Bash-5.0-alpha available

From: Chet Ramey Subject: Bash-5.0-alpha available Date: Wed, 23 May 2018 15:28:33 -0400

The first alpha release of bash-5.0 is now available with the URL ftp://ftp.cwru.edu/pub/bash/bash-5.0-alpha.tar.gz and from the bash-5.0-testing branch in the bash git repository (http://git.savannah.gnu.org/cgit/bash.git/log/?h=bash-5.0-testing). This tar file includes the formatted documentation (you should be able to generate updated versions yourself). This release fixes several outstanding bugs in bash-4.4 and introduces several new features. The most significant bug fixes are an overhaul of how nameref variables resolve and a number of potential out-of-bounds memory errors discovered via fuzzing. There are a number of changes to the expansion of $@ and $* in various contexts where word splitting is not performed to conform to a Posix standard interpretation. The most notable new features are several new shell variables: BASH_ARGV0, EPOCHSECONDS, and EPOCHREALTIME. The `history' builtin can remove ranges of history entries and understands negative arguments as offsets from the end of the history list. There is an option to allow local variables to inherit the value of a variable with the same name at a preceding scope. There is a new shell option that, when enabled, causes the shell to attempt to expand associative array subscripts only once (this is an issue when they are used in arithmetic expressions). There are a few incompatible changes between bash-4.4 and bash-5.0. The changes to how nameref variables are resolved means that some uses of namerefs will behave differently, though I have tried to minimize the compatibility issues. By default, the shell only sets BASH_ARGC and BASH_ARGV at startup if extended debugging mode is enabled; it was an oversight that it was set unconditionally and caused performance issues when scripts were passed large numbers of arguments. `bashbug' may be used to report bugs with this version. It will send mail to address@hidden if the shell's `release status' is alpha or beta. As always, thanks for your help. Chet +========== CHANGES ==========+ This document details the changes between this version, bash-5.0-alpha, and the previous version, bash-4.4-release. 1. Changes to Bash a. Fixed a bug that could cause traps in background jobs to give the terminal to the wrong process group. b. Fixed a bug that caused `kill -l 0' to print an out-of-range error. c. Fixed a problem that could result in here-documents being displayed in the wrong order. d. Fixed a number of out-of-bounds and free memory read errors found via fuzzing. e. Fixed a subshell inheritance problem that could cause a subshell to wait for the wrong process. f. Fixed a bug that caused SHLVL to be incremented one too many times when creating subshells. g. A job dying due to SIGINT can now interrupt sourcing a file in a shell with job control enabled. h. Fixed a spurious warning about unterminated ${ or $( constructs during word completion. i. The shell no longer runs traps if a signal arrives while reading command substitution output. j. Fixed an arithmetic expansion error that could allow ++var++ as valid syntax. k. Fixed an error that allowed out-of-bounds references to the directory stack. l. The shell does a better job of saving multi-line history entries with embedded comments. m. Fixed a bug that could cause quoted bracket expressions in regular expression arguments to `[[' to not match correctly. n. Fixed a bug that could cause an IFS character in a word to result in an extra '\001' character in the expansion. o. A trailing backslash in a glob pattern can match a trailing backslash in the string. p. Fixed a memory leak in the process creation code path when job control is enabled. q. Fixed a bug that caused `printf' to output broken surrogate pairs for Japanese locales. r. Fixed a bug that caused a SIGINT generated from `kill' in a dot script to kill an interactive shell. s. Fixed a bug that could cause the `read' builtin to not fully read a multibyte character. t. Fixed a bug that could cause identifiers to be evaluated in conditional arithmetic expressions even when evaluation is suppressed. u. Fixed a bug that could result in command substitution, when executed in a context where word splitting is not performed, to leave a stray '\001' character in the string. v. Fixed a bug that could cause history expansion to be disabled in a non- interactive shell even if `-o histexpand' is supplied at startup. w. Fixed a bug that caused `read -N' to strip leading whitespace IFS characters. x. Fixed a bug that caused spurious tilde expansion in arithmetic expressions. y. If indirect expansion attempts to indirectly reference through an unset variable, report an error. z. Added a guard to prevent the shell from looping while receiving an endless stream of SIGTTIN at shell startup. aa. Fixed a bug with parsing here documents inside a command substitution when looking for the closing delimiter. bb. Fixed a bug that caused printf to not quote all <blank> characters in the current locale when using the `%q' format specifier. cc. Fixed a bug with bash's internal buffered I/O system that caused the input pointer to not be reset when read(2) returned an EOF. dd. Bash now installs its SIGWINCH signal handler with SA_RESTART, so it will not interrupt open/read/write system calls. ee. The ERR trap now reports line numbers more reliably. ff. The shell no longer tries to manipulate the terminal process group if a command or process substitution is killed by SIGTERM when job control is enabled. gg. Fixed a bug that caused extglob patterns to match filenames beginning with a period. hh. File descriptors open for writing to here documents are no longer available to subshells. ii. Make sure word completion doesn't perform command or process substitution. jj. Fixed a bug with parsing $$'...' inside a command substitution. kk. Fixed a bug that caused bash to remove backslash-newline pairs from the body of a here-document with a quoted delimiter inside a command substitution. ll. Fixed a bug that could cause the shell to hang when adding a pid to the table of background process exit statuses. mm. Fixed a bug that could cause 0x01 characters to be doubled in the output of process substitution. nn. Restricted shells now clear the hash table before making the PATH variable read-only. oo. There are a number of changes to the expansion of $* and $@ in contexts where word splitting does not occur (quoted and unquoted), with IFS set to NULL or a non-standard value, mostly to deal with the consequences of the behavior defined in Posix interpretation 888. pp. There are a number of changes to nameref variable handling to avoid creating variables with invalid names. qq. A non-interactive posix mode shell no longer exits when an assignment statement fails if the assignment is utimately being performed by the `command' builtin. rr. When using character class names for globbing, don't allow case insensitivity, even if nocaseglob is enabled. ss. Fixed a bug that allowed some redirections to stay in place if a later redirection failed. tt. Fixed a bug in how command and process substitutions are recognized within other parameter expansions. uu. Fixed a bug that caused bash to loop under certain circumstances when performing arithmetic expansion on a variable whose value is an invalid expression. vv. Fixed a bug that could cause bash to expand aliases inappropriately while parsing compound commands like `case'. ww. Fixed a bug that could cause `read -N' to fail to read complete multibyte characters, even when the sequences are incomplete or invalid, with or without readline. xx. Fixed a bug that could cause `case' to fail to match patterns containing 0x01 characters. yy. Fixed a bug that caused exported functions to contain stray 0x01 characters. zz. Fixed some inconsistencies with how the history number is handled in the various prompt strings. aaa. Fixed a bug that could cause a core dump if READLINE_LINE was unset inside a shell function bound to a key sequence with `bind -x'. bbb. Fixed a bug that could cause bash to not read a token terminator correctly if a command substitution was used inside an arithmetic `for' command. ccc. Fixed problems that could occur with a fatal arithmetic expansion error in a context (like prompt expansion) where you can't jump back to the top level. ddd. Expression errors in arithmetic `for' commands are treated more like shell syntax errors. eee. Fixed a parser synchronization error resulting from a syntax error followed immediately by an EOF. fff. When executing a shell function, the first line in the function ($LINENO) is line 1 instead of line 0, as Posix requires. ggg. In Posix mode, bash will canonicalize the value of PWD it inherits from the environment and use that to set its idea of the current directory. hhh. If LINENO is exported, bash needs to regenerate its value each time it constructs the environment. iii. Fixed a bug with restoring the SIGINT handler when using `wait -n'. jjj. Make sure the `coproc' command returns an appropriate status if the NAME argument is invalid. kkk. Fixed a problem with arithmetic expressions containing array references that contain arithmetic expressions with syntax errors. lll. The `select' command and help builtin will use $COLUMNS before the window size returned from the kernel as the terminal width. mmm. `read -n 0' and `read -N 0' now try a zero-length read to attempt to detect file descriptor errors. nnn. The `read' builtin now does a better job of acting on signals that don't interrrupt read(2). ooo. Fixed some cases where `printf -v' did not return failure status on a variable assignment error. ppp. Fixed temporary environment propagation back to the current environment so that it doesn't happen for special builtins run by the `command' builtin. qqq. Fixed a bug when searhing for the end of a here-document delimiter in a command substitution. rrr. Fixed a bug that could cause `cd ${DIRSTACK[0]}' to fail. sss. Fixed a bug that could cause reserved words to not be recognized in a for statement without the `in' inside a command substitution. ttt. Fixed a bug that could cause a double-free in a timed command with an expansion error. uuu. Fixed a bug that could cause a core dump if a script switches from a UTF-8 locale to a different locale after displaying a lone surrogate character. vvv. Fixed cases where bash prematurely removed FIFOs attached to process substitutions. www. Fixed a problem with calculating the size of the table that stores exit statuses from background processes when the child process resource limit is very large. xxx. Fixed a memory leak with functions using `return' when using FIFOs for standard input. yyy. `wait' without arguments attempts to wait for all active process substitution processes. zzz. Fixed a bug where an indirect parameter was subjected to word splitting when trying to find the indirected variable name. aaaa. Fixed a bug that could allow restricted shell users to add commands to the hash table. bbbb. When using the `!(patlist)' extended globbing operator, a filename beginning with a `.' that doesn't match any of the patterns is not returned as a match if leading dots must be matched explicitly. cccc. Fixed a bug that could cause line number and source file information for a function definition to be incorrect if there are multiple definitions. dddd. Fixed a bug that could cause builtins like `readonly' to behave differently when applied to arrays and scalar variables within functions. eeee. Fixed a bug that could cause alias expansion to add an extra space to a quoted string that begins outside the alias expansion. ffff. Fixed a bug that could result in unwanted alias expansion after timing the null command. gggg. Fixed a bug that could cause a core dump if a timestamp in a history file overflowed a time_t. hhhh. Restricted shells can no longer redirect from /dev/tcp or /dev/udp, since the kernel calls make those file descriptors read-write. iiii. Fixed a problem with splitting double-quoted words for programmable completion when the double quote immediately follows another word delimiter. jjjj. Fixed a bug resulting in a use-after-free if two file descriptors share the same input buffer. kkkk. The error message resulting from ${x:?} and ${x?} now differs depending on whether the variable is null or unset. llll. In Posix mode, the shell exits if a variable assignment fails and precedes an empty simple command (after expansion). mmmm. Fixed a timing problem with SIGALRM that could cause the read builtin to drop characters. nnnn. Added code to deal with kill(2) failing to send the shell a fatal signal due to Linux pid namespace peculiarities. oooo. Fixed a bug that made \C-@ (NUL) unusable in key sequences used for `bind -x' commands. pppp. Fixed a bug that could cause SIGINT recursion when running an external command in a trap the shell takes after a command exits due to SIGINT. qqqq. Make sure the shell turns off job control before running the command- not-found handle, so the command doesn't try to manipulate process groups. rrrr. Fixed a problem with timing process substitutions that caused the shell to print timing information for the calling command. ssss. Fixed a bug that caused backquotes in a here-document delimiter to mark the delimiter as quoted (inhibiting expansion of the here-document contents). tttt. Fixed several problems with 0x01 and 0x177 in case pattern lists and conditional command pattern matches. uuuu. Fixed a bug that could cause the pattern matching engine to not recognize locale-specific character classes. vvvv. The auto-configuration now tests for /dev/stdin and /dev/fd independently. wwww. The `globstar' code now skips over symbolic links to directories, preventing them from being scanned twice. xxxx. When running `bind -x' commands, bash now sets READLINE_POINT based on the number of characters in the readline line buffer, not the number of bytes. yyyy. Fixed a problem that could cause recursive trap evaluation of the RETURN trap when using `eval return'. zzzz. Fixed a bug with expanding 0x01 in an unquoted here-document. aaaaa. The process substitution code now closes and unlinks FIFOs when the process on the other side exits, in order to prevent SIGPIPE or waiting until a FIFO opened for read has a writer. bbbbb. Fixed a bug with recursive calls to the parser overwriting the token in an {id}>foo construct. ccccc. After a Posix discussion, the pattern matching engine just skips over invalid character classes in bracket expressions, instead of matching them like individual characters in the expression. ddddd. Fixed a posix-mode problem with variable scoping when creating variables from assignment statements preceding special builtins. eeeee. Fixed a bug that could cause patterns containing backslashes to not be run through the pattern matching engine. fffff. Fixed a bug that could cause redirections to compound commands to not be `undone' if the file descriptor in the redirection was closed when the redirection was initially processed. ggggg. Fixed a bug that could cause buffer corruption when using `bind -x' in a command execute as a result of a key binding installed by `bind -x'. 2. Changes to Readline a. Added a guard to prevent nested macros from causing an infinite expansion loop. b. Instead of allocating enough history list entries to hold the maximum list size, cap the number allocated initially. c. Added a strategy to avoid allocating huge amounts of memory if a block of history entries without timestamps occurs after a block with timestamps. d. Added support for keyboard timeouts when an ESC character is the last character in a macro. e. There are several performance improvements when in a UTF-8 locale. f. Readline does a better job of preserving the original set of blocked = signals when using pselect() to wait for input. g. Fixed a bug that caused multibyte characters in macros to be mishandled. h. Fixed several bugs in the code that calculates line breaks when expanding prompts that span several lines, contain multibyte characters, and contain invisible character seqeuences. i. Fixed several bugs in cursor positioning when displaying lines with prompts containing invisible characters and multibyte characters. j. When performing case-insensitive completion, Readline no longer sorts the list of matches unless directed to do so. k. Fixed a problem with key sequences ending with a backslash. l. Fixed out-of-bounds and free memory read errors found via fuzzing. m. Fixed several cases where the mark was set to an invalid value. n. Fixed a problem with the case-changing operators in the case where the lower and upper case versions of a character do not have the same number of bytes. o. Handle incremental and non-incremental search character reads returning EOF. p. Handle the case where a failing readline command at the end of a multi-key sequence could be misinterpreted. q. The history library now prints a meaningful error message if the history file isn't a regular file. r. Fixed a problem with vi-mode redo (`.') on a command when trying to replace a multibyte character. s. The key binding code now attempts to remove a keymap if a key unbinding leaves it empty. t. Fixed a line-wrapping issue that caused problems for some terminal emulators. u. If there is a key bound to the tty's VDISCARD special character, readline disables VDISCARD while it is active. v. Fixed a problem with exiting bracketed paste mode on terminals that assume the bracketed paste mode character sequence contains visible characters. w. Fixed a bug that could cause a key binding command to refer to an uninitialized variable. 3. New Features in Bash a. The `wait' builtin can now wait for the last process substitution created. b. There is an EPOCHSECONDS variable, which expands to the time in seconds since the Unix epoch. c. There is an EPOCHREALTIME variable, which expands to the time in seconds since the Unix epoch with microsecond granularity. d. New loadable builtins: rm, stat, fdflags. e. BASH_ARGV0: a new variable that expands to $0 and sets $0 on assignment. f. When supplied a numeric argument, the shell-expand-line bindable readline command does not perform quote removal and suppresses command and process substitution. g. `history -d' understands negative arguments: negative arguments offset from the end of the history list. h. The `name' argument to the `coproc' reserved word now undergoes word expansion, so unique coprocs can be created in loops. i. A nameref name resolution loop in a function now resolves to a variable by that name in the global scope. j. The `wait' builtin now has a `-f' option, which signfies to wait until the specified job or process terminates, instead of waiting until it changes state. k. There is a define in config-top.h that allows the shell to use a static value for $PATH, overriding whatever is in the environment at startup, for use by the restricted shell. l. Process substitution does not inherit the `v' option, like command substitution. m. If a non-interactive shell with job control enabled detects that a foreground job died due to SIGINT, it acts as if it received the SIGINT. n. The SIGCHLD trap is run once for each exiting child process even if job control is not enabled when the shell is in Posix mode. o. A new shopt option: localvar_inherit; if set, a local variable inherits the value of a variable with the same name at the nearest preceding scope. p. `bind -r' now checks whether a key sequence is bound before binding it to NULL, to avoid creating keymaps for a multi-key sequence. q. A numeric argument to the line editing `operate-and-get-next' command specifies which history entry to use. r. The positional parameters are now assigned before running the shell startup files, so startup files can use address@hidden s. There is a compile-time option that forces the shell to disable the check for an inherited OLDPWD being a directory. t. The `history' builtin can now delete ranges of history entries using `-d start-end'. u. The `vi-edit-and-execute-command' bindable readline command now puts readline back in vi insertion mode after executing commands from the edited file. v. The command completion code now matches aliases and shell function names case-insensitively if the readline completion-ignore-case variable is set. w. There is a new `assoc_expand_once' shell option that attempts to expand associative array subscripts only once. x. The shell only sets up BASH_ARGV and BASH_ARGC at startup if extended debugging mode is active. The old behavior of unconditionally setting them is available as part of the shell compatibility options. y. The `umask' builtin now allows modes and masks greater than octal 777. z. The `times' builtin now honors the current locale when printing a decimal point. aa. There is a new (disabled by default, undocumented) shell option to enable and disable sending history to syslog at runtime. 4. New Features in Readline a. Non-incremental vi-mode search (`N', `n') can search for a shell pattern, as Posix specifies (uses fnmatch(3) if available). b. There are new `next-screen-line' and `previous-screen-line' bindable commands, which move the cursor to the same column in the next, or previous, physical line, respectively. c. There are default key bindings for control-arrow-key key combinations. d. A negative argument (-N) to `quoted-insert' means to insert the next N characters using quoted-insert. e. New public function: rl_check_signals(), which allows applications to respond to signals that readline catches while waiting for input using a custom read function. f. There is new support for conditionally testing the readline version in an inputrc file, with a full set of arithmetic comparison operators available. g. There is a simple variable comparison facility available for use within an inputrc file. Allowable operators are equality and inequality; string variables may be compared to a value; boolean variables must be compared to either `on' or `off'; variable names are separated from the operator by whitespace. -- ``The lyf so short, the craft so long to lerne.'' - Chaucer ``Ars longa, vita brevis'' - Hippocrates Chet Ramey, UTech, CWRU address@hidden http://tiswww.cwru.edu/~chet/

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