mksh R40b introduces several desired fixes:

• Don’t busy-loop on nameref ARY=ARY (LHS = RHS)
• Tabcomplete ~foo like $FOO (LP: #710539)
• Code cleanup, style, and minor assorted fixes
• Tabcomplete ~foo/M↹ (with slash) economically
• Add new experimental global builtin, doing the same as local (typeset, really – but that doesn’t deserve its name) does, except localising all parameters it touches
• Better error messages with non-integral environment imports
• $RANDOM environment import accepts any string now
• Add setenv cshism to dot.mkshrc
• Allow ^C to interrupt the built-in cat(1)
• Fix mksh taking down the entire terminal, hard, when scripts use $COLUMNS and fork off utilities; regression introduced in mksh R37 (sorry, no regression test possible)
• Properly mark need-ctty regression tests
• MKSH_NO_EXTERNAL_CAT – Quell the external cat(1) calls magic
• Yes, “echo” is not portable, document
• Improve content and look of the manual page
• Move /etc/{,suid_}profile to /system/etc/ on Android
• Prevent more compiler warnings; catch build errors earlier

mksh R40 is a major everything release:

• Correct small mistakes in manpage and build script
• Port to Haiku (and probably, implicitly, BeOS; this is not tested though)
• Add Haiku specific RLIMIT_NOVMON as ‘V’ to ulimit builtin
• Let Build.sh cope with dirname(1) unavailability
• In the Emacs editing mode, hi-bit7 octets are now considered “motion characters” for word boundaries – Esc+b, Esc+f, ^W, …
• Make EXECSHELL default configurable at compile time (embedded)
• If MKSH_SMALL do not compile in “set -o bgnice” by default
• Rework how RLIMIT_{AS,RSS,VMEM} map to ‘m’ and ‘v’ ulimits
• Add some more OS specific limits seen in zsh
• SUSv4 ${v=a\ b} and "${v=a\ b}" and ${v-a\ b} compliance, tests
• Make "~/.mkshrc" path configurable at compile time (embedded)
• Fix SUNWcc 12.1 error message scan in build phase=u
• Fix variable assignment scope during command execution (expansion vs. assignment execution environment); [Herbert Xu, Geoff Clare] Add more regression tests for this
• Fix single quotes in "${foo#bar}" (differs from "${foo-bar}")
• Fix mknod(8) usage message: b|c are not optional
• Fix "${x#?}" expansion when quoted (quotes, space)
• Make default temporary directory configurable at compile time
• Fix performance deficiencies in the built-in realpath function
• Deprecate Build.sh -longoptions in favour of short ones: -valgrind becomes -g (like debug), -combine and -llvm become -c {combine,llvm} and the LLVM optimiser flags are passed via -O = -o -std-compile-opts
• New Build.sh options -c dragonegg (for using the LLVM plugin to GCC 4.5 with inter-module optimisation), -v (version)
• Document another way to get a coloured PS1 in the manpage
• Disallow some more kinds to trim a vector; Debian #581867
• Simplify some code; RCSID and comment sync with OpenBSD ksh
• Apply diff from manuel giraud to keep track of LINENO in a trap
• Remove arc4random(3) functionality; seed an LCG depending on the OS doing Address Space Layout Randomisation; speed up (we will use either arc4random_pushb_fast(3) if it exists or arc4random_pushb(3) if forced by the user with -DMKSH_A4PB e.g. on Cygwin)
• Fix spelling mistakes in dot.mkshrc
• Implement “live” window resize for the Emacs editing mode
• More fixes for bugs found by Valgrind and LLVM+Clang scan-build
• For script compatibility support “set ±o arc4random” during a transition period until R40 is out (but issue a warning to stderr)
• Add (, ), (( to reserved words in the manual page and fix some formatting errors with GNU groff’s mdoc
• Make printf.c.1.15 use mksh’s shf_* routines instead of stdio
• Fix -Wc++-compat except implicit casts from/to "void *"
• Correct shf buffer I/O routines to avoid a memory corruption bug discovered by Waldemar Brodkorb and other bad effects
• Fix NULL pointer dereference during iteration loop when checking for alias recursion; discovered by Michal Hlavinka
• More int → bool conversion, whitespace and general code cleanup
• Fix window size not being checked during runtime of external programmes by not relying on SIGWINCH so much but instead checking before every interactive editing of a command line
• Improve mksh(1) manpage coverage, remove mentions of not-mksh
• Use wcwidth() from system on MirBSD
• u_int32_t is no longer needed (only for OpenBSD’s pre-ISO-C99 arc4random API, which we no longer call), so don’t provide it from Build.sh any longer
• Scan for uint8_t and provide if not found
• Fix realpath builtin for “/file/” arguments wrt. POSIX
• Do not generate <stdint.h> from Build.sh as file any more if it is missing; rather let sh.h define the types appropriately and fix related compiler warnings
• Add “cat” builtin (defers to external if options are given)
• Reduce size by improved string pooling, improving struct packing, lowering size of some allocation chunks, and better code
• Document 「x=$(eval $(cat)) <<'EOF'」 workaround for the $(…) parsing bug in the mksh(1) manual page and on the Red Hat Bugzilla
• Add support for handling a “--” argument to more builtins
• Correct some error messages and typos
• Don’t alias stop, suspend on Android (system specific conflict for stop; suspend just joined the boat)
• Address what few concerns Chris Palmer (Android security team) had: check all multiplications and some additions for integer overflows, mostly in allocation context, and check setres{u,g}id/setuid for EAGAIN iff the target OS is known to be returning it (Linux only, right now)
• Some small manpage fixes
• Clean up mirtoconf and build warnings with some compilers
• Fix \c? vs. \c~ mis-documentation in mksh(1)
• Remove the somewhat-portable setmode.c from the mksh source distribution and demote mknod(8) to an optional builtin, disabled by default, manually re-enabled in the installer only on MirBSD
• Regenerate wcwidth table from Unicode 6.0.0
• Change behaviour of argument-less exit in traps to match SUSv4, original patch from Jonathan Nieder (Debian Closes: #599484)
• dot.mkshrc no longer exports $PS1, as recommended by Frank Terbeck, to avoid confusing other shells
• The character width table is now in sync with Unicode 6.0.0
• MKSH_SMALL doesn’t imply HAVE_REVOKE=0 any longer
• Ignore a ‘$’ preceding ‘"…"’ (like bash, ksh93)
• Make “foo=<<EOF” a direct assignment of here document (or here string) to string variable
• Add KSHEGID, KSHGID, KSHUID variables (idea from Richard K.)
• Option -d to read specifies a delimiter, like ksh93 (10x dgk)
• Extension ${foo@#} expands to hash of $foo (mksh specific)
• Emacs prev-hist-word resets the counter if other editing commands were run in between; repeat calling works, even together with arguments, now; arguments are 0-based (Debian Closes: #603801)
• Introduce MKSH_NOPROSPECTOFWORK which implies MKSH_UNEMPLOYED and additionally disables job signals, |&, sigprocmask(2), etc.
• POSIX: trap 'echo foo' UNKNOWN is not a syntax error
• Do not use <sys/file.h> unless it exists
• dot.mkshrc: When we set a UTF-8 locale (e.g. for the GNU OS), we must also set -o utf8-mode to match it
• Don’t append a space after tab-completing a parameter substitution that doesn’t contain a glob/extglob (LP: #710539)
• Limit history file size to 1 GiB for sanity
• Add smores, a more(1)-like pager, as shell function to dot.mkshrc (not control character safe but tty aware)
• Make builtins directly callable; utf8-mode is determined by LC_ALL/LC_CTYPE/LANG environment variables in that case
• If the interactive shell uses setlocale(3)/nl_langinfo(3) to divine utf8-mode, fall back to environment variables unless success
• From a direct builtin call, echo(1) behaves POSIXish
• Replace some MirBSD utilities with links to mksh(1) and ensure some integration to keep compatibility
• Add a microsecond capable sleep(1) builtin [updated 20110213]
• If the built-in cat is invoked from a direct builtin call, it now properly handles the POSIXly demanded ‘-u’ option (as a no-op)
• Support the PIPESTATUS array (like GNU bash)
• Port to MiNT / FreeMiNT (Atari m68k operating system)
• Do not close filedescriptor #3 (controlling tty) on UWIN
• Make the tree printing code safe for re-entrancy of output
• Implement recursive parser for $(…) to fix RedHat BZ#496791
• Use the existing state machine, a recursive parser and retracing the input stream for correct x=(…$((…$(…)…))…) parsing
• complain about ${x:1:2:3} instead of crashing
• make optional printf(1) builtin __CRAZY=Yes clean and prevent it from crashing by reading past end of (invalid) format strings
• abort(3) on rogue pointers #ifdef DEBUG
• Correct some documentation, code commentary, etc.
• Handle the UTF-8 Byte Order Mark in $(…) expressions
• Speed up reading input by checking for the BOM only once
• Fix mis-detection of gcc format attribute (false negative)
• Include some Android specific hacks (no change on other OEs)
• In ${foo/bar/baz} expressions, when adjourning empty patterns to avoid running into a busy-wait loop, remember to skip the anchor characters (‘#’ or ‘%’) at the beginning, yet keep the special meaning replacing a string begin or end with a string has
• Write a pattern optimiser that is run internally before calls to the pattern matching code always (currently, replaces a@(b@(c)d)e with abcde but keeps @(a|a), then (in a second pass) collapses adjacent asterisk (‘*’) wildcards into a single one; this fixes some of the symptoms of severe performance issues our pattern matching code has to the extent that it can prevent busy-looping (found by Jb_boin)
• Handle pathnames with exactly two leading slashes well (SUSv4 3.266)
• Fix here documents, add testcases
• Fix corner case ${##1}, add tests for that and ${##} and ${#?}
• Bring back “test -H” ifdef S_ISCDF (for HP-UX) from pdksh
• Align read-only variable behaviour with (future) POSIX
• Permit ${foo%(*} on FSH (Debian Closes: #619947)
• Allow skipping testcases that need a controlling tty
• Correct skipping the UTF-8 BOM when identifying a file
• Do not use <stdbool.h> any longer
• Use double-underscore-framed __attribute__s
• Always catch SIGALRM (for the sleep builtin)
• Functions now inherit a global set -x
• Do not explicitly initialise static globals to 0/NULL
• Eliminate some dead code (functions, globals)
• Correct more tree handling bugs and merge similar code
• Add “+=” to concatenate scalars and append to arrays
• Support empty here document delimiters
• Fix the four-argument form of test(1)
• Drop the pre-POSIX ability to “test -t” without specifying “fd”
• Defer dropping an alias in favour of a POSIX function to when the function is actually defined and check for the closing parenthesis too
• Implement a new regression test attribute need-pass: {yes|no} and exit 1 if unexpected fails occur
• Add ;& and ;| for case
• Rewrite the read builtin and its documentation; adding -A (read IFS words into array), -a (read octets/wide characters into array), -N/-n (read only / up to z bytes), -t (read with timeout)
• Add -e option to cd -P (POSIX 2011)
• Update dot.mkshrc to use the new features
• Fix gsf’s ifs.sh tests of the read builtin
• Improve support for AIX, Cygwin, IBM XL C
• Add tests for x+=(y z) and ;;& extensions
• Fix regression in tab completion result display
• Fix parsing x=(…) expressions
• Increase hash table limit; don’t crash when reaching the limit; work around bug in GCC 4.1 on Debian Etch
• New -c lto option to use Link Time Optimisation (GCC) with automatic fallback to -c combine if unavailable
• Improvements for -c dragonegg, -c llvm (with gcc+dragonegg, or llvm-gcc and clang, respectively), and TenDRA
• Let code samples in check.t and dot.mkshrc take care of the new features; fix some longstanding bugs in them
• Add missing flush in rewritten read builtin for prompting
• Minix builds now automatically disable the ulimit builtin