack = (union type_stack_elt *)
 738         xrealloc ((char *) type_stack, type_stack_size * sizeof (*type_stack));
 739     }
 740   type_stack[type_stack_depth++].piece = tp;
 741 }
 742
 743 void
 744 push_type_int (n)
 745      int n;
 746 {
 747   if (type_stack_depth == type_stack_size)
 748     {
 749       type_stack_size *= 2;
 750       type_stack = (union type_stack_elt *)
 751         xrealloc ((char *) type_stack, type_stack_size * sizeof (*type_stack));
 752     }
 753   type_stack[type_stack_depth++].int_val = n;
 754 }
 755
 756 enum type_pieces
 757 pop_type ()
 758 {
 759   if (type_stack_depth)
 760     return type_stack[--type_stack_depth].piece;
 761   return tp_end;
 762 }
 763
 764 int
 765 pop_type_int ()
 766 {
 767   if (type_stack_depth)
 768     return type_stack[--type_stack_depth].int_val;
 769   /* "Can't happen".  */
 770   return 0;
 771 }
 772
 773 void
 774 _initialize_parse ()
 775 {
 776   type_stack_size = 80;
 777   type_stack_depth = 0;
 778   type_stack = (union type_stack_elt *)
 779     xmalloc (type_stack_size * sizeof (*type_stack));
 780 }