234 lines
7.2 KiB
C
234 lines
7.2 KiB
C
/*
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* Copyright 1988, 1989 Hans-J. Boehm, Alan J. Demers
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* Copyright (c) 1991-1994 by Xerox Corporation. All rights reserved.
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*
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* THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
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* OR IMPLIED. ANY USE IS AT YOUR OWN RISK.
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*
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* Permission is hereby granted to use or copy this program
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* for any purpose, provided the above notices are retained on all copies.
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* Permission to modify the code and to distribute modified code is granted,
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* provided the above notices are retained, and a notice that the code was
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* modified is included with the above copyright notice.
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*/
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/* Boehm, July 11, 1995 11:54 am PDT */
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# ifndef GC_HEADERS_H
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# define GC_HEADERS_H
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typedef struct hblkhdr hdr;
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# if CPP_WORDSZ != 32 && CPP_WORDSZ < 36
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--> Get a real machine.
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# endif
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/*
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* The 2 level tree data structure that is used to find block headers.
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* If there are more than 32 bits in a pointer, the top level is a hash
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* table.
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*
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* This defines HDR, GET_HDR, and SET_HDR, the main macros used to
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* retrieve and set object headers.
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*
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* Since 5.0 alpha 5, we can also take advantage of a header lookup
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* cache. This is a locally declared direct mapped cache, used inside
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* the marker. The HC_GET_HDR macro uses and maintains this
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* cache. Assuming we get reasonable hit rates, this shaves a few
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* memory references from each pointer validation.
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*/
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# if CPP_WORDSZ > 32
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# define HASH_TL
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# endif
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/* Define appropriate out-degrees for each of the two tree levels */
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# ifdef SMALL_CONFIG
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# define LOG_BOTTOM_SZ 11
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/* Keep top index size reasonable with smaller blocks. */
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# else
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# define LOG_BOTTOM_SZ 10
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# endif
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# ifndef HASH_TL
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# define LOG_TOP_SZ (WORDSZ - LOG_BOTTOM_SZ - LOG_HBLKSIZE)
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# else
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# define LOG_TOP_SZ 11
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# endif
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# define TOP_SZ (1 << LOG_TOP_SZ)
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# define BOTTOM_SZ (1 << LOG_BOTTOM_SZ)
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#ifndef SMALL_CONFIG
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# define USE_HDR_CACHE
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#endif
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/* #define COUNT_HDR_CACHE_HITS */
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extern hdr * GC_invalid_header; /* header for an imaginary block */
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/* containing no objects. */
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/* Check whether p and corresponding hhdr point to long or invalid */
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/* object. If so, advance hhdr to */
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/* beginning of block, or set hhdr to GC_invalid_header. */
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#define ADVANCE(p, hhdr, source) \
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{ \
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hdr * new_hdr = GC_invalid_header; \
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p = GC_find_start(p, hhdr, &new_hdr); \
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hhdr = new_hdr; \
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}
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#ifdef USE_HDR_CACHE
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# ifdef COUNT_HDR_CACHE_HITS
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extern word GC_hdr_cache_hits;
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extern word GC_hdr_cache_misses;
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# define HC_HIT() ++GC_hdr_cache_hits
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# define HC_MISS() ++GC_hdr_cache_misses
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# else
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# define HC_HIT()
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# define HC_MISS()
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# endif
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typedef struct hce {
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word block_addr; /* right shifted by LOG_HBLKSIZE */
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hdr * hce_hdr;
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} hdr_cache_entry;
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# define HDR_CACHE_SIZE 8 /* power of 2 */
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# define DECLARE_HDR_CACHE \
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hdr_cache_entry hdr_cache[HDR_CACHE_SIZE]
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# define INIT_HDR_CACHE BZERO(hdr_cache, sizeof(hdr_cache));
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# define HCE(h) hdr_cache + (((word)(h) >> LOG_HBLKSIZE) & (HDR_CACHE_SIZE-1))
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# define HCE_VALID_FOR(hce,h) ((hce) -> block_addr == \
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((word)(h) >> LOG_HBLKSIZE))
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# define HCE_HDR(h) ((hce) -> hce_hdr)
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/* Analogous to GET_HDR, except that in the case of large objects, it */
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/* Returns the header for the object beginning, and updates p. */
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/* Returns &GC_bad_header instead of 0. All of this saves a branch */
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/* in the fast path. */
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# define HC_GET_HDR(p, hhdr, source) \
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{ \
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hdr_cache_entry * hce = HCE(p); \
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if (HCE_VALID_FOR(hce, p)) { \
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HC_HIT(); \
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hhdr = hce -> hce_hdr; \
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} else { \
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HC_MISS(); \
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GET_HDR(p, hhdr); \
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if (IS_FORWARDING_ADDR_OR_NIL(hhdr)) { \
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ADVANCE(p, hhdr, source); \
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} else { \
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hce -> block_addr = (word)(p) >> LOG_HBLKSIZE; \
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hce -> hce_hdr = hhdr; \
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} \
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} \
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}
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#else /* !USE_HDR_CACHE */
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# define DECLARE_HDR_CACHE
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# define INIT_HDR_CACHE
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# define HC_GET_HDR(p, hhdr, source) \
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{ \
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GET_HDR(p, hhdr); \
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if (IS_FORWARDING_ADDR_OR_NIL(hhdr)) { \
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ADVANCE(p, hhdr, source); \
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} \
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}
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#endif
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typedef struct bi {
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hdr * index[BOTTOM_SZ];
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/*
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* The bottom level index contains one of three kinds of values:
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* 0 means we're not responsible for this block,
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* or this is a block other than the first one in a free block.
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* 1 < (long)X <= MAX_JUMP means the block starts at least
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* X * HBLKSIZE bytes before the current address.
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* A valid pointer points to a hdr structure. (The above can't be
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* valid pointers due to the GET_MEM return convention.)
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*/
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struct bi * asc_link; /* All indices are linked in */
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/* ascending order... */
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struct bi * desc_link; /* ... and in descending order. */
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word key; /* high order address bits. */
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# ifdef HASH_TL
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struct bi * hash_link; /* Hash chain link. */
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# endif
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} bottom_index;
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/* extern bottom_index GC_all_nils; - really part of GC_arrays */
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/* extern bottom_index * GC_top_index []; - really part of GC_arrays */
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/* Each entry points to a bottom_index. */
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/* On a 32 bit machine, it points to */
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/* the index for a set of high order */
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/* bits equal to the index. For longer */
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/* addresses, we hash the high order */
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/* bits to compute the index in */
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/* GC_top_index, and each entry points */
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/* to a hash chain. */
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/* The last entry in each chain is */
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/* GC_all_nils. */
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# define MAX_JUMP (HBLKSIZE - 1)
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# define HDR_FROM_BI(bi, p) \
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((bi)->index[((word)(p) >> LOG_HBLKSIZE) & (BOTTOM_SZ - 1)])
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# ifndef HASH_TL
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# define BI(p) (GC_top_index \
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[(word)(p) >> (LOG_BOTTOM_SZ + LOG_HBLKSIZE)])
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# define HDR_INNER(p) HDR_FROM_BI(BI(p),p)
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# ifdef SMALL_CONFIG
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# define HDR(p) GC_find_header((ptr_t)(p))
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# else
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# define HDR(p) HDR_INNER(p)
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# endif
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# define GET_BI(p, bottom_indx) (bottom_indx) = BI(p)
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# define GET_HDR(p, hhdr) (hhdr) = HDR(p)
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# define SET_HDR(p, hhdr) HDR_INNER(p) = (hhdr)
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# define GET_HDR_ADDR(p, ha) (ha) = &(HDR_INNER(p))
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# else /* hash */
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/* Hash function for tree top level */
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# define TL_HASH(hi) ((hi) & (TOP_SZ - 1))
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/* Set bottom_indx to point to the bottom index for address p */
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# define GET_BI(p, bottom_indx) \
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{ \
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register word hi = \
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(word)(p) >> (LOG_BOTTOM_SZ + LOG_HBLKSIZE); \
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register bottom_index * _bi = GC_top_index[TL_HASH(hi)]; \
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\
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while (_bi -> key != hi && _bi != GC_all_nils) \
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_bi = _bi -> hash_link; \
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(bottom_indx) = _bi; \
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}
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# define GET_HDR_ADDR(p, ha) \
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{ \
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register bottom_index * bi; \
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\
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GET_BI(p, bi); \
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(ha) = &(HDR_FROM_BI(bi, p)); \
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}
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# define GET_HDR(p, hhdr) { register hdr ** _ha; GET_HDR_ADDR(p, _ha); \
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(hhdr) = *_ha; }
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# define SET_HDR(p, hhdr) { register hdr ** _ha; GET_HDR_ADDR(p, _ha); \
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*_ha = (hhdr); }
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# define HDR(p) GC_find_header((ptr_t)(p))
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# endif
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/* Is the result a forwarding address to someplace closer to the */
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/* beginning of the block or NIL? */
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# define IS_FORWARDING_ADDR_OR_NIL(hhdr) ((unsigned long) (hhdr) <= MAX_JUMP)
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/* Get an HBLKSIZE aligned address closer to the beginning of the block */
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/* h. Assumes hhdr == HDR(h) and IS_FORWARDING_ADDR(hhdr). */
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# define FORWARDED_ADDR(h, hhdr) ((struct hblk *)(h) - (unsigned long)(hhdr))
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# endif /* GC_HEADERS_H */
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