gdb/parse.c

   1 /* Parse expressions for GDB.
   2    Copyright (C) 1986, 1989, 1990, 1991, 1994 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 <string.h>
  33 #include "symtab.h"
  34 #include "gdbtypes.h"
  35 #include "frame.h"
  36 #include "expression.h"
  37 #include "value.h"
  38 #include "command.h"
  39 #include "language.h"
  40 #include "parser-defs.h"
  41 \f
  42 /* Global variables declared in parser-defs.h (and commented there).  */
  43 struct expression *expout;
  44 int expout_size;
  45 int expout_ptr;
  46 struct block *expression_context_block;
  47 struct block *innermost_block;
  48 int arglist_len;
  49 union type_stack_elt *type_stack;
  50 int type_stack_depth, type_stack_size;
  51 char *lexptr;
  52 char *namecopy;
  53 int paren_depth;
  54 int comma_terminates;
  55 \f
  56 static void
  57 free_funcalls PARAMS ((void));
  58
  59 static void
  60 prefixify_expression PARAMS ((struct expression *));
  61
  62 static int
  63 length_of_subexp PARAMS ((struct expression *, int));
  64
  65 static void
  66 prefixify_subexp PARAMS ((struct expression *, struct expression *, int, int));
  67
  68 /* Data structure for saving values of arglist_len for function calls whose
  69    arguments contain other function calls.  */
  70
  71 struct funcall
  72   {
  73     struct funcall *next;
  74     int arglist_len;
  75   };
  76
  77 static struct funcall *funcall_chain;
  78
  79 /* Assign machine-independent names to certain registers
  80    (unless overridden by the REGISTER_NAMES table) */
  81
  82 #ifdef NO_STD_REGS
  83 unsigned num_std_regs = 0;
  84 struct std_regs std_regs[1];
  85 #else
  86 struct std_regs std_regs[] = {
  87
  88 #ifdef PC_REGNUM
  89         { "pc", PC_REGNUM },
  90 #endif
  91 #ifdef FP_REGNUM
  92         { "fp", FP_REGNUM },
  93 #endif
  94 #ifdef SP_REGNUM
  95         { "sp", SP_REGNUM },
  96 #endif
  97 #ifdef PS_REGNUM
  98         { "ps", PS_REGNUM },
  99 #endif
 100
 101 };
 102
 103 unsigned num_std_regs = (sizeof std_regs / sizeof std_regs[0]);
 104
 105 #endif
 106
 107
 108 /* Begin counting arguments for a function call,
 109    saving the data about any containing call.  */
 110
 111 void
 112 start_arglist ()
 113 {
 114   register struct funcall *new;
 115
 116   new = (struct funcall *) xmalloc (sizeof (struct funcall));
 117   new->next = funcall_chain;
 118   new->arglist_len = arglist_len;
 119   arglist_len = 0;
 120   funcall_chain = new;
 121 }
 122
 123 /* Return the number of arguments in a function call just terminated,
 124    and restore the data for the containing function call.  */
 125
 126 int
 127 end_arglist ()
 128 {
 129   register int val = arglist_len;
 130   register struct funcall *call = funcall_chain;
 131   funcall_chain = call->next;
 132   arglist_len = call->arglist_len;
 133   free ((PTR)call);
 134   return val;
 135 }
 136
 137 /* Free everything in the funcall chain.
 138    Used when there is an error inside parsing.  */
 139
 140 static void
 141 free_funcalls ()
 142 {
 143   register struct funcall *call, *next;
 144
 145   for (call = funcall_chain; call; call = next)
 146     {
 147       next = call->next;
 148       free ((PTR)call);
 149     }
 150 }
 151 \f
 152 /* This page contains the functions for adding data to the  struct expression
 153    being constructed.  */
 154
 155 /* Add one element to the end of the expression.  */
 156
 157 /* To avoid a bug in the Sun 4 compiler, we pass things that can fit into
 158    a register through here */
 159
 160 void
 161 write_exp_elt (expelt)
 162      union exp_element expelt;
 163 {
 164   if (expout_ptr >= expout_size)
 165     {
 166       expout_size *= 2;
 167       expout = (struct expression *)
 168         xrealloc ((char *) expout, sizeof (struct expression)
 169                   + EXP_ELEM_TO_BYTES (expout_size));
 170     }
 171   expout->elts[expout_ptr++] = expelt;
 172 }
 173
 174 void
 175 write_exp_elt_opcode (expelt)
 176      enum exp_opcode expelt;
 177 {
 178   union exp_element tmp;
 179
 180   tmp.opcode = expelt;
 181
 182   write_exp_elt (tmp);
 183 }
 184
 185 void
 186 write_exp_elt_sym (expelt)
 187      struct symbol *expelt;
 188 {
 189   union exp_element tmp;
 190
 191   tmp.symbol = expelt;
 192
 193   write_exp_elt (tmp);
 194 }
 195
 196 void
 197 write_exp_elt_block (b)
 198      struct block *b;
 199 {
 200   union exp_element tmp;
 201   tmp.block = b;
 202   write_exp_elt (tmp);
 203 }
 204
 205 void
 206 write_exp_elt_longcst (expelt)
 207      LONGEST expelt;
 208 {
 209   union exp_element tmp;
 210
 211   tmp.longconst = expelt;
 212
 213   write_exp_elt (tmp);
 214 }
 215
 216 void
 217 write_exp_elt_dblcst (expelt)
 218      double expelt;
 219 {
 220   union exp_element tmp;
 221
 222   tmp.doubleconst = expelt;
 223
 224   write_exp_elt (tmp);
 225 }
 226
 227 void
 228 write_exp_elt_type (expelt)
 229      struct type *expelt;
 230 {
 231   union exp_element tmp;
 232
 233   tmp.type = expelt;
 234
 235   write_exp_elt (tmp);
 236 }
 237
 238 void
 239 write_exp_elt_intern (expelt)
 240      struct internalvar *expelt;
 241 {
 242   union exp_element tmp;
 243
 244   tmp.internalvar = expelt;
 245
 246   write_exp_elt (tmp);
 247 }
 248
 249 /* Add a string constant to the end of the expression.
 250
 251    String constants are stored by first writing an expression element
 252    that contains the length of the string, then stuffing the string
 253    constant itself into however many expression elements are needed
 254    to hold it, and then writing another expression element that contains
 255    the length of the string.  I.E. an expression element at each end of
 256    the string records the string length, so you can skip over the
 257    expression elements containing the actual string bytes from either
 258    end of the string.  Note that this also allows gdb to handle
 259    strings with embedded null bytes, as is required for some languages.
 260
 261    Don't be fooled by the fact that the string is null byte terminated,
 262    this is strictly for the convenience of debugging gdb itself.  Gdb
 263    Gdb does not depend up the string being null terminated, since the
 264    actual length is recorded in expression elements at each end of the
 265    string.  The null byte is taken into consideration when computing how
 266    many expression elements are required to hold the string constant, of
 267    course. */
 268
 269
 270 void
 271 write_exp_string (str)
 272      struct stoken str;
 273 {
 274   register int len = str.length;
 275   register int lenelt;
 276   register char *strdata;
 277
 278   /* Compute the number of expression elements required to hold the string
 279      (including a null byte terminator), along with one expression element
 280      at each end to record the actual string length (not including the
 281      null byte terminator). */
 282
 283   lenelt = 2 + BYTES_TO_EXP_ELEM (len + 1);
 284
 285   /* Ensure that we have enough available expression elements to store
 286      everything. */
 287
 288   if ((expout_ptr + lenelt) >= expout_size)
 289     {
 290       expout_size = max (expout_size * 2, expout_ptr + lenelt + 10);
 291       expout = (struct expression *)
 292         xrealloc ((char *) expout, (sizeof (struct expression)
 293                                     + EXP_ELEM_TO_BYTES (expout_size)));
 294     }
 295
 296   /* Write the leading length expression element (which advances the current
 297      expression element index), then write the string constant followed by a
 298      terminating null byte, and then write the trailing length expression
 299      element. */
 300
 301   write_exp_elt_longcst ((LONGEST) len);
 302   strdata = (char *) &expout->elts[expout_ptr];
 303   memcpy (strdata, str.ptr, len);
 304   *(strdata + len) = '\0';
 305   expout_ptr += lenelt - 2;
 306   write_exp_elt_longcst ((LONGEST) len);
 307 }
 308
 309 /* Add a bitstring constant to the end of the expression.
 310
 311    Bitstring constants are stored by first writing an expression element
 312    that contains the length of the bitstring (in bits), then stuffing the
 313    bitstring constant itself into however many expression elements are
 314    needed to hold it, and then writing another expression element that
 315    contains the length of the bitstring.  I.E. an expression element at
 316    each end of the bitstring records the bitstring length, so you can skip
 317    over the expression elements containing the actual bitstring bytes from
 318    either end of the bitstring. */
 319
 320 void
 321 write_exp_bitstring (str)
 322      struct stoken str;
 323 {
 324   register int bits = str.length;       /* length in bits */
 325   register int len = (bits + HOST_CHAR_BIT - 1) / HOST_CHAR_BIT;
 326   register int lenelt;
 327   register char *strdata;
 328
 329   /* Compute the number of expression elements required to hold the bitstring,
 330      along with one expression element at each end to record the actual
 331      bitstring length in bits. */
 332
 333   lenelt = 2 + BYTES_TO_EXP_ELEM (len);
 334
 335   /* Ensure that we have enough available expression elements to store
 336      everything. */
 337
 338   if ((expout_ptr + lenelt) >= expout_size)
 339     {
 340       expout_size = max (expout_size * 2, expout_ptr + lenelt + 10);
 341       expout = (struct expression *)
 342         xrealloc ((char *) expout, (sizeof (struct expression)
 343                                     + EXP_ELEM_TO_BYTES (expout_size)));
 344     }
 345
 346   /* Write the leading length expression element (which advances the current
 347      expression element index), then write the bitstring constant, and then
 348      write the trailing length expression element. */
 349
 350   write_exp_elt_longcst ((LONGEST) bits);
 351   strdata = (char *) &expout->elts[expout_ptr];
 352   memcpy (strdata, str.ptr, len);
 353   expout_ptr += lenelt - 2;
 354   write_exp_elt_longcst ((LONGEST) bits);
 355 }
 356
 357 /* Add the appropriate elements for a minimal symbol to the end of
 358    the expression.  The rationale behind passing in text_symbol_type and
 359    data_symbol_type was so that Modula-2 could pass in WORD for
 360    data_symbol_type.  Perhaps it still is useful to have those types vary
 361    based on the language, but they no longer have names like "int", so
 362    the initial rationale is gone.  */
 363
 364 static struct type *msym_text_symbol_type;
 365 static struct type *msym_data_symbol_type;
 366 static struct type *msym_unknown_symbol_type;
 367
 368 void
 369 write_exp_msymbol (msymbol, text_symbol_type, data_symbol_type)
 370      struct minimal_symbol *msymbol;
 371      struct type *text_symbol_type;
 372      struct type *data_symbol_type;
 373 {
 374   write_exp_elt_opcode (OP_LONG);
 375   write_exp_elt_type (lookup_pointer_type (builtin_type_void));
 376   write_exp_elt_longcst ((LONGEST) SYMBOL_VALUE_ADDRESS (msymbol));
 377   write_exp_elt_opcode (OP_LONG);
 378
 379   write_exp_elt_opcode (UNOP_MEMVAL);
 380   switch (msymbol -> type)
 381     {
 382     case mst_text:
 383     case mst_file_text:
 384     case mst_solib_trampoline:
 385       write_exp_elt_type (msym_text_symbol_type);
 386       break;
 387
 388     case mst_data:
 389     case mst_file_data:
 390     case mst_bss:
 391     case mst_file_bss:
 392       write_exp_elt_type (msym_data_symbol_type);
 393       break;
 394
 395     default:
 396       write_exp_elt_type (msym_unknown_symbol_type);
 397       break;
 398     }
 399   write_exp_elt_opcode (UNOP_MEMVAL);
 400 }
 401 \f
 402 /* Return a null-terminated temporary copy of the name
 403    of a string token.  */
 404
 405 char *
 406 copy_name (token)
 407      struct stoken token;
 408 {
 409   memcpy (namecopy, token.ptr, token.length);
 410   namecopy[token.length] = 0;
 411   return namecopy;
 412 }
 413 \f
 414 /* Reverse an expression from suffix form (in which it is constructed)
 415    to prefix form (in which we can conveniently print or execute it).  */
 416
 417 static void
 418 prefixify_expression (expr)
 419      register struct expression *expr;
 420 {
 421   register int len =
 422     sizeof (struct expression) + EXP_ELEM_TO_BYTES (expr->nelts);
 423   register struct expression *temp;
 424   register int inpos = expr->nelts, outpos = 0;
 425
 426   temp = (struct expression *) alloca (len);
 427
 428   /* Copy the original expression into temp.  */
 429   memcpy (temp, expr, len);
 430
 431   prefixify_subexp (temp, expr, inpos, outpos);
 432 }
 433
 434 /* Return the number of exp_elements in the subexpression of EXPR
 435    whose last exp_element is at index ENDPOS - 1 in EXPR.  */
 436
 437 static int
 438 length_of_subexp (expr, endpos)
 439      register struct expression *expr;
 440      register int endpos;
 441 {
 442   register int oplen = 1;
 443   register int args = 0;
 444   register int i;
 445
 446   if (endpos < 1)
 447     error ("?error in length_of_subexp");
 448
 449   i = (int) expr->elts[endpos - 1].opcode;
 450
 451   switch (i)
 452     {
 453       /* C++  */
 454     case OP_SCOPE:
 455       oplen = longest_to_int (expr->elts[endpos - 2].longconst);
 456       oplen = 5 + BYTES_TO_EXP_ELEM (oplen + 1);
 457       break;
 458
 459     case OP_LONG:
 460     case OP_DOUBLE:
 461     case OP_VAR_VALUE:
 462       oplen = 4;
 463       break;
 464
 465     case OP_TYPE:
 466     case OP_BOOL:
 467     case OP_LAST:
 468     case OP_REGISTER:
 469     case OP_INTERNALVAR:
 470       oplen = 3;
 471       break;
 472
 473     case OP_F77_LITERAL_COMPLEX:
 474       oplen = 1;
 475       args = 2;
 476       break;
 477
 478     case OP_F77_SUBSTR:
 479       oplen = 1;
 480       args = 2;
 481       break;
 482
 483     case OP_FUNCALL:
 484     case OP_F77_UNDETERMINED_ARGLIST:
 485       oplen = 3;
 486       args = 1 + longest_to_int (expr->elts[endpos - 2].longconst);
 487       break;
 488
 489     case UNOP_MAX:
 490     case UNOP_MIN:
 491       oplen = 3;
 492       break;
 493
 494    case BINOP_VAL:
 495    case UNOP_CAST:
 496    case UNOP_MEMVAL:
 497       oplen = 3;
 498       args = 1;
 499       break;
 500
 501     case UNOP_ABS:
 502     case UNOP_CAP:
 503     case UNOP_CHR:
 504     case UNOP_FLOAT:
 505     case UNOP_HIGH:
 506     case UNOP_ODD:
 507     case UNOP_ORD:
 508     case UNOP_TRUNC:
 509       oplen = 1;
 510       args = 1;
 511       break;
 512
 513     case STRUCTOP_STRUCT:
 514     case STRUCTOP_PTR:
 515       args = 1;
 516       /* fall through */
 517     case OP_M2_STRING:
 518     case OP_STRING:
 519       oplen = longest_to_int (expr->elts[endpos - 2].longconst);
 520       oplen = 4 + BYTES_TO_EXP_ELEM (oplen + 1);
 521       break;
 522
 523     case OP_BITSTRING:
 524       oplen = longest_to_int (expr->elts[endpos - 2].longconst);
 525       oplen = (oplen + HOST_CHAR_BIT - 1) / HOST_CHAR_BIT;
 526       oplen = 4 + BYTES_TO_EXP_ELEM (oplen);
 527       break;
 528
 529     case OP_ARRAY:
 530       oplen = 4;
 531       args = longest_to_int (expr->elts[endpos - 2].longconst);
 532       args -= longest_to_int (expr->elts[endpos - 3].longconst);
 533       args += 1;
 534       break;
 535
 536     case TERNOP_COND:
 537       args = 3;
 538       break;
 539
 540       /* Modula-2 */
 541    case MULTI_SUBSCRIPT:
 542       /* Fortran */
 543    case MULTI_F77_SUBSCRIPT:
 544       oplen = 3;
 545       args = 1 + longest_to_int (expr->elts[endpos- 2].longconst);
 546       break;
 547
 548     case BINOP_ASSIGN_MODIFY:
 549       oplen = 3;
 550       args = 2;
 551       break;
 552
 553       /* C++ */
 554     case OP_THIS:
 555       oplen = 2;
 556       break;
 557
 558     default:
 559       args = 1 + (i < (int) BINOP_END);
 560     }
 561
 562   while (args > 0)
 563     {
 564       oplen += length_of_subexp (expr, endpos - oplen);
 565       args--;
 566     }
 567
 568   return oplen;
 569 }
 570
 571 /* Copy the subexpression ending just before index INEND in INEXPR
 572    into OUTEXPR, starting at index OUTBEG.
 573    In the process, convert it from suffix to prefix form.  */
 574
 575 static void
 576 prefixify_subexp (inexpr, outexpr, inend, outbeg)
 577      register struct expression *inexpr;
 578      struct expression *outexpr;
 579      register int inend;
 580      int outbeg;
 581 {
 582   register int oplen = 1;
 583   register int args = 0;
 584   register int i;
 585   int *arglens;
 586   enum exp_opcode opcode;
 587
 588   /* Compute how long the last operation is (in OPLEN),
 589      and also how many preceding subexpressions serve as
 590      arguments for it (in ARGS).  */
 591
 592   opcode = inexpr->elts[inend - 1].opcode;
 593   switch (opcode)
 594     {
 595       /* C++  */
 596     case OP_SCOPE:
 597       oplen = longest_to_int (inexpr->elts[inend - 2].longconst);
 598       oplen = 5 + BYTES_TO_EXP_ELEM (oplen + 1);
 599       break;
 600
 601     case OP_LONG:
 602     case OP_DOUBLE:
 603     case OP_VAR_VALUE:
 604       oplen = 4;
 605       break;
 606
 607     case OP_TYPE:
 608     case OP_BOOL:
 609     case OP_LAST:
 610     case OP_REGISTER:
 611     case OP_INTERNALVAR:
 612       oplen = 3;
 613       break;
 614
 615     case OP_F77_LITERAL_COMPLEX:
 616       oplen = 1;
 617       args = 2;
 618       break;
 619
 620    case OP_F77_SUBSTR:
 621       oplen = 1;
 622       args = 2;
 623       break;
 624
 625     case OP_FUNCALL:
 626     case OP_F77_UNDETERMINED_ARGLIST:
 627       oplen = 3;
 628       args = 1 + longest_to_int (inexpr->elts[inend - 2].longconst);
 629       break;
 630
 631     case UNOP_MIN:
 632     case UNOP_MAX:
 633       oplen = 3;
 634       break;
 635
 636     case UNOP_CAST:
 637     case UNOP_MEMVAL:
 638       oplen = 3;
 639       args = 1;
 640       break;
 641
 642     case UNOP_ABS:
 643     case UNOP_CAP:
 644     case UNOP_CHR:
 645     case UNOP_FLOAT:
 646     case UNOP_HIGH:
 647     case UNOP_ODD:
 648     case UNOP_ORD:
 649     case UNOP_TRUNC:
 650       oplen=1;
 651       args=1;
 652       break;
 653
 654     case STRUCTOP_STRUCT:
 655     case STRUCTOP_PTR:
 656       args = 1;
 657       /* fall through */
 658     case OP_M2_STRING:
 659     case OP_STRING:
 660       oplen = longest_to_int (inexpr->elts[inend - 2].longconst);
 661       oplen = 4 + BYTES_TO_EXP_ELEM (oplen + 1);
 662       break;
 663
 664     case OP_BITSTRING:
 665       oplen = longest_to_int (inexpr->elts[inend - 2].longconst);
 666       oplen = (oplen + HOST_CHAR_BIT - 1) / HOST_CHAR_BIT;
 667       oplen = 4 + BYTES_TO_EXP_ELEM (oplen);
 668       break;
 669
 670     case OP_ARRAY:
 671       oplen = 4;
 672       args = longest_to_int (inexpr->elts[inend - 2].longconst);
 673       args -= longest_to_int (inexpr->elts[inend - 3].longconst);
 674       args += 1;
 675       break;
 676
 677     case TERNOP_COND:
 678       args = 3;
 679       break;
 680
 681     case BINOP_ASSIGN_MODIFY:
 682       oplen = 3;
 683       args = 2;
 684       break;
 685
 686       /* Modula-2 */
 687    case MULTI_SUBSCRIPT:
 688       /* Fortran */
 689    case MULTI_F77_SUBSCRIPT:
 690       oplen = 3;
 691       args = 1 + longest_to_int (inexpr->elts[inend - 2].longconst);
 692       break;
 693
 694       /* C++ */
 695     case OP_THIS:
 696       oplen = 2;
 697       break;
 698
 699     default:
 700       args = 1 + ((int) opcode < (int) BINOP_END);
 701     }
 702
 703   /* Copy the final operator itself, from the end of the input
 704      to the beginning of the output.  */
 705   inend -= oplen;
 706   memcpy (&outexpr->elts[outbeg], &inexpr->elts[inend],
 707           EXP_ELEM_TO_BYTES (oplen));
 708   outbeg += oplen;
 709
 710   /* Find the lengths of the arg subexpressions.  */
 711   arglens = (int *) alloca (args * sizeof (int));
 712   for (i = args - 1; i >= 0; i--)
 713     {
 714       oplen = length_of_subexp (inexpr, inend);
 715       arglens[i] = oplen;
 716       inend -= oplen;
 717     }
 718
 719   /* Now copy each subexpression, preserving the order of
 720      the subexpressions, but prefixifying each one.
 721      In this loop, inend starts at the beginning of
 722      the expression this level is working on
 723      and marches forward over the arguments.
 724      outbeg does similarly in the output.  */
 725   for (i = 0; i < args; i++)
 726     {
 727       oplen = arglens[i];
 728       inend += oplen;
 729       prefixify_subexp (inexpr, outexpr, inend, outbeg);
 730       outbeg += oplen;
 731     }
 732 }
 733 \f
 734 /* This page contains the two entry points to this file.  */
 735
 736 /* Read an expression from the string *STRINGPTR points to,
 737    parse it, and return a pointer to a  struct expression  that we malloc.
 738    Use block BLOCK as the lexical context for variable names;
 739    if BLOCK is zero, use the block of the selected stack frame.
 740    Meanwhile, advance *STRINGPTR to point after the expression,
 741    at the first nonwhite character that is not part of the expression
 742    (possibly a null character).
 743
 744    If COMMA is nonzero, stop if a comma is reached.  */
 745
 746 struct expression *
 747 parse_exp_1 (stringptr, block, comma)
 748      char **stringptr;
 749      struct block *block;
 750      int comma;
 751 {
 752   struct cleanup *old_chain;
 753
 754   lexptr = *stringptr;
 755
 756   paren_depth = 0;
 757   type_stack_depth = 0;
 758
 759   comma_terminates = comma;
 760
 761   if (lexptr == 0 || *lexptr == 0)
 762     error_no_arg ("expression to compute");
 763
 764   old_chain = make_cleanup (free_funcalls, 0);
 765   funcall_chain = 0;
 766
 767   expression_context_block = block ? block : get_selected_block ();
 768
 769   namecopy = (char *) alloca (strlen (lexptr) + 1);
 770   expout_size = 10;
 771   expout_ptr = 0;
 772   expout = (struct expression *)
 773     xmalloc (sizeof (struct expression) + EXP_ELEM_TO_BYTES (expout_size));
 774   expout->language_defn = current_language;
 775   make_cleanup (free_current_contents, &expout);
 776
 777   if (current_language->la_parser ())
 778     current_language->la_error (NULL);
 779
 780   discard_cleanups (old_chain);
 781
 782   /* Record the actual number of expression elements, and then
 783      reallocate the expression memory so that we free up any
 784      excess elements. */
 785
 786   expout->nelts = expout_ptr;
 787   expout = (struct expression *)
 788     xrealloc ((char *) expout,
 789               sizeof (struct expression) + EXP_ELEM_TO_BYTES (expout_ptr));;
 790
 791   /* Convert expression from postfix form as generated by yacc
 792      parser, to a prefix form. */
 793
 794   DUMP_EXPRESSION (expout, gdb_stdout, "before conversion to prefix form");
 795   prefixify_expression (expout);
 796   DUMP_EXPRESSION (expout, gdb_stdout, "after conversion to prefix form");
 797
 798   *stringptr = lexptr;
 799   return expout;
 800 }
 801
 802 /* Parse STRING as an expression, and complain if this fails
 803    to use up all of the contents of STRING.  */
 804
 805 struct expression *
 806 parse_expression (string)
 807      char *string;
 808 {
 809   register struct expression *exp;
 810   exp = parse_exp_1 (&string, 0, 0);
 811   if (*string)
 812     error ("Junk after end of expression.");
 813   return exp;
 814 }
 815 \f
 816 /* Stuff for maintaining a stack of types.  Currently just used by C, but
 817    probably useful for any language which declares its types "backwards".  */
 818
 819 void
 820 push_type (tp)
 821      enum type_pieces tp;
 822 {
 823   if (type_stack_depth == type_stack_size)
 824     {
 825       type_stack_size *= 2;
 826       type_stack = (union type_stack_elt *)
 827         xrealloc ((char *) type_stack, type_stack_size * sizeof (*type_stack));
 828     }
 829   type_stack[type_stack_depth++].piece = tp;
 830 }
 831
 832 void
 833 push_type_int (n)
 834      int n;
 835 {
 836   if (type_stack_depth == type_stack_size)
 837     {
 838       type_stack_size *= 2;
 839       type_stack = (union type_stack_elt *)
 840         xrealloc ((char *) type_stack, type_stack_size * sizeof (*type_stack));
 841     }
 842   type_stack[type_stack_depth++].int_val = n;
 843 }
 844
 845 enum type_pieces
 846 pop_type ()
 847 {
 848   if (type_stack_depth)
 849     return type_stack[--type_stack_depth].piece;
 850   return tp_end;
 851 }
 852
 853 int
 854 pop_type_int ()
 855 {
 856   if (type_stack_depth)
 857     return type_stack[--type_stack_depth].int_val;
 858   /* "Can't happen".  */
 859   return 0;
 860 }
 861
 862 /* Pop the type stack and return the type which corresponds to FOLLOW_TYPE
 863    as modified by all the stuff on the stack.  */
 864 struct type *
 865 follow_types (follow_type)
 866      struct type *follow_type;
 867 {
 868   int done = 0;
 869   int array_size;
 870   struct type *range_type;
 871
 872   while (!done)
 873     switch (pop_type ())
 874       {
 875       case tp_end:
 876         done = 1;
 877         break;
 878       case tp_pointer:
 879         follow_type = lookup_pointer_type (follow_type);
 880         break;
 881       case tp_reference:
 882         follow_type = lookup_reference_type (follow_type);
 883         break;
 884       case tp_array:
 885         array_size = pop_type_int ();
 886         if (array_size != -1)
 887           {
 888             range_type =
 889               create_range_type ((struct type *) NULL,
 890                                  builtin_type_int, 0,
 891                                  array_size - 1);
 892             follow_type =
 893               create_array_type ((struct type *) NULL,
 894                                  follow_type, range_type);
 895           }
 896         else
 897           follow_type = lookup_pointer_type (follow_type);
 898         break;
 899       case tp_function:
 900         follow_type = lookup_function_type (follow_type);
 901         break;
 902       }
 903   return follow_type;
 904 }
 905 \f
 906 void
 907 _initialize_parse ()
 908 {
 909   type_stack_size = 80;
 910   type_stack_depth = 0;
 911   type_stack = (union type_stack_elt *)
 912     xmalloc (type_stack_size * sizeof (*type_stack));
 913
 914   msym_text_symbol_type =
 915     init_type (TYPE_CODE_FUNC, 1, 0, "<text variable, no debug info>", NULL);
 916   TYPE_TARGET_TYPE (msym_text_symbol_type) = builtin_type_int;
 917   msym_data_symbol_type =
 918     init_type (TYPE_CODE_INT, TARGET_INT_BIT / HOST_CHAR_BIT, 0,
 919                "<data variable, no debug info>", NULL);
 920   msym_unknown_symbol_type =
 921     init_type (TYPE_CODE_INT, 1, 0,
 922                "<variable (not text or data), no debug info>",
 923                NULL);
 924 }