SBCL 2.4.4

• minor incompatible change: after-GC hooks are now called in the finalizer
  thread on threaded builds.
• platform support:
  ** on win32 on 64-bit systems, clear x87 state as well as SSE state after
  an exception. (lp#2000435, reported by David Scherfgen)
• enhancement: type assertions resulting from declarations involving variable
  numbers of multiple values are now checked.
• enhancement: support for memory allocation arenas is now available on the
  arm64 platform.
• enhancement: the cross-referencing facility is now able to handle
  anonymous functions.
• enhacnement: the SB-INTROSPECT contrib finds callees in methods of generic
  functions.
• bug fix: inconsistency in VOP definitions implementing DPB. (lp#2059842)
• bug fix: MASK-FIELD miscompilation. (lp#2059849)
• bug fix: caching a state-dependent type function leads to wrong type
  inference further down the line. (lp#2059888)
• bug fix: internal consistency violation after failing to apply a
  MAKE-ARRAY transform. (lp#2060083)
• bug fix: check the array index before constant-folding an array reference.
  (lp#2060347)
• bug fix: don't try to apply type constraints from SATISFIES
  types. (lp#2060756)
• bug fix: the JOIN-THREAD-PROBLEM function is now exported from the
  SB-THREAD package. (lp#2063385, thanks to Benjamin Lee)
• bug fix: compare-and-swap works as expected on SLOT-VALUE of
  FUNCALLABLE-STANDARD-OBJECT instances. (reported by qhong)
• bug fix: on arm64, and x86-64 with some non-default build options, integer
  rounding functions treat minus zero more consistently.
• bug fix: disassembly of stack allocation of vectors caused a crash.
  (reported by bohonghuang)
• bug fix: don't leak memory when decompressing a compressed core.
• optimization: the amount of space needed for debug-info is about 50% less,
  leading to a total default image size reduction of more than 10%.
• optimization: on arm64 and x86-64, encoding constants in machine code is
  sometimes smaller.
• optimization: on arm64 and x86-64, list accumulation is done with less
  space overhead.
• optimization: APPLY can apply a function to the REST of a &REST list
  without additional consing.

SBCL 2.4.3

• enhancement: when dumping debug information to fasl files, the system
  respects the SOURCE_DATE_EPOCH environment variable (if set) as the latest
  timestamp to be used.
• contributed module: the sb-perf contributed module, an interface
  originally by Luke Gorrie to Linux's perf, is now included by default on
  Linux. (Thanks to Philipp Marek)
• platform support:
  ** on Linux and BSD variants, timezone querying is now faster.
  ** Arm64/Darwin: allow configuring the system with a relocatable static
  space.
  ** PPC64: allow configuring the system with fasteval.
• bug fix: erroneous transform of EQUALP on characters (lp#2055425)
• bug fix: float rounders (FTRUNCATE and related functions) handle minus
  zero more consistently, returning minus zero as the primary value when
  rounding to zero from a negative value.
• bug fix: type checks for (VECTOR T) were giving the wrong answer for
  vectors displayed to simple multi-dimensional arrays. (reported by
  _death)
• bug fix: do not transform away division by BIT when the BIT might still
  include 0. (lp#2056184, reported by xizang)
• bug fix: various errors related to imperfections in the perfect hash
  generator. (lp#2055794, lp#2056341)
• bug fix: respect declarations for symbol macros inside defmethod.
  (lp#2056514, reported by Jonathan Braud)
• bug fix: failure to set structure slots to floats on Arm64. (lp#2058148,
  reported by Bibek Panthi)
• optimization: improvements to the implementation of CASE.
• optimization: faster PARSE-INTEGER :radix 10/16 on word-sized integers.
• optimization: improvements to LOGBITP.

SBCL 2.4.2

• bug fix: restore the ability to inherit from both SEQUENCE and
  SB-MOP:FUNCALLABLE-STANDARD-OBJECT. (lp#2050088, reported by Christophe
  Junke)
• bug fix: COERCE will not convert lambda forms to functions if given a type
  naming a (strict) subclass of FUNCTION.
• bug fix: LOG with a double-float and a ratio argument (in either order) do
  not lose precision through a single-float intermediate argument.
• bug fix: LOG to the base 2 of integer powers of 2 are more likely to get
  the mathematically precise answer.
• bug fix: LOG on ratios very near 1 with numerator or denominator being
  near a power of 2 will use log1p and so will lose less precision.
• bug fix: the utf-8 external format with Unix line-endings updates its
  character size information when taking the fast path for a buffer of ascii
  characters. (lp#2054169, reported by John Carroll)
• bug fix: don't print the contents of a possibly no-longer-valid
  dynamic-extent cons in PRINT-OBJECT method for THREAD objects.
  (lp#2026195, reported by Jake Connor)
• bug fix: place external entry points for functions consistently before any
  local functions. (lp#2051169, reported by Fedorov Alexander)
• bug fix: remove unactionable optimization notes for backquoted forms and
  ordinary calls to APPEND at high speed. (lp#2051401, reported by Robert
  Brown)
• bug fix: infinite loop in COPY-SEQ on zero-length arrays of element-type
  NIL. (lp#2051759, reported by Devon Sean McCullough)
• bug fix: fix compilation of non-top-level struct constructors.
  (lp#2052329, reported by Robert Poitras)
• bug fixes in SB-SIMD:
  ** improve bounds checking in SB-SIMD. (lp#2012010, reported by Patrick
  Poitras)
  ** fix SB-SIMD AVX f64.4-reverse (lp#2012986, thanks to Ari Projansky)
  ** fix SB-SIMD shuffles on AVX and SSE2 (lp#2012990, reported by Ari
  Projansky)
  ** fix lifetimes in sse+xmm0 VOPs (lp#2015329, reported by Ari Projansky)
• optimization: a number of internal tables, particularly those related to
  Unicode support have been converted to use perfect hash mechanisms,
  improving both speed and space.
• optimization: FIND, POSITION, ASSOC and RASSOC with constant sequence
  arguments containing symbols as keys are compiled to perfect hash lookups.
• optimization: the compiler runs a jump-to-jump elimination pass on x86-64.
• system integrity: compiling the system itself on x86-64/linux now produces
  bitwise-identical cross-compiled fasls whether the build host is cmucl,
  ccl, clisp or sbcl itself.

SBCL 2.4.1

• enhancement: compact instance headers are partially supported with the
  mark-region parallel garbage collector.
• enhancement: functions with declared return types have their return values
  type-checked in optimization regimes with high SAFETY and (DEBUG 3).
• platform support:
  ** disable ASLR on FreeBSD. (lp#2047655, thanks to Konstantin Belousov)
  ** link to libpthread on FreeBSD. (thanks to Konstantin Belousov)
  ** restore build on 64-bit riscv. (lp#2034713, lp#2048869, reported by
  Guillaume LE VAILLANT)
  ** restore build on 64-bit ppc.
  ** fix case in referring to a header file. (lp#2047726, thanks to Andrew Kravchuk)
  ** the fastrem-32 feature (for optimized computations of FLOOR) is now
  available on all platforms.
• bug fix: resweep moved lines after compaction in the mark-region parallel
  garbage collector.
• bug fix: infinite loops in the compiler on some constructs with SATISFIES
  types. (lp#2047289, lp#2047706, lp#2049631)
• optimization: various hash tables implementing part of the system
  (packages, Unicode data tables) have been converted to use perfect hash
  functions.
• optimization: TYPECASE on structure class hierarchies is implemented using
  a perfect hash.
• optimization: eliminate bound checks with relative offsets. (lp#1830314)
• optimization: the compiler has more knowledge of how to optimize
  DIGIT-CHAR.
• optimization: the compiler can elide intermediates for some calls to
  APPLY, CONCATENATE and MAKE-ARRAY with arguments that are freshly-consed
  modifications of existing sequences.
• optimization: (LOOP FOR X IN (REVERSE LIST) ...) is now faster and conses
  less.
• optimization: (LOOP ... APPEND ...) is more compact, and does less work if
  appending NIL.
• optimization: type tests of various array types are faster and shorter.

SBCL 2.4.0

• minor incompatible change: *COMPILE-VERBOSE* and *LOAD-VERBOSE* are bound
  to NIL when the system is started with the --script command-line argument.
  (reported by Hraban Luyat, thanks to Nicolas Martyanoff)
• minor incompatible change: when looking for its core file, the system
  checks the validity of whatever is pointed to by /proc/self/exe, and
  assesses argv[0] if /proc/self/exe is invalid. (thanks to Philipp Marek)
• minor incompatible change: the system no longer provides type names on the
  standard (CL) symbols ARRAY-RANK, ARRAY-TOTAL-SIZE, PATHNAME-HOST,
  PATHNAME-TYPE, PATHNAME-DIRECTORY, FLOAT-RADIX or FLOAT-DIGITS.
  (lp#2045559)
• platform support
  ** the mark-region parallel garbage collector can be enabled on arm64.
  (Thanks to Hayley Patton)
  ** fix build on modern FreeBSDs. (lp#2046966, thanks to David J. Flander)
• bug fix: restore compiler type inference correctness on calls to REDUCE
  with :INITIAL-VALUE but no :FROM-END. (lp#2044856, reported by Patrick
  Poitras)
• bug fix: compiler error when declaring SB-EXT:MUFFLE-CONDITIONS on an
  unknown type. (lp#2045442)
• bug fix: the disassembler provided non-pretty output for registers in some
  cases. (lp#2046004, reported by Fedorov Alexander)
• bug fix: the system is slightly less likely to exhaust the stack again
  when reporting a control stack exhaustion error.
• optimization: GC write barriers are eliminated in more cases.
• optimization: improved type derivation of iteration variables with mixed
  types.
• optimization: remove unused initial values from LET bindings, improving
  register type selection.
• optimization: lower EQUALP/EQUAL/EQL to EQL/EQ in FIND/MEMBER based on the
  input types.
• optimization: better type derivation for DPB, LOGIOR.

SBCL 2.3.11

• minor incompatible change: streams with an external-format specified with
  :REPLACEMENT will use their replacement data once per stream unit that
  causes a decoding error (rather than, in some cases, once for a sequence
  of bytes none of which is a valid character start position for that
  external-format).
• minor incompatible change: external-format designators with unsupported or
  unrecognized options now signal an error when used.
• enhancement: During generic function dispatch, for a generic function
  using standard- or short-method-combination, if there are no applicable
  primary methods the system will call the generic function
  SB-PCL:NO-PRIMARY-METHOD, whose default behaviour is to signal an error.
  Users may define methods on this generic function.
• enhancement: external formats for unibyte encodings and utf-8 now support
  newline variants.
• enhancement: character decoding and encoding errors signalled by stream or
  octet functions now provide a USE-VALUE restart for handlers to provide
  replacement input or output.
• enhancement: READ-SEQUENCE and WRITE-SEQUENCE support user-defined
  sequences; the default implementation proceeds element-by-element, reading
  or writing single bytes or characters to or from the stream as
  appropriate.
• bug fix: OCTETS-TO-STRING using unibyte external formats with unallocated
  codepoints (e.g. iso-8859-3) correctly signal or use replacements rather
  than taking bits from the address of NIL and converting those bits to
  a character.
• bug fix: FILE-STRING-LENGTH now returns NIL if the input datum is not
  encodable in the stream's external format.
• bug fix: table-based multibyte external formats (EUC-JP, Shift-JIS, GBK)
  now honour a replacement character (in the external format or through
  restarts) when encoding to octets.
• bug fix: converting from octets using the UCS-2, UCS-4 and UTF-32 external
  formats no longer reads past the end of an octet array with a non-integral
  number of two- or four-byte units.
• bug fix: converting from octets using the UCS-2, UCS-4, UTF-16 or UTF-32
  external formats now returns a simple string, as required by the type
  declaration of OCTETS-TO-STRING.
• bug fix: providing an invalid external format argument to OPEN or
  WITH-OPEN-FILE (or the internal MAKE-FD-STREAM) no longer leaks a file
  descriptor.
• bug fix: SB-ROTATE-BYTE recognizes out-of-relevant-range BYTE
  specifications for integers before attempting to cons up enormous bignums
  for masking and shifting. (lp#2042937)
• bug fix: fix type derivation on compiling SB-ROTATE-BYTE forms with
  non-zero POSITION in the byte specifier. (lp#2042775)
• bug fix: fix multiple assembler errors when compiling MAKE-ARRAY,
  MAKE-STRING and similar with a large constant size. (lp#2037347, lp#2038744)
• bug fix: fix internal error when compiling (SETF SBIT) with a large
  constant index. (lp#2037415)
• bug fix: fix internal compiler error on invalid lambda list parameters in
  LABELS. (lp#2040334)
• bug fix: fix internal compiler error when compiling some
  infinitely-recursive LABELS forms. (lp#2042704)
• bug fix: fix internal compiler error when attempting to inline a jump to a
  label that has been deleted. (lp#2043262)
• bug fix: FILL-POINTER should never be made to go negative. (lp#2042452)
• optimization: external formats with :REPLACEMENT no longer bind handlers
  for coding errors around conversion functions, and so should cons less and
  be faster.
• optimization: when the :EXTERNAL-FORMAT argument to STRING-TO-OCTETS or
  OCTETS-TO-STRING is a compile-time constant, the external format is
  resolved at load time rather than on each call.
• optimization: the compiler is able to constrain the types of inputs to
  some functions given a derived or asserted type of the function's return
  value.
• optimization: the compiler performs fewer redundant type checks in ASSOC,
  GETF and similar functions.

SBCL 2.3.10

• enhancement: The compiler now allows stack allocating vectors of any size
  on all safety levels, not just those which it can prove are of sub-page
  sizes. It can do this because it now inserts code to check for stack
  overflow explicitly on higher safety levels.
• enhancements to the disassembler:
  ** on arm64, x86-64, DISASSEMBLE annotates references to static symbols.
• bug fix: calls to generic functions now detect erroneous keywords (in the
  sense of CLHS 7.6.5) passed as arguments even when auxiliary methods are
  applicable.
• bug fix: the standard method on SB-MOP:COMPUTE-EFFECTIVE-METHOD no longer
  inserts calls to implementation-defined local macros. (reported by Daniel
  Kochmański)
• bug fix: compiler error from state-machine-like LABELS forms in some
  circumstances. (lp#2037318)
• bug fix: fix compile-time error in constant-folding RATIONAL on literal
  float infinities. (lp#2037455)
• bug fix: failure on x86-64 to assemble code for EQL tests of comparisons
  with immediates. (lp#2037456)
• bug fix: infinite loop in the compiler for simplification of type tests of
  complicated union types. (lp#2038112, reported by Paul M. Rodriguez)
• bug fix: inability to dump a literal displaced array containing copies of
  its displacement target. (lp#2038233, reported by James Kalenius)
• bug fix: compiler error in LOGBITP type derivation. (lp#2038241)
• bug fix: compiler error in AREF type derivation. (lp#2038659)
• bug fix: compiler internal consistency failure in overflow type checks.
  (lp#2038736)
• bug fix: work around an infinite loop in type simplification by not
  providing such types from the compiler. (lp#2038980, reported by Richard
  Holcombe)
• bug fix: spurious run-time argument count errors from generic function
  calls on arm64. (lp#2039006, reported by fiddlerwoaroof)
• bug fix: errors in SCALE-FLOAT on floating-point infinities. (lp#2039613)
• bug fix: ROOM is slightly more robust to incompletely-initialized
  instances at the point of running ROOM. (Reported by Andreas Franke)
• bug fix: finalizers saved through SAVE-LISP-AND-DIE and subsequently
  executed do not trigger memory faults. (Reported by Bohong Huang)
• optimization: improvements to type derivation for ISQRT, INTEGER-LENGTH,
  LOGCOUNT, LOG, DENOMINATOR.

SBCL 2.3.9

• enhancement: stack allocation via DYNAMIC-EXTENT now applies to all values
  that a variable can take on (for example via SETQ), not just the initial
  binding. This permits for example building complex or recursive structures
  on the stack more easily via iteration. See the updated manual entry for
  more details.
• minor incompatible change: some interfaces in the SB-POSIX contrib module
  adhere to the spec that a NULL result from the C library is an error if
  and only if errno was altered by the call. SYSCALL-ERROR will be signaled
  if so.
• enhancement: the SB-POSIX contrib module provides DO-PASSWDS and DO-GROUPS
  to allow users to iterate over password and group databases safely.
• platform support:
  ** support for Darwin on x86 and PowerPC has been restored. (lp#2033287,
  thanks to Kirill A. Korinsky, Sergey Fedorov and barracuda156)
• bug fix: miscompilation due to erroneous type derivation in the presence
  of multiplication of fixnums by ratios. (lp#2033695, reported by Patrick
  Dussud)
• bug fix: compiler error when compiling signed- and unsigned 64-bit type
  checks in some cases. (lp#2033997, reported by Eric Smith)
• bug fix: compiler error when the :INITIAL-CONTENTS argument to MAKE-ARRAY
  is a constant non-sequence. (lp#2037328)
• bug fix: compiler error when constant-folding sequence functions with
  :TEST or :KEY functions erroring on the given sequence. (lp#2037341)
• bug fix: compiler error when arguments to array or sequence functions
  imply a very large sequence size. (lp#2037443, lp#2037348)
• bug fix: compiler error when the return value of ADJUST-ARRAY is not used.
  (lp#2037450)
• optimization: function types derived by the compiler can in some cases be
  propagated backwards through the intermediate representation.
• optimization: better type derivations for LDB, LOGBITP, RATIO.
• optimization: eliminate bound checks in more cases involving transitive
  comparisons.

SBCL 2.3.8

• enhancement: a mark-region parallel garbage collector is available as a
  build-time option; it can be enabled by adding
  --without-gencgc --with-mark-region-gc
  to the build command line. (Thanks to Hayley Patton)
• enhancement: Stack allocation via DYNAMIC-EXTENT is now possible for
  conditionals even when not all branches are stack-allocatable. Previously
  all branches needed to be stack-allocatable for the otherwise-inaccessible
  subparts to get stack allocated.
• platform support:
  ** on Mac OS X Sonoma, loading the memory image no longer fails.
  (lp#2029430, reported by cladur)
  ** on Darwin, we no longer reimplement nanosleep().
  ** on PPC64, undefined function errors now work.
  ** on ARM64/OpenBSD, enable the GCC TLS feature. (thanks to Sébastien
  Marie)
  ** when building the system, only display a reasonable amount of timing
  precision. (thanks to Philipp Marek)
• bug fix: handling of inlining functions compiled to return unboxed values
  no longer crashes the compiler. (lp#2029020, reported by Pascal
  J. Bourguignon)
• bug fix: the source location for code executed within a top-level
  (EVAL-WHEN (:COMPILE-TOPLEVEL) ...) form is now more useful.
• bug fix: address a race between user threads cancelling finalizers and the
  finalizer thread executing them. (lp#2029306)
• bug fix: complex division returns the same value when evaluated inline and
  out-of-line. (lp#2030097)
• bug fix: the pretty-printer no longer deletes syntactically-significant
  whitespace immediately preceding a newline. (lp#1985814, reported by Mark
  David)
• optimization: the compiler is more aware of the result type of the
  NUMERATOR function.
• optimization: EQUAL and EQUALP compile to more efficient code when the two
  arguments are known to be of the same nullable type.
• optimization: converting bignums to floats uses no intermediate memory.

SBCL 2.3.7

• minor incompatible change: MACROLET macro functions are now compiled with
  (SPEED 1), leading to fewer efficiency notes being emitted when compiled
  in otherwise high-SPEED environments.
• minor incompatible change: when coalescing list data, the file compiler
  respects substructure equality more accurately, with the side-effect of
  coalescing along CDR chains as well as CARs. (lp#2025086)
• minor incompatible change: FUNCTION type declarations for local variables
  generate assertions around their use when called.
• platform support
  ** on OpenBSD, the regression test suite expectations have been updated.
  (lp#2026809, thanks to Sebastien Marie)
  ** on OpenBSD, the data limit is now 1GB. (lp#2027536, thanks to
  Sebastien Marie)
  ** on Darwin with the SB-FUTEX feature, do not use unpaired
  mach_thread_self() syscalls, avoiding resource leaks when creating
  threads.
  ** on 64-bit RISCV, add support for some REM-by-multiplication
  optimizations.
  ** on Windows, work around a C compiler bug relating to SYSV_ABI.
• bug fix: FILE-POSITION on string output streams no longer crashes or
  causes arbitrary memory overwrites. (lp#1839040)
• bug fix: the compiler no longer constant-folds POSITION to NIL if the
  START or END arguments are not valid.
• optimization: the compiler derives types of &KEY arguments in local calls.
  (lp#655562)
• optimization: type tests of values of known union type can be faster if
  the type being tested for has a non-trivial intersection with the known
  type.
• optimization: the low-level implementation of NUMBERP, REALP and RATIONALP
  has been improved on x86-64 and arm64.
• optimization: the compiler removes known-NIL arguments from calls to
  APPEND and NCONC, and empty sequences from calls to CONCATENATE.
• optimization: checks for symbols being bindable are now memoized, speeding
  up compiled uses of PROGV.
• optimization: SLOT-VALUE on STRUCTURE-OBJECTs with non-constant slot-name
  argument is faster.