commit bash-20160812 snapshot

[thirdparty/bash.git] / CHANGES-4.4

This document details the changes between this version, bash-4.4-rc2, and
the previous version, bash-4.4-beta2.

1.  Changes to Bash

a.  Fixed an out-of-bounds read in the redirection operator completion code.

b.  Fixed execution context so `until continue' doesn't disable execution for
    subsequent commands.

c.  Fixed trap handling code so traps don't inherit a command's temporary
    environment.

d.  Fixed a bug that resulted in incorrect line numbers when a function is defined
    as part of another function's execution.

e.  Fixed a bug in the expansion of ${a[@]} in contexts where word splitting is not
    performed and $IFS is not the default.

f.  Fixed a bug that caused ''"$@" to not expand to an empty argument when there are
    no positional parameters.

g.  Fixed a bug that caused a shell compiled without job control to use the incorrect
    exit status for builtin commands preceded by a command executed from the file
    system that causes the shell to call waitpid().

h.  Improved word completion for quoted strings containing unterminated command
    substitutions with embedded double quotes.

2.  Changes to Readline

a.  Fixed a bug that caused mode strings to be displayed incorrectly if the prompt was
    shorter than the mode string.

3.  New Features in Bash

a.  Using ${a[@]} or ${a[*]} with an array without any assigned elements when
    the nounset option is enabled no longer throws an unbound variable error.

4.  New Features in Readline

a.  New application-callable function: rl_pending_signal(): returns the signal
    number of any signal readline has caught but not yet handled.

b.  New application-settable variable: rl_persistent_signal_handlers: if set to a
    non-zero value, readline will enable the readline-6.2 signal handler behavior
    in callback mode: handlers are installed when rl_callback_handler_install is
    called and removed removed when a complete line has been read.

------------------------------------------------------------------------------
This document details the changes between this version, bash-4.4-beta2, and
the previous version, bash-4.4-rc1.

1.  Changes to Bash

a.  Fixed a memory leak when processing ${!var[@]}.

b.  Fixed a bug that caused subshells to free trap strings associated with
    inherited signals.

c.  Inheriting BASHOPTS from the environment now works to force actions
    associated with enabling an option, instead of just marking the option
    as enabled.

d.  Fixed a bug that allowed assignments to BASH_CMDS when the shell was in
    restricted mode.

e.  Fixed a bug caused by an accidental omission of part of the original patch
    for EXECIGNORE.

e.  Prompt expansion now quotes the results of the \s, \h, and \H expansions.

f.  Fixed a bug that caused parsing errors in command substitutions with
    consecutive case statements separated by newlines.

g.  Updated logic used to decide whether bash is running inside an emacs
    terminal emulator to work with future emacs versions.

h.  Fixed two extended pattern matching bugs caused by premature short-
    circuiting.

i.  Fixed a memory leak in the code that removes duplicate history entries.

j.  There are a number of bug fixes to coproc, mapfile, declare, unset,
    and assignment statements that prevent nameref variables from creating
    and unsetting variables with invalid names.

k.  Fixed a bug that caused variables to be inadvertently marked as both an
    associative and an indexed array.

l.  Fixed a bug that caused `bash -c' to not run a trap specified in the
    command string.

j.  There are a number of bug fixes to coproc, mapfile, declare, and assignment
    statements that prevent nameref variables from overwriting or modifying
    attributes of readonly variables.

k.  Fixed a bug that caused command substitution to attempt to set the
    terminal's process group incorrectly.
    
l.  Fixed a bug that could cause prompt string expansion to display error
    messages when the `nounset' shell option is set.

m.  Fixed a bug that caused "$@" to not expand to an empty string under the
    circumstances when Posix says it should ("${@-${@-$@}}").

n.  Fixed several bugs caused by referencing nameref variables whose values
    are names of unset variables (or names that are valid for referencing
    but not assignment), including creating variables in the temporary
    environment.

o.  Function tracing and error tracing are disabled if --debugger is supplied
    at startup but the shell can't find the debugger start file.

p.  Fixed a bug when IFS is used as the control variable in a for statement.

q.  Fixed a bug with SIGINT received by a command substitution in an interactive
    shell.

r.  The checks for nameref variable self-references are more thorough.

s.  Fixed several bugs with multi-line aliases.

t.  Fixed `test' to handle the four-argument case where $1 == '(' and
    $4 == ')'.

u.  Fixed a bug in the expansion of $* in the cases where word splitting is
    not performed.

v.  Fixed a bug in execution of case statements where IFS includes the
    pattern matching characters.

2.  Changes to Readline

a.  When refreshing the line as the result of a key sequence, Readline attempts
    to redraw only the last line of a multiline prompt.

b.  Fixed an issue that caused completion of git commands to display
    incorrectly when using colored-completion-prefix.

c.  Fixed several redisplay bugs having to do with multibyte characters and
    invisible characters in prompt strings.

3.  New Features in Bash

a.  Value conversions (arithmetic expansions, case modification, etc.) now
    happen when assigning elements of an array using compound assignment.

b.  There is a new option settable in config-top.h that makes multiple
    directory arguments to `cd' a fatal error.

c.  Bash now uses mktemp() when creating internal temporary files; it produces
    a warning at build time on many Linux systems.

4.  New Features in Readline

a.  The default binding for ^W in vi mode now uses word boundaries specified
    by Posix (vi-unix-word-rubout is bindable command name).

b.  rl_clear_visible_line: new application-callable function; clears all
    screen lines occupied by the current visible readline line.

c.  rl_tty_set_echoing: application-callable function that controls whether
    or not readline thinks it is echoing terminal output.

d.  Handle >| and strings of digits preceding and following redirection
    specifications as single tokens when tokenizing the line for history
    expansion.

e.  Fixed a bug with displaying completions when the prefix display length
    is greater than the length of the completions to be displayed.

f.  The :p history modifier now applies to the entire line, so any expansion
    specifying :p causes the line to be printed instead of expanded.

------------------------------------------------------------------------------
This document details the changes between this version, bash-4.4-rc1, and
the previous version, bash-4.4-beta.

1.  Changes to Bash

a.  Fixed several problems with bash completion not special-casing bash syntax
    constructs.

b.  Fixed a bug that caused the mapfile builtin to not create array variables
    when a variable of the same name appears in the temporary environment.

c.  Fixed a bug that caused prompt expansion to loop when PS1 contained a
    syntax error.

d.  Fixed a bug that caused the ${array[@]@A} expansion to split the results even
    when double-quoted.

e.  There is a new implementation of the code that saves the last CHILD_MAX
    exited background pids so their status can be queried later.

f.  Bash-4.4 can now be configured and built on very old versions of Solaris 2.

g.  Fixed problems with --help support for several builtins.

h.  Fixed values added to BASH_SOURCE and BASH_LINENO for functions inherited from
    the environment.

i.  Fixed a bug that caused background processes run from non-interactive shells
    with job control enabled to place the terminal in the wrong process group
    under certain circumstances.

j.  Fixed a bug that caused `fc' to return an incorrect exit status when
    executing commands from the history list.

k.  Fixed a bug that caused the shell to exit when a process substitution received
    a SIGINT when run in certain terminal emulators.

l.  EXECIGNORE now honors the setting of `extglob' when attempting to match
    executable names.

m.  Fixed a bug where `return' used the wrong exit status when executed in a
    DEBUG trap.

n.  Fixed a bug that caused a command containing a here-document and an escaped
    newline to be stored in the history list incorrectly.

o.  Fixed a bug that caused set -e to be honored in cases of builtins invoking
    other builtins when it should be ignored.

p.  Fixed a bug that caused `readonly' and `export' to create local array
    variables when used within shell functions.

q.  Fixed a bug that allowed subshells begun to execute process substitutions to
    have access to the command's temporary environment.

r.  Fixed a bug that could cause the shell to dump core when receiving a SIGCHLD
    for which a trap has been set while running in posix mode.

s.  Fixed a bug that caused bash to not restore BASH_ARGC, BASH_ARGV, BASH_SOURCE,
    BASH_LINENO, and FUNCNAME if the shell received a SIGINT while reading
    commands from a file while executing  `.'.

t.  Fixed a bug that caused the `-o history' option to have no effect when
    supplied on the command line when starting a new shell.

u.  Fixed a bug that caused history expansions occurring in command substitutions
    to not be performed.

v.  Fixed a bug that caused `eval' run in a non-interactive shell to disable
    history expansion for the remainder of the shell script, even if the script
    had previously enabled it.

w.  Fixed a bug that caused "$@" to not expand to multiple words when IFS is set
    to the empty string.

x.  Fixed a bug that caused process and command substitution to inherit output
    buffered in the stdio library but not written.

y.  Fixed a bug that caused a terminating signal received during `echo' to run
    an exit trap in a signal handler context.

z.  Fixed a bug that caused a builtin command containing a process substitution to
    return the wrong exit status.

aa. Fixed a bug that caused `()' subshells with piped input to incorrectly redirect
    the standard input of some of the commands in the subshell from /dev/null.

bb. The history builtin now uses more descriptive error messages for missing or
    invalid timestamps.

2.  Changes to Readline

a.  The history file writing functions only attempt to create and use a backup
    history file if the history file exists and is a regular file.

b.  Fixed an out-of-bounds read in readline's internal tilde expansion interface.

c.  Fixed several redisplay bugs with prompt strings containing multibyte
    and non-visible characters whose physical length is longer than the screen
    width.

d.  Fixed a redisplay bug with prompt strings containing invisible characters
    whose physical length exceeds the screen width and using incremental search.

e.  Readline prints more descriptive error messages when it encounters errors
    while reading an inputrc file.

f.  Fixed a bug in the character insertion code that attempts to optimize
    typeahead when it reads a character that is not bound to self-insert and
    resets the key sequence state.

3.  New Features in Bash

a.  BASH_COMPAT and FUNCNEST can be inherited and set from the shell's initial
    environment.

b.  inherit_errexit: a new `shopt' option that, when set, causes command
    substitutions to inherit the -e option.  By default, those subshells disable
    -e.  It's enabled as part of turning on posix mode.

c.  New prompt string: PS0.  Expanded and displayed by interactive shells after
    reading a complete command but before executing it.

d.  Interactive shells now behave as if SIGTSTP/SIGTTIN/SIGTTOU are set to SIG_DFL
    when the shell is started, so they are set to SIG_DFL in child processes.

e.  Posix-mode shells now allow double quotes to quote the history expansion
    character.

f.  OLDPWD can be inherited from the environment if it names a directory.

g.  Shells running as root no longer inherit PS4 from the environment, closing a
    security hole involving PS4 expansion performing command substitution.

h.  If executing an implicit `cd' when the `autocd' option is set, bash will now
    invoke a function named `cd' if one exists before executing the `cd' builtin.

4.  New Features in Readline

a.  If an incremental search string has its last character removed with DEL, the
    resulting empty search string no longer matches the previous line.

b.  If readline reads a history file that begins with `#' (or the value of
    the history comment character) and has enabled history timestamps, the history
    entries are assumed to be delimited by timestamps.  This allows multi-line
    history entries.

c.  Readline now throws an error if it parses a key binding without a terminating
    `:' or whitespace.

------------------------------------------------------------------------------
This document details the changes between this version, bash-4.4-beta, and
the previous version, bash-4.4-alpha.

1.  Changes to Bash

a.  Fixed two bugs that caused out-of-bounds reads when skipping over assignment
    statements while finding the word on which to perform programmable
    completion.

b.  Fixed a memory leak in programmable completion.

c.  Fixed a bug that could cause the shell to crash when interrupting the
    wait builtin.

d.  Fixed a bug that caused ${!vvv@} to be interpreted as introducing the new
    `@' operator.

e.  Fixed a bug that caused the && and || operators to be incorrectly optimized.

f.  The shell now undoes redirections before exiting the shell when the `-e'
    option is enabled, and a shell function fails.

g.  History expansion now skips over the history expansion character in command
    and process substitution.

h.  Fixed a bug that caused stray '\001' characters to be added to the output
    of `declare -p'.

i.  Fixed a memory leak when processing declare commands that perform compound
    array assignments.

j.  Fixed a bug that could cause the shell to crash when reading input from a
    file and the limit on open file descriptors is high.

k.  Fixed a bug that caused the ERR and RETURN traps to be unset if they were
    set in a shell function but unset previously.

l.  Fixed a bug that caused several signals to be ignored if `exec' failed in
    an interactive shell.

m.  A posix-mode non-interactive shell now considers a parameter expansion error
    to be a fatal error.

n.  The `time' command now prints timing statistics for failed commands when
    the -e option is enabled.

o.  Fixed a bug that caused the shell to crash when attempting to indirectly
    expand a shell variable with an invalid name.

p.  Fixed a bug that caused the shell to crash when running a trap containing
    a process substitution.

q.  Bash now prints the keyword `function' before a function with the same name
    as a reserved word when using `declare -f' to avoid parse errors when
    reusing the output as input.

r.  Fixed a bug that caused the shell to crash when using declare -g to attempt
    to redefine an existing global indexed array variable as an associative
    array.

s.  Fixed a memory leak that occurred when interrupting brace expansions
    generating a sequence.

t.  Fixed a bug that resulted in alias expansion in redirections.

u.  The `declare -a' and `declare -A' commands now print fewer warnings when
    attempting to create and initialize an array at the same time, but
    relying on word expansions to construct the compound assignment.

v.  The `help' builtin now behaves better in locales where each wide
    character occupies more than one display column.

w.  The `read' builtin no longer has a possible race condition when a timeout
    occurs.

x.  Fixed several expansion problems encountered when IFS="'".

y.  Fixed a problem with the expansion of $'\c?'.

z.  Bash no longer splits the expansion of here-strings, as the documentation
    has always said.

aa. Bash now puts `s' in the value of $- if the shell is reading from standard
    input, as Posix requires.

bb. Fixed a bug that caused the shell to crash if invoked with a NULL
    environment.

cc. The shell now only trusts an inherited value for $PWD if it begins with a
    `/'.

dd. Fixed a memory leak when creating local array variables and assigning to
    them using compound assignment with the `declare' builtin.

ee. Fixed a bug that could cause the shell to crash when processing nested here
    documents inside a command substitution.

ff. Array keys and values are now displayed using $'...' quoting where
    appropriate.

gg. Fixed a bug that could cause the shell to crash if the replacement string
    in pattern substitution was NULL.

hh. Fixed a bug that could cause the shell to crash if a command substitution
    contained a non-fatal syntax error.

ii. Fixed a bug that could cause the shell to crash if variable indirection
    resulted in a NULL variable.

jj. Fixed a bug that could cause the shell to crash if a long string contained
    multiple unterminated parameter expansion constructs.

kk. Improved the code that acts on SIGINT received while waiting for a child
    process only if the child exits due to SIGINT.

ll. $BASH_SUBSHELL now has more consistent values in asynchronous simple
    commands.

2.  Changes to Readline

a.  Colored completion prefixes are now displayed using a different color, less
    likely to collide with files.

b.  Fixed a bug that caused vi-mode character search to misbehave when
    running in callback mode.

c.  Fixed a bug that caused output to be delayed when input is coming from a
    macro in vi-mode.

d.  Fixed a bug that caused the vi-mode `.' command to misbehave when redoing
    a multi-key key sequence via a macro.

e.  Fixed a bug that caused problems with applications that supply their own
    input function when performing completion.

f.  When read returns -1/EIO when attempting to read a key, return an error
    instead of line termination back to the caller.

g.  Updated tty auditing feature based on patch from Red Hat.

h.  Fixed a bug that could cause the history library to crash on overflows
    introduced by malicious editing of timestamps in the history file.

3.  New Features in Bash

a.  `make install' now installs the example loadable builtins and a set of
    bash headers to use when developing new loadable builtins.

b.  `enable -f' now attempts to call functions named BUILTIN_builtin_load when
    loading BUILTIN, and BUILTIN_builtin_unload when deleting it.  This allows
    loadable builtins to run initialization and cleanup code.

c.  There is a new BASH_LOADABLES_PATH variable containing a list of directories
    where the `enable -f' command looks for shared objects containing loadable
    builtins.

d.  The `complete_fullquote' option to `shopt' changes filename completion to
    quote all shell metacharacters in filenames and directory names.

e.  The `kill' builtin now has a `-L' option, equivalent to `-l', for
    compatibility with Linux standalone versions of kill.

4.  New Features in Readline
------------------------------------------------------------------------------
This document details the changes between this version, bash-4.4-alpha, and
the previous version, bash-4.3-release.

1.  Changes to Bash

a.  A bug that caused pipelines to be corrupted while running the DEBUG trap
    was fixed.

b.  A bug that accidentally omitted the `-R' unary operator from `test' was
    fixed.

c.  A bug that could cause the shell to not restore the terminal's process
    group on shell exit was fixed.

d.  Several changes were made to programmable completion to accommodate
    assumptions made by the bash-completion package.

e.  Bash no longer inhibits C-style escape processing ($'...') while performing
    pattern substitution word expansions.

f.  Fixed a bug that caused `return' executed from a trap handler to use the
    wrong return status when one was not supplied as an argument.

g.  In Posix mode, defining a function with the same name as a special
    builtin is now an error, fatal only when the shell is not interactive.

h.  Fixed a bug that caused compound array assignments to discard unset or null
    variables used as subscripts, thereby making it appear as if the index was
    not present.

i.  Fixed a bug that caused extended glob patterns to incorrectly match
    filenames with a leading `.'.

j.  Fixed a bug involving sign extension when reallocating the input line
    after a history expansion, causing segmentation faults.

k.  Bash now does a better job at identifying syntax errors during word
    completion and tailoring completion appropriately.

l.  Bash now uses the current locale's decimal point in comamnd timing output.

m.  Fixed a bug that caused segmentation faults while reading here documents if
    PS2 contains a command substitution.

n.  There are several changes to how $@ is expanded when unquoted but in a
    context where word splitting is not performed (e.g., on the rhs of an
    assignment or in a conditional command).

o.  Bash now quotes command hash table entries that contain shell metacharacters
    when displaying hash table contents.

p.  Fixed a potential file descriptor leak when dup2() fails while performing a
    redirection.

q.  Fixed a bug that caused directory names evaluated during word completion to
    be dequoted twice.

r.  Fixed several bugs which could result in indirect variable expansion and
    namerefs creating variables with invalid names or referencing variables
    set to the empty string.

s.  Fixed a bug that caused bash to not expand $0 in word expansions where it
    should.

t.  Fixed a bug that caused bash to perform process substitution if <(
    appeared inside an arithmetic context.

u.  Fixed a bug in extglob pattern parsing that caused slashes in the pattern
    to be confused as directory names.

v.  Fixed several bugs with treatment of invisible variables (variables with
    attributes that are unset because they have never been assigned values).

w.  Fixed a bug that caused the `read' builtin to not clean up readline's
    state when using the -e and -t options together and the read timed out.

x.  Fixed a bug that caused the shell to exit with the wrong (but non-zero)
    value if a command was not found or was not executable.

y.  Fixed a bug that caused the `time' reserved word to not be recognized as
    such in all contexts where it should have been.

z.  Fixed a bug that caused the shell to close process subsitution file
    descriptors when executing a script without the `#!' leading line.

aa. Fixed a typo that caused the `compat42' shell option to set the wrong
    compatibility level.

bb. The shell now handles process substitution commands with embedded
    parentheses the same way as it does when parsing command substitution.

cc. Fixed a bug that caused nested pipelines and the `lastpipe' shell option
    to produce core dumps.

dd. Fixed a bug that caused patterns containing `*' to match pathnames in cases
    where slashes must be matched explicitly.

ee. Fixed a problem with patterns containing `:' in colon-separated variables
    lik GLOBIGNORE. 

ff. Fixed a bug that caused indirect variable expansion using indexed arrays to
    always use index 0.

gg. Fixed a parsing problem that caused quoted newlines immediately following a
    command substitution to be mishandled in certain cases.

hh. Fixed a potential buffer overflow on systems without locale_charset or the
    bash replacement.

ii. Fixed a bug that caused background processes to modify the terminal's
    process group under certain circumstances.

jj. Asynchronous commands now always set $? to 0 and are not affected by
    whether or not the command's exit status is being inverted.

kk. Fixed a problem that caused a line ending with an escaped newline and
    containingh a prior `eval' to be incorrectly parsed.

ll. Fixed an issue with programmable completion and `!' in extglob patterns
    used as arguments to `compgen -X'.

mm. Word completion now treats the two-character token `>|' as requiring
    filename expansion.

nn. Bash no longer expands tildes in $PATH elements while in Posix mode.

oo. Fixed a bug that caused bash to not clean up readline's state, including
    the terminal settings, if it received a fatal signal while in a readline()
    call (including `read -e' and `read -s').

pp. Fixed bug that caused importing shell functions from the environment to
    execute additional commands following the function.

qq. Fixed a bug that caused the parser to return a lookahead character pushed
    back by a previous call, even when on another line.

rr. Fixed a bug that caused many here-documents or many nested case statements
    to overflow an internal stack.

ss. Changed the way bash encodes exported functions for inclusion in the
    environment to avoid name collisions with valid variable names and to
    indicate that they are exported functions.

tt. Fixed a bug that could result in an invalid memory access when processing
    a here document delimited by end of file or end of string.

uu. Fixed a bug that could cause an invalid memory access if a command was run
    before initializing the job control framework.

vv. When in Posix mode, bash prints shell function definitions as Posix
    specifies them, without the leading `function' keyword.

ww. The variable attribute display builtins no longer display variables with
    invalid names that were imported from the environment.

xx. Fixed a bug that could allow `break' or `continue' executed from shell
    functions to affect loops running outside of the function.

yy. Fixed a bug that could cause a restricted shell to attempt to import shell
    functions from the environment.

zz. The shell now allows double-quoted identifiers in arithmetic expressions.

aaa. Fixed a bug that could allow scalar variables subscripted using [@] in
     word expansions to be incorrectly quoted.

bbb. The shell now makes sure to ignore SIGTSTP/SIGTTIN/SIGTTOU in child
     processes if they were ignored at shell startup, even if job control is
     in effect.

ccc. Fixed a bug that could cause $* to be split on spaces when IFS is set to
     the empty string.

ddd. Posix says that expanding $* in a pattern context where the expansion is
     double-quoted should not treat $* as if it were double quoted.

eee. Bash now restores getopts' internal state between calls to getopts even if
     a shell function declares a local copy of OPTIND.

fff. Fixed a bug that could cause `history -r' or `history -n' to read identical
     lines from the history file more than once.

ggg. The commands executed by `bind -x' now redisplay at most the final line
     of a multi-line prompt, and those commands may return 124 to indicate that
     the entire prompt should be redrawn.

hhh. Fixed a bug that could cause `mapfile' to create variables with invalid
     names.

iii. The shell only goes into debugging mode when --debugger is supplied if
     the debugger initialization file is present.

jjj. Fixed a bug that disallowed an assignment to (implicit) subscript 0 of an
     existing array in a declare command that set the readonly attribute.

kkk. Fixed a bug that inadvertently allowed assignments to FUNCNAME to disable
     its special status.

lll. Appending to an existing array variable using the compound assignment
     syntax (var+=(aaa)) should not affect assignments to existing subscripts
     appearing in the compound assignment.

mmm. Fixed a bug that could cause the shell to crash when a variable with a
     null value was passed in the temporary environment and the variable's
     attributes are modified using `declare' while performing a redirection.

nnn. Fixed a bug in printf so that a missing precision specifier after a `.'
     is treated as 0.

ooo. Fixed a bug that attempted to use the internal command timing to time
     pipeline components if the pipeline elements are separated by newlines.

ppp. Fixed a bug that caused `declare -al foo=(ONE TWO THREE)' to not lowercase
     the values on assignment.

qqq. Bash does a better job of determining whether or not files are executable
     when running on Windows, since the X_OK flag to access(2) is not supported.

rrr. Fixed a bug that caused some of the shell's internal traps (e.g., ERR) to
     be interrupted (and leave incorrect state) by pending SIGINTs.

sss. Fixed a bug in the bash interface to history expansion to avoid attempting
     expansion if the history expansion character occurs in a command
     substitution.

ttt. Fixed a bug that caused the select command to crash if the REPLY variable
     ends up empty (e.g., if it's made readonly)

uuu. Bash handles backslash-quoting of multibyte characters better when quoting
     output that is intended to be reused.

vvv. System-specific changes for: Windows, Cygwin.

www. Fixes for upper and lower-casing multibyte characters, some locales have
     characters whose upper and lowercase versions have different numbers of
     bytes.

xxx. Fixed a bug that caused the ERR trap in a shell function to have the
     wrong value for $LINENO.

yyy. Fixed a bug that resulted in incorrect quoting of regexps for the =~
     operator when an open brace appears without a close brace.

zzz. Fixed a bug in the array unset operation that caused it to attempt to
     parse embedded single and double quotes.

aaaa. Fixed a bug that caused $* to not expand with the first character of
      $IFS as a separator in a context where word splitting will not take
      place.

bbbb. Fixed two bugs that could cause the shell to dereference a null pointer
      while attempting to print an error message from arithmetic expansion.

cccc. Fixed a bug that resulted in short-circuited evaluation when reading
      commands from a string ending in an unquoted backslash, or when sourcing
      a file that ends with an unquoted backslash.

dddd. Fixed a bug that resulted in the no-fork optimization not cleaning up
      any FIFOs created by process substitution.

eeee. If the -T option is not set, allow the source builtin and shell functions
      to set a DEBUG trap that persists after the sourced file or function
      returns, instead of restoring the old (unset) value unconditionally.

ffff. Fixed a bug that caused redirections to not be undone on some syntax
      errors, e.g., when parsing a command substitution.

gggg. Bash only adds asynchronous commands to the table of background pids
      whose status it remembers, to avoid it growing too large during scripts
      that create and reap large numbers of child processes.  This means that
      `wait' no longer works on synchronous jobs, but $? can be used to get
      the exit status in those cases.

hhhh. Bash now checks whether or not a shell script argument is a directory
      before trying to open it; Posix says implementations may allow open(2)
      on a directory.

iiii. Fixed a bug that could cause the shell to set the terminal's process
      group to a background process group when running as part of a pipeline.

jjjj. Made a few changes to strings to avoid possible potential negative effects
      caused by malicious translations.

kkkk. Fixed a bug that caused the `unset' builtin to continue to treat its
      arguments as functions after unsetting a function when invoked with no
      options.

llll. Fixed a bug that would not replace empty strings using pattern
      substitution even if the pattern matched the empty string.

mmmm. Fixed a bug with word completion that prevented some characters from
      being backslash-quoted (backquote, dollar sign).

nnnn. Fixed a bug that prevented a command from the history re-executed by the
      `fc' builtin from setting verbose mode.

oooo. Fixed a bug that caused the shell to not enable and disable function
      tracing with changes to the `extdebug' shell option.

pppp. Fixed a bug that caused assignments to nameref variables pointing to
      unset variables with attributes but no values to create variables with
      incorrect names.

qqqq. Fixed a bug that caused `unset' on nameref variables (without -n) to
      unset the wrong variable under certain circumstances.

rrrr. Fixed a bug that caused close braces occurring in brace expansions within
      command substitutions to incorrectly terminate parameter expansions.

ssss. Fixed a bug that caused `command -p' to temporarily alter $PATH.

tttt. Fixed a bug that caused interactive shells compiled without job control
      to return incorrect status values for child processes when running a
      single command that creates enough children to use the entire PID space.

uuuu. `esac' should not be recognized as a reserved word when it appears as the
      second or later pattern in a case statement pattern list.

vvvv. Fixed a bug that caused the completion code to read past the end of the
      readline line buffer while skipping assignment statements to find the
      command name.

wwww. Fixed a bug that caused case statements within loops contained in a
      command substitution to be parsed incorrectly.

xxxx. Fixed a bug that could cause SIGCHLD handling to be delayed after
      running `wait' with no arguments and interrupting it with ^C without
      a trap handler installed.

2.  Changes to Readline

a.  A bug that caused vi-mode `.' to be unable to redo `c', `d', and `y'
    commands with modifiers was fixed.

b.  Fixed a bug that caused callback mode to dump core when reading a
    multiple-key sequence (e.g., arrow keys).

c.  Fixed a bug that caused the redisplay code to erase some of the line when
    using horizontal scrolling with incremental search.

d.  Readline's input handler now performs signal processing if read(2) is
    interrupted by SIGALRM or SIGVTALRM.

e.  Fixed a problem with revert-all-at-newline freeing freed memory.

f.  Clarified the documentation for the history_quotes_inhibit_expansion
    variable to note that it inhibits scanning for the history comment
    character and that it only affects double-quoted strings.

g.  Fixed an off-by-one error in the prompt printed when performing searches.

h.  Use pselect(2), if available, to wait for input before calling read(2), so
    a SIGWINCH can interrupt it, since it doesn't interrupt read(2).

i.  Some memory leaks caused by signals interrupting filename completion have
    been fixed.

j.  Reading EOF twice on a non-empty line causes EOF to be returned, rather
    than the partial line.  This can cause partial lines to be executed on
    SIGHUP, for example.

k.  Fixed a bug concerning deleting multibyte characters from the search
    string while performing an incremental search.

l.  Fixed a bug with tilde expanding directory names in filename completion.

m.  Fixed a bug that did not allow binding sequences beginning with a `\'.

n.  Fixed a redisplay bug involving incorrect line wrapping when the prompt
    contains a multibyte character in the last screen column.

o.  Fixed a bug that caused history expansion to disregard characters that are
    documented to delimit a history event specifier without requiring `:'.

p.  Fixed a bug that could cause reading past the end of a string when reading
    the value when binding the set of isearch terminators.

q.  Fixed a bug that caused readline commands that depend on knowing which
    key invoked them to misbehave when dispatching key sequences that are
    prefixes of other key bindings.

r.  Paren matching now works in vi insert mode.

3.  New Features in Bash

a.  There is now a settable configuration #define that will cause the shell
    to exit if the shell is running setuid without the -p option and setuid
    to the real uid fails.

b.  Command and process substitutions now turn off the `-v' option when
    executing, as other shells seem to do.

c.  The default value for the `checkhash' shell option may now be set at
    compile time with a #define.

d.  The `mapfile' builtin now has a -d option to use an arbitrary character
    as the record delimiter, and a -t option  to strip the delimiter as
    supplied with -d.

e.  The maximum number of nested recursive calls to `eval' is now settable in
    config-top.h; the default is no limit.

f.  The `-p' option to declare and similar builtins will display attributes for
    named variables even when those variables have not been assigned values
    (which are technically unset).

g.  The maximum number of nested recursive calls to `source' is now settable
    in config-top.h; the default is no limit.

h.  All builtin commands recognize the `--help' option and print a usage
    summary.

i.  Bash does not allow function names containing `/' and `=' to be exported.

j.  The `ulimit' builtin has new -k (kqueues) and -P (pseudoterminals) options.

k.  The shell now allows `time ; othercommand' to time null commands.

l.  There is a new `--enable-function-import' configuration option to allow
    importing shell functions from the environment; import is enabled by
    default.

m.  `printf -v var ""' will now set `var' to the empty string, as if `var=""'
    had been executed.

n.  GLOBIGNORE, the pattern substitution word expansion, and programmable
    completion match filtering now honor the value of the `nocasematch' option.

o.  There is a new ${parameter@spec} family of operators to transform the
    value of `parameter'.

p.  Bash no longer attempts to perform compound assignment if a variable on the
    rhs of an assignment statement argument to `declare' has the form of a
    compound assignment (e.g., w='(word)' ; declare foo=$w); compound
    assignments are accepted if the variable was already declared as an array,
    but with a warning.

q.  The declare builtin no longer displays array variables using the compound
    assignment syntax with quotes; that will generate warnings when re-used as
    input, and isn't necessary.

r.  Executing the rhs of && and || will no longer cause the shell to fork if
    it's not necessary.

s.  The `local' builtin takes a new argument: `-', which will cause it to save
    the single-letter shell options and restore their previous values at
    function return.

t.  `complete' and `compgen' have a new `-o nosort' option, which forces
    readline to not sort the completion matches.

u.  Bash now allows waiting for the most recent process substitution, since it
    appears as $!.

v.  The `unset' builtin now unsets a scalar variable if it is subscripted with
    a `0', analogous to the ${var[0]} expansion.

w.  `set -i' is no longer valid, as in other shells.

x.  BASH_SUBSHELL is now updated for process substitution and group commands
    in pipelines, and is available with the same value when running any exit
    trap.

y.  Bash now checks $INSIDE_EMACS as well as $EMACS when deciding whether or
    not bash is being run in a GNU Emacs shell window.

z.  Bash now treats SIGINT received when running a non-builtin command in a
    loop the way it has traditionally treated running a builtin command:
    running any trap handler and breaking out of the loop.

aa. New variable: EXECIGNORE; a colon-separate list of patterns that will
    cause matching filenames to be ignored when searching for commands.

bb. Aliases whose value ends in a shell metacharacter now expand in a way to
    allow them to be `pasted' to the next token, which can potentially change
    the meaning of a command (e.g., turning `&' into `&&').

4.  New Features in Readline

a.  The history truncation code now uses the same error recovery mechansim as
    the history writing code, and restores the old version of the history file
    on error.  The error recovery mechanism handles symlinked history files.

b.  There is a new bindable variable, `enable-bracketed-paste', which enables
    support for a terminal's bracketed paste mode.

c.  The editing mode indicators can now be strings and are user-settable
    (new `emacs-mode-string', `vi-cmd-mode-string' and `vi-ins-mode-string'
    variables).  Mode strings can contain invisible character sequences.
    Setting mode strings to null strings restores the defaults.

d.  Prompt expansion adds the mode string to the last line of a multi-line
    prompt (one with embedded newlines).

e.  There is a new bindable variable, `colored-completion-prefix', which, if
    set, causes the common prefix of a set of possible completions to be
    displayed in color.

f.  There is a new bindable command `vi-yank-pop', a vi-mode version of emacs-
    mode yank-pop.

g.  The redisplay code underwent several efficiency improvements for multibyte
    locales.

h.  The insert-char function attempts to batch-insert all pending typeahead
    that maps to self-insert, as long as it is coming from the terminal.

i.  rl_callback_sigcleanup: a new application function that can clean up and
    unset any state set by readline's callback mode.  Intended to be used
    after a signal.