boehm-gc/mallocx.c

   1 /*
   2  * Copyright 1988, 1989 Hans-J. Boehm, Alan J. Demers
   3  * Copyright (c) 1991-1994 by Xerox Corporation.  All rights reserved.
   4  * Copyright (c) 1996 by Silicon Graphics.  All rights reserved.
   5  * Copyright (c) 2000 by Hewlett-Packard Company.  All rights reserved.
   6  *
   7  * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
   8  * OR IMPLIED.  ANY USE IS AT YOUR OWN RISK.
   9  *
  10  * Permission is hereby granted to use or copy this program
  11  * for any purpose,  provided the above notices are retained on all copies.
  12  * Permission to modify the code and to distribute modified code is granted,
  13  * provided the above notices are retained, and a notice that the code was
  14  * modified is included with the above copyright notice.
  15  */
  16
  17 /*
  18  * These are extra allocation routines which are likely to be less
  19  * frequently used than those in malloc.c.  They are separate in the
  20  * hope that the .o file will be excluded from statically linked
  21  * executables.  We should probably break this up further.
  22  */
  23
  24 #include <stdio.h>
  25 #include "private/gc_priv.h"
  26
  27 extern ptr_t GC_clear_stack();  /* in misc.c, behaves like identity */
  28 void GC_extend_size_map();      /* in misc.c. */
  29 GC_bool GC_alloc_reclaim_list();        /* in malloc.c */
  30
  31 /* Some externally visible but unadvertised variables to allow access to */
  32 /* free lists from inlined allocators without including gc_priv.h        */
  33 /* or introducing dependencies on internal data structure layouts.       */
  34 ptr_t * GC_CONST GC_objfreelist_ptr = GC_objfreelist;
  35 ptr_t * GC_CONST GC_aobjfreelist_ptr = GC_aobjfreelist;
  36 ptr_t * GC_CONST GC_uobjfreelist_ptr = GC_uobjfreelist;
  37 # ifdef ATOMIC_UNCOLLECTABLE
  38     ptr_t * GC_CONST GC_auobjfreelist_ptr = GC_auobjfreelist;
  39 # endif
  40
  41
  42 GC_PTR GC_generic_or_special_malloc(lb,knd)
  43 word lb;
  44 int knd;
  45 {
  46     switch(knd) {
  47 #     ifdef STUBBORN_ALLOC
  48         case STUBBORN:
  49             return(GC_malloc_stubborn((size_t)lb));
  50 #     endif
  51         case PTRFREE:
  52             return(GC_malloc_atomic((size_t)lb));
  53         case NORMAL:
  54             return(GC_malloc((size_t)lb));
  55         case UNCOLLECTABLE:
  56             return(GC_malloc_uncollectable((size_t)lb));
  57 #       ifdef ATOMIC_UNCOLLECTABLE
  58           case AUNCOLLECTABLE:
  59             return(GC_malloc_atomic_uncollectable((size_t)lb));
  60 #       endif /* ATOMIC_UNCOLLECTABLE */
  61         default:
  62             return(GC_generic_malloc(lb,knd));
  63     }
  64 }
  65
  66
  67 /* Change the size of the block pointed to by p to contain at least   */
  68 /* lb bytes.  The object may be (and quite likely will be) moved.     */
  69 /* The kind (e.g. atomic) is the same as that of the old.             */
  70 /* Shrinking of large blocks is not implemented well.                 */
  71 # ifdef __STDC__
  72     GC_PTR GC_realloc(GC_PTR p, size_t lb)
  73 # else
  74     GC_PTR GC_realloc(p,lb)
  75     GC_PTR p;
  76     size_t lb;
  77 # endif
  78 {
  79 register struct hblk * h;
  80 register hdr * hhdr;
  81 register word sz;        /* Current size in bytes       */
  82 register word orig_sz;   /* Original sz in bytes        */
  83 int obj_kind;
  84
  85     if (p == 0) return(GC_malloc(lb));  /* Required by ANSI */
  86     h = HBLKPTR(p);
  87     hhdr = HDR(h);
  88     sz = hhdr -> hb_sz;
  89     obj_kind = hhdr -> hb_obj_kind;
  90     sz = WORDS_TO_BYTES(sz);
  91     orig_sz = sz;
  92
  93     if (sz > MAXOBJBYTES) {
  94         /* Round it up to the next whole heap block */
  95           register word descr;
  96
  97           sz = (sz+HBLKSIZE-1) & (~HBLKMASK);
  98           hhdr -> hb_sz = BYTES_TO_WORDS(sz);
  99           descr = GC_obj_kinds[obj_kind].ok_descriptor;
 100           if (GC_obj_kinds[obj_kind].ok_relocate_descr) descr += sz;
 101           hhdr -> hb_descr = descr;
 102           if (IS_UNCOLLECTABLE(obj_kind)) GC_non_gc_bytes += (sz - orig_sz);
 103           /* Extra area is already cleared by GC_alloc_large_and_clear. */
 104     }
 105     if (ADD_SLOP(lb) <= sz) {
 106         if (lb >= (sz >> 1)) {
 107 #           ifdef STUBBORN_ALLOC
 108                 if (obj_kind == STUBBORN) GC_change_stubborn(p);
 109 #           endif
 110             if (orig_sz > lb) {
 111               /* Clear unneeded part of object to avoid bogus pointer */
 112               /* tracing.                                             */
 113               /* Safe for stubborn objects.                           */
 114                 BZERO(((ptr_t)p) + lb, orig_sz - lb);
 115             }
 116             return(p);
 117         } else {
 118             /* shrink */
 119               GC_PTR result =
 120                         GC_generic_or_special_malloc((word)lb, obj_kind);
 121
 122               if (result == 0) return(0);
 123                   /* Could also return original object.  But this       */
 124                   /* gives the client warning of imminent disaster.     */
 125               BCOPY(p, result, lb);
 126 #             ifndef IGNORE_FREE
 127                 GC_free(p);
 128 #             endif
 129               return(result);
 130         }
 131     } else {
 132         /* grow */
 133           GC_PTR result =
 134                 GC_generic_or_special_malloc((word)lb, obj_kind);
 135
 136           if (result == 0) return(0);
 137           BCOPY(p, result, sz);
 138 #         ifndef IGNORE_FREE
 139             GC_free(p);
 140 #         endif
 141           return(result);
 142     }
 143 }
 144
 145 # if defined(REDIRECT_MALLOC) && !defined(REDIRECT_REALLOC)
 146 #   define REDIRECT_REALLOC GC_realloc
 147 # endif
 148
 149 # ifdef REDIRECT_REALLOC
 150 # ifdef __STDC__
 151     GC_PTR realloc(GC_PTR p, size_t lb)
 152 # else
 153     GC_PTR realloc(p,lb)
 154     GC_PTR p;
 155     size_t lb;
 156 # endif
 157   {
 158     return(REDIRECT_REALLOC(p, lb));
 159   }
 160 # endif /* REDIRECT_REALLOC */
 161
 162
 163 /* The same thing, except caller does not hold allocation lock. */
 164 /* We avoid holding allocation lock while we clear memory.      */
 165 ptr_t GC_generic_malloc_ignore_off_page(lb, k)
 166 register size_t lb;
 167 register int k;
 168 {
 169     register ptr_t result;
 170     word lw;
 171     word n_blocks;
 172     GC_bool init;
 173     DCL_LOCK_STATE;
 174
 175     if (SMALL_OBJ(lb))
 176         return(GC_generic_malloc((word)lb, k));
 177     lw = ROUNDED_UP_WORDS(lb);
 178     n_blocks = OBJ_SZ_TO_BLOCKS(lw);
 179     init = GC_obj_kinds[k].ok_init;
 180     if (GC_have_errors) GC_print_all_errors();
 181     GC_INVOKE_FINALIZERS();
 182     DISABLE_SIGNALS();
 183     LOCK();
 184     result = (ptr_t)GC_alloc_large(lw, k, IGNORE_OFF_PAGE);
 185     if (0 != result) {
 186         if (GC_debugging_started) {
 187             BZERO(result, n_blocks * HBLKSIZE);
 188         } else {
 189 #           ifdef THREADS
 190               /* Clear any memory that might be used for GC descriptors */
 191               /* before we release the lock.                          */
 192                 ((word *)result)[0] = 0;
 193                 ((word *)result)[1] = 0;
 194                 ((word *)result)[lw-1] = 0;
 195                 ((word *)result)[lw-2] = 0;
 196 #           endif
 197         }
 198     }
 199     GC_words_allocd += lw;
 200     UNLOCK();
 201     ENABLE_SIGNALS();
 202     if (0 == result) {
 203         return((*GC_oom_fn)(lb));
 204     } else {
 205         if (init & !GC_debugging_started) {
 206             BZERO(result, n_blocks * HBLKSIZE);
 207         }
 208         return(result);
 209     }
 210 }
 211
 212 # if defined(__STDC__) || defined(__cplusplus)
 213   void * GC_malloc_ignore_off_page(size_t lb)
 214 # else
 215   char * GC_malloc_ignore_off_page(lb)
 216   register size_t lb;
 217 # endif
 218 {
 219     return((GC_PTR)GC_generic_malloc_ignore_off_page(lb, NORMAL));
 220 }
 221
 222 # if defined(__STDC__) || defined(__cplusplus)
 223   void * GC_malloc_atomic_ignore_off_page(size_t lb)
 224 # else
 225   char * GC_malloc_atomic_ignore_off_page(lb)
 226   register size_t lb;
 227 # endif
 228 {
 229     return((GC_PTR)GC_generic_malloc_ignore_off_page(lb, PTRFREE));
 230 }
 231
 232 /* Increment GC_words_allocd from code that doesn't have direct access  */
 233 /* to GC_arrays.                                                        */
 234 # ifdef __STDC__
 235 void GC_incr_words_allocd(size_t n)
 236 {
 237     GC_words_allocd += n;
 238 }
 239
 240 /* The same for GC_mem_freed.                           */
 241 void GC_incr_mem_freed(size_t n)
 242 {
 243     GC_mem_freed += n;
 244 }
 245 # endif /* __STDC__ */
 246
 247 /* Analogous to the above, but assumes a small object size, and         */
 248 /* bypasses MERGE_SIZES mechanism.  Used by gc_inline.h.                */
 249 ptr_t GC_generic_malloc_words_small_inner(lw, k)
 250 register word lw;
 251 register int k;
 252 {
 253 register ptr_t op;
 254 register ptr_t *opp;
 255 register struct obj_kind * kind = GC_obj_kinds + k;
 256
 257     opp = &(kind -> ok_freelist[lw]);
 258     if( (op = *opp) == 0 ) {
 259         if (!GC_is_initialized) {
 260             GC_init_inner();
 261         }
 262         if (kind -> ok_reclaim_list != 0 || GC_alloc_reclaim_list(kind)) {
 263             op = GC_clear_stack(GC_allocobj((word)lw, k));
 264         }
 265         if (op == 0) {
 266             UNLOCK();
 267             ENABLE_SIGNALS();
 268             return ((*GC_oom_fn)(WORDS_TO_BYTES(lw)));
 269         }
 270     }
 271     *opp = obj_link(op);
 272     obj_link(op) = 0;
 273     GC_words_allocd += lw;
 274     return((ptr_t)op);
 275 }
 276
 277 /* Analogous to the above, but assumes a small object size, and         */
 278 /* bypasses MERGE_SIZES mechanism.  Used by gc_inline.h.                */
 279 #ifdef __STDC__
 280      ptr_t GC_generic_malloc_words_small(size_t lw, int k)
 281 #else
 282      ptr_t GC_generic_malloc_words_small(lw, k)
 283      register word lw;
 284      register int k;
 285 #endif
 286 {
 287 register ptr_t op;
 288 DCL_LOCK_STATE;
 289
 290     if (GC_have_errors) GC_print_all_errors();
 291     GC_INVOKE_FINALIZERS();
 292     DISABLE_SIGNALS();
 293     LOCK();
 294     op = GC_generic_malloc_words_small_inner(lw, k);
 295     UNLOCK();
 296     ENABLE_SIGNALS();
 297     return((ptr_t)op);
 298 }
 299
 300 #if defined(THREADS) && !defined(SRC_M3)
 301
 302 extern signed_word GC_mem_found;   /* Protected by GC lock.  */
 303
 304 #ifdef PARALLEL_MARK
 305 volatile signed_word GC_words_allocd_tmp = 0;
 306                         /* Number of words of memory allocated since    */
 307                         /* we released the GC lock.  Instead of         */
 308                         /* reacquiring the GC lock just to add this in, */
 309                         /* we add it in the next time we reacquire      */
 310                         /* the lock.  (Atomically adding it doesn't     */
 311                         /* work, since we would have to atomically      */
 312                         /* update it in GC_malloc, which is too         */
 313                         /* expensive.                                   */
 314 #endif /* PARALLEL_MARK */
 315
 316 /* See reclaim.c: */
 317 extern ptr_t GC_reclaim_generic();
 318
 319 /* Return a list of 1 or more objects of the indicated size, linked     */
 320 /* through the first word in the object.  This has the advantage that   */
 321 /* it acquires the allocation lock only once, and may greatly reduce    */
 322 /* time wasted contending for the allocation lock.  Typical usage would */
 323 /* be in a thread that requires many items of the same size.  It would  */
 324 /* keep its own free list in thread-local storage, and call             */
 325 /* GC_malloc_many or friends to replenish it.  (We do not round up      */
 326 /* object sizes, since a call indicates the intention to consume many   */
 327 /* objects of exactly this size.)                                       */
 328 /* We return the free-list by assigning it to *result, since it is      */
 329 /* not safe to return, e.g. a linked list of pointer-free objects,      */
 330 /* since the collector would not retain the entire list if it were      */
 331 /* invoked just as we were returning.                                   */
 332 /* Note that the client should usually clear the link field.            */
 333 void GC_generic_malloc_many(lb, k, result)
 334 register word lb;
 335 register int k;
 336 ptr_t *result;
 337 {
 338 ptr_t op;
 339 ptr_t p;
 340 ptr_t *opp;
 341 word lw;
 342 word my_words_allocd = 0;
 343 struct obj_kind * ok = &(GC_obj_kinds[k]);
 344 DCL_LOCK_STATE;
 345
 346 #   if defined(GATHERSTATS) || defined(PARALLEL_MARK)
 347 #     define COUNT_ARG , &my_words_allocd
 348 #   else
 349 #     define COUNT_ARG
 350 #     define NEED_TO_COUNT
 351 #   endif
 352     if (!SMALL_OBJ(lb)) {
 353         op = GC_generic_malloc(lb, k);
 354         if(0 != op) obj_link(op) = 0;
 355         *result = op;
 356         return;
 357     }
 358     lw = ALIGNED_WORDS(lb);
 359     if (GC_have_errors) GC_print_all_errors();
 360     GC_INVOKE_FINALIZERS();
 361     DISABLE_SIGNALS();
 362     LOCK();
 363     if (!GC_is_initialized) GC_init_inner();
 364     /* Do our share of marking work */
 365       if (GC_incremental && !GC_dont_gc) {
 366         ENTER_GC();
 367         GC_collect_a_little_inner(1);
 368         EXIT_GC();
 369       }
 370     /* First see if we can reclaim a page of objects waiting to be */
 371     /* reclaimed.                                                  */
 372     {
 373         struct hblk ** rlh = ok -> ok_reclaim_list;
 374         struct hblk * hbp;
 375         hdr * hhdr;
 376
 377         rlh += lw;
 378         while ((hbp = *rlh) != 0) {
 379             hhdr = HDR(hbp);
 380             *rlh = hhdr -> hb_next;
 381             hhdr -> hb_last_reclaimed = (unsigned short) GC_gc_no;
 382 #           ifdef PARALLEL_MARK
 383                 {
 384                   signed_word my_words_allocd_tmp = GC_words_allocd_tmp;
 385
 386                   GC_ASSERT(my_words_allocd_tmp >= 0);
 387                   /* We only decrement it while holding the GC lock.    */
 388                   /* Thus we can't accidentally adjust it down in more  */
 389                   /* than one thread simultaneously.                    */
 390                   if (my_words_allocd_tmp != 0) {
 391                     (void)GC_atomic_add(
 392                                 (volatile GC_word *)(&GC_words_allocd_tmp),
 393                                 (GC_word)(-my_words_allocd_tmp));
 394                     GC_words_allocd += my_words_allocd_tmp;
 395                   }
 396                 }
 397                 GC_acquire_mark_lock();
 398                 ++ GC_fl_builder_count;
 399                 UNLOCK();
 400                 ENABLE_SIGNALS();
 401                 GC_release_mark_lock();
 402 #           endif
 403             op = GC_reclaim_generic(hbp, hhdr, lw,
 404                                     ok -> ok_init, 0 COUNT_ARG);
 405             if (op != 0) {
 406 #             ifdef NEED_TO_COUNT
 407                 /* We are neither gathering statistics, nor marking in  */
 408                 /* parallel.  Thus GC_reclaim_generic doesn't count     */
 409                 /* for us.                                              */
 410                 for (p = op; p != 0; p = obj_link(p)) {
 411                   my_words_allocd += lw;
 412                 }
 413 #             endif
 414 #             if defined(GATHERSTATS)
 415                 /* We also reclaimed memory, so we need to adjust       */
 416                 /* that count.                                          */
 417                 /* This should be atomic, so the results may be         */
 418                 /* inaccurate.                                          */
 419                 GC_mem_found += my_words_allocd;
 420 #             endif
 421 #             ifdef PARALLEL_MARK
 422                 *result = op;
 423                 (void)GC_atomic_add(
 424                                 (volatile GC_word *)(&GC_words_allocd_tmp),
 425                                 (GC_word)(my_words_allocd));
 426                 GC_acquire_mark_lock();
 427                 -- GC_fl_builder_count;
 428                 if (GC_fl_builder_count == 0) GC_notify_all_builder();
 429                 GC_release_mark_lock();
 430                 (void) GC_clear_stack(0);
 431                 return;
 432 #             else
 433                 GC_words_allocd += my_words_allocd;
 434                 goto out;
 435 #             endif
 436             }
 437 #           ifdef PARALLEL_MARK
 438               GC_acquire_mark_lock();
 439               -- GC_fl_builder_count;
 440               if (GC_fl_builder_count == 0) GC_notify_all_builder();
 441               GC_release_mark_lock();
 442               DISABLE_SIGNALS();
 443               LOCK();
 444               /* GC lock is needed for reclaim list access.     We      */
 445               /* must decrement fl_builder_count before reaquiring GC   */
 446               /* lock.  Hopefully this path is rare.                    */
 447 #           endif
 448         }
 449     }
 450     /* Next try to use prefix of global free list if there is one.      */
 451     /* We don't refill it, but we need to use it up before allocating   */
 452     /* a new block ourselves.                                           */
 453       opp = &(GC_obj_kinds[k].ok_freelist[lw]);
 454       if ( (op = *opp) != 0 ) {
 455         *opp = 0;
 456         my_words_allocd = 0;
 457         for (p = op; p != 0; p = obj_link(p)) {
 458           my_words_allocd += lw;
 459           if (my_words_allocd >= BODY_SZ) {
 460             *opp = obj_link(p);
 461             obj_link(p) = 0;
 462             break;
 463           }
 464         }
 465         GC_words_allocd += my_words_allocd;
 466         goto out;
 467       }
 468     /* Next try to allocate a new block worth of objects of this size.  */
 469     {
 470         struct hblk *h = GC_allochblk(lw, k, 0);
 471         if (h != 0) {
 472           if (IS_UNCOLLECTABLE(k)) GC_set_hdr_marks(HDR(h));
 473           GC_words_allocd += BYTES_TO_WORDS(HBLKSIZE)
 474                                - BYTES_TO_WORDS(HBLKSIZE) % lw;
 475 #         ifdef PARALLEL_MARK
 476             GC_acquire_mark_lock();
 477             ++ GC_fl_builder_count;
 478             UNLOCK();
 479             ENABLE_SIGNALS();
 480             GC_release_mark_lock();
 481 #         endif
 482
 483           op = GC_build_fl(h, lw, ok -> ok_init, 0);
 484 #         ifdef PARALLEL_MARK
 485             *result = op;
 486             GC_acquire_mark_lock();
 487             -- GC_fl_builder_count;
 488             if (GC_fl_builder_count == 0) GC_notify_all_builder();
 489             GC_release_mark_lock();
 490             (void) GC_clear_stack(0);
 491             return;
 492 #         else
 493             goto out;
 494 #         endif
 495         }
 496     }
 497
 498     /* As a last attempt, try allocating a single object.  Note that    */
 499     /* this may trigger a collection or expand the heap.                */
 500       op = GC_generic_malloc_inner(lb, k);
 501       if (0 != op) obj_link(op) = 0;
 502
 503   out:
 504     *result = op;
 505     UNLOCK();
 506     ENABLE_SIGNALS();
 507     (void) GC_clear_stack(0);
 508 }
 509
 510 GC_PTR GC_malloc_many(size_t lb)
 511 {
 512     ptr_t result;
 513     GC_generic_malloc_many(lb, NORMAL, &result);
 514     return result;
 515 }
 516
 517 /* Note that the "atomic" version of this would be unsafe, since the    */
 518 /* links would not be seen by the collector.                            */
 519 # endif
 520
 521 /* Allocate lb bytes of pointerful, traced, but not collectable data */
 522 # ifdef __STDC__
 523     GC_PTR GC_malloc_uncollectable(size_t lb)
 524 # else
 525     GC_PTR GC_malloc_uncollectable(lb)
 526     size_t lb;
 527 # endif
 528 {
 529 register ptr_t op;
 530 register ptr_t *opp;
 531 register word lw;
 532 DCL_LOCK_STATE;
 533
 534     if( SMALL_OBJ(lb) ) {
 535 #       ifdef MERGE_SIZES
 536           if (EXTRA_BYTES != 0 && lb != 0) lb--;
 537                   /* We don't need the extra byte, since this won't be  */
 538                   /* collected anyway.                                  */
 539           lw = GC_size_map[lb];
 540 #       else
 541           lw = ALIGNED_WORDS(lb);
 542 #       endif
 543         opp = &(GC_uobjfreelist[lw]);
 544         FASTLOCK();
 545         if( FASTLOCK_SUCCEEDED() && (op = *opp) != 0 ) {
 546             /* See above comment on signals.    */
 547             *opp = obj_link(op);
 548             obj_link(op) = 0;
 549             GC_words_allocd += lw;
 550             /* Mark bit ws already set on free list.  It will be        */
 551             /* cleared only temporarily during a collection, as a       */
 552             /* result of the normal free list mark bit clearing.        */
 553             GC_non_gc_bytes += WORDS_TO_BYTES(lw);
 554             FASTUNLOCK();
 555             return((GC_PTR) op);
 556         }
 557         FASTUNLOCK();
 558         op = (ptr_t)GC_generic_malloc((word)lb, UNCOLLECTABLE);
 559     } else {
 560         op = (ptr_t)GC_generic_malloc((word)lb, UNCOLLECTABLE);
 561     }
 562     if (0 == op) return(0);
 563     /* We don't need the lock here, since we have an undisguised        */
 564     /* pointer.  We do need to hold the lock while we adjust            */
 565     /* mark bits.                                                       */
 566     {
 567         register struct hblk * h;
 568
 569         h = HBLKPTR(op);
 570         lw = HDR(h) -> hb_sz;
 571
 572         DISABLE_SIGNALS();
 573         LOCK();
 574         GC_set_mark_bit(op);
 575         GC_non_gc_bytes += WORDS_TO_BYTES(lw);
 576         UNLOCK();
 577         ENABLE_SIGNALS();
 578         return((GC_PTR) op);
 579     }
 580 }
 581
 582 #ifdef __STDC__
 583 /* Not well tested nor integrated.      */
 584 /* Debug version is tricky and currently missing.       */
 585 #include <limits.h>
 586
 587 GC_PTR GC_memalign(size_t align, size_t lb)
 588 {
 589     size_t new_lb;
 590     size_t offset;
 591     ptr_t result;
 592
 593 #   ifdef ALIGN_DOUBLE
 594         if (align <= WORDS_TO_BYTES(2) && lb > align) return GC_malloc(lb);
 595 #   endif
 596     if (align <= WORDS_TO_BYTES(1)) return GC_malloc(lb);
 597     if (align >= HBLKSIZE/2 || lb >= HBLKSIZE/2) {
 598         if (align > HBLKSIZE) return GC_oom_fn(LONG_MAX-1024) /* Fail */;
 599         return GC_malloc(lb <= HBLKSIZE? HBLKSIZE : lb);
 600             /* Will be HBLKSIZE aligned.        */
 601     }
 602     /* We could also try to make sure that the real rounded-up object size */
 603     /* is a multiple of align.  That would be correct up to HBLKSIZE.      */
 604     new_lb = lb + align - 1;
 605     result = GC_malloc(new_lb);
 606     offset = (word)result % align;
 607     if (offset != 0) {
 608         offset = align - offset;
 609         if (!GC_all_interior_pointers) {
 610             if (offset >= VALID_OFFSET_SZ) return GC_malloc(HBLKSIZE);
 611             GC_register_displacement(offset);
 612         }
 613     }
 614     result = (GC_PTR) ((ptr_t)result + offset);
 615     GC_ASSERT((word)result % align == 0);
 616     return result;
 617 }
 618 #endif
 619
 620 # ifdef ATOMIC_UNCOLLECTABLE
 621 /* Allocate lb bytes of pointerfree, untraced, uncollectable data       */
 622 /* This is normally roughly equivalent to the system malloc.            */
 623 /* But it may be useful if malloc is redefined.                         */
 624 # ifdef __STDC__
 625     GC_PTR GC_malloc_atomic_uncollectable(size_t lb)
 626 # else
 627     GC_PTR GC_malloc_atomic_uncollectable(lb)
 628     size_t lb;
 629 # endif
 630 {
 631 register ptr_t op;
 632 register ptr_t *opp;
 633 register word lw;
 634 DCL_LOCK_STATE;
 635
 636     if( SMALL_OBJ(lb) ) {
 637 #       ifdef MERGE_SIZES
 638           if (EXTRA_BYTES != 0 && lb != 0) lb--;
 639                   /* We don't need the extra byte, since this won't be  */
 640                   /* collected anyway.                                  */
 641           lw = GC_size_map[lb];
 642 #       else
 643           lw = ALIGNED_WORDS(lb);
 644 #       endif
 645         opp = &(GC_auobjfreelist[lw]);
 646         FASTLOCK();
 647         if( FASTLOCK_SUCCEEDED() && (op = *opp) != 0 ) {
 648             /* See above comment on signals.    */
 649             *opp = obj_link(op);
 650             obj_link(op) = 0;
 651             GC_words_allocd += lw;
 652             /* Mark bit was already set while object was on free list. */
 653             GC_non_gc_bytes += WORDS_TO_BYTES(lw);
 654             FASTUNLOCK();
 655             return((GC_PTR) op);
 656         }
 657         FASTUNLOCK();
 658         op = (ptr_t)GC_generic_malloc((word)lb, AUNCOLLECTABLE);
 659     } else {
 660         op = (ptr_t)GC_generic_malloc((word)lb, AUNCOLLECTABLE);
 661     }
 662     if (0 == op) return(0);
 663     /* We don't need the lock here, since we have an undisguised        */
 664     /* pointer.  We do need to hold the lock while we adjust            */
 665     /* mark bits.                                                       */
 666     {
 667         register struct hblk * h;
 668
 669         h = HBLKPTR(op);
 670         lw = HDR(h) -> hb_sz;
 671
 672         DISABLE_SIGNALS();
 673         LOCK();
 674         GC_set_mark_bit(op);
 675         GC_non_gc_bytes += WORDS_TO_BYTES(lw);
 676         UNLOCK();
 677         ENABLE_SIGNALS();
 678         return((GC_PTR) op);
 679     }
 680 }
 681
 682 #endif /* ATOMIC_UNCOLLECTABLE */