root/gc/mark.c

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DEFINITIONS

This source file includes following definitions.
  1. GC_noop
  2. GC_noop
  3. GC_noop1
  4. GC_collection_in_progress
  5. GC_clear_hdr_marks
  6. GC_set_hdr_marks
  7. clear_marks_for_block
  8. GC_set_mark_bit
  9. GC_clear_mark_bit
  10. GC_is_marked
  11. GC_clear_marks
  12. GC_initiate_gc
  13. GC_mark_some_inner
  14. ext_ex_regn
  15. mark_ex_handler
  16. GC_mark_some
  17. GC_mark_stack_empty
  18. GC_find_start
  19. GC_invalidate_mark_state
  20. GC_signal_mark_stack_overflow
  21. GC_mark_from
  22. GC_steal_mark_stack
  23. GC_return_mark_stack
  24. GC_do_local_mark
  25. GC_mark_local
  26. GC_do_parallel_mark
  27. GC_help_marker
  28. alloc_mark_stack
  29. GC_mark_init
  30. GC_push_all
  31. GC_push_selected
  32. GC_true_func
  33. GC_push_conditional
  34. GC_push_one
  35. GC_mark_and_push
  36. GC_mark_and_push_stack
  37. GC_add_trace_entry
  38. GC_print_trace
  39. GC_push_all_eager
  40. GC_push_all_stack_partially_eager
  41. GC_push_all_stack
  42. GC_push_marked1
  43. GC_push_marked2
  44. GC_push_marked4
  45. GC_push_marked
  46. GC_block_was_dirty
  47. GC_push_next_marked
  48. GC_push_next_marked_dirty
  49. GC_push_next_marked_uncollectable

   1 
   2 /*
   3  * Copyright 1988, 1989 Hans-J. Boehm, Alan J. Demers
   4  * Copyright (c) 1991-1995 by Xerox Corporation.  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 
  19 # include <stdio.h>
  20 # include "private/gc_pmark.h"
  21 
  22 #if defined(MSWIN32) && defined(__GNUC__)
  23 # include <excpt.h>
  24 #endif
  25 
  26 /* We put this here to minimize the risk of inlining. */
  27 /*VARARGS*/
  28 #ifdef __WATCOMC__
  29   void GC_noop(void *p, ...) {}
  30 #else
  31   void GC_noop() {}
  32 #endif
  33 
  34 /* Single argument version, robust against whole program analysis. */
  35 void GC_noop1(x)
  36 word x;
  37 {
  38     static VOLATILE word sink;
  39 
  40     sink = x;
  41 }
  42 
  43 /* mark_proc GC_mark_procs[MAX_MARK_PROCS] = {0} -- declared in gc_priv.h */
  44 
  45 word GC_n_mark_procs = GC_RESERVED_MARK_PROCS;
  46 
  47 /* Initialize GC_obj_kinds properly and standard free lists properly.   */
  48 /* This must be done statically since they may be accessed before       */
  49 /* GC_init is called.                                                   */
  50 /* It's done here, since we need to deal with mark descriptors.         */
  51 struct obj_kind GC_obj_kinds[MAXOBJKINDS] = {
  52 /* PTRFREE */ { &GC_aobjfreelist[0], 0 /* filled in dynamically */,
  53                 0 | GC_DS_LENGTH, FALSE, FALSE },
  54 /* NORMAL  */ { &GC_objfreelist[0], 0,
  55                 0 | GC_DS_LENGTH,  /* Adjusted in GC_init_inner for EXTRA_BYTES */
  56                 TRUE /* add length to descr */, TRUE },
  57 /* UNCOLLECTABLE */
  58               { &GC_uobjfreelist[0], 0,
  59                 0 | GC_DS_LENGTH, TRUE /* add length to descr */, TRUE },
  60 # ifdef ATOMIC_UNCOLLECTABLE
  61    /* AUNCOLLECTABLE */
  62               { &GC_auobjfreelist[0], 0,
  63                 0 | GC_DS_LENGTH, FALSE /* add length to descr */, FALSE },
  64 # endif
  65 # ifdef STUBBORN_ALLOC
  66 /*STUBBORN*/ { &GC_sobjfreelist[0], 0,
  67                 0 | GC_DS_LENGTH, TRUE /* add length to descr */, TRUE },
  68 # endif
  69 };
  70 
  71 # ifdef ATOMIC_UNCOLLECTABLE
  72 #   ifdef STUBBORN_ALLOC
  73       int GC_n_kinds = 5;
  74 #   else
  75       int GC_n_kinds = 4;
  76 #   endif
  77 # else
  78 #   ifdef STUBBORN_ALLOC
  79       int GC_n_kinds = 4;
  80 #   else
  81       int GC_n_kinds = 3;
  82 #   endif
  83 # endif
  84 
  85 
  86 # ifndef INITIAL_MARK_STACK_SIZE
  87 #   define INITIAL_MARK_STACK_SIZE (1*HBLKSIZE)
  88                 /* INITIAL_MARK_STACK_SIZE * sizeof(mse) should be a    */
  89                 /* multiple of HBLKSIZE.                                */
  90                 /* The incremental collector actually likes a larger    */
  91                 /* size, since it want to push all marked dirty objs    */
  92                 /* before marking anything new.  Currently we let it    */
  93                 /* grow dynamically.                                    */
  94 # endif
  95 
  96 /*
  97  * Limits of stack for GC_mark routine.
  98  * All ranges between GC_mark_stack(incl.) and GC_mark_stack_top(incl.) still
  99  * need to be marked from.
 100  */
 101 
 102 word GC_n_rescuing_pages;       /* Number of dirty pages we marked from */
 103                                 /* excludes ptrfree pages, etc.         */
 104 
 105 mse * GC_mark_stack;
 106 
 107 mse * GC_mark_stack_limit;
 108 
 109 word GC_mark_stack_size = 0;
 110  
 111 #ifdef PARALLEL_MARK
 112   mse * VOLATILE GC_mark_stack_top;
 113 #else
 114   mse * GC_mark_stack_top;
 115 #endif
 116 
 117 static struct hblk * scan_ptr;
 118 
 119 mark_state_t GC_mark_state = MS_NONE;
 120 
 121 GC_bool GC_mark_stack_too_small = FALSE;
 122 
 123 GC_bool GC_objects_are_marked = FALSE;  /* Are there collectable marked */
 124                                         /* objects in the heap?         */
 125 
 126 /* Is a collection in progress?  Note that this can return true in the  */
 127 /* nonincremental case, if a collection has been abandoned and the      */
 128 /* mark state is now MS_INVALID.                                        */
 129 GC_bool GC_collection_in_progress()
 130 {
 131     return(GC_mark_state != MS_NONE);
 132 }
 133 
 134 /* clear all mark bits in the header */
 135 void GC_clear_hdr_marks(hhdr)
 136 register hdr * hhdr;
 137 {
 138 #   ifdef USE_MARK_BYTES
 139       BZERO(hhdr -> hb_marks, MARK_BITS_SZ);
 140 #   else
 141       BZERO(hhdr -> hb_marks, MARK_BITS_SZ*sizeof(word));
 142 #   endif
 143 }
 144 
 145 /* Set all mark bits in the header.  Used for uncollectable blocks. */
 146 void GC_set_hdr_marks(hhdr)
 147 register hdr * hhdr;
 148 {
 149     register int i;
 150 
 151     for (i = 0; i < MARK_BITS_SZ; ++i) {
 152 #     ifdef USE_MARK_BYTES
 153         hhdr -> hb_marks[i] = 1;
 154 #     else
 155         hhdr -> hb_marks[i] = ONES;
 156 #     endif
 157     }
 158 }
 159 
 160 /*
 161  * Clear all mark bits associated with block h.
 162  */
 163 /*ARGSUSED*/
 164 # if defined(__STDC__) || defined(__cplusplus)
 165     static void clear_marks_for_block(struct hblk *h, word dummy)
 166 # else
 167     static void clear_marks_for_block(h, dummy)
 168     struct hblk *h;
 169     word dummy;
 170 # endif
 171 {
 172     register hdr * hhdr = HDR(h);
 173     
 174     if (IS_UNCOLLECTABLE(hhdr -> hb_obj_kind)) return;
 175         /* Mark bit for these is cleared only once the object is        */
 176         /* explicitly deallocated.  This either frees the block, or     */
 177         /* the bit is cleared once the object is on the free list.      */
 178     GC_clear_hdr_marks(hhdr);
 179 }
 180 
 181 /* Slow but general routines for setting/clearing/asking about mark bits */
 182 void GC_set_mark_bit(p)
 183 ptr_t p;
 184 {
 185     register struct hblk *h = HBLKPTR(p);
 186     register hdr * hhdr = HDR(h);
 187     register int word_no = (word *)p - (word *)h;
 188     
 189     set_mark_bit_from_hdr(hhdr, word_no);
 190 }
 191 
 192 void GC_clear_mark_bit(p)
 193 ptr_t p;
 194 {
 195     register struct hblk *h = HBLKPTR(p);
 196     register hdr * hhdr = HDR(h);
 197     register int word_no = (word *)p - (word *)h;
 198     
 199     clear_mark_bit_from_hdr(hhdr, word_no);
 200 }
 201 
 202 GC_bool GC_is_marked(p)
 203 ptr_t p;
 204 {
 205     register struct hblk *h = HBLKPTR(p);
 206     register hdr * hhdr = HDR(h);
 207     register int word_no = (word *)p - (word *)h;
 208     
 209     return(mark_bit_from_hdr(hhdr, word_no));
 210 }
 211 
 212 
 213 /*
 214  * Clear mark bits in all allocated heap blocks.  This invalidates
 215  * the marker invariant, and sets GC_mark_state to reflect this.
 216  * (This implicitly starts marking to reestablish the invariant.)
 217  */
 218 void GC_clear_marks()
 219 {
 220     GC_apply_to_all_blocks(clear_marks_for_block, (word)0);
 221     GC_objects_are_marked = FALSE;
 222     GC_mark_state = MS_INVALID;
 223     scan_ptr = 0;
 224 #   ifdef GATHERSTATS
 225         /* Counters reflect currently marked objects: reset here */
 226         GC_composite_in_use = 0;
 227         GC_atomic_in_use = 0;
 228 #   endif
 229 
 230 }
 231 
 232 /* Initiate a garbage collection.  Initiates a full collection if the   */
 233 /* mark state is invalid.                                               */
 234 /*ARGSUSED*/
 235 void GC_initiate_gc()
 236 {
 237     if (GC_dirty_maintained) GC_read_dirty();
 238 #   ifdef STUBBORN_ALLOC
 239         GC_read_changed();
 240 #   endif
 241 #   ifdef CHECKSUMS
 242         {
 243             extern void GC_check_dirty();
 244             
 245             if (GC_dirty_maintained) GC_check_dirty();
 246         }
 247 #   endif
 248     GC_n_rescuing_pages = 0;
 249     if (GC_mark_state == MS_NONE) {
 250         GC_mark_state = MS_PUSH_RESCUERS;
 251     } else if (GC_mark_state != MS_INVALID) {
 252         ABORT("unexpected state");
 253     } /* else this is really a full collection, and mark        */
 254       /* bits are invalid.                                      */
 255     scan_ptr = 0;
 256 }
 257 
 258 
 259 static void alloc_mark_stack();
 260 
 261 /* Perform a small amount of marking.                   */
 262 /* We try to touch roughly a page of memory.            */
 263 /* Return TRUE if we just finished a mark phase.        */
 264 /* Cold_gc_frame is an address inside a GC frame that   */
 265 /* remains valid until all marking is complete.         */
 266 /* A zero value indicates that it's OK to miss some     */
 267 /* register values.                                     */
 268 /* We hold the allocation lock.  In the case of         */
 269 /* incremental collection, the world may not be stopped.*/
 270 #ifdef MSWIN32
 271   /* For win32, this is called after we establish a structured  */
 272   /* exception handler, in case Windows unmaps one of our root  */
 273   /* segments.  See below.  In either case, we acquire the      */
 274   /* allocator lock long before we get here.                    */
 275   GC_bool GC_mark_some_inner(cold_gc_frame)
 276   ptr_t cold_gc_frame;
 277 #else
 278   GC_bool GC_mark_some(cold_gc_frame)
 279   ptr_t cold_gc_frame;
 280 #endif
 281 {
 282     switch(GC_mark_state) {
 283         case MS_NONE:
 284             return(FALSE);
 285             
 286         case MS_PUSH_RESCUERS:
 287             if (GC_mark_stack_top
 288                 >= GC_mark_stack_limit - INITIAL_MARK_STACK_SIZE/2) {
 289                 /* Go ahead and mark, even though that might cause us to */
 290                 /* see more marked dirty objects later on.  Avoid this   */
 291                 /* in the future.                                        */
 292                 GC_mark_stack_too_small = TRUE;
 293                 MARK_FROM_MARK_STACK();
 294                 return(FALSE);
 295             } else {
 296                 scan_ptr = GC_push_next_marked_dirty(scan_ptr);
 297                 if (scan_ptr == 0) {
 298 #                   ifdef CONDPRINT
 299                       if (GC_print_stats) {
 300                         GC_printf1("Marked from %lu dirty pages\n",
 301                                    (unsigned long)GC_n_rescuing_pages);
 302                       }
 303 #                   endif
 304                     GC_push_roots(FALSE, cold_gc_frame);
 305                     GC_objects_are_marked = TRUE;
 306                     if (GC_mark_state != MS_INVALID) {
 307                         GC_mark_state = MS_ROOTS_PUSHED;
 308                     }
 309                 }
 310             }
 311             return(FALSE);
 312         
 313         case MS_PUSH_UNCOLLECTABLE:
 314             if (GC_mark_stack_top
 315                 >= GC_mark_stack + GC_mark_stack_size/4) {
 316 #               ifdef PARALLEL_MARK
 317                   /* Avoid this, since we don't parallelize the marker  */
 318                   /* here.                                              */
 319                   if (GC_parallel) GC_mark_stack_too_small = TRUE;
 320 #               endif
 321                 MARK_FROM_MARK_STACK();
 322                 return(FALSE);
 323             } else {
 324                 scan_ptr = GC_push_next_marked_uncollectable(scan_ptr);
 325                 if (scan_ptr == 0) {
 326                     GC_push_roots(TRUE, cold_gc_frame);
 327                     GC_objects_are_marked = TRUE;
 328                     if (GC_mark_state != MS_INVALID) {
 329                         GC_mark_state = MS_ROOTS_PUSHED;
 330                     }
 331                 }
 332             }
 333             return(FALSE);
 334         
 335         case MS_ROOTS_PUSHED:
 336 #           ifdef PARALLEL_MARK
 337               /* In the incremental GC case, this currently doesn't     */
 338               /* quite do the right thing, since it runs to             */
 339               /* completion.  On the other hand, starting a             */
 340               /* parallel marker is expensive, so perhaps it is         */
 341               /* the right thing?                                       */
 342               /* Eventually, incremental marking should run             */
 343               /* asynchronously in multiple threads, without grabbing   */
 344               /* the allocation lock.                                   */
 345                 if (GC_parallel) {
 346                   GC_do_parallel_mark();
 347                   GC_ASSERT(GC_mark_stack_top < GC_first_nonempty);
 348                   GC_mark_stack_top = GC_mark_stack - 1;
 349                   if (GC_mark_stack_too_small) {
 350                     alloc_mark_stack(2*GC_mark_stack_size);
 351                   }
 352                   if (GC_mark_state == MS_ROOTS_PUSHED) {
 353                     GC_mark_state = MS_NONE;
 354                     return(TRUE);
 355                   } else {
 356                     return(FALSE);
 357                   }
 358                 }
 359 #           endif
 360             if (GC_mark_stack_top >= GC_mark_stack) {
 361                 MARK_FROM_MARK_STACK();
 362                 return(FALSE);
 363             } else {
 364                 GC_mark_state = MS_NONE;
 365                 if (GC_mark_stack_too_small) {
 366                     alloc_mark_stack(2*GC_mark_stack_size);
 367                 }
 368                 return(TRUE);
 369             }
 370             
 371         case MS_INVALID:
 372         case MS_PARTIALLY_INVALID:
 373             if (!GC_objects_are_marked) {
 374                 GC_mark_state = MS_PUSH_UNCOLLECTABLE;
 375                 return(FALSE);
 376             }
 377             if (GC_mark_stack_top >= GC_mark_stack) {
 378                 MARK_FROM_MARK_STACK();
 379                 return(FALSE);
 380             }
 381             if (scan_ptr == 0 && GC_mark_state == MS_INVALID) {
 382                 /* About to start a heap scan for marked objects. */
 383                 /* Mark stack is empty.  OK to reallocate.        */
 384                 if (GC_mark_stack_too_small) {
 385                     alloc_mark_stack(2*GC_mark_stack_size);
 386                 }
 387                 GC_mark_state = MS_PARTIALLY_INVALID;
 388             }
 389             scan_ptr = GC_push_next_marked(scan_ptr);
 390             if (scan_ptr == 0 && GC_mark_state == MS_PARTIALLY_INVALID) {
 391                 GC_push_roots(TRUE, cold_gc_frame);
 392                 GC_objects_are_marked = TRUE;
 393                 if (GC_mark_state != MS_INVALID) {
 394                     GC_mark_state = MS_ROOTS_PUSHED;
 395                 }
 396             }
 397             return(FALSE);
 398         default:
 399             ABORT("GC_mark_some: bad state");
 400             return(FALSE);
 401     }
 402 }
 403 
 404 
 405 #ifdef MSWIN32
 406 
 407 # ifdef __GNUC__
 408 
 409     typedef struct {
 410       EXCEPTION_REGISTRATION ex_reg;
 411       void *alt_path;
 412     } ext_ex_regn;
 413 
 414 
 415     static EXCEPTION_DISPOSITION mark_ex_handler(
 416         struct _EXCEPTION_RECORD *ex_rec, 
 417         void *est_frame,
 418         struct _CONTEXT *context,
 419         void *disp_ctxt)
 420     {
 421         if (ex_rec->ExceptionCode == STATUS_ACCESS_VIOLATION) {
 422           ext_ex_regn *xer = (ext_ex_regn *)est_frame;
 423 
 424           /* Unwind from the inner function assuming the standard */
 425           /* function prologue.                                   */
 426           /* Assumes code has not been compiled with              */
 427           /* -fomit-frame-pointer.                                */
 428           context->Esp = context->Ebp;
 429           context->Ebp = *((DWORD *)context->Esp);
 430           context->Esp = context->Esp - 8;
 431 
 432           /* Resume execution at the "real" handler within the    */
 433           /* wrapper function.                                    */
 434           context->Eip = (DWORD )(xer->alt_path);
 435 
 436           return ExceptionContinueExecution;
 437 
 438         } else {
 439             return ExceptionContinueSearch;
 440         }
 441     }
 442 # endif /* __GNUC__ */
 443 
 444 
 445   GC_bool GC_mark_some(cold_gc_frame)
 446   ptr_t cold_gc_frame;
 447   {
 448       GC_bool ret_val;
 449 
 450 #   ifndef __GNUC__
 451       /* Windows 98 appears to asynchronously create and remove  */
 452       /* writable memory mappings, for reasons we haven't yet    */
 453       /* understood.  Since we look for writable regions to      */
 454       /* determine the root set, we may try to mark from an      */
 455       /* address range that disappeared since we started the     */
 456       /* collection.  Thus we have to recover from faults here.  */
 457       /* This code does not appear to be necessary for Windows   */
 458       /* 95/NT/2000. Note that this code should never generate   */
 459       /* an incremental GC write fault.                          */
 460 
 461       __try {
 462 
 463 #   else /* __GNUC__ */
 464 
 465       /* Manually install an exception handler since GCC does    */
 466       /* not yet support Structured Exception Handling (SEH) on  */
 467       /* Win32.                                                  */
 468 
 469       ext_ex_regn er;
 470 
 471       er.alt_path = &&handle_ex;
 472       er.ex_reg.handler = mark_ex_handler;
 473       asm volatile ("movl %%fs:0, %0" : "=r" (er.ex_reg.prev));
 474       asm volatile ("movl %0, %%fs:0" : : "r" (&er));
 475 
 476 #   endif /* __GNUC__ */
 477 
 478           ret_val = GC_mark_some_inner(cold_gc_frame);
 479 
 480 #   ifndef __GNUC__
 481 
 482       } __except (GetExceptionCode() == EXCEPTION_ACCESS_VIOLATION ?
 483                 EXCEPTION_EXECUTE_HANDLER : EXCEPTION_CONTINUE_SEARCH) {
 484 
 485 #   else /* __GNUC__ */
 486 
 487           /* Prevent GCC from considering the following code unreachable */
 488           /* and thus eliminating it.                                    */
 489           if (er.alt_path != 0)
 490               goto rm_handler;
 491 
 492 handle_ex:
 493           /* Execution resumes from here on an access violation. */
 494 
 495 #   endif /* __GNUC__ */
 496 
 497 #         ifdef CONDPRINT
 498             if (GC_print_stats) {
 499               GC_printf0("Caught ACCESS_VIOLATION in marker. "
 500                          "Memory mapping disappeared.\n");
 501             }
 502 #         endif /* CONDPRINT */
 503 
 504           /* We have bad roots on the stack.  Discard mark stack.  */
 505           /* Rescan from marked objects.  Redetermine roots.     */
 506           GC_invalidate_mark_state();   
 507           scan_ptr = 0;
 508 
 509           ret_val = FALSE;
 510 
 511 #   ifndef __GNUC__
 512 
 513       }
 514 
 515 #   else /* __GNUC__ */
 516 
 517 rm_handler:
 518       /* Uninstall the exception handler */
 519       asm volatile ("mov %0, %%fs:0" : : "r" (er.ex_reg.prev));
 520 
 521 #   endif /* __GNUC__ */
 522 
 523       return ret_val;
 524   }
 525 #endif /* MSWIN32 */
 526 
 527 
 528 GC_bool GC_mark_stack_empty()
 529 {
 530     return(GC_mark_stack_top < GC_mark_stack);
 531 }       
 532 
 533 #ifdef PROF_MARKER
 534     word GC_prof_array[10];
 535 #   define PROF(n) GC_prof_array[n]++
 536 #else
 537 #   define PROF(n)
 538 #endif
 539 
 540 /* Given a pointer to someplace other than a small object page or the   */
 541 /* first page of a large object, either:                                */
 542 /*      - return a pointer to somewhere in the first page of the large  */
 543 /*        object, if current points to a large object.                  */
 544 /*        In this case *hhdr is replaced with a pointer to the header   */
 545 /*        for the large object.                                         */
 546 /*      - just return current if it does not point to a large object.   */
 547 /*ARGSUSED*/
 548 ptr_t GC_find_start(current, hhdr, new_hdr_p)
 549 register ptr_t current;
 550 register hdr *hhdr, **new_hdr_p;
 551 {
 552     if (GC_all_interior_pointers) {
 553         if (hhdr != 0) {
 554             register ptr_t orig = current;
 555             
 556             current = (ptr_t)HBLKPTR(current);
 557             do {
 558               current = current - HBLKSIZE*(word)hhdr;
 559               hhdr = HDR(current);
 560             } while(IS_FORWARDING_ADDR_OR_NIL(hhdr));
 561             /* current points to near the start of the large object */
 562             if (hhdr -> hb_flags & IGNORE_OFF_PAGE) return(orig);
 563             if ((word *)orig - (word *)current
 564                  >= (ptrdiff_t)(hhdr->hb_sz)) {
 565                 /* Pointer past the end of the block */
 566                 return(orig);
 567             }
 568             *new_hdr_p = hhdr;
 569             return(current);
 570         } else {
 571             return(current);
 572         }
 573     } else {
 574         return(current);
 575     }
 576 }
 577 
 578 void GC_invalidate_mark_state()
 579 {
 580     GC_mark_state = MS_INVALID;
 581     GC_mark_stack_top = GC_mark_stack-1;
 582 }
 583 
 584 mse * GC_signal_mark_stack_overflow(msp)
 585 mse * msp;
 586 {
 587     GC_mark_state = MS_INVALID;
 588     GC_mark_stack_too_small = TRUE;
 589 #   ifdef CONDPRINT
 590       if (GC_print_stats) {
 591         GC_printf1("Mark stack overflow; current size = %lu entries\n",
 592                     GC_mark_stack_size);
 593       }
 594 #   endif
 595     return(msp - GC_MARK_STACK_DISCARDS);
 596 }
 597 
 598 /*
 599  * Mark objects pointed to by the regions described by
 600  * mark stack entries between GC_mark_stack and GC_mark_stack_top,
 601  * inclusive.  Assumes the upper limit of a mark stack entry
 602  * is never 0.  A mark stack entry never has size 0.
 603  * We try to traverse on the order of a hblk of memory before we return.
 604  * Caller is responsible for calling this until the mark stack is empty.
 605  * Note that this is the most performance critical routine in the
 606  * collector.  Hence it contains all sorts of ugly hacks to speed
 607  * things up.  In particular, we avoid procedure calls on the common
 608  * path, we take advantage of peculiarities of the mark descriptor
 609  * encoding, we optionally maintain a cache for the block address to
 610  * header mapping, we prefetch when an object is "grayed", etc. 
 611  */
 612 mse * GC_mark_from(mark_stack_top, mark_stack, mark_stack_limit)
 613 mse * mark_stack_top;
 614 mse * mark_stack;
 615 mse * mark_stack_limit;
 616 {
 617   int credit = HBLKSIZE;        /* Remaining credit for marking work    */
 618   register word * current_p;    /* Pointer to current candidate ptr.    */
 619   register word current;        /* Candidate pointer.                   */
 620   register word * limit;        /* (Incl) limit of current candidate    */
 621                                 /* range                                */
 622   register word descr;
 623   register ptr_t greatest_ha = GC_greatest_plausible_heap_addr;
 624   register ptr_t least_ha = GC_least_plausible_heap_addr;
 625   DECLARE_HDR_CACHE;
 626 
 627 # define SPLIT_RANGE_WORDS 128  /* Must be power of 2.          */
 628 
 629   GC_objects_are_marked = TRUE;
 630   INIT_HDR_CACHE;
 631 # ifdef OS2 /* Use untweaked version to circumvent compiler problem */
 632   while (mark_stack_top >= mark_stack && credit >= 0) {
 633 # else
 634   while ((((ptr_t)mark_stack_top - (ptr_t)mark_stack) | credit)
 635         >= 0) {
 636 # endif
 637     current_p = mark_stack_top -> mse_start;
 638     descr = mark_stack_top -> mse_descr;
 639   retry:
 640     /* current_p and descr describe the current object.         */
 641     /* *mark_stack_top is vacant.                               */
 642     /* The following is 0 only for small objects described by a simple  */
 643     /* length descriptor.  For many applications this is the common     */
 644     /* case, so we try to detect it quickly.                            */
 645     if (descr & ((~(WORDS_TO_BYTES(SPLIT_RANGE_WORDS) - 1)) | GC_DS_TAGS)) {
 646       word tag = descr & GC_DS_TAGS;
 647       
 648       switch(tag) {
 649         case GC_DS_LENGTH:
 650           /* Large length.                                              */
 651           /* Process part of the range to avoid pushing too much on the */
 652           /* stack.                                                     */
 653           GC_ASSERT(descr < (word)GC_greatest_plausible_heap_addr
 654                             - (word)GC_least_plausible_heap_addr);
 655 #         ifdef PARALLEL_MARK
 656 #           define SHARE_BYTES 2048
 657             if (descr > SHARE_BYTES && GC_parallel
 658                 && mark_stack_top < mark_stack_limit - 1) {
 659               int new_size = (descr/2) & ~(sizeof(word)-1);
 660               mark_stack_top -> mse_start = current_p;
 661               mark_stack_top -> mse_descr = new_size + sizeof(word);
 662                                         /* makes sure we handle         */
 663                                         /* misaligned pointers.         */
 664               mark_stack_top++;
 665               current_p = (word *) ((char *)current_p + new_size);
 666               descr -= new_size;
 667               goto retry;
 668             }
 669 #         endif /* PARALLEL_MARK */
 670           mark_stack_top -> mse_start =
 671                 limit = current_p + SPLIT_RANGE_WORDS-1;
 672           mark_stack_top -> mse_descr =
 673                         descr - WORDS_TO_BYTES(SPLIT_RANGE_WORDS-1);
 674           /* Make sure that pointers overlapping the two ranges are     */
 675           /* considered.                                                */
 676           limit = (word *)((char *)limit + sizeof(word) - ALIGNMENT);
 677           break;
 678         case GC_DS_BITMAP:
 679           mark_stack_top--;
 680           descr &= ~GC_DS_TAGS;
 681           credit -= WORDS_TO_BYTES(WORDSZ/2); /* guess */
 682           while (descr != 0) {
 683             if ((signed_word)descr < 0) {
 684               current = *current_p;
 685               FIXUP_POINTER(current);
 686               if ((ptr_t)current >= least_ha && (ptr_t)current < greatest_ha) {
 687                 PREFETCH((ptr_t)current);
 688                 HC_PUSH_CONTENTS((ptr_t)current, mark_stack_top,
 689                               mark_stack_limit, current_p, exit1);
 690               }
 691             }
 692             descr <<= 1;
 693             ++ current_p;
 694           }
 695           continue;
 696         case GC_DS_PROC:
 697           mark_stack_top--;
 698           credit -= GC_PROC_BYTES;
 699           mark_stack_top =
 700               (*PROC(descr))
 701                     (current_p, mark_stack_top,
 702                     mark_stack_limit, ENV(descr));
 703           continue;
 704         case GC_DS_PER_OBJECT:
 705           if ((signed_word)descr >= 0) {
 706             /* Descriptor is in the object.     */
 707             descr = *(word *)((ptr_t)current_p + descr - GC_DS_PER_OBJECT);
 708           } else {
 709             /* Descriptor is in type descriptor pointed to by first     */
 710             /* word in object.                                          */
 711             ptr_t type_descr = *(ptr_t *)current_p;
 712             /* type_descr is either a valid pointer to the descriptor   */
 713             /* structure, or this object was on a free list.  If it     */
 714             /* it was anything but the last object on the free list,    */
 715             /* we will misinterpret the next object on the free list as */
 716             /* the type descriptor, and get a 0 GC descriptor, which    */
 717             /* is ideal.  Unfortunately, we need to check for the last  */
 718             /* object case explicitly.                                  */
 719             if (0 == type_descr) {
 720                 /* Rarely executed.     */
 721                 mark_stack_top--;
 722                 continue;
 723             }
 724             descr = *(word *)(type_descr
 725                               - (descr - (GC_DS_PER_OBJECT
 726                                           - GC_INDIR_PER_OBJ_BIAS)));
 727           }
 728           if (0 == descr) {
 729               /* Can happen either because we generated a 0 descriptor  */
 730               /* or we saw a pointer to a free object.                  */
 731               mark_stack_top--;
 732               continue;
 733           }
 734           goto retry;
 735       }
 736     } else /* Small object with length descriptor */ {
 737       mark_stack_top--;
 738       limit = (word *)(((ptr_t)current_p) + (word)descr);
 739     }
 740     /* The simple case in which we're scanning a range. */
 741     GC_ASSERT(!((word)current_p & (ALIGNMENT-1)));
 742     credit -= (ptr_t)limit - (ptr_t)current_p;
 743     limit -= 1;
 744     {
 745 #     define PREF_DIST 4
 746 
 747 #     ifndef SMALL_CONFIG
 748         word deferred;
 749 
 750         /* Try to prefetch the next pointer to be examined asap.        */
 751         /* Empirically, this also seems to help slightly without        */
 752         /* prefetches, at least on linux/X86.  Presumably this loop     */
 753         /* ends up with less register pressure, and gcc thus ends up    */
 754         /* generating slightly better code.  Overall gcc code quality   */
 755         /* for this loop is still not great.                            */
 756         for(;;) {
 757           PREFETCH((ptr_t)limit - PREF_DIST*CACHE_LINE_SIZE);
 758           GC_ASSERT(limit >= current_p);
 759           deferred = *limit;
 760           FIXUP_POINTER(deferred);
 761           limit = (word *)((char *)limit - ALIGNMENT);
 762           if ((ptr_t)deferred >= least_ha && (ptr_t)deferred <  greatest_ha) {
 763             PREFETCH((ptr_t)deferred);
 764             break;
 765           }
 766           if (current_p > limit) goto next_object;
 767           /* Unroll once, so we don't do too many of the prefetches     */
 768           /* based on limit.                                            */
 769           deferred = *limit;
 770           FIXUP_POINTER(deferred);
 771           limit = (word *)((char *)limit - ALIGNMENT);
 772           if ((ptr_t)deferred >= least_ha && (ptr_t)deferred <  greatest_ha) {
 773             PREFETCH((ptr_t)deferred);
 774             break;
 775           }
 776           if (current_p > limit) goto next_object;
 777         }
 778 #     endif
 779 
 780       while (current_p <= limit) {
 781         /* Empirically, unrolling this loop doesn't help a lot. */
 782         /* Since HC_PUSH_CONTENTS expands to a lot of code,     */
 783         /* we don't.                                            */
 784         current = *current_p;
 785         FIXUP_POINTER(current);
 786         PREFETCH((ptr_t)current_p + PREF_DIST*CACHE_LINE_SIZE);
 787         if ((ptr_t)current >= least_ha && (ptr_t)current <  greatest_ha) {
 788           /* Prefetch the contents of the object we just pushed.  It's  */
 789           /* likely we will need them soon.                             */
 790           PREFETCH((ptr_t)current);
 791           HC_PUSH_CONTENTS((ptr_t)current, mark_stack_top,
 792                            mark_stack_limit, current_p, exit2);
 793         }
 794         current_p = (word *)((char *)current_p + ALIGNMENT);
 795       }
 796 
 797 #     ifndef SMALL_CONFIG
 798         /* We still need to mark the entry we previously prefetched.    */
 799         /* We alrady know that it passes the preliminary pointer        */
 800         /* validity test.                                               */
 801         HC_PUSH_CONTENTS((ptr_t)deferred, mark_stack_top,
 802                          mark_stack_limit, current_p, exit4);
 803         next_object:;
 804 #     endif
 805     }
 806   }
 807   return mark_stack_top;
 808 }
 809 
 810 #ifdef PARALLEL_MARK
 811 
 812 /* We assume we have an ANSI C Compiler.        */
 813 GC_bool GC_help_wanted = FALSE;
 814 unsigned GC_helper_count = 0;
 815 unsigned GC_active_count = 0;
 816 mse * VOLATILE GC_first_nonempty;
 817 word GC_mark_no = 0;
 818 
 819 #define LOCAL_MARK_STACK_SIZE HBLKSIZE
 820         /* Under normal circumstances, this is big enough to guarantee  */
 821         /* We don't overflow half of it in a single call to             */
 822         /* GC_mark_from.                                                */
 823 
 824 
 825 /* Steal mark stack entries starting at mse low into mark stack local   */
 826 /* until we either steal mse high, or we have max entries.              */
 827 /* Return a pointer to the top of the local mark stack.                 */
 828 /* *next is replaced by a pointer to the next unscanned mark stack      */
 829 /* entry.                                                               */
 830 mse * GC_steal_mark_stack(mse * low, mse * high, mse * local,
 831                           unsigned max, mse **next)
 832 {
 833     mse *p;
 834     mse *top = local - 1;
 835     unsigned i = 0;
 836 
 837     /* Make sure that prior writes to the mark stack are visible. */
 838     /* On some architectures, the fact that the reads are         */
 839     /* volatile should suffice.                                   */
 840 #   if !defined(IA64) && !defined(HP_PA) && !defined(I386)
 841       GC_memory_barrier();
 842 #   endif
 843     GC_ASSERT(high >= low-1 && high - low + 1 <= GC_mark_stack_size);
 844     for (p = low; p <= high && i <= max; ++p) {
 845         word descr = *(volatile word *) &(p -> mse_descr);
 846         /* In the IA64 memory model, the following volatile store is    */
 847         /* ordered after this read of descr.  Thus a thread must read   */
 848         /* the original nonzero value.  HP_PA appears to be similar,    */
 849         /* and if I'm reading the P4 spec correctly, X86 is probably    */
 850         /* also OK.  In some other cases we need a barrier.             */
 851 #       if !defined(IA64) && !defined(HP_PA) && !defined(I386)
 852           GC_memory_barrier();
 853 #       endif
 854         if (descr != 0) {
 855             *(volatile word *) &(p -> mse_descr) = 0;
 856             /* More than one thread may get this entry, but that's only */
 857             /* a minor performance problem.                             */
 858             ++top;
 859             top -> mse_descr = descr;
 860             top -> mse_start = p -> mse_start;
 861             GC_ASSERT(  (top -> mse_descr & GC_DS_TAGS) != GC_DS_LENGTH || 
 862                         top -> mse_descr < (ptr_t)GC_greatest_plausible_heap_addr
 863                                            - (ptr_t)GC_least_plausible_heap_addr);
 864             /* If this is a big object, count it as                     */
 865             /* size/256 + 1 objects.                                    */
 866             ++i;
 867             if ((descr & GC_DS_TAGS) == GC_DS_LENGTH) i += (descr >> 8);
 868         }
 869     }
 870     *next = p;
 871     return top;
 872 }
 873 
 874 /* Copy back a local mark stack.        */
 875 /* low and high are inclusive bounds.   */
 876 void GC_return_mark_stack(mse * low, mse * high)
 877 {
 878     mse * my_top;
 879     mse * my_start;
 880     size_t stack_size;
 881 
 882     if (high < low) return;
 883     stack_size = high - low + 1;
 884     GC_acquire_mark_lock();
 885     my_top = GC_mark_stack_top;
 886     my_start = my_top + 1;
 887     if (my_start - GC_mark_stack + stack_size > GC_mark_stack_size) {
 888 #     ifdef CONDPRINT
 889         if (GC_print_stats) {
 890           GC_printf0("No room to copy back mark stack.");
 891         }
 892 #     endif
 893       GC_mark_state = MS_INVALID;
 894       GC_mark_stack_too_small = TRUE;
 895       /* We drop the local mark stack.  We'll fix things later. */
 896     } else {
 897       BCOPY(low, my_start, stack_size * sizeof(mse));
 898       GC_ASSERT(GC_mark_stack_top = my_top);
 899 #     if !defined(IA64) && !defined(HP_PA)
 900         GC_memory_barrier();
 901 #     endif
 902         /* On IA64, the volatile write acts as a release barrier. */
 903       GC_mark_stack_top = my_top + stack_size;
 904     }
 905     GC_release_mark_lock();
 906     GC_notify_all_marker();
 907 }
 908 
 909 /* Mark from the local mark stack.              */
 910 /* On return, the local mark stack is empty.    */
 911 /* But this may be achieved by copying the      */
 912 /* local mark stack back into the global one.   */
 913 void GC_do_local_mark(mse *local_mark_stack, mse *local_top)
 914 {
 915     unsigned n;
 916 #   define N_LOCAL_ITERS 1
 917 
 918 #   ifdef GC_ASSERTIONS
 919       /* Make sure we don't hold mark lock. */
 920         GC_acquire_mark_lock();
 921         GC_release_mark_lock();
 922 #   endif
 923     for (;;) {
 924         for (n = 0; n < N_LOCAL_ITERS; ++n) {
 925             local_top = GC_mark_from(local_top, local_mark_stack,
 926                                      local_mark_stack + LOCAL_MARK_STACK_SIZE);
 927             if (local_top < local_mark_stack) return;
 928             if (local_top - local_mark_stack >= LOCAL_MARK_STACK_SIZE/2) {
 929                 GC_return_mark_stack(local_mark_stack, local_top);
 930                 return;
 931             }
 932         }
 933         if (GC_mark_stack_top < GC_first_nonempty &&
 934             GC_active_count < GC_helper_count
 935             && local_top > local_mark_stack + 1) {
 936             /* Try to share the load, since the main stack is empty,    */
 937             /* and helper threads are waiting for a refill.             */
 938             /* The entries near the bottom of the stack are likely      */
 939             /* to require more work.  Thus we return those, eventhough  */
 940             /* it's harder.                                             */
 941             mse * p;
 942             mse * new_bottom = local_mark_stack
 943                                 + (local_top - local_mark_stack)/2;
 944             GC_ASSERT(new_bottom > local_mark_stack
 945                       && new_bottom < local_top);
 946             GC_return_mark_stack(local_mark_stack, new_bottom - 1);
 947             memmove(local_mark_stack, new_bottom,
 948                     (local_top - new_bottom + 1) * sizeof(mse));
 949             local_top -= (new_bottom - local_mark_stack);
 950         }
 951     }
 952 }
 953 
 954 #define ENTRIES_TO_GET 5
 955 
 956 long GC_markers = 2;            /* Normally changed by thread-library-  */
 957                                 /* -specific code.                      */
 958 
 959 /* Mark using the local mark stack until the global mark stack is empty */
 960 /* and there are no active workers. Update GC_first_nonempty to reflect */
 961 /* progress.                                                            */
 962 /* Caller does not hold mark lock.                                      */
 963 /* Caller has already incremented GC_helper_count.  We decrement it,    */
 964 /* and maintain GC_active_count.                                        */
 965 void GC_mark_local(mse *local_mark_stack, int id)
 966 {
 967     mse * my_first_nonempty;
 968 
 969     GC_acquire_mark_lock();
 970     GC_active_count++;
 971     my_first_nonempty = GC_first_nonempty;
 972     GC_ASSERT(GC_first_nonempty >= GC_mark_stack && 
 973               GC_first_nonempty <= GC_mark_stack_top + 1);
 974 #   ifdef PRINTSTATS
 975         GC_printf1("Starting mark helper %lu\n", (unsigned long)id);
 976 #   endif
 977     GC_release_mark_lock();
 978     for (;;) {
 979         size_t n_on_stack;
 980         size_t n_to_get;
 981         mse *next;
 982         mse * my_top;
 983         mse * local_top;
 984         mse * global_first_nonempty = GC_first_nonempty;
 985 
 986         GC_ASSERT(my_first_nonempty >= GC_mark_stack && 
 987                   my_first_nonempty <= GC_mark_stack_top + 1);
 988         GC_ASSERT(global_first_nonempty >= GC_mark_stack && 
 989                   global_first_nonempty <= GC_mark_stack_top + 1);
 990         if (my_first_nonempty < global_first_nonempty) {
 991             my_first_nonempty = global_first_nonempty;
 992         } else if (global_first_nonempty < my_first_nonempty) {
 993             GC_compare_and_exchange((word *)(&GC_first_nonempty), 
 994                                    (word) global_first_nonempty,
 995                                    (word) my_first_nonempty);
 996             /* If this fails, we just go ahead, without updating        */
 997             /* GC_first_nonempty.                                       */
 998         }
 999         /* Perhaps we should also update GC_first_nonempty, if it */
1000         /* is less.  But that would require using atomic updates. */
1001         my_top = GC_mark_stack_top;
1002         n_on_stack = my_top - my_first_nonempty + 1;
1003         if (0 == n_on_stack) {
1004             GC_acquire_mark_lock();
1005             my_top = GC_mark_stack_top;
1006             n_on_stack = my_top - my_first_nonempty + 1;
1007             if (0 == n_on_stack) {
1008                 GC_active_count--;
1009                 GC_ASSERT(GC_active_count <= GC_helper_count);
1010                 /* Other markers may redeposit objects  */
1011                 /* on the stack.                                */
1012                 if (0 == GC_active_count) GC_notify_all_marker();
1013                 while (GC_active_count > 0
1014                        && GC_first_nonempty > GC_mark_stack_top) {
1015                     /* We will be notified if either GC_active_count    */
1016                     /* reaches zero, or if more objects are pushed on   */
1017                     /* the global mark stack.                           */
1018                     GC_wait_marker();
1019                 }
1020                 if (GC_active_count == 0 &&
1021                     GC_first_nonempty > GC_mark_stack_top) { 
1022                     GC_bool need_to_notify = FALSE;
1023                     /* The above conditions can't be falsified while we */
1024                     /* hold the mark lock, since neither                */
1025                     /* GC_active_count nor GC_mark_stack_top can        */
1026                     /* change.  GC_first_nonempty can only be           */
1027                     /* incremented asynchronously.  Thus we know that   */
1028                     /* both conditions actually held simultaneously.    */
1029                     GC_helper_count--;
1030                     if (0 == GC_helper_count) need_to_notify = TRUE;
1031 #                   ifdef PRINTSTATS
1032                       GC_printf1(
1033                         "Finished mark helper %lu\n", (unsigned long)id);
1034 #                   endif
1035                     GC_release_mark_lock();
1036                     if (need_to_notify) GC_notify_all_marker();
1037                     return;
1038                 }
1039                 /* else there's something on the stack again, or        */
1040                 /* another helper may push something.                   */
1041                 GC_active_count++;
1042                 GC_ASSERT(GC_active_count > 0);
1043                 GC_release_mark_lock();
1044                 continue;
1045             } else {
1046                 GC_release_mark_lock();
1047             }
1048         }
1049         n_to_get = ENTRIES_TO_GET;
1050         if (n_on_stack < 2 * ENTRIES_TO_GET) n_to_get = 1;
1051         local_top = GC_steal_mark_stack(my_first_nonempty, my_top,
1052                                         local_mark_stack, n_to_get,
1053                                         &my_first_nonempty);
1054         GC_ASSERT(my_first_nonempty >= GC_mark_stack && 
1055                   my_first_nonempty <= GC_mark_stack_top + 1);
1056         GC_do_local_mark(local_mark_stack, local_top);
1057     }
1058 }
1059 
1060 /* Perform Parallel mark.                       */
1061 /* We hold the GC lock, not the mark lock.      */
1062 /* Currently runs until the mark stack is       */
1063 /* empty.                                       */
1064 void GC_do_parallel_mark()
1065 {
1066     mse local_mark_stack[LOCAL_MARK_STACK_SIZE];
1067     mse * local_top;
1068     mse * my_top;
1069 
1070     GC_acquire_mark_lock();
1071     GC_ASSERT(I_HOLD_LOCK());
1072     /* This could be a GC_ASSERT, but it seems safer to keep it on      */
1073     /* all the time, especially since it's cheap.                       */
1074     if (GC_help_wanted || GC_active_count != 0 || GC_helper_count != 0)
1075         ABORT("Tried to start parallel mark in bad state");
1076 #   ifdef PRINTSTATS
1077         GC_printf1("Starting marking for mark phase number %lu\n",
1078                    (unsigned long)GC_mark_no);
1079 #   endif
1080     GC_first_nonempty = GC_mark_stack;
1081     GC_active_count = 0;
1082     GC_helper_count = 1;
1083     GC_help_wanted = TRUE;
1084     GC_release_mark_lock();
1085     GC_notify_all_marker();
1086         /* Wake up potential helpers.   */
1087     GC_mark_local(local_mark_stack, 0);
1088     GC_acquire_mark_lock();
1089     GC_help_wanted = FALSE;
1090     /* Done; clean up.  */
1091     while (GC_helper_count > 0) GC_wait_marker();
1092     /* GC_helper_count cannot be incremented while GC_help_wanted == FALSE */
1093 #   ifdef PRINTSTATS
1094         GC_printf1(
1095             "Finished marking for mark phase number %lu\n",
1096             (unsigned long)GC_mark_no);
1097 #   endif
1098     GC_mark_no++;
1099     GC_release_mark_lock();
1100     GC_notify_all_marker();
1101 }
1102 
1103 
1104 /* Try to help out the marker, if it's running.         */
1105 /* We do not hold the GC lock, but the requestor does.  */
1106 void GC_help_marker(word my_mark_no)
1107 {
1108     mse local_mark_stack[LOCAL_MARK_STACK_SIZE];
1109     unsigned my_id;
1110     mse * my_first_nonempty;
1111 
1112     if (!GC_parallel) return;
1113     GC_acquire_mark_lock();
1114     while (GC_mark_no < my_mark_no
1115            || !GC_help_wanted && GC_mark_no == my_mark_no) {
1116       GC_wait_marker();
1117     }
1118     my_id = GC_helper_count;
1119     if (GC_mark_no != my_mark_no || my_id >= GC_markers) {
1120       /* Second test is useful only if original threads can also        */
1121       /* act as helpers.  Under Linux they can't.                       */
1122       GC_release_mark_lock();
1123       return;
1124     }
1125     GC_helper_count = my_id + 1;
1126     GC_release_mark_lock();
1127     GC_mark_local(local_mark_stack, my_id);
1128     /* GC_mark_local decrements GC_helper_count. */
1129 }
1130 
1131 #endif /* PARALLEL_MARK */
1132 
1133 /* Allocate or reallocate space for mark stack of size s words  */
1134 /* May silently fail.                                           */
1135 static void alloc_mark_stack(n)
1136 word n;
1137 {
1138     mse * new_stack = (mse *)GC_scratch_alloc(n * sizeof(struct GC_ms_entry));
1139     
1140     GC_mark_stack_too_small = FALSE;
1141     if (GC_mark_stack_size != 0) {
1142         if (new_stack != 0) {
1143           word displ = (word)GC_mark_stack & (GC_page_size - 1);
1144           signed_word size = GC_mark_stack_size * sizeof(struct GC_ms_entry);
1145           
1146           /* Recycle old space */
1147               if (0 != displ) displ = GC_page_size - displ;
1148               size = (size - displ) & ~(GC_page_size - 1);
1149               if (size > 0) {
1150                 GC_add_to_heap((struct hblk *)
1151                                 ((word)GC_mark_stack + displ), (word)size);
1152               }
1153           GC_mark_stack = new_stack;
1154           GC_mark_stack_size = n;
1155           GC_mark_stack_limit = new_stack + n;
1156 #         ifdef CONDPRINT
1157             if (GC_print_stats) {
1158               GC_printf1("Grew mark stack to %lu frames\n",
1159                          (unsigned long) GC_mark_stack_size);
1160             }
1161 #         endif
1162         } else {
1163 #         ifdef CONDPRINT
1164             if (GC_print_stats) {
1165               GC_printf1("Failed to grow mark stack to %lu frames\n",
1166                          (unsigned long) n);
1167             }
1168 #         endif
1169         }
1170     } else {
1171         if (new_stack == 0) {
1172             GC_err_printf0("No space for mark stack\n");
1173             EXIT();
1174         }
1175         GC_mark_stack = new_stack;
1176         GC_mark_stack_size = n;
1177         GC_mark_stack_limit = new_stack + n;
1178     }
1179     GC_mark_stack_top = GC_mark_stack-1;
1180 }
1181 
1182 void GC_mark_init()
1183 {
1184     alloc_mark_stack(INITIAL_MARK_STACK_SIZE);
1185 }
1186 
1187 /*
1188  * Push all locations between b and t onto the mark stack.
1189  * b is the first location to be checked. t is one past the last
1190  * location to be checked.
1191  * Should only be used if there is no possibility of mark stack
1192  * overflow.
1193  */
1194 void GC_push_all(bottom, top)
1195 ptr_t bottom;
1196 ptr_t top;
1197 {
1198     register word length;
1199     
1200     bottom = (ptr_t)(((word) bottom + ALIGNMENT-1) & ~(ALIGNMENT-1));
1201     top = (ptr_t)(((word) top) & ~(ALIGNMENT-1));
1202     if (top == 0 || bottom == top) return;
1203     GC_mark_stack_top++;
1204     if (GC_mark_stack_top >= GC_mark_stack_limit) {
1205         ABORT("unexpected mark stack overflow");
1206     }
1207     length = top - bottom;
1208 #   if GC_DS_TAGS > ALIGNMENT - 1
1209         length += GC_DS_TAGS;
1210         length &= ~GC_DS_TAGS;
1211 #   endif
1212     GC_mark_stack_top -> mse_start = (word *)bottom;
1213     GC_mark_stack_top -> mse_descr = length;
1214 }
1215 
1216 /*
1217  * Analogous to the above, but push only those pages h with dirty_fn(h) != 0.
1218  * We use push_fn to actually push the block.
1219  * Used both to selectively push dirty pages, or to push a block
1220  * in piecemeal fashion, to allow for more marking concurrency.
1221  * Will not overflow mark stack if push_fn pushes a small fixed number
1222  * of entries.  (This is invoked only if push_fn pushes a single entry,
1223  * or if it marks each object before pushing it, thus ensuring progress
1224  * in the event of a stack overflow.)
1225  */
1226 void GC_push_selected(bottom, top, dirty_fn, push_fn)
1227 ptr_t bottom;
1228 ptr_t top;
1229 int (*dirty_fn) GC_PROTO((struct hblk * h));
1230 void (*push_fn) GC_PROTO((ptr_t bottom, ptr_t top));
1231 {
1232     register struct hblk * h;
1233 
1234     bottom = (ptr_t)(((long) bottom + ALIGNMENT-1) & ~(ALIGNMENT-1));
1235     top = (ptr_t)(((long) top) & ~(ALIGNMENT-1));
1236 
1237     if (top == 0 || bottom == top) return;
1238     h = HBLKPTR(bottom + HBLKSIZE);
1239     if (top <= (ptr_t) h) {
1240         if ((*dirty_fn)(h-1)) {
1241             (*push_fn)(bottom, top);
1242         }
1243         return;
1244     }
1245     if ((*dirty_fn)(h-1)) {
1246         (*push_fn)(bottom, (ptr_t)h);
1247     }
1248     while ((ptr_t)(h+1) <= top) {
1249         if ((*dirty_fn)(h)) {
1250             if ((word)(GC_mark_stack_top - GC_mark_stack)
1251                 > 3 * GC_mark_stack_size / 4) {
1252                 /* Danger of mark stack overflow */
1253                 (*push_fn)((ptr_t)h, top);
1254                 return;
1255             } else {
1256                 (*push_fn)((ptr_t)h, (ptr_t)(h+1));
1257             }
1258         }
1259         h++;
1260     }
1261     if ((ptr_t)h != top) {
1262         if ((*dirty_fn)(h)) {
1263             (*push_fn)((ptr_t)h, top);
1264         }
1265     }
1266     if (GC_mark_stack_top >= GC_mark_stack_limit) {
1267         ABORT("unexpected mark stack overflow");
1268     }
1269 }
1270 
1271 # ifndef SMALL_CONFIG
1272 
1273 #ifdef PARALLEL_MARK
1274     /* Break up root sections into page size chunks to better spread    */
1275     /* out work.                                                        */
1276     GC_bool GC_true_func(struct hblk *h) { return TRUE; }
1277 #   define GC_PUSH_ALL(b,t) GC_push_selected(b,t,GC_true_func,GC_push_all);
1278 #else
1279 #   define GC_PUSH_ALL(b,t) GC_push_all(b,t);
1280 #endif
1281 
1282 
1283 void GC_push_conditional(bottom, top, all)
1284 ptr_t bottom;
1285 ptr_t top;
1286 int all;
1287 {
1288     if (all) {
1289       if (GC_dirty_maintained) {
1290 #       ifdef PROC_VDB
1291             /* Pages that were never dirtied cannot contain pointers    */
1292             GC_push_selected(bottom, top, GC_page_was_ever_dirty, GC_push_all);
1293 #       else
1294             GC_push_all(bottom, top);
1295 #       endif
1296       } else {
1297         GC_push_all(bottom, top);
1298       }
1299     } else {
1300         GC_push_selected(bottom, top, GC_page_was_dirty, GC_push_all);
1301     }
1302 }
1303 #endif
1304 
1305 # if defined(MSWIN32) || defined(MSWINCE)
1306   void __cdecl GC_push_one(p)
1307 # else
1308   void GC_push_one(p)
1309 # endif
1310 word p;
1311 {
1312     GC_PUSH_ONE_STACK(p, MARKED_FROM_REGISTER);
1313 }
1314 
1315 struct GC_ms_entry *GC_mark_and_push(obj, mark_stack_ptr, mark_stack_limit, src)
1316 GC_PTR obj;
1317 struct GC_ms_entry * mark_stack_ptr;
1318 struct GC_ms_entry * mark_stack_limit;
1319 GC_PTR *src;
1320 {
1321    PREFETCH(obj);
1322    PUSH_CONTENTS(obj, mark_stack_ptr /* modified */, mark_stack_limit, src,
1323                  was_marked /* internally generated exit label */);
1324    return mark_stack_ptr;
1325 }
1326 
1327 # ifdef __STDC__
1328 #   define BASE(p) (word)GC_base((void *)(p))
1329 # else
1330 #   define BASE(p) (word)GC_base((char *)(p))
1331 # endif
1332 
1333 /* Mark and push (i.e. gray) a single object p onto the main    */
1334 /* mark stack.  Consider p to be valid if it is an interior     */
1335 /* pointer.                                                     */
1336 /* The object p has passed a preliminary pointer validity       */
1337 /* test, but we do not definitely know whether it is valid.     */
1338 /* Mark bits are NOT atomically updated.  Thus this must be the */
1339 /* only thread setting them.                                    */
1340 # if defined(PRINT_BLACK_LIST) || defined(KEEP_BACK_PTRS)
1341     void GC_mark_and_push_stack(p, source)
1342     ptr_t source;
1343 # else
1344     void GC_mark_and_push_stack(p)
1345 #   define source 0
1346 # endif
1347 register word p;
1348 {
1349     register word r;
1350     register hdr * hhdr; 
1351     register int displ;
1352   
1353     GET_HDR(p, hhdr);
1354     if (IS_FORWARDING_ADDR_OR_NIL(hhdr)) {
1355         if (hhdr != 0) {
1356           r = BASE(p);
1357           hhdr = HDR(r);
1358           displ = BYTES_TO_WORDS(HBLKDISPL(r));
1359         }
1360     } else {
1361         register map_entry_type map_entry;
1362         
1363         displ = HBLKDISPL(p);
1364         map_entry = MAP_ENTRY((hhdr -> hb_map), displ);
1365         if (map_entry >= MAX_OFFSET) {
1366           if (map_entry == OFFSET_TOO_BIG || !GC_all_interior_pointers) {
1367               r = BASE(p);
1368               displ = BYTES_TO_WORDS(HBLKDISPL(r));
1369               if (r == 0) hhdr = 0;
1370           } else {
1371               /* Offset invalid, but map reflects interior pointers     */
1372               hhdr = 0;
1373           }
1374         } else {
1375           displ = BYTES_TO_WORDS(displ);
1376           displ -= map_entry;
1377           r = (word)((word *)(HBLKPTR(p)) + displ);
1378         }
1379     }
1380     /* If hhdr != 0 then r == GC_base(p), only we did it faster. */
1381     /* displ is the word index within the block.                 */
1382     if (hhdr == 0) {
1383 #       ifdef PRINT_BLACK_LIST
1384           GC_add_to_black_list_stack(p, source);
1385 #       else
1386           GC_add_to_black_list_stack(p);
1387 #       endif
1388 #       undef source  /* In case we had to define it. */
1389     } else {
1390         if (!mark_bit_from_hdr(hhdr, displ)) {
1391             set_mark_bit_from_hdr(hhdr, displ);
1392             GC_STORE_BACK_PTR(source, (ptr_t)r);
1393             PUSH_OBJ((word *)r, hhdr, GC_mark_stack_top,
1394                      GC_mark_stack_limit);
1395         }
1396     }
1397 }
1398 
1399 # ifdef TRACE_BUF
1400 
1401 # define TRACE_ENTRIES 1000
1402 
1403 struct trace_entry {
1404     char * kind;
1405     word gc_no;
1406     word words_allocd;
1407     word arg1;
1408     word arg2;
1409 } GC_trace_buf[TRACE_ENTRIES];
1410 
1411 int GC_trace_buf_ptr = 0;
1412 
1413 void GC_add_trace_entry(char *kind, word arg1, word arg2)
1414 {
1415     GC_trace_buf[GC_trace_buf_ptr].kind = kind;
1416     GC_trace_buf[GC_trace_buf_ptr].gc_no = GC_gc_no;
1417     GC_trace_buf[GC_trace_buf_ptr].words_allocd = GC_words_allocd;
1418     GC_trace_buf[GC_trace_buf_ptr].arg1 = arg1 ^ 0x80000000;
1419     GC_trace_buf[GC_trace_buf_ptr].arg2 = arg2 ^ 0x80000000;
1420     GC_trace_buf_ptr++;
1421     if (GC_trace_buf_ptr >= TRACE_ENTRIES) GC_trace_buf_ptr = 0;
1422 }
1423 
1424 void GC_print_trace(word gc_no, GC_bool lock)
1425 {
1426     int i;
1427     struct trace_entry *p;
1428     
1429     if (lock) LOCK();
1430     for (i = GC_trace_buf_ptr-1; i != GC_trace_buf_ptr; i--) {
1431         if (i < 0) i = TRACE_ENTRIES-1;
1432         p = GC_trace_buf + i;
1433         if (p -> gc_no < gc_no || p -> kind == 0) return;
1434         printf("Trace:%s (gc:%d,words:%d) 0x%X, 0x%X\n",
1435                 p -> kind, p -> gc_no, p -> words_allocd,
1436                 (p -> arg1) ^ 0x80000000, (p -> arg2) ^ 0x80000000);
1437     }
1438     printf("Trace incomplete\n");
1439     if (lock) UNLOCK();
1440 }
1441 
1442 # endif /* TRACE_BUF */
1443 
1444 /*
1445  * A version of GC_push_all that treats all interior pointers as valid
1446  * and scans the entire region immediately, in case the contents
1447  * change.
1448  */
1449 void GC_push_all_eager(bottom, top)
1450 ptr_t bottom;
1451 ptr_t top;
1452 {
1453     word * b = (word *)(((word) bottom + ALIGNMENT-1) & ~(ALIGNMENT-1));
1454     word * t = (word *)(((word) top) & ~(ALIGNMENT-1));
1455     register word *p;
1456     register word q;
1457     register word *lim;
1458     register ptr_t greatest_ha = GC_greatest_plausible_heap_addr;
1459     register ptr_t least_ha = GC_least_plausible_heap_addr;
1460 #   define GC_greatest_plausible_heap_addr greatest_ha
1461 #   define GC_least_plausible_heap_addr least_ha
1462 
1463     if (top == 0) return;
1464     /* check all pointers in range and push if they appear      */
1465     /* to be valid.                                             */
1466       lim = t - 1 /* longword */;
1467       for (p = b; p <= lim; p = (word *)(((char *)p) + ALIGNMENT)) {
1468         q = *p;
1469         GC_PUSH_ONE_STACK(q, p);
1470       }
1471 #   undef GC_greatest_plausible_heap_addr
1472 #   undef GC_least_plausible_heap_addr
1473 }
1474 
1475 #ifndef THREADS
1476 /*
1477  * A version of GC_push_all that treats all interior pointers as valid
1478  * and scans part of the area immediately, to make sure that saved
1479  * register values are not lost.
1480  * Cold_gc_frame delimits the stack section that must be scanned
1481  * eagerly.  A zero value indicates that no eager scanning is needed.
1482  */
1483 void GC_push_all_stack_partially_eager(bottom, top, cold_gc_frame)
1484 ptr_t bottom;
1485 ptr_t top;
1486 ptr_t cold_gc_frame;
1487 {
1488   if (!NEED_FIXUP_POINTER && GC_all_interior_pointers) {
1489 #   define EAGER_BYTES 1024
1490     /* Push the hot end of the stack eagerly, so that register values   */
1491     /* saved inside GC frames are marked before they disappear.         */
1492     /* The rest of the marking can be deferred until later.             */
1493     if (0 == cold_gc_frame) {
1494         GC_push_all_stack(bottom, top);
1495         return;
1496     }
1497     GC_ASSERT(bottom <= cold_gc_frame && cold_gc_frame <= top);
1498 #   ifdef STACK_GROWS_DOWN
1499         GC_push_all(cold_gc_frame - sizeof(ptr_t), top);
1500         GC_push_all_eager(bottom, cold_gc_frame);
1501 #   else /* STACK_GROWS_UP */
1502         GC_push_all(bottom, cold_gc_frame + sizeof(ptr_t));
1503         GC_push_all_eager(cold_gc_frame, top);
1504 #   endif /* STACK_GROWS_UP */
1505   } else {
1506     GC_push_all_eager(bottom, top);
1507   }
1508 # ifdef TRACE_BUF
1509       GC_add_trace_entry("GC_push_all_stack", bottom, top);
1510 # endif
1511 }
1512 #endif /* !THREADS */
1513 
1514 void GC_push_all_stack(bottom, top)
1515 ptr_t bottom;
1516 ptr_t top;
1517 {
1518   if (!NEED_FIXUP_POINTER && GC_all_interior_pointers) {
1519     GC_push_all(bottom, top);
1520   } else {
1521     GC_push_all_eager(bottom, top);
1522   }
1523 }
1524 
1525 #if !defined(SMALL_CONFIG) && !defined(USE_MARK_BYTES)
1526 /* Push all objects reachable from marked objects in the given block */
1527 /* of size 1 objects.                                                */
1528 void GC_push_marked1(h, hhdr)
1529 struct hblk *h;
1530 register hdr * hhdr;
1531 {
1532     word * mark_word_addr = &(hhdr->hb_marks[0]);
1533     register word *p;
1534     word *plim;
1535     register int i;
1536     register word q;
1537     register word mark_word;
1538     register ptr_t greatest_ha = GC_greatest_plausible_heap_addr;
1539     register ptr_t least_ha = GC_least_plausible_heap_addr;
1540     register mse * mark_stack_top = GC_mark_stack_top;
1541     register mse * mark_stack_limit = GC_mark_stack_limit;
1542 #   define GC_mark_stack_top mark_stack_top
1543 #   define GC_mark_stack_limit mark_stack_limit
1544 #   define GC_greatest_plausible_heap_addr greatest_ha
1545 #   define GC_least_plausible_heap_addr least_ha
1546     
1547     p = (word *)(h->hb_body);
1548     plim = (word *)(((word)h) + HBLKSIZE);
1549 
1550     /* go through all words in block */
1551         while( p < plim )  {
1552             mark_word = *mark_word_addr++;
1553             i = 0;
1554             while(mark_word != 0) {
1555               if (mark_word & 1) {
1556                   q = p[i];
1557                   GC_PUSH_ONE_HEAP(q, p + i);
1558               }
1559               i++;
1560               mark_word >>= 1;
1561             }
1562             p += WORDSZ;
1563         }
1564 #   undef GC_greatest_plausible_heap_addr
1565 #   undef GC_least_plausible_heap_addr        
1566 #   undef GC_mark_stack_top
1567 #   undef GC_mark_stack_limit
1568     GC_mark_stack_top = mark_stack_top;
1569 }
1570 
1571 
1572 #ifndef UNALIGNED
1573 
1574 /* Push all objects reachable from marked objects in the given block */
1575 /* of size 2 objects.                                                */
1576 void GC_push_marked2(h, hhdr)
1577 struct hblk *h;
1578 register hdr * hhdr;
1579 {
1580     word * mark_word_addr = &(hhdr->hb_marks[0]);
1581     register word *p;
1582     word *plim;
1583     register int i;
1584     register word q;
1585     register word mark_word;
1586     register ptr_t greatest_ha = GC_greatest_plausible_heap_addr;
1587     register ptr_t least_ha = GC_least_plausible_heap_addr;
1588     register mse * mark_stack_top = GC_mark_stack_top;
1589     register mse * mark_stack_limit = GC_mark_stack_limit;
1590 #   define GC_mark_stack_top mark_stack_top
1591 #   define GC_mark_stack_limit mark_stack_limit
1592 #   define GC_greatest_plausible_heap_addr greatest_ha
1593 #   define GC_least_plausible_heap_addr least_ha
1594     
1595     p = (word *)(h->hb_body);
1596     plim = (word *)(((word)h) + HBLKSIZE);
1597 
1598     /* go through all words in block */
1599         while( p < plim )  {
1600             mark_word = *mark_word_addr++;
1601             i = 0;
1602             while(mark_word != 0) {
1603               if (mark_word & 1) {
1604                   q = p[i];
1605                   GC_PUSH_ONE_HEAP(q, p + i);
1606                   q = p[i+1];
1607                   GC_PUSH_ONE_HEAP(q, p + i);
1608               }
1609               i += 2;
1610               mark_word >>= 2;
1611             }
1612             p += WORDSZ;
1613         }
1614 #   undef GC_greatest_plausible_heap_addr
1615 #   undef GC_least_plausible_heap_addr        
1616 #   undef GC_mark_stack_top
1617 #   undef GC_mark_stack_limit
1618     GC_mark_stack_top = mark_stack_top;
1619 }
1620 
1621 /* Push all objects reachable from marked objects in the given block */
1622 /* of size 4 objects.                                                */
1623 /* There is a risk of mark stack overflow here.  But we handle that. */
1624 /* And only unmarked objects get pushed, so it's not very likely.    */
1625 void GC_push_marked4(h, hhdr)
1626 struct hblk *h;
1627 register hdr * hhdr;
1628 {
1629     word * mark_word_addr = &(hhdr->hb_marks[0]);
1630     register word *p;
1631     word *plim;
1632     register int i;
1633     register word q;
1634     register word mark_word;
1635     register ptr_t greatest_ha = GC_greatest_plausible_heap_addr;
1636     register ptr_t least_ha = GC_least_plausible_heap_addr;
1637     register mse * mark_stack_top = GC_mark_stack_top;
1638     register mse * mark_stack_limit = GC_mark_stack_limit;
1639 #   define GC_mark_stack_top mark_stack_top
1640 #   define GC_mark_stack_limit mark_stack_limit
1641 #   define GC_greatest_plausible_heap_addr greatest_ha
1642 #   define GC_least_plausible_heap_addr least_ha
1643     
1644     p = (word *)(h->hb_body);
1645     plim = (word *)(((word)h) + HBLKSIZE);
1646 
1647     /* go through all words in block */
1648         while( p < plim )  {
1649             mark_word = *mark_word_addr++;
1650             i = 0;
1651             while(mark_word != 0) {
1652               if (mark_word & 1) {
1653                   q = p[i];
1654                   GC_PUSH_ONE_HEAP(q, p + i);
1655                   q = p[i+1];
1656                   GC_PUSH_ONE_HEAP(q, p + i + 1);
1657                   q = p[i+2];
1658                   GC_PUSH_ONE_HEAP(q, p + i + 2);
1659                   q = p[i+3];
1660                   GC_PUSH_ONE_HEAP(q, p + i + 3);
1661               }
1662               i += 4;
1663               mark_word >>= 4;
1664             }
1665             p += WORDSZ;
1666         }
1667 #   undef GC_greatest_plausible_heap_addr
1668 #   undef GC_least_plausible_heap_addr        
1669 #   undef GC_mark_stack_top
1670 #   undef GC_mark_stack_limit
1671     GC_mark_stack_top = mark_stack_top;
1672 }
1673 
1674 #endif /* UNALIGNED */
1675 
1676 #endif /* SMALL_CONFIG */
1677 
1678 /* Push all objects reachable from marked objects in the given block */
1679 void GC_push_marked(h, hhdr)
1680 struct hblk *h;
1681 register hdr * hhdr;
1682 {
1683     register int sz = hhdr -> hb_sz;
1684     register int descr = hhdr -> hb_descr;
1685     register word * p;
1686     register int word_no;
1687     register word * lim;
1688     register mse * GC_mark_stack_top_reg;
1689     register mse * mark_stack_limit = GC_mark_stack_limit;
1690     
1691     /* Some quick shortcuts: */
1692         if ((0 | GC_DS_LENGTH) == descr) return;
1693         if (GC_block_empty(hhdr)/* nothing marked */) return;
1694     GC_n_rescuing_pages++;
1695     GC_objects_are_marked = TRUE;
1696     if (sz > MAXOBJSZ) {
1697         lim = (word *)h;
1698     } else {
1699         lim = (word *)(h + 1) - sz;
1700     }
1701     
1702     switch(sz) {
1703 #   if !defined(SMALL_CONFIG) && !defined(USE_MARK_BYTES)   
1704      case 1:
1705        GC_push_marked1(h, hhdr);
1706        break;
1707 #   endif
1708 #   if !defined(SMALL_CONFIG) && !defined(UNALIGNED) && \
1709        !defined(USE_MARK_BYTES)
1710      case 2:
1711        GC_push_marked2(h, hhdr);
1712        break;
1713      case 4:
1714        GC_push_marked4(h, hhdr);
1715        break;
1716 #   endif       
1717      default:
1718       GC_mark_stack_top_reg = GC_mark_stack_top;
1719       for (p = (word *)h, word_no = 0; p <= lim; p += sz, word_no += sz) {
1720          if (mark_bit_from_hdr(hhdr, word_no)) {
1721            /* Mark from fields inside the object */
1722              PUSH_OBJ((word *)p, hhdr, GC_mark_stack_top_reg, mark_stack_limit);
1723 #            ifdef GATHERSTATS
1724                 /* Subtract this object from total, since it was        */
1725                 /* added in twice.                                      */
1726                 GC_composite_in_use -= sz;
1727 #            endif
1728          }
1729       }
1730       GC_mark_stack_top = GC_mark_stack_top_reg;
1731     }
1732 }
1733 
1734 #ifndef SMALL_CONFIG
1735 /* Test whether any page in the given block is dirty    */
1736 GC_bool GC_block_was_dirty(h, hhdr)
1737 struct hblk *h;
1738 register hdr * hhdr;
1739 {
1740     register int sz = hhdr -> hb_sz;
1741     
1742     if (sz <= MAXOBJSZ) {
1743          return(GC_page_was_dirty(h));
1744     } else {
1745          register ptr_t p = (ptr_t)h;
1746          sz = WORDS_TO_BYTES(sz);
1747          while (p < (ptr_t)h + sz) {
1748              if (GC_page_was_dirty((struct hblk *)p)) return(TRUE);
1749              p += HBLKSIZE;
1750          }
1751          return(FALSE);
1752     }
1753 }
1754 #endif /* SMALL_CONFIG */
1755 
1756 /* Similar to GC_push_next_marked, but return address of next block     */
1757 struct hblk * GC_push_next_marked(h)
1758 struct hblk *h;
1759 {
1760     register hdr * hhdr;
1761     
1762     h = GC_next_used_block(h);
1763     if (h == 0) return(0);
1764     hhdr = HDR(h);
1765     GC_push_marked(h, hhdr);
1766     return(h + OBJ_SZ_TO_BLOCKS(hhdr -> hb_sz));
1767 }
1768 
1769 #ifndef SMALL_CONFIG
1770 /* Identical to above, but mark only from dirty pages   */
1771 struct hblk * GC_push_next_marked_dirty(h)
1772 struct hblk *h;
1773 {
1774     register hdr * hhdr;
1775     
1776     if (!GC_dirty_maintained) { ABORT("dirty bits not set up"); }
1777     for (;;) {
1778         h = GC_next_used_block(h);
1779         if (h == 0) return(0);
1780         hhdr = HDR(h);
1781 #       ifdef STUBBORN_ALLOC
1782           if (hhdr -> hb_obj_kind == STUBBORN) {
1783             if (GC_page_was_changed(h) && GC_block_was_dirty(h, hhdr)) {
1784                 break;
1785             }
1786           } else {
1787             if (GC_block_was_dirty(h, hhdr)) break;
1788           }
1789 #       else
1790           if (GC_block_was_dirty(h, hhdr)) break;
1791 #       endif
1792         h += OBJ_SZ_TO_BLOCKS(hhdr -> hb_sz);
1793     }
1794     GC_push_marked(h, hhdr);
1795     return(h + OBJ_SZ_TO_BLOCKS(hhdr -> hb_sz));
1796 }
1797 #endif
1798 
1799 /* Similar to above, but for uncollectable pages.  Needed since we      */
1800 /* do not clear marks for such pages, even for full collections.        */
1801 struct hblk * GC_push_next_marked_uncollectable(h)
1802 struct hblk *h;
1803 {
1804     register hdr * hhdr = HDR(h);
1805     
1806     for (;;) {
1807         h = GC_next_used_block(h);
1808         if (h == 0) return(0);
1809         hhdr = HDR(h);
1810         if (hhdr -> hb_obj_kind == UNCOLLECTABLE) break;
1811         h += OBJ_SZ_TO_BLOCKS(hhdr -> hb_sz);
1812     }
1813     GC_push_marked(h, hhdr);
1814     return(h + OBJ_SZ_TO_BLOCKS(hhdr -> hb_sz));
1815 }
1816 
1817 

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