boehm-gc/typd_mlc.c

   1 /*
   2  * Copyright (c) 1991-1994 by Xerox Corporation.  All rights reserved.
   3  * opyright (c) 1999-2000 by Hewlett-Packard Company.  All rights reserved.
   4  *
   5  * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
   6  * OR IMPLIED.  ANY USE IS AT YOUR OWN RISK.
   7  *
   8  * Permission is hereby granted to use or copy this program
   9  * for any purpose,  provided the above notices are retained on all copies.
  10  * Permission to modify the code and to distribute modified code is granted,
  11  * provided the above notices are retained, and a notice that the code was
  12  * modified is included with the above copyright notice.
  13  *
  14  */
  15
  16
  17 /*
  18  * Some simple primitives for allocation with explicit type information.
  19  * Simple objects are allocated such that they contain a GC_descr at the
  20  * end (in the last allocated word).  This descriptor may be a procedure
  21  * which then examines an extended descriptor passed as its environment.
  22  *
  23  * Arrays are treated as simple objects if they have sufficiently simple
  24  * structure.  Otherwise they are allocated from an array kind that supplies
  25  * a special mark procedure.  These arrays contain a pointer to a
  26  * complex_descriptor as their last word.
  27  * This is done because the environment field is too small, and the collector
  28  * must trace the complex_descriptor.
  29  *
  30  * Note that descriptors inside objects may appear cleared, if we encounter a
  31  * false refrence to an object on a free list.  In the GC_descr case, this
  32  * is OK, since a 0 descriptor corresponds to examining no fields.
  33  * In the complex_descriptor case, we explicitly check for that case.
  34  *
  35  * MAJOR PARTS OF THIS CODE HAVE NOT BEEN TESTED AT ALL and are not testable,
  36  * since they are not accessible through the current interface.
  37  */
  38
  39 #include "private/gc_pmark.h"
  40 #include "gc_typed.h"
  41
  42 # define TYPD_EXTRA_BYTES (sizeof(word) - EXTRA_BYTES)
  43
  44 GC_bool GC_explicit_typing_initialized = FALSE;
  45
  46 int GC_explicit_kind;   /* Object kind for objects with indirect        */
  47                         /* (possibly extended) descriptors.             */
  48
  49 int GC_array_kind;      /* Object kind for objects with complex         */
  50                         /* descriptors and GC_array_mark_proc.          */
  51
  52 /* Extended descriptors.  GC_typed_mark_proc understands these. */
  53 /* These are used for simple objects that are larger than what  */
  54 /* can be described by a BITMAP_BITS sized bitmap.              */
  55 typedef struct {
  56         word ed_bitmap; /* lsb corresponds to first word.       */
  57         GC_bool ed_continued;   /* next entry is continuation.  */
  58 } ext_descr;
  59
  60 /* Array descriptors.  GC_array_mark_proc understands these.    */
  61 /* We may eventually need to add provisions for headers and     */
  62 /* trailers.  Hence we provide for tree structured descriptors, */
  63 /* though we don't really use them currently.                   */
  64 typedef union ComplexDescriptor {
  65     struct LeafDescriptor {     /* Describes simple array       */
  66         word ld_tag;
  67 #       define LEAF_TAG 1
  68         word ld_size;           /* bytes per element    */
  69                                 /* multiple of ALIGNMENT        */
  70         word ld_nelements;      /* Number of elements.  */
  71         GC_descr ld_descriptor; /* A simple length, bitmap,     */
  72                                 /* or procedure descriptor.     */
  73     } ld;
  74     struct ComplexArrayDescriptor {
  75         word ad_tag;
  76 #       define ARRAY_TAG 2
  77         word ad_nelements;
  78         union ComplexDescriptor * ad_element_descr;
  79     } ad;
  80     struct SequenceDescriptor {
  81         word sd_tag;
  82 #       define SEQUENCE_TAG 3
  83         union ComplexDescriptor * sd_first;
  84         union ComplexDescriptor * sd_second;
  85     } sd;
  86 } complex_descriptor;
  87 #define TAG ld.ld_tag
  88
  89 ext_descr * GC_ext_descriptors; /* Points to array of extended  */
  90                                 /* descriptors.                 */
  91
  92 word GC_ed_size = 0;    /* Current size of above arrays.        */
  93 # define ED_INITIAL_SIZE 100;
  94
  95 word GC_avail_descr = 0;        /* Next available slot.         */
  96
  97 int GC_typed_mark_proc_index;   /* Indices of my mark           */
  98 int GC_array_mark_proc_index;   /* procedures.                  */
  99
 100 /* Add a multiword bitmap to GC_ext_descriptors arrays.  Return */
 101 /* starting index.                                              */
 102 /* Returns -1 on failure.                                       */
 103 /* Caller does not hold allocation lock.                        */
 104 signed_word GC_add_ext_descriptor(bm, nbits)
 105 GC_bitmap bm;
 106 word nbits;
 107 {
 108     register size_t nwords = divWORDSZ(nbits + WORDSZ-1);
 109     register signed_word result;
 110     register word i;
 111     register word last_part;
 112     register int extra_bits;
 113     DCL_LOCK_STATE;
 114
 115     DISABLE_SIGNALS();
 116     LOCK();
 117     while (GC_avail_descr + nwords >= GC_ed_size) {
 118         ext_descr * new;
 119         size_t new_size;
 120         word ed_size = GC_ed_size;
 121
 122         UNLOCK();
 123         ENABLE_SIGNALS();
 124         if (ed_size == 0) {
 125             new_size = ED_INITIAL_SIZE;
 126         } else {
 127             new_size = 2 * ed_size;
 128             if (new_size > MAX_ENV) return(-1);
 129         }
 130         new = (ext_descr *) GC_malloc_atomic(new_size * sizeof(ext_descr));
 131         if (new == 0) return(-1);
 132         DISABLE_SIGNALS();
 133         LOCK();
 134         if (ed_size == GC_ed_size) {
 135             if (GC_avail_descr != 0) {
 136                 BCOPY(GC_ext_descriptors, new,
 137                       GC_avail_descr * sizeof(ext_descr));
 138             }
 139             GC_ed_size = new_size;
 140             GC_ext_descriptors = new;
 141         }  /* else another thread already resized it in the meantime */
 142     }
 143     result = GC_avail_descr;
 144     for (i = 0; i < nwords-1; i++) {
 145         GC_ext_descriptors[result + i].ed_bitmap = bm[i];
 146         GC_ext_descriptors[result + i].ed_continued = TRUE;
 147     }
 148     last_part = bm[i];
 149     /* Clear irrelevant bits. */
 150     extra_bits = nwords * WORDSZ - nbits;
 151     last_part <<= extra_bits;
 152     last_part >>= extra_bits;
 153     GC_ext_descriptors[result + i].ed_bitmap = last_part;
 154     GC_ext_descriptors[result + i].ed_continued = FALSE;
 155     GC_avail_descr += nwords;
 156     UNLOCK();
 157     ENABLE_SIGNALS();
 158     return(result);
 159 }
 160
 161 /* Table of bitmap descriptors for n word long all pointer objects.     */
 162 GC_descr GC_bm_table[WORDSZ/2];
 163
 164 /* Return a descriptor for the concatenation of 2 nwords long objects,  */
 165 /* each of which is described by descriptor.                            */
 166 /* The result is known to be short enough to fit into a bitmap          */
 167 /* descriptor.                                                          */
 168 /* Descriptor is a GC_DS_LENGTH or GC_DS_BITMAP descriptor.             */
 169 GC_descr GC_double_descr(descriptor, nwords)
 170 register GC_descr descriptor;
 171 register word nwords;
 172 {
 173     if ((descriptor & GC_DS_TAGS) == GC_DS_LENGTH) {
 174         descriptor = GC_bm_table[BYTES_TO_WORDS((word)descriptor)];
 175     };
 176     descriptor |= (descriptor & ~GC_DS_TAGS) >> nwords;
 177     return(descriptor);
 178 }
 179
 180 complex_descriptor * GC_make_sequence_descriptor();
 181
 182 /* Build a descriptor for an array with nelements elements,     */
 183 /* each of which can be described by a simple descriptor.       */
 184 /* We try to optimize some common cases.                        */
 185 /* If the result is COMPLEX, then a complex_descr* is returned  */
 186 /* in *complex_d.                                                       */
 187 /* If the result is LEAF, then we built a LeafDescriptor in     */
 188 /* the structure pointed to by leaf.                            */
 189 /* The tag in the leaf structure is not set.                    */
 190 /* If the result is SIMPLE, then a GC_descr                     */
 191 /* is returned in *simple_d.                                    */
 192 /* If the result is NO_MEM, then                                */
 193 /* we failed to allocate the descriptor.                        */
 194 /* The implementation knows that GC_DS_LENGTH is 0.             */
 195 /* *leaf, *complex_d, and *simple_d may be used as temporaries  */
 196 /* during the construction.                                     */
 197 # define COMPLEX 2
 198 # define LEAF 1
 199 # define SIMPLE 0
 200 # define NO_MEM (-1)
 201 int GC_make_array_descriptor(nelements, size, descriptor,
 202                              simple_d, complex_d, leaf)
 203 word size;
 204 word nelements;
 205 GC_descr descriptor;
 206 GC_descr *simple_d;
 207 complex_descriptor **complex_d;
 208 struct LeafDescriptor * leaf;
 209 {
 210 #   define OPT_THRESHOLD 50
 211         /* For larger arrays, we try to combine descriptors of adjacent */
 212         /* descriptors to speed up marking, and to reduce the amount    */
 213         /* of space needed on the mark stack.                           */
 214     if ((descriptor & GC_DS_TAGS) == GC_DS_LENGTH) {
 215       if ((word)descriptor == size) {
 216         *simple_d = nelements * descriptor;
 217         return(SIMPLE);
 218       } else if ((word)descriptor == 0) {
 219         *simple_d = (GC_descr)0;
 220         return(SIMPLE);
 221       }
 222     }
 223     if (nelements <= OPT_THRESHOLD) {
 224       if (nelements <= 1) {
 225         if (nelements == 1) {
 226             *simple_d = descriptor;
 227             return(SIMPLE);
 228         } else {
 229             *simple_d = (GC_descr)0;
 230             return(SIMPLE);
 231         }
 232       }
 233     } else if (size <= BITMAP_BITS/2
 234                && (descriptor & GC_DS_TAGS) != GC_DS_PROC
 235                && (size & (sizeof(word)-1)) == 0) {
 236       int result =
 237           GC_make_array_descriptor(nelements/2, 2*size,
 238                                    GC_double_descr(descriptor,
 239                                                    BYTES_TO_WORDS(size)),
 240                                    simple_d, complex_d, leaf);
 241       if ((nelements & 1) == 0) {
 242           return(result);
 243       } else {
 244           struct LeafDescriptor * one_element =
 245               (struct LeafDescriptor *)
 246                 GC_malloc_atomic(sizeof(struct LeafDescriptor));
 247
 248           if (result == NO_MEM || one_element == 0) return(NO_MEM);
 249           one_element -> ld_tag = LEAF_TAG;
 250           one_element -> ld_size = size;
 251           one_element -> ld_nelements = 1;
 252           one_element -> ld_descriptor = descriptor;
 253           switch(result) {
 254             case SIMPLE:
 255             {
 256               struct LeafDescriptor * beginning =
 257                 (struct LeafDescriptor *)
 258                   GC_malloc_atomic(sizeof(struct LeafDescriptor));
 259               if (beginning == 0) return(NO_MEM);
 260               beginning -> ld_tag = LEAF_TAG;
 261               beginning -> ld_size = size;
 262               beginning -> ld_nelements = 1;
 263               beginning -> ld_descriptor = *simple_d;
 264               *complex_d = GC_make_sequence_descriptor(
 265                                 (complex_descriptor *)beginning,
 266                                 (complex_descriptor *)one_element);
 267               break;
 268             }
 269             case LEAF:
 270             {
 271               struct LeafDescriptor * beginning =
 272                 (struct LeafDescriptor *)
 273                   GC_malloc_atomic(sizeof(struct LeafDescriptor));
 274               if (beginning == 0) return(NO_MEM);
 275               beginning -> ld_tag = LEAF_TAG;
 276               beginning -> ld_size = leaf -> ld_size;
 277               beginning -> ld_nelements = leaf -> ld_nelements;
 278               beginning -> ld_descriptor = leaf -> ld_descriptor;
 279               *complex_d = GC_make_sequence_descriptor(
 280                                 (complex_descriptor *)beginning,
 281                                 (complex_descriptor *)one_element);
 282               break;
 283             }
 284             case COMPLEX:
 285               *complex_d = GC_make_sequence_descriptor(
 286                                 *complex_d,
 287                                 (complex_descriptor *)one_element);
 288               break;
 289           }
 290           return(COMPLEX);
 291       }
 292     }
 293     {
 294         leaf -> ld_size = size;
 295         leaf -> ld_nelements = nelements;
 296         leaf -> ld_descriptor = descriptor;
 297         return(LEAF);
 298     }
 299 }
 300
 301 complex_descriptor * GC_make_sequence_descriptor(first, second)
 302 complex_descriptor * first;
 303 complex_descriptor * second;
 304 {
 305     struct SequenceDescriptor * result =
 306         (struct SequenceDescriptor *)
 307                 GC_malloc(sizeof(struct SequenceDescriptor));
 308     /* Can't result in overly conservative marking, since tags are      */
 309     /* very small integers. Probably faster than maintaining type       */
 310     /* info.                                                            */
 311     if (result != 0) {
 312         result -> sd_tag = SEQUENCE_TAG;
 313         result -> sd_first = first;
 314         result -> sd_second = second;
 315     }
 316     return((complex_descriptor *)result);
 317 }
 318
 319 #ifdef UNDEFINED
 320 complex_descriptor * GC_make_complex_array_descriptor(nelements, descr)
 321 word nelements;
 322 complex_descriptor * descr;
 323 {
 324     struct ComplexArrayDescriptor * result =
 325         (struct ComplexArrayDescriptor *)
 326                 GC_malloc(sizeof(struct ComplexArrayDescriptor));
 327
 328     if (result != 0) {
 329         result -> ad_tag = ARRAY_TAG;
 330         result -> ad_nelements = nelements;
 331         result -> ad_element_descr = descr;
 332     }
 333     return((complex_descriptor *)result);
 334 }
 335 #endif
 336
 337 ptr_t * GC_eobjfreelist;
 338
 339 ptr_t * GC_arobjfreelist;
 340
 341 mse * GC_typed_mark_proc GC_PROTO((register word * addr,
 342                                    register mse * mark_stack_ptr,
 343                                    mse * mark_stack_limit,
 344                                    word env));
 345
 346 mse * GC_array_mark_proc GC_PROTO((register word * addr,
 347                                    register mse * mark_stack_ptr,
 348                                    mse * mark_stack_limit,
 349                                    word env));
 350
 351 /* Caller does not hold allocation lock. */
 352 void GC_init_explicit_typing()
 353 {
 354     register int i;
 355     DCL_LOCK_STATE;
 356
 357
 358 #   ifdef PRINTSTATS
 359         if (sizeof(struct LeafDescriptor) % sizeof(word) != 0)
 360             ABORT("Bad leaf descriptor size");
 361 #   endif
 362     DISABLE_SIGNALS();
 363     LOCK();
 364     if (GC_explicit_typing_initialized) {
 365       UNLOCK();
 366       ENABLE_SIGNALS();
 367       return;
 368     }
 369     GC_explicit_typing_initialized = TRUE;
 370     /* Set up object kind with simple indirect descriptor. */
 371       GC_eobjfreelist = (ptr_t *)GC_new_free_list_inner();
 372       GC_explicit_kind = GC_new_kind_inner(
 373                             (void **)GC_eobjfreelist,
 374                             (((word)WORDS_TO_BYTES(-1)) | GC_DS_PER_OBJECT),
 375                             TRUE, TRUE);
 376                 /* Descriptors are in the last word of the object. */
 377       GC_typed_mark_proc_index = GC_new_proc_inner(GC_typed_mark_proc);
 378     /* Set up object kind with array descriptor. */
 379       GC_arobjfreelist = (ptr_t *)GC_new_free_list_inner();
 380       GC_array_mark_proc_index = GC_new_proc_inner(GC_array_mark_proc);
 381       GC_array_kind = GC_new_kind_inner(
 382                             (void **)GC_arobjfreelist,
 383                             GC_MAKE_PROC(GC_array_mark_proc_index, 0),
 384                             FALSE, TRUE);
 385       for (i = 0; i < WORDSZ/2; i++) {
 386           GC_descr d = (((word)(-1)) >> (WORDSZ - i)) << (WORDSZ - i);
 387           d |= GC_DS_BITMAP;
 388           GC_bm_table[i] = d;
 389       }
 390     UNLOCK();
 391     ENABLE_SIGNALS();
 392 }
 393
 394 # if defined(__STDC__) || defined(__cplusplus)
 395     mse * GC_typed_mark_proc(register word * addr,
 396                              register mse * mark_stack_ptr,
 397                              mse * mark_stack_limit,
 398                              word env)
 399 # else
 400     mse * GC_typed_mark_proc(addr, mark_stack_ptr, mark_stack_limit, env)
 401     register word * addr;
 402     register mse * mark_stack_ptr;
 403     mse * mark_stack_limit;
 404     word env;
 405 # endif
 406 {
 407     register word bm = GC_ext_descriptors[env].ed_bitmap;
 408     register word * current_p = addr;
 409     register word current;
 410     register ptr_t greatest_ha = GC_greatest_plausible_heap_addr;
 411     register ptr_t least_ha = GC_least_plausible_heap_addr;
 412
 413     for (; bm != 0; bm >>= 1, current_p++) {
 414         if (bm & 1) {
 415             current = *current_p;
 416             FIXUP_POINTER(current);
 417             if ((ptr_t)current >= least_ha && (ptr_t)current <= greatest_ha) {
 418                 PUSH_CONTENTS((ptr_t)current, mark_stack_ptr,
 419                               mark_stack_limit, current_p, exit1);
 420             }
 421         }
 422     }
 423     if (GC_ext_descriptors[env].ed_continued) {
 424         /* Push an entry with the rest of the descriptor back onto the  */
 425         /* stack.  Thus we never do too much work at once.  Note that   */
 426         /* we also can't overflow the mark stack unless we actually     */
 427         /* mark something.                                              */
 428         mark_stack_ptr++;
 429         if (mark_stack_ptr >= mark_stack_limit) {
 430             mark_stack_ptr = GC_signal_mark_stack_overflow(mark_stack_ptr);
 431         }
 432         mark_stack_ptr -> mse_start = addr + WORDSZ;
 433         mark_stack_ptr -> mse_descr =
 434                 GC_MAKE_PROC(GC_typed_mark_proc_index, env+1);
 435     }
 436     return(mark_stack_ptr);
 437 }
 438
 439 /* Return the size of the object described by d.  It would be faster to */
 440 /* store this directly, or to compute it as part of                     */
 441 /* GC_push_complex_descriptor, but hopefully it doesn't matter.         */
 442 word GC_descr_obj_size(d)
 443 register complex_descriptor *d;
 444 {
 445     switch(d -> TAG) {
 446       case LEAF_TAG:
 447         return(d -> ld.ld_nelements * d -> ld.ld_size);
 448       case ARRAY_TAG:
 449         return(d -> ad.ad_nelements
 450                * GC_descr_obj_size(d -> ad.ad_element_descr));
 451       case SEQUENCE_TAG:
 452         return(GC_descr_obj_size(d -> sd.sd_first)
 453                + GC_descr_obj_size(d -> sd.sd_second));
 454       default:
 455         ABORT("Bad complex descriptor");
 456         /*NOTREACHED*/ return 0; /*NOTREACHED*/
 457     }
 458 }
 459
 460 /* Push descriptors for the object at addr with complex descriptor d    */
 461 /* onto the mark stack.  Return 0 if the mark stack overflowed.         */
 462 mse * GC_push_complex_descriptor(addr, d, msp, msl)
 463 word * addr;
 464 register complex_descriptor *d;
 465 register mse * msp;
 466 mse * msl;
 467 {
 468     register ptr_t current = (ptr_t) addr;
 469     register word nelements;
 470     register word sz;
 471     register word i;
 472
 473     switch(d -> TAG) {
 474       case LEAF_TAG:
 475         {
 476           register GC_descr descr = d -> ld.ld_descriptor;
 477
 478           nelements = d -> ld.ld_nelements;
 479           if (msl - msp <= (ptrdiff_t)nelements) return(0);
 480           sz = d -> ld.ld_size;
 481           for (i = 0; i < nelements; i++) {
 482               msp++;
 483               msp -> mse_start = (word *)current;
 484               msp -> mse_descr = descr;
 485               current += sz;
 486           }
 487           return(msp);
 488         }
 489       case ARRAY_TAG:
 490         {
 491           register complex_descriptor *descr = d -> ad.ad_element_descr;
 492
 493           nelements = d -> ad.ad_nelements;
 494           sz = GC_descr_obj_size(descr);
 495           for (i = 0; i < nelements; i++) {
 496               msp = GC_push_complex_descriptor((word *)current, descr,
 497                                                 msp, msl);
 498               if (msp == 0) return(0);
 499               current += sz;
 500           }
 501           return(msp);
 502         }
 503       case SEQUENCE_TAG:
 504         {
 505           sz = GC_descr_obj_size(d -> sd.sd_first);
 506           msp = GC_push_complex_descriptor((word *)current, d -> sd.sd_first,
 507                                            msp, msl);
 508           if (msp == 0) return(0);
 509           current += sz;
 510           msp = GC_push_complex_descriptor((word *)current, d -> sd.sd_second,
 511                                            msp, msl);
 512           return(msp);
 513         }
 514       default:
 515         ABORT("Bad complex descriptor");
 516         /*NOTREACHED*/ return 0; /*NOTREACHED*/
 517    }
 518 }
 519
 520 /*ARGSUSED*/
 521 # if defined(__STDC__) || defined(__cplusplus)
 522     mse * GC_array_mark_proc(register word * addr,
 523                              register mse * mark_stack_ptr,
 524                              mse * mark_stack_limit,
 525                              word env)
 526 # else
 527     mse * GC_array_mark_proc(addr, mark_stack_ptr, mark_stack_limit, env)
 528     register word * addr;
 529     register mse * mark_stack_ptr;
 530     mse * mark_stack_limit;
 531     word env;
 532 # endif
 533 {
 534     register hdr * hhdr = HDR(addr);
 535     register word sz = hhdr -> hb_sz;
 536     register complex_descriptor * descr = (complex_descriptor *)(addr[sz-1]);
 537     mse * orig_mark_stack_ptr = mark_stack_ptr;
 538     mse * new_mark_stack_ptr;
 539
 540     if (descr == 0) {
 541         /* Found a reference to a free list entry.  Ignore it. */
 542         return(orig_mark_stack_ptr);
 543     }
 544     /* In use counts were already updated when array descriptor was     */
 545     /* pushed.  Here we only replace it by subobject descriptors, so    */
 546     /* no update is necessary.                                          */
 547     new_mark_stack_ptr = GC_push_complex_descriptor(addr, descr,
 548                                                     mark_stack_ptr,
 549                                                     mark_stack_limit-1);
 550     if (new_mark_stack_ptr == 0) {
 551         /* Doesn't fit.  Conservatively push the whole array as a unit  */
 552         /* and request a mark stack expansion.                          */
 553         /* This cannot cause a mark stack overflow, since it replaces   */
 554         /* the original array entry.                                    */
 555         GC_mark_stack_too_small = TRUE;
 556         new_mark_stack_ptr = orig_mark_stack_ptr + 1;
 557         new_mark_stack_ptr -> mse_start = addr;
 558         new_mark_stack_ptr -> mse_descr = WORDS_TO_BYTES(sz) | GC_DS_LENGTH;
 559     } else {
 560         /* Push descriptor itself */
 561         new_mark_stack_ptr++;
 562         new_mark_stack_ptr -> mse_start = addr + sz - 1;
 563         new_mark_stack_ptr -> mse_descr = sizeof(word) | GC_DS_LENGTH;
 564     }
 565     return(new_mark_stack_ptr);
 566 }
 567
 568 #if defined(__STDC__) || defined(__cplusplus)
 569   GC_descr GC_make_descriptor(GC_bitmap bm, size_t len)
 570 #else
 571   GC_descr GC_make_descriptor(bm, len)
 572   GC_bitmap bm;
 573   size_t len;
 574 #endif
 575 {
 576     register signed_word last_set_bit = len - 1;
 577     register word result;
 578     register int i;
 579 #   define HIGH_BIT (((word)1) << (WORDSZ - 1))
 580
 581     if (!GC_explicit_typing_initialized) GC_init_explicit_typing();
 582     while (last_set_bit >= 0 && !GC_get_bit(bm, last_set_bit)) last_set_bit --;
 583     if (last_set_bit < 0) return(0 /* no pointers */);
 584 #   if ALIGNMENT == CPP_WORDSZ/8
 585     {
 586       register GC_bool all_bits_set = TRUE;
 587       for (i = 0; i < last_set_bit; i++) {
 588         if (!GC_get_bit(bm, i)) {
 589             all_bits_set = FALSE;
 590             break;
 591         }
 592       }
 593       if (all_bits_set) {
 594         /* An initial section contains all pointers.  Use length descriptor. */
 595         return(WORDS_TO_BYTES(last_set_bit+1) | GC_DS_LENGTH);
 596       }
 597     }
 598 #   endif
 599     if (last_set_bit < BITMAP_BITS) {
 600         /* Hopefully the common case.                   */
 601         /* Build bitmap descriptor (with bits reversed) */
 602         result = HIGH_BIT;
 603         for (i = last_set_bit - 1; i >= 0; i--) {
 604             result >>= 1;
 605             if (GC_get_bit(bm, i)) result |= HIGH_BIT;
 606         }
 607         result |= GC_DS_BITMAP;
 608         return(result);
 609     } else {
 610         signed_word index;
 611
 612         index = GC_add_ext_descriptor(bm, (word)last_set_bit+1);
 613         if (index == -1) return(WORDS_TO_BYTES(last_set_bit+1) | GC_DS_LENGTH);
 614                                 /* Out of memory: use conservative      */
 615                                 /* approximation.                       */
 616         result = GC_MAKE_PROC(GC_typed_mark_proc_index, (word)index);
 617         return(result);
 618     }
 619 }
 620
 621 ptr_t GC_clear_stack();
 622
 623 #define GENERAL_MALLOC(lb,k) \
 624     (GC_PTR)GC_clear_stack(GC_generic_malloc((word)lb, k))
 625
 626 #define GENERAL_MALLOC_IOP(lb,k) \
 627     (GC_PTR)GC_clear_stack(GC_generic_malloc_ignore_off_page(lb, k))
 628
 629 #if defined(__STDC__) || defined(__cplusplus)
 630   void * GC_malloc_explicitly_typed(size_t lb, GC_descr d)
 631 #else
 632   char * GC_malloc_explicitly_typed(lb, d)
 633   size_t lb;
 634   GC_descr d;
 635 #endif
 636 {
 637 register ptr_t op;
 638 register ptr_t * opp;
 639 register word lw;
 640 DCL_LOCK_STATE;
 641
 642     lb += TYPD_EXTRA_BYTES;
 643     if( SMALL_OBJ(lb) ) {
 644 #       ifdef MERGE_SIZES
 645           lw = GC_size_map[lb];
 646 #       else
 647           lw = ALIGNED_WORDS(lb);
 648 #       endif
 649         opp = &(GC_eobjfreelist[lw]);
 650         FASTLOCK();
 651         if( !FASTLOCK_SUCCEEDED() || (op = *opp) == 0 ) {
 652             FASTUNLOCK();
 653             op = (ptr_t)GENERAL_MALLOC((word)lb, GC_explicit_kind);
 654             if (0 == op) return 0;
 655 #           ifdef MERGE_SIZES
 656                 lw = GC_size_map[lb];   /* May have been uninitialized. */
 657 #           endif
 658         } else {
 659             *opp = obj_link(op);
 660             obj_link(op) = 0;
 661             GC_words_allocd += lw;
 662             FASTUNLOCK();
 663         }
 664    } else {
 665        op = (ptr_t)GENERAL_MALLOC((word)lb, GC_explicit_kind);
 666        if (op != NULL)
 667             lw = BYTES_TO_WORDS(GC_size(op));
 668    }
 669    if (op != NULL)
 670        ((word *)op)[lw - 1] = d;
 671    return((GC_PTR) op);
 672 }
 673
 674 #if defined(__STDC__) || defined(__cplusplus)
 675   void * GC_malloc_explicitly_typed_ignore_off_page(size_t lb, GC_descr d)
 676 #else
 677   char * GC_malloc_explicitly_typed_ignore_off_page(lb, d)
 678   size_t lb;
 679   GC_descr d;
 680 #endif
 681 {
 682 register ptr_t op;
 683 register ptr_t * opp;
 684 register word lw;
 685 DCL_LOCK_STATE;
 686
 687     lb += TYPD_EXTRA_BYTES;
 688     if( SMALL_OBJ(lb) ) {
 689 #       ifdef MERGE_SIZES
 690           lw = GC_size_map[lb];
 691 #       else
 692           lw = ALIGNED_WORDS(lb);
 693 #       endif
 694         opp = &(GC_eobjfreelist[lw]);
 695         FASTLOCK();
 696         if( !FASTLOCK_SUCCEEDED() || (op = *opp) == 0 ) {
 697             FASTUNLOCK();
 698             op = (ptr_t)GENERAL_MALLOC_IOP(lb, GC_explicit_kind);
 699 #           ifdef MERGE_SIZES
 700                 lw = GC_size_map[lb];   /* May have been uninitialized. */
 701 #           endif
 702         } else {
 703             *opp = obj_link(op);
 704             obj_link(op) = 0;
 705             GC_words_allocd += lw;
 706             FASTUNLOCK();
 707         }
 708    } else {
 709        op = (ptr_t)GENERAL_MALLOC_IOP(lb, GC_explicit_kind);
 710        if (op != NULL)
 711        lw = BYTES_TO_WORDS(GC_size(op));
 712    }
 713    if (op != NULL)
 714        ((word *)op)[lw - 1] = d;
 715    return((GC_PTR) op);
 716 }
 717
 718 #if defined(__STDC__) || defined(__cplusplus)
 719   void * GC_calloc_explicitly_typed(size_t n,
 720                                     size_t lb,
 721                                     GC_descr d)
 722 #else
 723   char * GC_calloc_explicitly_typed(n, lb, d)
 724   size_t n;
 725   size_t lb;
 726   GC_descr d;
 727 #endif
 728 {
 729 register ptr_t op;
 730 register ptr_t * opp;
 731 register word lw;
 732 GC_descr simple_descr;
 733 complex_descriptor *complex_descr;
 734 register int descr_type;
 735 struct LeafDescriptor leaf;
 736 DCL_LOCK_STATE;
 737
 738     descr_type = GC_make_array_descriptor((word)n, (word)lb, d,
 739                                           &simple_descr, &complex_descr, &leaf);
 740     switch(descr_type) {
 741         case NO_MEM: return(0);
 742         case SIMPLE: return(GC_malloc_explicitly_typed(n*lb, simple_descr));
 743         case LEAF:
 744             lb *= n;
 745             lb += sizeof(struct LeafDescriptor) + TYPD_EXTRA_BYTES;
 746             break;
 747         case COMPLEX:
 748             lb *= n;
 749             lb += TYPD_EXTRA_BYTES;
 750             break;
 751     }
 752     if( SMALL_OBJ(lb) ) {
 753 #       ifdef MERGE_SIZES
 754           lw = GC_size_map[lb];
 755 #       else
 756           lw = ALIGNED_WORDS(lb);
 757 #       endif
 758         opp = &(GC_arobjfreelist[lw]);
 759         FASTLOCK();
 760         if( !FASTLOCK_SUCCEEDED() || (op = *opp) == 0 ) {
 761             FASTUNLOCK();
 762             op = (ptr_t)GENERAL_MALLOC((word)lb, GC_array_kind);
 763             if (0 == op) return(0);
 764 #           ifdef MERGE_SIZES
 765                 lw = GC_size_map[lb];   /* May have been uninitialized. */
 766 #           endif
 767         } else {
 768             *opp = obj_link(op);
 769             obj_link(op) = 0;
 770             GC_words_allocd += lw;
 771             FASTUNLOCK();
 772         }
 773    } else {
 774        op = (ptr_t)GENERAL_MALLOC((word)lb, GC_array_kind);
 775        if (0 == op) return(0);
 776        lw = BYTES_TO_WORDS(GC_size(op));
 777    }
 778    if (descr_type == LEAF) {
 779        /* Set up the descriptor inside the object itself. */
 780        VOLATILE struct LeafDescriptor * lp =
 781            (struct LeafDescriptor *)
 782                ((word *)op
 783                 + lw - (BYTES_TO_WORDS(sizeof(struct LeafDescriptor)) + 1));
 784
 785        lp -> ld_tag = LEAF_TAG;
 786        lp -> ld_size = leaf.ld_size;
 787        lp -> ld_nelements = leaf.ld_nelements;
 788        lp -> ld_descriptor = leaf.ld_descriptor;
 789        ((VOLATILE word *)op)[lw - 1] = (word)lp;
 790    } else {
 791        extern unsigned GC_finalization_failures;
 792        unsigned ff = GC_finalization_failures;
 793
 794        ((word *)op)[lw - 1] = (word)complex_descr;
 795        /* Make sure the descriptor is cleared once there is any danger  */
 796        /* it may have been collected.                                   */
 797        (void)
 798          GC_general_register_disappearing_link((GC_PTR *)
 799                                                   ((word *)op+lw-1),
 800                                                   (GC_PTR) op);
 801        if (ff != GC_finalization_failures) {
 802            /* Couldn't register it due to lack of memory.  Punt.        */
 803            /* This will probably fail too, but gives the recovery code  */
 804            /* a chance.                                                 */
 805            return(GC_malloc(n*lb));
 806        }
 807    }
 808    return((GC_PTR) op);
 809 }