SBCL 2.4.8

• bug fix: the elftool utility finds a writeable directory in more
  situations. (thanks to Shinmera)
• bug fix: SLOT-MAKUNBOUND does not attempt to dereference a PROGN variable
  in the interpreter.
• bug fix: READ-SEQUENCE into displaced arrays with a non-zero offset now
  writes to the right memory location.
• bug fix: fix some erroneous file position calculations in the editcore
  utility (exposed by a change in the libzstd compression implementation).
• bug fix: do not break the build on STYLE-WARNINGs for earlier SBCL build
  hosts. (lp#2064671, reported by Patrick Poitras)
• bug fix: various bug fixes for ppc64le (lp#2074275, reported by Claude R. C.)
• bug fix: address a rounding error in the TAN type deriver which led to a
  miscompile in cl-pdf. (lp#2077100, reported by Gian Pierro Carrubba)
• bug fix: overoptimization of FIND with a :TEST of CHAR-EQUAL. (lp#2077539)
• optimization: detection of duplicate names in loaded code now scales
  subquadratically.
• optimization: switch from Floyd's to Brent's cycle detection for lists.
• optimization: EQUAL on lists should be faster.
• optimization: fewer filesystem operations are performed when working out
  what to LOAD.
• optimization: various microoptimizations on hash tables and
  associated operations.
• optimization: strings are now hashed using FNV-1A, replacing Bob Jenkins'
  one-at-a-time hash.
• optimization: fewer redundant validations of the sequence bounding indices
  in POSITION on strings.
• optimization: many improvements to type derivation on the arguments to and
  results of standard functions
• optimization: adding many (hundreds) methods to a generic function can be
  done faster.

SBCL 2.4.7

• minor incompatible change: the compiler will emit optimization notes
  related to complex type checks only at high SPEED optimization settings.
• minor incompatible change: the GET-FOREGROUND symbol is now exported from
  the SB-THREAD package. (thanks to Philipp Marek)
• minor incompatible change: code objects are now printed with their ending
  address as well as their start address.
• platform support:
  ** fix occasional saved core corruption on Win32. (reported by Luís
  Borges de Oliveira)
  ** address some crashing cases in arena support. (reported by Andreas
  Franke)
  ** fix a hard-coded path to cp. (thanks to Hraban Luyat)
  ** address relocation issues on PIC-flavoured arm64. (lp#2067153, thanks
  to leafze)
  ** fix a crash in the arm64-dissassembler if a code component is missing.
  ** fix a crash on 32-bit musl libc systems. (reported by Will Sinatra)
  ** fix building with link-time optimization. (lp#2072800, reported by Eli
  Schwartz)
  ** fix building with newer llvm. (lp#2071545, reported by Yan)
  ** mitigate the lack of gc-safety in SB-VM::REMOVE-STATIC-LINKS.
  (lp#2045433)
• bug fix: COMPILE installs its second argument as the value of its non-null
  NAME argument, even if the second argument was already compiled.
  (lp#2071324, reported by Tim Bradshaw)
• bug fix: allow the hashing routines in sb-md5 to work on arrays with more
  than 2^29 elements.
• bug fix: allow READ-SEQUENCE and WRITE-SEQUENCE to read and write files
  bigger than 4GB.
• bug fix: READ-SEQUENCE returns the index of the first unmodified element
  of its sequence. (reported by Janis Dzerins)
• optimization: various improvements to floating point rounding routines.
• optimization: PHASE called on the result of COMPLEX now elides the
  intermediate COMPLEX object.
• optimization: the compiler is more aware of the types of COMPLEX, ATAN,
  APPEND and NCONC.

SBCL 2.4.6

• enhancement: name conflicts resulting from colliding symbols in IMPORT and
  USE-PACKAGE are resolved once for each name, rather than between pairwise
  colliding symbols.
• enhancement: calls to structure constructors with type mismatches in
  default initforms cause compile-time warnings.
• platform support:
  ** fix constant-folding of %log1p and %log2 on 32-bit x86.
  ** fix the encoding of popcntd on ppc64
• bug fix: EXPORT could be tricked into exporting two distinct symbols of
  the same name from the same package.
• bug fix: two-argument calls to LOG with arguments of different precision
  do not lose accuracy through insufficiently-precise intermediate values.
• bug fix: :NEWLINE options in DEFAULT-EXTERNAL-FORMAT are respected when
  opening files. (reported by Marco Antoniotti)
• bug fix: extend type declarations for the iteration variable of DOLIST
  with NULL during the evaluation of the result clause. (lp#942237)
• bug fix: #\uE0 (LATIN CAPITAL LETTER A WITH GRAVE) was incorrectly not
  downcased with STRING-DOWNCASE. (lp#2067841, reported by Matt Kaufmann)
• bug fix: backquoted lists as arguments to MAKE-ARRAY were miscompiled.
  (lp#2069345, reported by Dan Bothell)
• bug fix: resolve the circularity between the type system and the CLOS
  metaobject protocol more robustly. (lp#2069502, reported by Jan Moringen)
• bug fix: misplaced tilde in a logical pathname error message.
  (lp#2069995, thanks to Marco Heisig)
• optimization: various speedups to UTF-8 based external format streams and
  other stream routines.

SBCL 2.4.5

• incompatible change: attempting to pass or return alien structs by value
  now signals errors. Previously, such attempts would silently tend to
  corrupt registers or memory; there is work in progress to allow such calls
  conforming to the platform ABI. (thanks to Rongcui Dong)
• minor incompatible change: function debug info is compressed only if the
  system is compiled with libzstd, rather than falling back to a pure-lisp
  compression implementation.
• minor incompatible change: the compiler will warn in more cases when it
  can detect incorrectly-typed arguments to FORMAT directives ~C and ~R
• minor incompatible change: strings are converted to a more compact
  representation if possible before being used as docstrings.
• platform support:
  ** explicitly include stdlib.h where needed on OpenBSD. (thanks to
  Sebastien Marie)
  ** make the editcore utility work on Windows. (thanks to Luís Borges de
  Oliveira)
  ** fix memory initialization in RUN-PROGRAM on Windows.
  ** resolve a deadlock in %INTERRUPT-THREAD on Darwin. (lp#2062940,
  reported by Yan)
  ** hang on startup under some terminal emulators on OS X 14.5.
  (lp#2067313, reported by Richard M Kreuter)
• enhancement: when (> debug 1), try to find source locations for code
  expanded from macros that copy their input forms.
• bug fix: the method-combination generic function caches were missing some
  of the generic functions constructed during the PCL build itself.
  (reported by Didier Verna)
• bug fix: SXHASH on equal PATHNAME objects could return different values in
  different cores. (reported by Luís Borges de Oliveira)
• bug fix: spurious compiler warnings on SORT in some circumstances.
  (lp#2065609, reported by William G Lederer)
• optimization: faster bignum addition and negation on arm64, x86-64.
• optimization: faster type tests for (unsigned-byte X) for X being
  multiples of the platform word size, on arm64, x86-64.

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.