Last updated 3 October 2020
Page 23, Diagram 2.5, the new free list should be S, U, V, ... (i.e. the order is reversed) . Thus,
Diagram 2.5 After
Pages 33 and 34, in the left-hand diagrams, the arrow from A' to B' in Diagram 2.10 and from A' to C' in Diagram 2.11 should be removed: the pointers are not written until the recursive step is complete .
Page 46, Deutsch-Bobrow algorithm. The first paragraph implies, but fails to state explicitly, that allocation of a new object causes a new entry to be added to the ZCT, risking overflow. .
Page 47, Algorithm 3.4, the test
x>t is better written
gcd(x,y) = -- assert: x >= y >= 0 if y == 0 return x t = x - y if y > t return gcd(y,t) else return gcd(t,yyuasa)Algorithm 3.4 Greatest common divisor.
Page 66, Algorithm 3.19, the caption to should refer to
Page 124, Diagram 6.5, the caption should read
left(F') is updated with the forwarding address found in
Page 148, Diagram 7.3, in attempting to correct a minor labelling error in the earlier printings, Diagram 7.3 instead repeats Diagram 7.2 . It should of course be:
Diagram 7.3 Overwriting
Rcreates old-young pointers.
Page 194: The discussion of how Steele allocates cells omits an account of allocation during the sweep phase, although this is described in Algorithm 8.6 . In summary,
Page 195, Algorithm 8.7,
colour(X) = blackshould be
mark_bit(X) = true -colour(X) is now blackNote also the omitted (if obvious) definitions,
marked(X) == (mark_bit(X) == true) unmarked(X) == (mark_bit(X) == false)
Page 204, Algorithm 8.12, the final test on
B should be
New(n) = if B >= T - n - Flip phase if scan < B abort "Haven't finished scavenging" flip() for root R R = copy(R) repeat k times while scan < B - scavenge a bit for P in Children(scan) *P = copy(*P) scan = scan + size(scan) if B >= T abort "Heap full" T = T - n return T read(T) = T' = copy(T) return T'Algorithm 8.12 Baker's incremental copying algorithm.
Page 204, line 2: the reference should be to Diagram 8.8 on the previous page .
Page 242, second paragraph: the block's count of free slots should be decremented, not incremented, and the allocator decrements the number of free, rather than allocated, blocks .
Page 262, last paragraph, second sentence, should refer to
Last updated 4 January 1999
The errors below were corrected in the January 1999 reprinting.
Page 3, first paragraph, last sentence: occam does not use static allocation.
Page 21, Algorithm 2.2,
Update should increment the reference
count of the new target before deleting the pointer to the old target to
prevent incorrect reclamation in the case that both targets are one and the
same and that this is the only reference to it. Thus,
Update(R, S) = RC(S) = RC(S) + 1 delete(*R) *R = SAlgorithm 2.2 Updating pointer fields under reference counting
Page 35, the constants in the formula for efficiency of mark-sweep should be transposed . Thus,
eMS = (1-r) / (br+c)
Similarly, the y-intercept for the Mark-Sweep curve in the graph in Diagram 2.12 should be 1/c .
All algorithms in this chapter should increment reference counts of new targets before deleting the pointers to the old targets.
Page 46, Algorithm 3.2
Update(R,S) = - R and S are heap objects incrementRC(S) delete(*R) remove S from ZCT *R = SAlgorithm 3.2 Deferred Reference Counting: updating pointer values.
Page 52, Algorithm 3.7
Update(R,S) = T = sticky(*S) if RC(*S) == unique *S = T delete(*R) *R = TAlgorithm 3.7 One-bit reference counting with tagged pointers.
Page 57, Algorithm 3.9
Update(R,S) = T = *R gr = group_no(R) if gr != group_no(S) - external reference increment_groupRC(S) if gr != group_no(T) - external reference decrement_groupRC(T) if groupRC(T) == 0 reclaim_group(T) *R = SAlgorithm 3.9 Bobrow's algorithm.
Page 59, Algorithm 3.11
Update(R,S) = WRC(S) = WRC(S) + 1 delete(*R) *R = S weaken(*R)Algorithm 3.11 Salkild's
Page 64, Algorithm 3.15
Update(R,S) = RC(S) = RC(S) + 1 colour(R) = black - `remove' R,S from control set colour(S) = black delete(*R) *R = SAlgorithm 3.15 Cyclic reference counting
Page 66, Algorithm 3.20, the cell being swept into the free-list must be coloured black before its children are examined (otherwise the algorithm does not terminate) .
collect_white(S) = if colour(S) == white colour(S) = black for T in Children(S) collect_white(*T) free(S)Algorithm 3.20
collect_whitesweeps white cells into the free-list.
Page 63, paragraph five,
Update should paint cells black not purple.
Page 69, last line: "method" should be "methods".
Page 78, Algorithm 4.2: if this version of
mark is used,
mark_heap should not set mark bits
Page 81, last paragraph, fifth sentence should read :
"If none of the node's children are unmarked, that stack slot is deemed to be empty and is squeezed out by sliding up the next useful entry."
Page 89, Algoritm 4.4 should sweep again after marking the heap.
allocate() = while sweep < Heap_top -- continue sweep if mark_bit(sweep) == marked mark_bit(sweep) = unmarked sweep = sweep + size(sweep) else result = sweep sweep = sweep + size(sweep) return result mark_heap() -- heap is full sweep = Heap_bottom while sweep < Heap_top -- try again if mark_bit(sweep) == marked mark_bit(sweep) = unmarked sweep = sweep + size(sweep) else result = sweep sweep = sweep + size(sweep) return result abort "Memory exhausted"Algorithm 4.4 Lazy sweeping.
Page 87, the shift in the code fragment in the centre of the page should be 3 . Thus
mark_bit(p) = return bitmap[p>>3]
Page 92, the names of several instructions
in Algorithms 4.5 and 4.6 of
Zorn's allocation sequence
sub does not set the condition codes, and
are not standard SPARC assembly instructions.
Furthermore, brackets were omitted from
The correct versions are:
-- is a collection needed? subcc %g_allocated, ConsSize, %g_allocated bg,a noCollect subcc %g_freeConsIndex, 4, %g_free_ConsIndex call Collect nop subcc %g_freeConsIndex, 4, %g_free_ConsIndex noCollect: -- need to sweep? bg,a done ld [%g_freeCons + %g_freeConsIndex], %result call lazySweep nop ld [%g_freeCons + %g_freeConsIndex], %result done: ...Algorithm 4.5 Zorn's allocation sequence for cons cells
lazySweep: ... -- %bitsLeft contains the remaining bits andcc %bitsLeft, 1, %thisBit bnz,a nextBit add %currentRef, ConsSize, %currentRef -- sweep the word into the cons free-list st %currentRef, [%g_freeCons + %g_freeConsIndex] add %g_freeConsIndex, 4, %g_free_ConsIndex add %currentRef, ConsSize, %currentRef nextBit: -- on to the next bit srl %bitsLeft, 1,%bitsLeftAlgorithm 4.6 The inner loop of Zorn's lazy-sweep allocator processes one bit of the bitmap.
Page 102, Algorithm 5.2 does not clear mark-bits .
relocate() = free=heap_bottom live=heap_top mark_bit(Heap[heap_top+1]) = unmarked - sentinel repeat while marked(free) - find the next hole mark_bit(Heap[free]) = unmarked free=free+1 while not marked(live) and live > free - find the previous live cell live=live-1 if live>free mark_bit(Heap[live]) = unmarked - unmark it move(live, free) Heap[live] = free - leave forwarding address free=free+1 live=live-1 until live <= freeAlgorithm 5.2 The first pass of the Two-Finger compaction algorithm
Page 104, Algorithm 5.5, the second line of
compute_addresses should read
P = Heap_bottom
Page 113, subsection Handling abnormal residencies should read: "Sansom has proposed..." .
Page 123, Algorithm 6.1 .
In order to fit with the procedure
New given in
Algorithm 2.7 on page 29 of Chapter 2 the flip should also
Page 123, penultimate paragraph .
All references to
C in the last two sentences should
be replaced by references to
"The scan finds a pointer to
This pointer is updated with the forwarding address
A (see diagram 6.5 on the next page)."
subcc %g_allocated, ConsSize, %g_allocated bg,a noCollect
Page 125, Algorithm 6.3: the first line should be indented by one tab .
Page 139, Algorithm 6.4: for compatibility with
flip should set
flip() = Fromspace, Tospace = Tospace, Fromspace top_of_space = Tospace + space_size scan, partial, free = TospaceAlgorithm 6.4 Moon's approximately depth-first algorithm.
for R in Roots R = copy(R)
while scan < free scan_partial() scan_all()
Page 140, Notes: in paragraph 3, the second sentence should read .
"Although they accepted Appel's general case, they found that heap allocation of procedure activation frames required an extra two instructions per call (to save the frame pointer and move the heap pointer) -- 18 percent more instructions than was needed for stack allocation."
Page 145: Apple's Smalltalk was never released.
Page 146, paragraph two should read :
"On the other hand, the strong generational hypothesis, that the older an object is the less likely it is to die, does not appear to hold generally."
Page 147, paragraph two: the reachable cells in the younger generation are
Page 147, final paragraph: the last phrase of the fifth sentence should be deleted. Thus:
"Third, the minor collection successfully reclaimed all short-lived cells in the graph."
Page 156, Diagram 7.9: the size of the area marked `reserve' should be zero . Thus
Diagram 7.9 Immediately after a major collection, but before the old generation is compacted.
The most recent versions of SML/NJ no longer use the simple two-generation collector described in the book and in Appel's 1989 paper Simple Generational Garbage Collection and Fast Allocation . SML/NJ now uses a multigeneration collector implemented by John Reppy and described in A High-Performance Garbage Collector for Standard ML.
Pages 157 and 158, the first lines of Algorithms 7.1 to 7.3 should be indented.
Page 169, Algorithm 7.4: the first line should be indented by one tab and the order of the arguments should be reversed . Thus,
st %ptr, [%obj] -- store ptr into obj st %obj, [%ssb] -- add obj to SSB add %ssb, 4, %ssbAlgorithm 7.4 The write-barrier for a sequential store buffer.
Page 169, penultimate paragraph, second sentence should read :
"Notice that hashing prevents duplicate entries from being introduced from the SSB."
all the code fragments given in Hölzle's
A Fast Write Barrier for Generational Garbage Collectors
share similar errors of
order of arguments to
sll instead of
srl for division
st instead of
stb for clearing bytes
st %ptr, [%obj + offset] -- store ptr into obj's field add %obj, offset, %temp -- calculate address of updated word srl %temp, k, %temp -- divide by card size, 2^k stb %g0, [%byte_map + %temp] -- clear byte in byte_mapAlgorithm 7.5 Chamber's write-barrier. k is log_2(card size).
st %ptr, [%obj + offset] -- store ptr into obj's field srl %temp, k, %temp -- calculate approximate byte index stb %g0, [%byte_map + %temp] -- clear byte in byte_mapAlgorithm 7.6 Hölzle's write-barrier.
Page 190, Algorithm 8.2 should refer to
The algorithm is also clearer, and more consistent stylistically with
Algorithm 8.3 if
free_count is explicitly incremented by
sweep rather than implicitly in
sweep(k3) = sweep k3 items i = 0 while i<k3 and sweeper <= Heap_top if mark_bit(sweeper) == unmarked free(sweeper) increment free_count else mark_bit(sweeper) = unmarked increment sweeper i = i+1Algorithm 8.2 Auxiliary procedures for Yuasa's algorithm.
There's also a stylistic inconsistency between Algorithms 8.2 and 8.3 on the
It would be better if
mark in Algorithm 8.3 also took
k1 as a parameter (rather than as a global variable).
Page 191, Algorithm 8.3 should also refer to
save_stack rather than
Page 193, penultimate line should read :
"The conservatism ..."
Page 195, Algorithm 8.7: in both cases in
finished should be set to
mark() = phase = mark_phase for R in Roots gcpush(R,mark_stack) mark1() for S in system_stack LOCK S, system_stack gcpush(S,mark_stack) mark1() LOCK gcstate finished = mark_stack==empty while not finished mark1() LOCK gcstate finished = mark_stack==emptyAlgorithm 8.7 Steele's concurrent marker.
Pages 200 and 224, final paragraph, incorrectly claims that the first implementation of concurrent reference counting was the DEC Systems Research Center Modula-2+ collector by Paul Rovner and Butler Lampson. In fact the first implementation was by Rovner for the Cedar implementation from Xerox PARC [rovn85] .
Page 230, penultimate paragraph, penultimate sentence: for code read data .
Page 237, Diagram 9.6 has the second block obscured by the shading.
Diagram 9.6 Space leaks in a cons-list are limited to the target of the false reference.
Page 242, first paragraph: the auxiliary list of unscanned blocks in Tospace is shown in Diagram 9.9 (not 9.8).
Page 243, Diagram 9.9 and the first paragraph, last sentence, could be improved as follows:
Diagram 9.9 Mostly Copying garbage collection.
"A drawback is that other objects in those blocks have also been retained (for example, object
Xin Diagram 9.9)."
Page 248, Algorithm 9.3: the first line should be indented by one tab .
Pages 260, 264 and 269, Algorithms 10.2 to 10.4: the first lines should be indented by one tab .
Page 260, Algorithm 10.2: the first line should be indented by one tab .
Page 289 says, "Goncalves and Appel confirm these predictions, using Appel's generational copying collector for SML/NJ." SML/NJ no longer uses the two-generation collector described in his 1989 paper Simple Generational Garbage Collection and Fast Allocation, but now uses a multigeneration collector implemented by John Reppy and described in A High-Performance Garbage Collector for Standard ML. It was this many-generation collector that the FPCA'95 paper measured .
Page 337, [Dickman, 1992] should refer to Peter Dickman's IWOOS'91 paper Effective Load Balancing in a Distributed Object-Support Operating System rather than his PhD thesis Distributed Object Management in a Non-Small Graph of Autonomous Networks with Few Failures .
Page 340, [Fiterman, 1995] was published in USENET comp.lang.c++ .
My thanks for pointing out errors go to:
Copyright © 1999 · Richard Jones