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