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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, 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 "gdb_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_COMPLEX:
 474       oplen = 1;
 475       args = 2;
 476       break;
 477
 478     case OP_FUNCALL:
 479     case OP_F77_UNDETERMINED_ARGLIST:
 480       oplen = 3;
 481       args = 1 + longest_to_int (expr->elts[endpos - 2].longconst);
 482       break;
 483
 484     case UNOP_MAX:
 485     case UNOP_MIN:
 486       oplen = 3;
 487       break;
 488
 489    case BINOP_VAL:
 490    case UNOP_CAST:
 491    case UNOP_MEMVAL:
 492       oplen = 3;
 493       args = 1;
 494       break;
 495
 496     case UNOP_ABS:
 497     case UNOP_CAP:
 498     case UNOP_CHR:
 499     case UNOP_FLOAT:
 500     case UNOP_HIGH:
 501     case UNOP_ODD:
 502     case UNOP_ORD:
 503     case UNOP_TRUNC:
 504       oplen = 1;
 505       args = 1;
 506       break;
 507
 508     case OP_LABELED:
 509     case STRUCTOP_STRUCT:
 510     case STRUCTOP_PTR:
 511       args = 1;
 512       /* fall through */
 513     case OP_M2_STRING:
 514     case OP_STRING:
 515     case OP_EXPRSTRING:
 516       oplen = longest_to_int (expr->elts[endpos - 2].longconst);
 517       oplen = 4 + BYTES_TO_EXP_ELEM (oplen + 1);
 518       break;
 519
 520     case OP_BITSTRING:
 521       oplen = longest_to_int (expr->elts[endpos - 2].longconst);
 522       oplen = (oplen + HOST_CHAR_BIT - 1) / HOST_CHAR_BIT;
 523       oplen = 4 + BYTES_TO_EXP_ELEM (oplen);
 524       break;
 525
 526     case OP_ARRAY:
 527       oplen = 4;
 528       args = longest_to_int (expr->elts[endpos - 2].longconst);
 529       args -= longest_to_int (expr->elts[endpos - 3].longconst);
 530       args += 1;
 531       break;
 532
 533     case TERNOP_COND:
 534     case TERNOP_SLICE:
 535     case TERNOP_SLICE_COUNT:
 536       args = 3;
 537       break;
 538
 539       /* Modula-2 */
 540    case MULTI_SUBSCRIPT:
 541       oplen = 3;
 542       args = 1 + longest_to_int (expr->elts[endpos- 2].longconst);
 543       break;
 544
 545     case BINOP_ASSIGN_MODIFY:
 546       oplen = 3;
 547       args = 2;
 548       break;
 549
 550       /* C++ */
 551     case OP_THIS:
 552       oplen = 2;
 553       break;
 554
 555     default:
 556       args = 1 + (i < (int) BINOP_END);
 557     }
 558
 559   while (args > 0)
 560     {
 561       oplen += length_of_subexp (expr, endpos - oplen);
 562       args--;
 563     }
 564
 565   return oplen;
 566 }
 567
 568 /* Copy the subexpression ending just before index INEND in INEXPR
 569    into OUTEXPR, starting at index OUTBEG.
 570    In the process, convert it from suffix to prefix form.  */
 571
 572 static void
 573 prefixify_subexp (inexpr, outexpr, inend, outbeg)
 574      register struct expression *inexpr;
 575      struct expression *outexpr;
 576      register int inend;
 577      int outbeg;
 578 {
 579   register int oplen = 1;
 580   register int args = 0;
 581   register int i;
 582   int *arglens;
 583   enum exp_opcode opcode;
 584
 585   /* Compute how long the last operation is (in OPLEN),
 586      and also how many preceding subexpressions serve as
 587      arguments for it (in ARGS).  */
 588
 589   opcode = inexpr->elts[inend - 1].opcode;
 590   switch (opcode)
 591     {
 592       /* C++  */
 593     case OP_SCOPE:
 594       oplen = longest_to_int (inexpr->elts[inend - 2].longconst);
 595       oplen = 5 + BYTES_TO_EXP_ELEM (oplen + 1);
 596       break;
 597
 598     case OP_LONG:
 599     case OP_DOUBLE:
 600     case OP_VAR_VALUE:
 601       oplen = 4;
 602       break;
 603
 604     case OP_TYPE:
 605     case OP_BOOL:
 606     case OP_LAST:
 607     case OP_REGISTER:
 608     case OP_INTERNALVAR:
 609       oplen = 3;
 610       break;
 611
 612     case OP_COMPLEX:
 613       oplen = 1;
 614       args = 2;
 615       break;
 616
 617     case OP_FUNCALL:
 618     case OP_F77_UNDETERMINED_ARGLIST:
 619       oplen = 3;
 620       args = 1 + longest_to_int (inexpr->elts[inend - 2].longconst);
 621       break;
 622
 623     case UNOP_MIN:
 624     case UNOP_MAX:
 625       oplen = 3;
 626       break;
 627
 628     case UNOP_CAST:
 629     case UNOP_MEMVAL:
 630       oplen = 3;
 631       args = 1;
 632       break;
 633
 634     case UNOP_ABS:
 635     case UNOP_CAP:
 636     case UNOP_CHR:
 637     case UNOP_FLOAT:
 638     case UNOP_HIGH:
 639     case UNOP_ODD:
 640     case UNOP_ORD:
 641     case UNOP_TRUNC:
 642       oplen=1;
 643       args=1;
 644       break;
 645
 646     case STRUCTOP_STRUCT:
 647     case STRUCTOP_PTR:
 648     case OP_LABELED:
 649       args = 1;
 650       /* fall through */
 651     case OP_M2_STRING:
 652     case OP_STRING:
 653     case OP_EXPRSTRING:
 654       oplen = longest_to_int (inexpr->elts[inend - 2].longconst);
 655       oplen = 4 + BYTES_TO_EXP_ELEM (oplen + 1);
 656       break;
 657
 658     case OP_BITSTRING:
 659       oplen = longest_to_int (inexpr->elts[inend - 2].longconst);
 660       oplen = (oplen + HOST_CHAR_BIT - 1) / HOST_CHAR_BIT;
 661       oplen = 4 + BYTES_TO_EXP_ELEM (oplen);
 662       break;
 663
 664     case OP_ARRAY:
 665       oplen = 4;
 666       args = longest_to_int (inexpr->elts[inend - 2].longconst);
 667       args -= longest_to_int (inexpr->elts[inend - 3].longconst);
 668       args += 1;
 669       break;
 670
 671     case TERNOP_COND:
 672     case TERNOP_SLICE:
 673     case TERNOP_SLICE_COUNT:
 674       args = 3;
 675       break;
 676
 677     case BINOP_ASSIGN_MODIFY:
 678       oplen = 3;
 679       args = 2;
 680       break;
 681
 682       /* Modula-2 */
 683    case MULTI_SUBSCRIPT:
 684       oplen = 3;
 685       args = 1 + longest_to_int (inexpr->elts[inend - 2].longconst);
 686       break;
 687
 688       /* C++ */
 689     case OP_THIS:
 690       oplen = 2;
 691       break;
 692
 693     default:
 694       args = 1 + ((int) opcode < (int) BINOP_END);
 695     }
 696
 697   /* Copy the final operator itself, from the end of the input
 698      to the beginning of the output.  */
 699   inend -= oplen;
 700   memcpy (&outexpr->elts[outbeg], &inexpr->elts[inend],
 701           EXP_ELEM_TO_BYTES (oplen));
 702   outbeg += oplen;
 703
 704   /* Find the lengths of the arg subexpressions.  */
 705   arglens = (int *) alloca (args * sizeof (int));
 706   for (i = args - 1; i >= 0; i--)
 707     {
 708       oplen = length_of_subexp (inexpr, inend);
 709       arglens[i] = oplen;
 710       inend -= oplen;
 711     }
 712
 713   /* Now copy each subexpression, preserving the order of
 714      the subexpressions, but prefixifying each one.
 715      In this loop, inend starts at the beginning of
 716      the expression this level is working on
 717      and marches forward over the arguments.
 718      outbeg does similarly in the output.  */
 719   for (i = 0; i < args; i++)
 720     {
 721       oplen = arglens[i];
 722       inend += oplen;
 723       prefixify_subexp (inexpr, outexpr, inend, outbeg);
 724       outbeg += oplen;
 725     }
 726 }
 727 \f
 728 /* This page contains the two entry points to this file.  */
 729
 730 /* Read an expression from the string *STRINGPTR points to,
 731    parse it, and return a pointer to a  struct expression  that we malloc.
 732    Use block BLOCK as the lexical context for variable names;
 733    if BLOCK is zero, use the block of the selected stack frame.
 734    Meanwhile, advance *STRINGPTR to point after the expression,
 735    at the first nonwhite character that is not part of the expression
 736    (possibly a null character).
 737
 738    If COMMA is nonzero, stop if a comma is reached.  */
 739
 740 struct expression *
 741 parse_exp_1 (stringptr, block, comma)
 742      char **stringptr;
 743      struct block *block;
 744      int comma;
 745 {
 746   struct cleanup *old_chain;
 747
 748   lexptr = *stringptr;
 749
 750   paren_depth = 0;
 751   type_stack_depth = 0;
 752
 753   comma_terminates = comma;
 754
 755   if (lexptr == 0 || *lexptr == 0)
 756     error_no_arg ("expression to compute");
 757
 758   old_chain = make_cleanup (free_funcalls, 0);
 759   funcall_chain = 0;
 760
 761   expression_context_block = block ? block : get_selected_block ();
 762
 763   namecopy = (char *) alloca (strlen (lexptr) + 1);
 764   expout_size = 10;
 765   expout_ptr = 0;
 766   expout = (struct expression *)
 767     xmalloc (sizeof (struct expression) + EXP_ELEM_TO_BYTES (expout_size));
 768   expout->language_defn = current_language;
 769   make_cleanup (free_current_contents, &expout);
 770
 771   if (current_language->la_parser ())
 772     current_language->la_error (NULL);
 773
 774   discard_cleanups (old_chain);
 775
 776   /* Record the actual number of expression elements, and then
 777      reallocate the expression memory so that we free up any
 778      excess elements. */
 779
 780   expout->nelts = expout_ptr;
 781   expout = (struct expression *)
 782     xrealloc ((char *) expout,
 783               sizeof (struct expression) + EXP_ELEM_TO_BYTES (expout_ptr));;
 784
 785   /* Convert expression from postfix form as generated by yacc
 786      parser, to a prefix form. */
 787
 788   DUMP_EXPRESSION (expout, gdb_stdout, "before conversion to prefix form");
 789   prefixify_expression (expout);
 790   DUMP_EXPRESSION (expout, gdb_stdout, "after conversion to prefix form");
 791
 792   *stringptr = lexptr;
 793   return expout;
 794 }
 795
 796 /* Parse STRING as an expression, and complain if this fails
 797    to use up all of the contents of STRING.  */
 798
 799 struct expression *
 800 parse_expression (string)
 801      char *string;
 802 {
 803   register struct expression *exp;
 804   exp = parse_exp_1 (&string, 0, 0);
 805   if (*string)
 806     error ("Junk after end of expression.");
 807   return exp;
 808 }
 809 \f
 810 /* Stuff for maintaining a stack of types.  Currently just used by C, but
 811    probably useful for any language which declares its types "backwards".  */
 812
 813 void
 814 push_type (tp)
 815      enum type_pieces tp;
 816 {
 817   if (type_stack_depth == type_stack_size)
 818     {
 819       type_stack_size *= 2;
 820       type_stack = (union type_stack_elt *)
 821         xrealloc ((char *) type_stack, type_stack_size * sizeof (*type_stack));
 822     }
 823   type_stack[type_stack_depth++].piece = tp;
 824 }
 825
 826 void
 827 push_type_int (n)
 828      int n;
 829 {
 830   if (type_stack_depth == type_stack_size)
 831     {
 832       type_stack_size *= 2;
 833       type_stack = (union type_stack_elt *)
 834         xrealloc ((char *) type_stack, type_stack_size * sizeof (*type_stack));
 835     }
 836   type_stack[type_stack_depth++].int_val = n;
 837 }
 838
 839 enum type_pieces
 840 pop_type ()
 841 {
 842   if (type_stack_depth)
 843     return type_stack[--type_stack_depth].piece;
 844   return tp_end;
 845 }
 846
 847 int
 848 pop_type_int ()
 849 {
 850   if (type_stack_depth)
 851     return type_stack[--type_stack_depth].int_val;
 852   /* "Can't happen".  */
 853   return 0;
 854 }
 855
 856 /* Pop the type stack and return the type which corresponds to FOLLOW_TYPE
 857    as modified by all the stuff on the stack.  */
 858 struct type *
 859 follow_types (follow_type)
 860      struct type *follow_type;
 861 {
 862   int done = 0;
 863   int array_size;
 864   struct type *range_type;
 865
 866   while (!done)
 867     switch (pop_type ())
 868       {
 869       case tp_end:
 870         done = 1;
 871         break;
 872       case tp_pointer:
 873         follow_type = lookup_pointer_type (follow_type);
 874         break;
 875       case tp_reference:
 876         follow_type = lookup_reference_type (follow_type);
 877         break;
 878       case tp_array:
 879         array_size = pop_type_int ();
 880         /* FIXME-type-allocation: need a way to free this type when we are
 881            done with it.  */
 882         range_type =
 883           create_range_type ((struct type *) NULL,
 884                              builtin_type_int, 0,
 885                              array_size >= 0 ? array_size - 1 : 0);
 886         follow_type =
 887           create_array_type ((struct type *) NULL,
 888                              follow_type, range_type);
 889         if (array_size < 0)
 890           TYPE_ARRAY_UPPER_BOUND_TYPE(follow_type)
 891             = BOUND_CANNOT_BE_DETERMINED;
 892         break;
 893       case tp_function:
 894         /* FIXME-type-allocation: need a way to free this type when we are
 895            done with it.  */
 896         follow_type = lookup_function_type (follow_type);
 897         break;
 898       }
 899   return follow_type;
 900 }
 901 \f
 902 void
 903 _initialize_parse ()
 904 {
 905   type_stack_size = 80;
 906   type_stack_depth = 0;
 907   type_stack = (union type_stack_elt *)
 908     xmalloc (type_stack_size * sizeof (*type_stack));
 909
 910   msym_text_symbol_type =
 911     init_type (TYPE_CODE_FUNC, 1, 0, "<text variable, no debug info>", NULL);
 912   TYPE_TARGET_TYPE (msym_text_symbol_type) = builtin_type_int;
 913   msym_data_symbol_type =
 914     init_type (TYPE_CODE_INT, TARGET_INT_BIT / HOST_CHAR_BIT, 0,
 915                "<data variable, no debug info>", NULL);
 916   msym_unknown_symbol_type =
 917     init_type (TYPE_CODE_INT, 1, 0,
 918                "<variable (not text or data), no debug info>",
 919                NULL);
 920 }