SIGNIFICANT USER-VISIBLE CHANGES:

• Calling && or || with LHS or (if evaluated) RHS of length greater
  than one is now always an error, with a report of the form

  'length = 4' in coercion to 'logical(1)'
  

  Environment variable _R_CHECK_LENGTH_1_LOGIC2_ no longer has any
  effect.

NEW FEATURES:

• The included BLAS sources have been updated to those shipped with
  LAPACK version 3.10.1. (This caused some platform-dependent
  changes to package check output.) And then to the sources from
  LAPACK version 3.11.0 (with changes only to double complex
  subroutines).

• The included LAPACK sources have been updated to include the four
  Fortran 90 routines rather than their Fortran 77 predecessors.
  This may give some different signs in SVDs or
  eigendecompositions.. (This completes the transition to LAPACK
  3.10.x begun in R 4.2.0.)

• The LAPACK sources have been updated to version 3.11.0. (No new
  subroutines have been added, so this almost entirely bug fixes:
  Those fixes do affect some computations with NaNs, including R's
  NA.)

• The parser now signals classed errors, notably in case of the
  pipe operator |>. The error object and message now give line and
  column numbers, mostly as proposed and provided by Duncan Murdoch
  in PR#18328.

• toeplitz() is now generalized for asymmetric cases, with a
  toeplitz2() variant.

• xy.coords() and xyz.coords() and consequently, e.g., plot(x,y, log = "y") now signal a classed warning about negative values
  of y (where log(.) is NA). Such a warning can be specifically
  suppressed or caught otherwise.

• Regular expression functions now check more thoroughly whether
  their inputs are valid strings (in their encoding, e.g. in
  UTF-8).

• The performance of grep(), sub(), gsub() and strsplit() has been
  improved, particularly with perl = TRUE and fixed = TRUE. Use of
  useBytes = TRUE for performance reasons should no longer be
  needed and is discouraged: it may lead to incorrect results.

• apropos() gains an argument dot_internals which is used by the
  completion (help(rcompgen)) engine to also see base internals
  such as .POSIXct().

• Support in tools::Rdiff() for comparing uncompressed PDF files is
  further reduced - see its help page.

• qqplot(x, y, ...) gains conf.level and conf.args arguments for
  computing and plotting a confidence band for the treatment
  function transforming the distribution of x into the distribution
  of y (Switzer, 1976, Biometrika). Contributed by Torsten
  Hothorn.

• Performance of package_dependencies() has been improved for cases
  when the number of dependencies is large.

• Strings newly created by gsub(), sub() and strsplit(), when any
  of the inputs is marked as "bytes", are also marked as "bytes".
  This reduces the risk of creating invalid strings and accidental
  substitution of bytes deemed invalid.

• Support for readLines(encoding = "bytes") has been added to allow
  processing special text files byte-by-byte, without creating
  invalid strings.

• iconv(from = "") now takes into account any declared encoding of
  the input elements and uses it in preference to the native
  encoding. This reduces the risk of accidental creation of
  invalid strings, particularly when different elements of the
  input have different encoding (including "bytes").

• Package repositories in getOption("repos") are now initialized
  from the repositories file when utils is loaded (if not already
  set, e.g., in .Rprofile). (From a report and patch proposal by
  Gabriel Becker in PR#18405.)

• compactPDF() gets a verbose option.

• type.convert() and hence read.table() get new option tryLogical = TRUE with back compatible default. When set to false, converts
  "F" or "T" columns to character.

• Added new unit prefixes "R" and "Q" for abbreviating
  (unrealistically large) sizes beyond 10^{27} in standard = "SI",
  thanks to Henrik Bengtsson's PR#18435.

• as.data.frame()'s default method now also works fine with atomic
  objects inheriting from classes such as "roman", "octmode" and
  "hexmode", such fulfilling the wish of PR#18421, by Benjamin
  Feakins.

• The as.data.frame.vector() utility now errors for wrong-length
  row.names. It warned for almost six years, with “Will be an
  error!”.

• sessionInfo() now also contains La_version() and reports codepage
  and timezone when relevant, in both print() and toLatex() methods
  which also get new option tzone for displaying timezone
  information when locale = FALSE.

• New function R_compiled_by() reports the C and Fortran compilers
  used to build R, if known.

• predict(<lm>, newdata = *) no longer unnecessarily creates an
  offset of all 0s.

• solve() for complex inputs now uses argument tol and by default
  checks for ‘computational singularity’ (as it long has done for
  numeric inputs).

• predict(<rank-deficient lm>, newdata=*) now obeys a new argument
  rankdeficient, with new default "warnif", warning only if there
  are non-estimable cases in newdata. Other options include
  rankdeficient = "NA", predicting NA for non-estimable newdata
  cases. This addresses PR#15072 by Russ Lenth and is based on his
  original proposal and discussions in PR#16158 also by David Firth
  and Elin Waring. Still somewhat experimental.

• Rgui console implementation now works better with the NVDA screen
  reader when the full blinking cursor is selected. The underlying
  improvements in cursor handling may help also other screen
  readers on Windows.

• The drop-field control in GraphApp can now be left with the TAB
  key and all controls can be navigated in the reverse order using
  the Shift+TAB key, improving accessibility of the Rgui
  configuration editor.

• qnorm(<very large negative>, log.p=TRUE) is now fully accurate
  (instead of to “only” minimally five digits).

• demo(error.catching) now also shows off withWarnings() and
  tryCatchWEMs().

• As an experimental feature the placeholder _ can now also be used
  in the rhs of a forward pipe |> expression as the first argument
  in an extraction call, such as _$coef. More generally, it can be
  used as the head of a chain of extractions, such as _$coef[[2]].

• Spaces in the environment variable used to choose the R session's
  temporary directory (TMPDIR, TMP and TEMP are tried in turn) are
  now fatal. (On Windows the ‘short path’ version of the path is
  tried and used if that does not contain a space.)

• all.equal.numeric() gets a new optional switch giveErr to return
  the numeric error as attribute. Relatedly,
  stopifnot(all.equal<some>(a, b, ..)) is as “smart” now, as
  stopifnot(all.equal(....)) has been already, thus allowing
  customized all.equal<Some>() wrappers.

• R on Windows is now able to work with path names longer than 260
  characters when these are enabled in the system (requires at
  least Windows 10 version 1607). Packages should be updated to
  work with long paths as well, instead of assuming PATH_MAX to be
  the maximum length. Custom front-ends and applications embedding
  R need to update their manifests if they wish to allow this
  feature. See
  https://blog.r-project.org/2023/03/07/path-length-limit-on-windows
  for more information.

• ‘Object not found’ and ‘Missing argument’ errors now give a more
  accurate error context. Patch provided by Lionel Henry in
  PR#18241.

• The @ operator is now an S3 generic. Based on contributions by
  Tomasz Kalinowski in PR#18482.

• New generic chooseOpsMethod() provides a mechanism for objects to
  resolve cases where two suitable methods are found for an Ops
  Group Generic. This supports experimenting with alternative
  object systems. Based on contributions by Tomasz Kalinowski in
  PR#18484.

• inherits(x, what) now accepts values other than a simple
  character vector for argument what. A new generic, nameOfClass(),
  is called to resolve the class name from what. This supports
  experimenting with alternative object systems. Based on
  contributions by Tomasz Kalinowski in PR#18485.

• Detection of BLAS/LAPACK in use (sessionInfo()) with FlexiBLAS
  now reports the current backend.

• The "data.frame" method for subset() now warns about extraneous
  arguments, typically catching the use of = instead of == in the
  subset expression.

• Calling a:b when numeric a or b is longer than one may now be
  made into an error by setting environment variable
  _R_CHECK_LENGTH_COLON_ to a true value, along the proposal in
  PR#18419 by Henrik Bengtsson.

• density(x, weights = *) now warns if automatic bandwidth
  selection happens without using weights; new optional warnWbw may
  suppress the warning. Prompted by Christoph Dalitz' PR#18490 and
  its discussants.

• rm(list = *) is faster and more readable thanks to Kevin Ushey's
  PR#18492.

• The plot.lm() function no longer produces a normal Q-Q plot for
  GLMs. Instead it plots a half-normal Q-Q plot of the absolute
  valu...

C-LEVEL FACILITIES:

• The definition of DL_FUNC in R_ext/Rdynload.h has been changed to
  be fully C-compliant. This means that functions loaded via for
  example R_GetCCallable need to be cast to an appropriate type if
  they have any arguments.

• .Machine has a new element sizeof.time_t to identify old systems
  with a 32-bit type and hence a limited range of date-times (and
  limited support for dates millions of years from present).

PACKAGE INSTALLATION:

• (Windows) The default C++ standard had accidentally been left at
  C++11 when it was changed to C++14 on Unix.

BUG FIXES:

• As "POSIXlt" objects may be “partially filled” and their list
  components meant to be recycled, length() now is the length of
  the longest component.

• as.POSIXlt.Date() could underflow for dates in the far past (more
  than half a million years BCE).

• as.Date.POSIXlt(x) would return "1970-01-01" instead of NA in R
  4.2.2, e.g., for

      x <- as.POSIXlt(c("2019-01-30","2001-1-1"))
      x$mon <- c(0L, NA); as.Date(x)
  

• R CMD check failed to apply enabled _R_CHECK_SUGGESTS_ONLY_ to
  examples and vignettes (regression in R 4.2.0).

• R CMD check did not re-build vignettes in separate processes by
  default (regression in R 4.2.0).

• Running examples from HTML documentation now restores previous
  knitr settings and options (PR#18420).

• Quartz: fonts are now located using Core Graphics API instead of
  deprecated ATS which is no longer supported in the macOS 13 SDK
  (PR#18426). This also addresses an issue where the currently
  used font in the Quartz device context was not correctly
  retained.

• (Windows) Math symbols in text drawing functions are again
  rendered correctly (PR#18440). This fixes a regression in R
  4.2.1 caused by a fix in PR#18382 which uncovered an issue in
  GraphApp due to which the symbol charset was not used with TT
  Symbol font face.

• (Windows) Installing a package with a src/Makefile.{win,ucrt}
  file includes ~/.R/Makevars.win64 in the search for user
  makevars, as documented in “R Installation and Administration”
  and done for packages with a src/Makevars.{win,ucrt} file.

• format(<POSIXlt_w/_unbalanced_sec>, "....%OS<n>") with n > 0 no
  longer accidentally uses the unbalanced seconds, thanks to
  Suharto Anggono's report (including patch) in PR#18448.

• solve.default(a, b) works around issues with some versions of
  LAPACK when a contains NA or NaN values.

• When UseMethod() cannot dispatch, it no longer segfaults
  producing the error message in case of a long class(), thanks to
  Joris Vankerschaver's report (including patch) in PR#18447.

• When example(foo, ..) produces graphics on an interactive device
  it needs to open itself, it now leaves devAskNewPage() unchanged
  even when it was FALSE, thus fixing a 14 years old ‘’.

• packageDescription() again catches errors from encoding
  conversions. This also fixes broken packageVersion() in C locale
  on systems where iconv does not support transliteration.

NEW FEATURES:

• tools::Rdiff(useDiff = TRUE) checks for the presence of an
  external diff command and switches to useDiff = FALSE if none is
  found. This allows R CMD Rdiff to always work.

• On Windows, environment variable R_LIBCURL_SSL_REVOKE_BEST_EFFORT
  can be used to switch to only ‘best-effort’ SSL certificate
  revocation checks with the default "libcurl" download method.
  This reduces security, but may be needed for downloads to work
  with MITM proxies (PR#18379).

• (macOS) The run-time check for libraries from XQuartz for X11 and
  Tcl/Tk no longer uses otool from the Apple Developer Tools
  (PR#18400).

• The LaTeX style for producing the PDF manuals, Rd.sty, now loads
  the standard amsmath, amsfonts and amssymb packages for greater
  coverage of math commands in the Rd \eqn and \deqn macros. The
  \mathscr LaTeX command is also provided (via the mathrsfs
  package, if available, or the amsfonts bundle otherwise),
  fulfilling the wish of PR#18398.

• (Windows) The default format of readClipboard() and
  writeClipboard() has been changed to 13 (CF_UNICODETEXT).

INSTALLATION on a UNIX-ALIKE:

• The PDF manuals (if built) can be compacted by the new target
  make compact-pdf (at the top level or in directory doc/manual).

• There is now configure support for LLVM clang 15 on Linux, which
  defaults to position-independent (PIE) executables whereas
  gfortran does not.

• Many small changes to ease compilation (and suppress warnings)
  with LLVM clang 15.

BUG FIXES:

• Rscript -e would fail if stdin were closed (Reported by Henrik
  Bengtsson.)

• qt(*, log.p=TRUE) in outer tails no longer produces NaN in its
  final steps, thus fixing PR#18360.

• tools::Rd2latex() now escapes hashes and ampersands when writing
  URLs, fixing LaTeX errors with such URLs in \tabular.

• When isGeneric(f, fdef=*) is used with mismatching names, the
  warning is better understandable; reported (with fix) in PR#18370
  by Gabe Becker.

• poly(x, n) now works again (and is now documented) when x is a
  "Date" or "POSIXct" object, or of another class while fulfilling
  mode(x) == "numeric". This also enables poly(x, *, raw=TRUE) for
  such variables. Reported by Michael Chirico to R-devel.

• write.table(), write.csv() and write.csv2() restore their
  numerical precision (internal equivalent of digits = 15) after an
  interrupt (PR#18384).

• One can now read also byte FF from a clipboard connection
  (PR#18385).

• source("") and source(character()) now give more helpful error
  messages.

• R CMD check --as-cran set _R_CHECK_TIMINGS_ too late to have the
  intended effect.

• as.POSIXlt(x) now also works with very large dates x, fixing
  PR#18401 reported by Hannes Mühleisen.

• Files can now be extracted even from very large zip archives
  (PR#18390, thanks to Martin Jakt).

• Non-finite objects of class "POSIXlt" are now correctly coerced
  to classes "Date" and "POSIXct"; following up on the extension to
  format() them correctly.

• Added methods for is.finite(), is.infinite() and is.nan() for
  "POSIXlt" date-time objects.

BUG FIXES on Windows:

• Non-ASCII characters are now properly displayed on Windows in
  windows created using GraphApp via e.g. winDialogString thanks to
  a workaround for an at least surprising Windows behavior with
  UTF-8 as the system encoding (PR#18382).

• Find and replace operations work again in the script editor in
  Rgui on Windows.

• Computation of window size based on requested client size in
  GraphApp when running in a multi-byte locale on Windows has been
  fixed (regression in R 4.2.0 for users of systems where R 4.1
  used a single-byte locale). Rgui again respects the number of
  console rows and columns given in Rconsole file.

• Rterm support for Alt+xxx sequences has been fixed to produce the
  corresponding character (only) once. This fixes pasting text with
  tilde on Italian keyboard (PR#18391).

NEW FEATURES:

• New function utils::findCRANmirror() to find out if a CRAN mirror
  has been selected, otherwise fallback to the main site. This
  behaves in the same way as tools::CRAN_package_db() and is
  intended for packages wishing to access CRAN for purposes other
  than installing packages.

  The need for this was shown by a day when the main CRAN website
  was offline and a dozen or so packages which had its URL
  hardcoded failed their checks.

INSTALLATION on a UNIX-ALIKE:

• The libraries searched for by --with-blas (without a value) now
  include BLIS (after OpenBLAS but before ATLAS). And on macOS,
  the Accelerate framework (after ATLAS). (This is patterned after
  the AX_BLAS macro from the Autoconf Archive.)

• The included LAPACK sources have been updated to 3.10.1.

UTILITIES:

• The (full path to) the command tidy to be used for HTML
  validation can be set by environment variable R_TIDYCMD.

• Setting environment variable _R_CHECK_RD_VALIDATE_RD2HTML_ to a
  false value will override R CMD check --as-cran and turn off HTML
  validation. This provides a way to circumvent a problematic
  tidy.

  The 2006 version that ships with macOS is always skipped.

C-LEVEL FACILITIES:

• The undocumented legacy declarations of Sint, Sfloat, SINT_MAX
  and SINT_MIN in header R.h are deprecated.

BUG FIXES:

• fisher.test(d) no longer segfaults for "large" d; fixing PR#18336
  by preventing/detecting an integer overflow reliably.

• tar(., files=*) now produces correctly the warning about invalid
  uid or gid of files, fixing PR#18344, reported by Martin Morgan.

• tk_choose.files() with multi = FALSE misbehaved on paths
  containing spaces (PR#18334) (regression introduced in R 4.0.0).

• sort(x, partial = ind, *) now works correctly notably for the
  non-default na.last = FALSE or TRUE, fixing PR#18335 reported by
  James Edwards.

• Environment variable _R_CHECK_XREFS_REPOSITORIES_ is only used
  for checking .Rd cross-references in R CMD check (as documented)
  and not for other uses looking for a CRAN mirror.

• The search for a CRAN mirror when checking packages now uses
  getOption("repos") if that specifies a CRAN mirror, even when it
  does not also specify all three Bioconductor repositories (as was
  previously required).

• The HTML code generated by tools::Rd2HTML() has been improved to
  pass tidy 5.8.0.

BUG FIXES on Windows:

• Writing to a clipboard connection works again, fixing a
  regression in R 4.2.0 (PR#18332). Re-using a closed clipboard
  connection longer issues a spurious warning about an ignored
  encoding argument.

• C function getlocale no longer attempts to query an unsupported
  category from the OS, even when requested at R level, which may
  cause crashes when R 4.2.0 (which uses UCRT) is embedded
  (reported by Kevin Ushey).

• Accent keys now work in GraphApp Unicode windows, which are used
  by Rgui whenever running in a multibyte locale (so also in UTF-8,
  hence fixing a regression in R 4.2.0 for users of systems where R
  4.1 used a single-byte locale).

• Completion in Rgui now works also with non-ASCII characters.

• Rgui no longer truncates usage information with --help.

• Text injection from external applications via SendInput now works
  in GraphApp Unicode windows, fixing a regression in R 4.2.0 for
  Rgui users of systems where R 4.1 used a single-byte locale but R
  4.2.0 uses UTF-8.

• Performance of txtProgressBar() in Rgui when running in a
  multi-byte locale has been improved (fixing a performance
  regression in R 4.2.0 for users of systems where R 4.1 used a
  single-byte locale).

• The script editor in Rgui now works also on systems using UTF-8
  as the native encoding. Users of the script editor have to
  convert their scripts with non-ASCII characters to UTF-8 before
  reading them in R 4.2.1 or newer (on recent Windows where UTF-8
  is used). This fixes a regression in R 4.2.0, which prevented
  some operations with scripts when they contained non-ASCII
  characters.

SIGNIFICANT USER-VISIBLE CHANGES:

• The formula method of aggregate() now matches the generic in
  naming its first argument x (resolving PR#18299 by Thomas
  Soeiro).

  This means that calling aggregate() with a formula as a named
  first argument requires name formula in earlier versions of R and
  name x now, so portable code should not name the argument (code
  in many packages did).

• Calling && or || with either argument of length greater than one
  now gives a warning (which it is intended will become an error).

• Calling if() or while() with a condition of length greater than
  one gives an error rather than a warning. Consequently,
  environment variable _R_CHECK_LENGTH_1_CONDITION_ no longer has
  any effect.

• Windows users should consult the WINDOWS section below for some
  profound changes including

  • Support for 32-bit builds has been dropped.

  • UTF-8 locales are used where available.

  • The default locations for the R installation and personal
    library folder have been changed.

  Thanks to Tomas Kalibera for months of work on the Windows port
  for this release.

NEW FEATURES:

• matrix(x, n, m) now warns in more cases where length(x) differs
  from n * m, as suggested by Abby Spurdle and Wolfgang Huber in
  Feb 2021 on the R-devel mailing list.

  This warning can be turned into an error by setting environment
  variable _R_CHECK_MATRIX_DATA_ to TRUE: R CMD check --as-cran
  does so unless it is already set.

• Function file_test() in package utils gains tests for symlinks,
  readability and writability.

• capabilities("libxml") is now false.

  The description of capabilities("http/ftp") now reflects that it
  refers to the default method, no longer the internal one.

• simplify2array() gains an except argument for controlling the
  exceptions used by sapply().

• Environment variables R_LIBS_USER and R_LIBS_SITE are both now
  set to the R system default if unset or empty, and can be set to
  NULL to indicate an empty list of user or site library
  directories.

• The warning for axis()(-like) calls in cases of relatively small
  ranges (typically in log-scale situations) is slightly improved
  and suppressed from explicit calls to .axisPars() as has always
  been the intention.

• The contrasts setter function contrasts<- gains an explicit
  default how.many = NULL rather than just using missing(how.many).

• grid.pretty() gains a new optional argument n = 5.

• There is a new function .pretty() with option bounds as a
  technical-utility version of pretty(). It and pretty() gain a
  new argument f.min with a better than back-compatible default.

• Function grDevices::axisTicks() and related functions such as
  graphics::axis() work better, notably for the log scale; partly
  because of the pretty() improvements, but also because care is
  taken e.g., when ylim is finite but diff(ylim) is infinite.

• nclass.FD() gains a digits option.

• The R Mathlib internal C function bd0() (called indirectly from a
  dozen probability density and distribution functions such as
  dpois(), dbinom(), dgamma(), pgamma() etc) has been
  complemented by a more sophisticated and (mostly) more accurate C
  function ebd0(), currently called only by internal dpois_raw()
  improving accuracy for R level dpois() and potentially others
  calling it such as dnbinom(), dgamma() or pgamma(). (Thanks to
  Morten Welinder's PR#15628.)

• write.ftable() gains sep = " " argument as suggested by Thomas
  Soeiro.

• The names of the locale categories supported by R's
  Sys.getlocale() and Sys.setlocale() are now provided by variable
  .LC.categories in the base namespace.

• The Date and POSIXt methods for hist() and the histogram method
  for plot() now also use the new default col = "lightgray" in
  consistency with the corresponding change to hist()'s default for
  R 4.0.0.

• hist.default() gains new fuzz argument, and the histogram plot
  method no longer uses fractional axis ticks when displaying
  counts ("Frequency").

• mapply() and hence Map() now also obey the "max-or-0-if-any"
  recycling rule, such that, e.g., Map(+, 1:3, 1[0]) is valid
  now.

• as.character(<obj>) for "hexmode" or "octmode" objects now
  fulfils the important basic rule as.character(x)[j] === as.character(x[j]).

• The set utility functions, notably intersect() have been tweaked
  to be more consistent and symmetric in their two set arguments,
  also preserving a common mode.

• substr(ch, start,end) <- new now e.g., preserves names(ch); ditto
  for substring(), thanks to a patch from Brodie Gaslam.

• plot(<lm>) gains a extend.ylim.f argument, in partial response to
  PR#15285; further PR#17784 is fixed thanks to several
  contributors and a patch by Elin Waring. The Cook's dist
  contours get customizable via cook.col and cook.lty with a
  different default color and their legend is nicer by default and
  customizable via cook.legendChanges.

• Attempting to subset an object that is not subsettable now
  signals an error of class notSubsettableError. The
  non-subsettable object is contained in the object field of the
  error condition.

• Subscript-out-of-bounds errors are now signaled as errors of
  class subscriptOutOfBoundsError.

• Stack-overflow errors are now signaled as errors inheriting from
  class stackOverflowError. See ?stackOverflowError for more
  details.

• New partly experimental Sys.setLanguage() utility, solving the
  main problem of PR#18055.

• gettext() and gettextf() get a new option trim = TRUE which when
  set to false allows translations for strings such as "Execution halted\n" typical for C code.

• An experimental implementation of hash tables is now available.
  See ?hashtab for more details.

• identical() gains a extptr.as.ref argument for requesting that
  external pointer objects be compared as reference objects.

• reorder() gets an argument decreasing which it passes to sort()
  for level creation; based on the wish and patch by Thomas Soeiro
  in PR#18243.

• as.vector() gains a data.frame method which returns a simple
  named list, also clearing a long standing 'FIXME' to enable
  as.vector(<data.frame>, mode="list"). This breaks code relying
  on as.vector(<data.frame>) to return the unchanged data frame.

• legend() is now vectorized for arguments cex, x.intersp, and
  text.width. The latter can now also be specified as a vector
  (one element for each column of the legend) or as NA for
  computing a proper column wise maximum value of strwidth(legend).
  The argument y.intersp can be specified as a vector with one
  entry for each row of the legend.

  legend() also gains new arguments title.cex and title.font.
  Thanks to Swetlana Herbrandt.

• Deparsing no longer remaps attribute names dim, dimnames, levels,
  names and tsp to historical S-compatible names (which structure()
  maps back).

• sample() and sample.int() have additional sanity checks on their
  size and n arguments.

  all.equal.numeric() gains a sanity check on its tolerance
  argument - calling all.equal(a, b, c) for three numeric vectors
  is a surprisingly common error.

  mean(na.rm =), rank(na.last =), barplot(legend.text =),
  boxplot(), contour(drawlabels =), polygon(border =) and
  methods::is(class2 =) have more robust sanity checks on their
  arguments.

  R CMD Rd2pdf (used by R CMD check) has a more robust sanity check
  on the format of \alias{} commands.

• psigamma(x, deriv) for negative x now also works for deriv = 4
  and 5; their underlying C level dpsifn() is documented in
  'Writing R Extensions'.

• The HTML help system now uses HTML5 (wish of PR#18149).

• ks.test() now provides exact p-values also with ties and MC
  p-values in the two-sample (Smirnov) case. By Torsten Hothorn.

• ks.test() gains a formula interface, with y ~ 1 for the
  one-sample (Kolmogorov) test and y ~ group for the two-sample
  (Smirnov) test. Contributed by Torsten Hothorn.

• The return value from ks.test() now has class c("ks.test", "htest") - packages using try() need to take care to use
  inherits() and not == on the class.

• New functions psmirnov(), qsmirnov() and rsmirnov() in package
  stats implementing the asymptotic and exact distributions of the
  two-sample Smirnov statistic.

• iconv() now allows sub = "c99" to use C99-style escapes for UTF-8
  inputs which cannot be converted to encoding to.

• In a forward pipe |> expression it is now possible to use a named
  argument with the placeholder _ in the rhs call to specify where
  the lhs is to be inserted. The placeholder can only appear once
  on the rhs.

• The included LAPACK sources have been updated to version 3.10.0,
  except for the four Fortran 77 routines which 3.10.0 has
  re-implemented in Fortran 90 (where the older versions have been
  retained as the R build process does not support Fortran 90).

• path.expand() and most other uses of tilde expansion now warn if
  a path would be too long if expanded. (An exception is
  file.exists(), which silently returns false.)

• trunc(<Date>, *) no...

• The default version of Bioconductor has been changed to 3.14.
  (This is used by setRepositories and the menus in GUIs.)

UTILITIES:

• R CMD check --as-cran has a workaround for a bug in versions of
  file up to at least 5.41 which mis-identify DBF files last
  changed in 2022 as executables.

C-LEVEL FACILITIES:

• The legacy S-compatibility macros SINGLE_* in R_ext/Constants.h
  (included by R.h) are deprecated and will be removed in R 4.2.0.

BUG FIXES:

• Initialization of self-starting nls() models with initialization
  functions following the pre-R-4.1.0 API (without the ...
  argument) works again for now, with a deprecation warning.

• Fixed quoting of ~autodetect~ in Java setting defaults to avoid
  inadvertent user lookup due to leading ~, reported in PR#18231 by
  Harold Gutch.

• substr(., start, stop) <- v now treats negative stop values
  correctly. Reported with a patch in PR#18228 by Brodie Gaslam.

• Subscripting an array x without dimnames by a
  length(dim(x))-column character matrix gave "random" non-sense,
  now an error; reported in PR#18244 by Mikael Jagan.

• ...names() now matches names(list(...)) closely, fixing PR#18247.

• all.equal(*, scale = s) now works as intended when length(s) > 1,
  partly thanks to Michael Chirico's PR#18272.

• print(x) for long vectors x now also works for named atomic
  vectors or lists and prints the correct number when reaching the
  getOption("max.print") limit; partly thanks to a report and
  proposal by Hugh Parsonage to the R-devel list.

• all.equal(<selfStart>, *) no longer signals a deprecation
  warning.

• reformulate(*, response=r) gives a helpful error message now when
  length(r) > 1, thanks to Bill Dunlap's PR#18281.

• Modifying globalCallingHandlers inside withCallingHandlers() now
  works or fails correctly, thanks to Henrik Bengtsson's PR#18257.

• hist(<Date>, breaks = "days") and hist(<POSIXt>, breaks = "secs")
  no longer fail for inputs of length 1.

• qbeta(.001, .9, .009) and similar cases now converge correctly
  thanks to Ben Bolker's report in PR#17746.

• window(x, start, end) no longer wrongly signals "'start' cannot
  be after 'end'", fixing PR#17527 and PR#18291.

• data() now checks that its (rarely used) list argument is a
  character vector - a couple of packages passed other types and
  gave incorrect results.

• which() now checks its arr.ind argument is TRUE rather coercing
  to logical and taking the first element - which gave incorrect
  results in package code.

• model.weights() and model.offset() more carefully extract their
  model components, thanks to Ben Bolker and Tim Taylor's R-devel
  post.

• list.files(recursive = TRUE) now shows all broken symlinks
  (previously, some of them may have been omitted, PR#18296).

• The workaround in headers R.h and Rmath.h (using namespace std;)
  for the Oracle Developer Studio compiler is no longer needed now
  C++11 is required so has been removed. A couple more usages of
  log() (which should have been std::log()) with an int argument
  are reported on Solaris.

• The undocumented limit of 4095 bytes on messages from the
  S-compatibility macros PROBLEM and MESSAGE is now documented and
  longer messages will be silently truncated rather than
  potentially causing segfaults.

• If the R_NO_SEGV_HANDLER environment variable is non-empty, the
  signal handler for SEGV/ILL/BUS signals (which offers recovery
  user interface) is not set. This allows more reliable debugging
  of crashes that involve the console.

DEPRECATED AND DEFUNCT:

• The legacy S-compatibility macros PROBLEM, MESSAGE, ERROR, WARN,
  WARNING, RECOVER, ... are deprecated and will be hidden in R
  4.2.0. R's native interface of Rf_error and Rf_warning has long
  been preferred.

BUG FIXES:

• .mapply(F, dots, .) no longer segfaults when dots is not a list
  and uses match.fun(F) as always documented; reported by Andrew
  Simmons in PR#18164.

• hist(<Date>, ...) and hist(<POSIXt>, ...) no longer pass
  arguments for rect() (such as col and density) to axis().
  (Thanks to Sebastian Meyer's PR#18171.)

• \Sexpr{ch} now preserves Encoding(ch). (Thanks to report and
  patch by Jeroen Ooms in PR#18152.)

• Setting the RNG to "Marsaglia-Multicarry" e.g., by RNGkind(), now
  warns in more places, thanks to Andr'e Gillibert's report and
  patch in PR#18168.

• gray(numeric(), alpha=1/2) no longer segfaults, fixing PR#18183,
  reported by Till Krenz.

• Fixed dnbinom(x, size=<very_small>, .., log=TRUE) regression,
  reported by Martin Morgan.

• as.Date.POSIXlt(x) now keeps names(x), thanks to Davis Vaughan's
  report and patch in PR#18188.

• model.response() now strips an "AsIs" class typically, thanks to
  Duncan Murdoch's report and other discussants in PR#18190.

• try() is considerably faster in case of an error and long call,
  as e.g., from some do.call(). Thanks to Alexander Kaever's
  suggestion posted to R-devel.

• qqline(y = <object>) such as y=I(.), now works, see also
  PR#18190.

• Non-integer mgp par() settings are now handled correctly in
  axis() and mtext(), thanks to Mikael Jagan and Duncan Murdoch's
  report and suggestion in PR#18194.

• formatC(x) returns length zero character() now, rather than ""
  when x is of length zero, as documented, thanks to Davis
  Vaughan's post to R-devel.

• removeSource(fn) now retains (other) attributes(fn).

NEW FEATURES:

• require(pkg, quietly = TRUE) is quieter and in particular does
  not warn if the package is not found.

DEPRECATED AND DEFUNCT:

• Use of ftp:// URIs should be regarded as deprecated, with
  on-going support confined to method = "libcurl" and not routinely
  tested. (Nowadays no major browser supports them.)

• The non-default method = "internal" is deprecated for http:// and
  ftp:// URIs for both download.file and url.

• On Windows, method = "wininet" is deprecated for http://,
  https:// and ftp:// URIs for both download.file and url. (A
  warning is only given for ftp://.)

  For ftp:// URIs the default method is now "libcurl" if available
  (which it is on CRAN builds).

  method = "wininet" remains the default for http:// and https://
  URIs but if libcurl is available, using method = "libcurl" is
  preferred.

INSTALLATION:

• make check now works also without a LaTeX installation. (Thanks
  to Sebastian Meyer's PR#18103.)

BUG FIXES:

• make check-devel works again in an R build configured with
  --without-recommended-packages.

• qnbinom(p, size, mu) for large size/mu is correct now in a range
  of cases (PR#18095); similarly for the (size, prob)
  parametrization of the negative binomial. Also qpois() and
  qbinom() are better and or faster for extreme cases. The
  underlying C code has been modularized and is common to all four
  cases of discrete distributions.

• gap.axis is now part of the axis() arguments which are passed
  from bxp(), and hence boxplot(). (Thanks to Martin Smith's
  report and suggestions in PR#18109.)

• .First and .Last can again be set from the site profile.

• seq.int(from, to, *) and seq.default(..) now work better in large
  range cases where from-to is infinite where the two boundaries
  are finite.

• all.equal(x,y) now returns TRUE correctly also when several
  entries of abs(x) and abs(y) are close to .Machine$double.xmax,
  the largest finite numeric.

• model.frame() now clears the object bit when removing the class
  attribute of a value via na.action (PR#18100).

• charClass() now works with multi-character strings on Windows
  (PR#18104, fixed by Bill Dunlap).

• encodeString() on Solaris now works again in Latin-1 encoding on
  characters represented differently in UTF-8. Support for
  surrogate pairs on Solaris has been improved.

• file.show() on Windows now works with non-ASCII path names
  representable in the current native encoding (PR#18132).

• Embedded R on Windows can now find R home directory via the
  registry even when installed only for the current user
  (PR#18135).

• pretty(x) with finite x now returns finite values also in the
  case where the extreme x values are close in size to the maximal
  representable number .Machine$double.xmax.

  Also, it's been tweaked for very small ranges and when a boundary
  is close (or equal) to zero; e.g., pretty(c(0,1e-317)) no longer
  has negative numbers, currently still warning about a very small
  range, and pretty(2^-(1024 - 2^-1/(c(24,10)))) is more accurate.

• The error message for not finding vignette files when weaving has
  correct file sizes now. (Thanks to Sebastian Meyer's PR#18154.)

• dnbinom(20, <large>, 1) now correctly gives 0, and similar cases
  are more accurate with underflow precaution. (Reported by
  Francisco Vera Alcivar in PR#18072.)