libobjc/encoding.c

   1 /* Encoding of types for Objective C.
   2    Copyright (C) 1993, 1995, 1996, 1997, 1998, 2000, 2002, 2004
   3    Free Software Foundation, Inc.
   4    Contributed by Kresten Krab Thorup
   5    Bitfield support by Ovidiu Predescu
   6
   7 This file is part of GCC.
   8
   9 GCC is free software; you can redistribute it and/or modify
  10 it under the terms of the GNU General Public License as published by
  11 the Free Software Foundation; either version 2, or (at your option)
  12 any later version.
  13
  14 GCC is distributed in the hope that it will be useful,
  15 but WITHOUT ANY WARRANTY; without even the implied warranty of
  16 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17 GNU General Public License for more details.
  18
  19 You should have received a copy of the GNU General Public License
  20 along with GCC; see the file COPYING.  If not, write to
  21 the Free Software Foundation, 51 Franklin Street, Fifth Floor,
  22 Boston, MA 02110-1301, USA.  */
  23
  24 /* As a special exception, if you link this library with files
  25    compiled with GCC to produce an executable, this does not cause
  26    the resulting executable to be covered by the GNU General Public License.
  27    This exception does not however invalidate any other reasons why
  28    the executable file might be covered by the GNU General Public License.  */
  29
  30 /* FIXME: This file has no business including tm.h.  */
  31
  32 #include "tconfig.h"
  33 #include "coretypes.h"
  34 #include "tm.h"
  35 #include "objc/objc-api.h"
  36 #include "objc/encoding.h"
  37 #include <stdlib.h>
  38
  39 #undef  MAX
  40 #define MAX(X, Y)                    \
  41   ({ typeof (X) __x = (X), __y = (Y); \
  42      (__x > __y ? __x : __y); })
  43
  44 #undef  MIN
  45 #define MIN(X, Y)                    \
  46   ({ typeof (X) __x = (X), __y = (Y); \
  47      (__x < __y ? __x : __y); })
  48
  49 #undef  ROUND
  50 #define ROUND(V, A) \
  51   ({ typeof (V) __v = (V); typeof (A) __a = (A); \
  52      __a * ((__v+__a - 1)/__a); })
  53
  54
  55 /* Various hacks for objc_layout_record. These are used by the target
  56    macros. */
  57
  58 #define TREE_CODE(TYPE) *(TYPE)
  59 #define TREE_TYPE(TREE) (TREE)
  60
  61 #define RECORD_TYPE     _C_STRUCT_B
  62 #define UNION_TYPE      _C_UNION_B
  63 #define QUAL_UNION_TYPE _C_UNION_B
  64 #define ARRAY_TYPE      _C_ARY_B
  65
  66 #define REAL_TYPE       _C_DBL
  67
  68 #define VECTOR_TYPE     _C_VECTOR
  69
  70 #define TYPE_FIELDS(TYPE)           ({const char *_field = (TYPE)+1; \
  71     while (*_field != _C_STRUCT_E && *_field != _C_STRUCT_B \
  72            && *_field != _C_UNION_B && *_field++ != '=') \
  73     /* do nothing */; \
  74     _field;})
  75
  76 #define DECL_MODE(TYPE) *(TYPE)
  77 #define TYPE_MODE(TYPE) *(TYPE)
  78
  79 #define DFmode          _C_DBL
  80
  81 #define get_inner_array_type(TYPE)      ({const char *_field = (TYPE); \
  82   while (*_field == _C_ARY_B)\
  83     {\
  84       while (isdigit ((unsigned char)*++_field))\
  85         ;\
  86     }\
  87     _field;})
  88
  89 /* Some ports (eg ARM) allow the structure size boundary to be
  90    selected at compile-time.  We override the normal definition with
  91    one that has a constant value for this compilation.  */
  92 #ifndef BITS_PER_UNIT
  93 #define BITS_PER_UNIT 8
  94 #endif
  95 #undef  STRUCTURE_SIZE_BOUNDARY
  96 #define STRUCTURE_SIZE_BOUNDARY (BITS_PER_UNIT * sizeof (struct{char a;}))
  97
  98 /* Some ROUND_TYPE_ALIGN macros use TARGET_foo, and consequently
  99    target_flags.  Define a dummy entry here to so we don't die.
 100    We have to rename it because target_flags may already have been
 101    declared extern.  */
 102 #define target_flags not_target_flags
 103 static int __attribute__ ((__unused__)) not_target_flags = 0;
 104
 105 /* Some ROUND_TYPE_ALIGN use ALTIVEC_VECTOR_MODE (rs6000 darwin).
 106    Define a dummy ALTIVEC_VECTOR_MODE so it will not die.  */
 107 #undef ALTIVEC_VECTOR_MODE
 108 #define ALTIVEC_VECTOR_MODE(MODE) (0)
 109
 110
 111 /*  FIXME: while this file has no business including tm.h, this
 112     definitely has no business defining this macro but it
 113     is only way around without really rewritting this file,
 114     should look after the branch of 3.4 to fix this.  */
 115 #define rs6000_special_round_type_align(STRUCT, COMPUTED, SPECIFIED)    \
 116   ({ const char *_fields = TYPE_FIELDS (STRUCT);                                \
 117   ((_fields != 0                                                        \
 118     && TYPE_MODE (TREE_CODE (TREE_TYPE (_fields)) == ARRAY_TYPE         \
 119                     ? get_inner_array_type (_fields)                    \
 120                     : TREE_TYPE (_fields)) == DFmode)                   \
 121    ? MAX (MAX (COMPUTED, SPECIFIED), 64)                                \
 122    : MAX (COMPUTED, SPECIFIED));})
 123
 124 /*
 125   return the size of an object specified by type
 126 */
 127
 128 int
 129 objc_sizeof_type (const char *type)
 130 {
 131   /* Skip the variable name if any */
 132   if (*type == '"')
 133     {
 134       for (type++; *type++ != '"';)
 135         /* do nothing */;
 136     }
 137
 138   switch (*type) {
 139   case _C_BOOL:
 140     return sizeof (_Bool);
 141     break;
 142
 143   case _C_ID:
 144     return sizeof (id);
 145     break;
 146
 147   case _C_CLASS:
 148     return sizeof (Class);
 149     break;
 150
 151   case _C_SEL:
 152     return sizeof (SEL);
 153     break;
 154
 155   case _C_CHR:
 156     return sizeof (char);
 157     break;
 158
 159   case _C_UCHR:
 160     return sizeof (unsigned char);
 161     break;
 162
 163   case _C_SHT:
 164     return sizeof (short);
 165     break;
 166
 167   case _C_USHT:
 168     return sizeof (unsigned short);
 169     break;
 170
 171   case _C_INT:
 172     return sizeof (int);
 173     break;
 174
 175   case _C_UINT:
 176     return sizeof (unsigned int);
 177     break;
 178
 179   case _C_LNG:
 180     return sizeof (long);
 181     break;
 182
 183   case _C_ULNG:
 184     return sizeof (unsigned long);
 185     break;
 186
 187   case _C_LNG_LNG:
 188     return sizeof (long long);
 189     break;
 190
 191   case _C_ULNG_LNG:
 192     return sizeof (unsigned long long);
 193     break;
 194
 195   case _C_FLT:
 196     return sizeof (float);
 197     break;
 198
 199   case _C_DBL:
 200     return sizeof (double);
 201     break;
 202
 203   case _C_VOID:
 204     return sizeof (void);
 205     break;
 206
 207   case _C_PTR:
 208   case _C_ATOM:
 209   case _C_CHARPTR:
 210     return sizeof (char *);
 211     break;
 212
 213   case _C_ARY_B:
 214     {
 215       int len = atoi (type + 1);
 216       while (isdigit ((unsigned char)*++type))
 217         ;
 218       return len * objc_aligned_size (type);
 219     }
 220     break;
 221
 222   case _C_BFLD:
 223     {
 224       /* The new encoding of bitfields is: b 'position' 'type' 'size' */
 225       int position, size;
 226       int startByte, endByte;
 227
 228       position = atoi (type + 1);
 229       while (isdigit ((unsigned char)*++type))
 230         ;
 231       size = atoi (type + 1);
 232
 233       startByte = position / BITS_PER_UNIT;
 234       endByte = (position + size) / BITS_PER_UNIT;
 235       return endByte - startByte;
 236     }
 237
 238   case _C_UNION_B:
 239   case _C_STRUCT_B:
 240     {
 241       struct objc_struct_layout layout;
 242       unsigned int size;
 243
 244       objc_layout_structure (type, &layout);
 245       while (objc_layout_structure_next_member (&layout))
 246         /* do nothing */ ;
 247       objc_layout_finish_structure (&layout, &size, NULL);
 248
 249       return size;
 250     }
 251
 252   case _C_COMPLEX:
 253     {
 254       type++; /* Skip after the 'j'. */
 255       switch (*type)
 256         {
 257             case _C_CHR:
 258               return sizeof (_Complex char);
 259               break;
 260
 261             case _C_UCHR:
 262               return sizeof (_Complex unsigned char);
 263               break;
 264
 265             case _C_SHT:
 266               return sizeof (_Complex short);
 267               break;
 268
 269             case _C_USHT:
 270               return sizeof (_Complex unsigned short);
 271               break;
 272
 273             case _C_INT:
 274               return sizeof (_Complex int);
 275               break;
 276
 277             case _C_UINT:
 278               return sizeof (_Complex unsigned int);
 279               break;
 280
 281             case _C_LNG:
 282               return sizeof (_Complex long);
 283               break;
 284
 285             case _C_ULNG:
 286               return sizeof (_Complex unsigned long);
 287               break;
 288
 289             case _C_LNG_LNG:
 290               return sizeof (_Complex long long);
 291               break;
 292
 293             case _C_ULNG_LNG:
 294               return sizeof (_Complex unsigned long long);
 295               break;
 296
 297             case _C_FLT:
 298               return sizeof (_Complex float);
 299               break;
 300
 301             case _C_DBL:
 302               return sizeof (_Complex double);
 303               break;
 304
 305             default:
 306               {
 307                 objc_error (nil, OBJC_ERR_BAD_TYPE, "unknown complex type %s\n",
 308                             type);
 309                 return 0;
 310               }
 311         }
 312     }
 313
 314   default:
 315     {
 316       objc_error (nil, OBJC_ERR_BAD_TYPE, "unknown type %s\n", type);
 317       return 0;
 318     }
 319   }
 320 }
 321
 322
 323 /*
 324   Return the alignment of an object specified by type
 325 */
 326
 327 int
 328 objc_alignof_type (const char *type)
 329 {
 330   /* Skip the variable name if any */
 331   if (*type == '"')
 332     {
 333       for (type++; *type++ != '"';)
 334         /* do nothing */;
 335     }
 336   switch (*type) {
 337   case _C_BOOL:
 338     return __alignof__ (_Bool);
 339     break;
 340
 341   case _C_ID:
 342     return __alignof__ (id);
 343     break;
 344
 345   case _C_CLASS:
 346     return __alignof__ (Class);
 347     break;
 348
 349   case _C_SEL:
 350     return __alignof__ (SEL);
 351     break;
 352
 353   case _C_CHR:
 354     return __alignof__ (char);
 355     break;
 356
 357   case _C_UCHR:
 358     return __alignof__ (unsigned char);
 359     break;
 360
 361   case _C_SHT:
 362     return __alignof__ (short);
 363     break;
 364
 365   case _C_USHT:
 366     return __alignof__ (unsigned short);
 367     break;
 368
 369   case _C_INT:
 370     return __alignof__ (int);
 371     break;
 372
 373   case _C_UINT:
 374     return __alignof__ (unsigned int);
 375     break;
 376
 377   case _C_LNG:
 378     return __alignof__ (long);
 379     break;
 380
 381   case _C_ULNG:
 382     return __alignof__ (unsigned long);
 383     break;
 384
 385   case _C_LNG_LNG:
 386     return __alignof__ (long long);
 387     break;
 388
 389   case _C_ULNG_LNG:
 390     return __alignof__ (unsigned long long);
 391     break;
 392
 393   case _C_FLT:
 394     return __alignof__ (float);
 395     break;
 396
 397   case _C_DBL:
 398     return __alignof__ (double);
 399     break;
 400
 401   case _C_PTR:
 402   case _C_ATOM:
 403   case _C_CHARPTR:
 404     return __alignof__ (char *);
 405     break;
 406
 407   case _C_ARY_B:
 408     while (isdigit ((unsigned char)*++type))
 409       /* do nothing */;
 410     return objc_alignof_type (type);
 411
 412   case _C_STRUCT_B:
 413   case _C_UNION_B:
 414     {
 415       struct objc_struct_layout layout;
 416       unsigned int align;
 417
 418       objc_layout_structure (type, &layout);
 419       while (objc_layout_structure_next_member (&layout))
 420         /* do nothing */;
 421       objc_layout_finish_structure (&layout, NULL, &align);
 422
 423       return align;
 424     }
 425
 426
 427   case _C_COMPLEX:
 428     {
 429       type++; /* Skip after the 'j'. */
 430       switch (*type)
 431         {
 432             case _C_CHR:
 433               return __alignof__ (_Complex char);
 434               break;
 435
 436             case _C_UCHR:
 437               return __alignof__ (_Complex unsigned char);
 438               break;
 439
 440             case _C_SHT:
 441               return __alignof__ (_Complex short);
 442               break;
 443
 444             case _C_USHT:
 445               return __alignof__ (_Complex unsigned short);
 446               break;
 447
 448             case _C_INT:
 449               return __alignof__ (_Complex int);
 450               break;
 451
 452             case _C_UINT:
 453               return __alignof__ (_Complex unsigned int);
 454               break;
 455
 456             case _C_LNG:
 457               return __alignof__ (_Complex long);
 458               break;
 459
 460             case _C_ULNG:
 461               return __alignof__ (_Complex unsigned long);
 462               break;
 463
 464             case _C_LNG_LNG:
 465               return __alignof__ (_Complex long long);
 466               break;
 467
 468             case _C_ULNG_LNG:
 469               return __alignof__ (_Complex unsigned long long);
 470               break;
 471
 472             case _C_FLT:
 473               return __alignof__ (_Complex float);
 474               break;
 475
 476             case _C_DBL:
 477               return __alignof__ (_Complex double);
 478               break;
 479
 480             default:
 481               {
 482                 objc_error (nil, OBJC_ERR_BAD_TYPE, "unknown complex type %s\n",
 483                             type);
 484                 return 0;
 485               }
 486         }
 487     }
 488
 489   default:
 490     {
 491       objc_error (nil, OBJC_ERR_BAD_TYPE, "unknown type %s\n", type);
 492       return 0;
 493     }
 494   }
 495 }
 496
 497 /*
 498   The aligned size if the size rounded up to the nearest alignment.
 499 */
 500
 501 int
 502 objc_aligned_size (const char *type)
 503 {
 504   int size, align;
 505
 506   /* Skip the variable name */
 507   if (*type == '"')
 508     {
 509       for (type++; *type++ != '"';)
 510         /* do nothing */;
 511     }
 512
 513   size = objc_sizeof_type (type);
 514   align = objc_alignof_type (type);
 515
 516   return ROUND (size, align);
 517 }
 518
 519 /*
 520   The size rounded up to the nearest integral of the wordsize, taken
 521   to be the size of a void *.
 522 */
 523
 524 int
 525 objc_promoted_size (const char *type)
 526 {
 527   int size, wordsize;
 528
 529   /* Skip the variable name */
 530   if (*type == '"')
 531     {
 532       for (type++; *type++ != '"';)
 533         /* do nothing */;
 534     }
 535
 536   size = objc_sizeof_type (type);
 537   wordsize = sizeof (void *);
 538
 539   return ROUND (size, wordsize);
 540 }
 541
 542 /*
 543   Skip type qualifiers.  These may eventually precede typespecs
 544   occurring in method prototype encodings.
 545 */
 546
 547 inline const char *
 548 objc_skip_type_qualifiers (const char *type)
 549 {
 550   while (*type == _C_CONST
 551          || *type == _C_IN
 552          || *type == _C_INOUT
 553          || *type == _C_OUT
 554          || *type == _C_BYCOPY
 555          || *type == _C_BYREF
 556          || *type == _C_ONEWAY
 557          || *type == _C_GCINVISIBLE)
 558     {
 559       type += 1;
 560     }
 561   return type;
 562 }
 563
 564
 565 /*
 566   Skip one typespec element.  If the typespec is prepended by type
 567   qualifiers, these are skipped as well.
 568 */
 569
 570 const char *
 571 objc_skip_typespec (const char *type)
 572 {
 573   /* Skip the variable name if any */
 574   if (*type == '"')
 575     {
 576       for (type++; *type++ != '"';)
 577         /* do nothing */;
 578     }
 579
 580   type = objc_skip_type_qualifiers (type);
 581
 582   switch (*type) {
 583
 584   case _C_ID:
 585     /* An id may be annotated by the actual type if it is known
 586        with the @"ClassName" syntax */
 587
 588     if (*++type != '"')
 589       return type;
 590     else
 591       {
 592         while (*++type != '"')
 593           /* do nothing */;
 594         return type + 1;
 595       }
 596
 597     /* The following are one character type codes */
 598   case _C_CLASS:
 599   case _C_SEL:
 600   case _C_CHR:
 601   case _C_UCHR:
 602   case _C_CHARPTR:
 603   case _C_ATOM:
 604   case _C_SHT:
 605   case _C_USHT:
 606   case _C_INT:
 607   case _C_UINT:
 608   case _C_LNG:
 609   case _C_BOOL:
 610   case _C_ULNG:
 611   case _C_LNG_LNG:
 612   case _C_ULNG_LNG:
 613   case _C_FLT:
 614   case _C_DBL:
 615   case _C_VOID:
 616   case _C_UNDEF:
 617     return ++type;
 618     break;
 619
 620   case _C_COMPLEX:
 621     return type + 2;
 622     break;
 623
 624   case _C_ARY_B:
 625     /* skip digits, typespec and closing ']' */
 626
 627     while (isdigit ((unsigned char)*++type))
 628       ;
 629     type = objc_skip_typespec (type);
 630     if (*type == _C_ARY_E)
 631       return ++type;
 632     else
 633       {
 634         objc_error (nil, OBJC_ERR_BAD_TYPE, "bad array type %s\n", type);
 635         return 0;
 636       }
 637
 638   case _C_BFLD:
 639     /* The new encoding of bitfields is: b 'position' 'type' 'size' */
 640     while (isdigit ((unsigned char)*++type))
 641       ; /* skip position */
 642     while (isdigit ((unsigned char)*++type))
 643       ; /* skip type and size */
 644     return type;
 645
 646   case _C_STRUCT_B:
 647     /* skip name, and elements until closing '}'  */
 648
 649     while (*type != _C_STRUCT_E && *type++ != '=')
 650       ;
 651     while (*type != _C_STRUCT_E)
 652       {
 653         type = objc_skip_typespec (type);
 654       }
 655     return ++type;
 656
 657   case _C_UNION_B:
 658     /* skip name, and elements until closing ')'  */
 659
 660     while (*type != _C_UNION_E && *type++ != '=')
 661       ;
 662     while (*type != _C_UNION_E)
 663       {
 664         type = objc_skip_typespec (type);
 665       }
 666     return ++type;
 667
 668   case _C_PTR:
 669     /* Just skip the following typespec */
 670
 671     return objc_skip_typespec (++type);
 672
 673   default:
 674     {
 675       objc_error (nil, OBJC_ERR_BAD_TYPE, "unknown type %s\n", type);
 676       return 0;
 677     }
 678   }
 679 }
 680
 681 /*
 682   Skip an offset as part of a method encoding.  This is prepended by a
 683   '+' if the argument is passed in registers.
 684 */
 685 inline const char *
 686 objc_skip_offset (const char *type)
 687 {
 688   if (*type == '+')
 689     type++;
 690   while (isdigit ((unsigned char) *++type))
 691     ;
 692   return type;
 693 }
 694
 695 /*
 696   Skip an argument specification of a method encoding.
 697 */
 698 const char *
 699 objc_skip_argspec (const char *type)
 700 {
 701   type = objc_skip_typespec (type);
 702   type = objc_skip_offset (type);
 703   return type;
 704 }
 705
 706 /*
 707   Return the number of arguments that the method MTH expects.
 708   Note that all methods need two implicit arguments `self' and
 709   `_cmd'.
 710 */
 711 int
 712 method_get_number_of_arguments (struct objc_method *mth)
 713 {
 714   int i = 0;
 715   const char *type = mth->method_types;
 716   while (*type)
 717     {
 718       type = objc_skip_argspec (type);
 719       i += 1;
 720     }
 721   return i - 1;
 722 }
 723
 724 /*
 725   Return the size of the argument block needed on the stack to invoke
 726   the method MTH.  This may be zero, if all arguments are passed in
 727   registers.
 728 */
 729
 730 int
 731 method_get_sizeof_arguments (struct objc_method *mth)
 732 {
 733   const char *type = objc_skip_typespec (mth->method_types);
 734   return atoi (type);
 735 }
 736
 737 /*
 738   Return a pointer to the next argument of ARGFRAME.  type points to
 739   the last argument.  Typical use of this look like:
 740
 741   {
 742     char *datum, *type;
 743     for (datum = method_get_first_argument (method, argframe, &type);
 744          datum; datum = method_get_next_argument (argframe, &type))
 745       {
 746         unsigned flags = objc_get_type_qualifiers (type);
 747         type = objc_skip_type_qualifiers (type);
 748         if (*type != _C_PTR)
 749           [portal encodeData: datum ofType: type];
 750         else
 751           {
 752             if ((flags & _F_IN) == _F_IN)
 753               [portal encodeData: *(char **) datum ofType: ++type];
 754           }
 755       }
 756   }
 757 */
 758
 759 char *
 760 method_get_next_argument (arglist_t argframe, const char **type)
 761 {
 762   const char *t = objc_skip_argspec (*type);
 763
 764   if (*t == '\0')
 765     return 0;
 766
 767   *type = t;
 768   t = objc_skip_typespec (t);
 769
 770   if (*t == '+')
 771     return argframe->arg_regs + atoi (++t);
 772   else
 773     return argframe->arg_ptr + atoi (t);
 774 }
 775
 776 /*
 777   Return a pointer to the value of the first argument of the method
 778   described in M with the given argumentframe ARGFRAME.  The type
 779   is returned in TYPE.  type must be passed to successive calls of
 780   method_get_next_argument.
 781 */
 782 char *
 783 method_get_first_argument (struct objc_method *m,
 784                            arglist_t argframe,
 785                            const char **type)
 786 {
 787   *type = m->method_types;
 788   return method_get_next_argument (argframe, type);
 789 }
 790
 791 /*
 792    Return a pointer to the ARGth argument of the method
 793    M from the frame ARGFRAME.  The type of the argument
 794    is returned in the value-result argument TYPE
 795 */
 796
 797 char *
 798 method_get_nth_argument (struct objc_method *m,
 799                          arglist_t argframe, int arg,
 800                          const char **type)
 801 {
 802   const char *t = objc_skip_argspec (m->method_types);
 803
 804   if (arg > method_get_number_of_arguments (m))
 805     return 0;
 806
 807   while (arg--)
 808     t = objc_skip_argspec (t);
 809
 810   *type = t;
 811   t = objc_skip_typespec (t);
 812
 813   if (*t == '+')
 814     return argframe->arg_regs + atoi (++t);
 815   else
 816     return argframe->arg_ptr + atoi (t);
 817 }
 818
 819 unsigned
 820 objc_get_type_qualifiers (const char *type)
 821 {
 822   unsigned res = 0;
 823   BOOL flag = YES;
 824
 825   while (flag)
 826     switch (*type++)
 827       {
 828       case _C_CONST:    res |= _F_CONST; break;
 829       case _C_IN:       res |= _F_IN; break;
 830       case _C_INOUT:    res |= _F_INOUT; break;
 831       case _C_OUT:      res |= _F_OUT; break;
 832       case _C_BYCOPY:   res |= _F_BYCOPY; break;
 833       case _C_BYREF:  res |= _F_BYREF; break;
 834       case _C_ONEWAY:   res |= _F_ONEWAY; break;
 835       case _C_GCINVISIBLE: res |= _F_GCINVISIBLE; break;
 836       default: flag = NO;
 837     }
 838
 839   return res;
 840 }
 841
 842
 843 /* The following three functions can be used to determine how a
 844    structure is laid out by the compiler. For example:
 845
 846   struct objc_struct_layout layout;
 847   int i;
 848
 849   objc_layout_structure (type, &layout);
 850   while (objc_layout_structure_next_member (&layout))
 851     {
 852       int position, align;
 853       const char *type;
 854
 855       objc_layout_structure_get_info (&layout, &position, &align, &type);
 856       printf ("element %d has offset %d, alignment %d\n",
 857               i++, position, align);
 858     }
 859
 860   These functions are used by objc_sizeof_type and objc_alignof_type
 861   functions to compute the size and alignment of structures. The
 862   previous method of computing the size and alignment of a structure
 863   was not working on some architectures, particulary on AIX, and in
 864   the presence of bitfields inside the structure. */
 865 void
 866 objc_layout_structure (const char *type,
 867                            struct objc_struct_layout *layout)
 868 {
 869   const char *ntype;
 870
 871   if (*type != _C_UNION_B && *type != _C_STRUCT_B)
 872     {
 873       objc_error (nil, OBJC_ERR_BAD_TYPE,
 874                  "record (or union) type expected in objc_layout_structure, got %s\n",
 875                  type);
 876     }
 877
 878   type ++;
 879   layout->original_type = type;
 880
 881   /* Skip "<name>=" if any. Avoid embedded structures and unions. */
 882   ntype = type;
 883   while (*ntype != _C_STRUCT_E && *ntype != _C_STRUCT_B && *ntype != _C_UNION_B
 884          && *ntype++ != '=')
 885     /* do nothing */;
 886
 887   /* If there's a "<name>=", ntype - 1 points to '='; skip the the name */
 888   if (*(ntype - 1) == '=')
 889     type = ntype;
 890
 891   layout->type = type;
 892   layout->prev_type = NULL;
 893   layout->record_size = 0;
 894   layout->record_align = BITS_PER_UNIT;
 895
 896   layout->record_align = MAX (layout->record_align, STRUCTURE_SIZE_BOUNDARY);
 897 }
 898
 899
 900 BOOL
 901 objc_layout_structure_next_member (struct objc_struct_layout *layout)
 902 {
 903   register int desired_align = 0;
 904
 905   /* The following are used only if the field is a bitfield */
 906   register const char *bfld_type = 0;
 907   register int bfld_type_size, bfld_type_align = 0, bfld_field_size = 0;
 908
 909   /* The current type without the type qualifiers */
 910   const char *type;
 911   BOOL unionp = layout->original_type[-1] == _C_UNION_B;
 912
 913   /* Add the size of the previous field to the size of the record.  */
 914   if (layout->prev_type)
 915     {
 916       type = objc_skip_type_qualifiers (layout->prev_type);
 917       if (unionp)
 918         layout->record_size = MAX (layout->record_size,
 919                                    objc_sizeof_type (type) * BITS_PER_UNIT);
 920
 921       else if (*type != _C_BFLD)
 922         layout->record_size += objc_sizeof_type (type) * BITS_PER_UNIT;
 923       else {
 924         /* Get the bitfield's type */
 925         for (bfld_type = type + 1;
 926              isdigit ((unsigned char)*bfld_type);
 927              bfld_type++)
 928           /* do nothing */;
 929
 930         bfld_type_size = objc_sizeof_type (bfld_type) * BITS_PER_UNIT;
 931         bfld_type_align = objc_alignof_type (bfld_type) * BITS_PER_UNIT;
 932         bfld_field_size = atoi (objc_skip_typespec (bfld_type));
 933         layout->record_size += bfld_field_size;
 934       }
 935     }
 936
 937   if ((unionp && *layout->type == _C_UNION_E)
 938       || (!unionp && *layout->type == _C_STRUCT_E))
 939     return NO;
 940
 941   /* Skip the variable name if any */
 942   if (*layout->type == '"')
 943     {
 944       for (layout->type++; *layout->type++ != '"';)
 945         /* do nothing */;
 946     }
 947
 948   type = objc_skip_type_qualifiers (layout->type);
 949
 950   if (*type != _C_BFLD)
 951     desired_align = objc_alignof_type (type) * BITS_PER_UNIT;
 952   else
 953     {
 954       desired_align = 1;
 955       /* Skip the bitfield's offset */
 956       for (bfld_type = type + 1;
 957            isdigit ((unsigned char) *bfld_type);
 958            bfld_type++)
 959         /* do nothing */;
 960
 961       bfld_type_size = objc_sizeof_type (bfld_type) * BITS_PER_UNIT;
 962       bfld_type_align = objc_alignof_type (bfld_type) * BITS_PER_UNIT;
 963       bfld_field_size = atoi (objc_skip_typespec (bfld_type));
 964     }
 965
 966 #ifdef BIGGEST_FIELD_ALIGNMENT
 967   desired_align = MIN (desired_align, BIGGEST_FIELD_ALIGNMENT);
 968 #endif
 969 #ifdef ADJUST_FIELD_ALIGN
 970   desired_align = ADJUST_FIELD_ALIGN (type, desired_align);
 971 #endif
 972
 973   /* Record must have at least as much alignment as any field.
 974      Otherwise, the alignment of the field within the record
 975      is meaningless.  */
 976 #ifndef PCC_BITFIELD_TYPE_MATTERS
 977   layout->record_align = MAX (layout->record_align, desired_align);
 978 #else   /* PCC_BITFIELD_TYPE_MATTERS */
 979   if (*type == _C_BFLD)
 980     {
 981       /* For these machines, a zero-length field does not
 982          affect the alignment of the structure as a whole.
 983          It does, however, affect the alignment of the next field
 984          within the structure.  */
 985       if (bfld_field_size)
 986         layout->record_align = MAX (layout->record_align, desired_align);
 987       else
 988         desired_align = objc_alignof_type (bfld_type) * BITS_PER_UNIT;
 989
 990       /* A named bit field of declared type `int'
 991          forces the entire structure to have `int' alignment.
 992          Q1: How is encoded this thing and how to check for it?
 993          Q2: How to determine maximum_field_alignment at runtime? */
 994
 995 /*        if (DECL_NAME (field) != 0) */
 996       {
 997         int type_align = bfld_type_align;
 998 #if 0
 999         if (maximum_field_alignment != 0)
1000           type_align = MIN (type_align, maximum_field_alignment);
1001         else if (DECL_PACKED (field))
1002           type_align = MIN (type_align, BITS_PER_UNIT);
1003 #endif
1004
1005         layout->record_align = MAX (layout->record_align, type_align);
1006       }
1007     }
1008   else
1009     layout->record_align = MAX (layout->record_align, desired_align);
1010 #endif  /* PCC_BITFIELD_TYPE_MATTERS */
1011
1012   /* Does this field automatically have alignment it needs
1013      by virtue of the fields that precede it and the record's
1014      own alignment?  */
1015
1016   if (*type == _C_BFLD)
1017     layout->record_size = atoi (type + 1);
1018   else if (layout->record_size % desired_align != 0)
1019     {
1020       /* No, we need to skip space before this field.
1021          Bump the cumulative size to multiple of field alignment.  */
1022       layout->record_size = ROUND (layout->record_size, desired_align);
1023     }
1024
1025   /* Jump to the next field in record. */
1026
1027   layout->prev_type = layout->type;
1028   layout->type = objc_skip_typespec (layout->type);      /* skip component */
1029
1030   return YES;
1031 }
1032
1033
1034 void objc_layout_finish_structure (struct objc_struct_layout *layout,
1035                                    unsigned int *size,
1036                                    unsigned int *align)
1037 {
1038   BOOL unionp = layout->original_type[-1] == _C_UNION_B;
1039   if (layout->type
1040       && ((!unionp && *layout->type == _C_STRUCT_E)
1041           || (unionp && *layout->type == _C_UNION_E)))
1042     {
1043       /* Work out the alignment of the record as one expression and store
1044          in the record type.  Round it up to a multiple of the record's
1045          alignment. */
1046 #if defined (ROUND_TYPE_ALIGN) && ! defined (__sparc__)
1047       layout->record_align = ROUND_TYPE_ALIGN (layout->original_type-1,
1048                                                1,
1049                                                layout->record_align);
1050 #else
1051       layout->record_align = MAX (1, layout->record_align);
1052 #endif
1053
1054 #ifdef ROUND_TYPE_SIZE
1055       layout->record_size = ROUND_TYPE_SIZE (layout->original_type,
1056                                              layout->record_size,
1057                                              layout->record_align);
1058 #else
1059       /* Round the size up to be a multiple of the required alignment */
1060       layout->record_size = ROUND (layout->record_size, layout->record_align);
1061 #endif
1062
1063       layout->type = NULL;
1064     }
1065   if (size)
1066     *size = layout->record_size / BITS_PER_UNIT;
1067   if (align)
1068     *align = layout->record_align / BITS_PER_UNIT;
1069 }
1070
1071
1072 void objc_layout_structure_get_info (struct objc_struct_layout *layout,
1073                                      unsigned int *offset,
1074                                      unsigned int *align,
1075                                      const char **type)
1076 {
1077   if (offset)
1078     *offset = layout->record_size / BITS_PER_UNIT;
1079   if (align)
1080     *align = layout->record_align / BITS_PER_UNIT;
1081   if (type)
1082     *type = layout->prev_type;
1083 }