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.