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Johnothan King 102868f850 Replace the hash alias with a proper builtin
This commit replaces the old hash alias with a proper builtin.
I based this builtin off of the code alias uses for handling
`alias -t --`, but with the hack for `--` removed as it has
no use in the new builtin. `alias -t --` will no longer work,
that hack is now gone.

While I was testing this builtin, I found a bug with hash tables
in non-forking subshells. If the hash table of a non-forking
subshell is changed, the parent shell's hash table is also changed.
As an example, running `(hash -r)` was resetting the parent shell's
hash table. The workaround is to force the subshell to fork if the
hash table will be changed.

src/cmd/ksh93/bltins/typeset.c:
 - Move the code for hash out of the alias builtin into a dedicated
   hash builtin. `alias -t --` is no longer supported.

src/cmd/ksh93/data/aliases.c:
 - Remove the old alias for hash from the table of predefined aliases.

src/cmd/ksh93/data/builtins.c:
 - Fix the broken entry for the hash builtin and add a man page for
   the new builtin.

src/cmd/ksh93/sh.1:
 - Replace the entry for the hash alias with a more detailed entry
   for the hash builtin.

src/cmd/ksh93/sh/name.c:
 - Force non-forking subshells to fork if the PATH is being reset
   to workaround a bug with the hash tree.

src/cmd/ksh93/tests/alias.sh:
 - Add a regression test for resetting a hash table, then adding
   a utility to the refreshed hash table.

src/cmd/ksh93/tests/subshell.sh:
 - Add regression tests for changing the hash table in subshells.

(cherry picked from commit d8428a833afe9270b61745ba3d6df355fe1d5499)
2020-06-12 01:45:18 +02:00

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TODO for AT&T ksh93, 93u+m bugfix branch
______
Fix regression test failures:
- On FreeBSD, there is a test failure in [[ -N file ]] in bracket.sh.
- On OpenBSD, there are 15 locale-related test failures in variables.sh.
______
Fix build system:
- ksh does not currently build on NetBSD, AIX, HP-UX, Solaris, or QNX.
- Reimport the removed nmake. It is necessary for changes in Makefiles
to take effect. The machine-generated Mamfiles are now used as a fallback,
but they are not meant to be edited by hand.
- Reimport the removed pty command (for scripting interactive sessions). This
is necessary for the pty.sh regression tests to work, which test ksh as an
interactive shell. We want to avoid breaking the interactive shell, too.
______
Fix or remove broken or misguided default aliases:
- Make a proper builtin out of the redirect='command exec' alias. It should
really only parse redirections. Currently, if an unwitting user notices this
alias and tries out something like 'redirect ls >file', it does 'exec ls
>file', so 'ls' replaces their shell and they get logged out. That is so
misdesigned I'm calling it a bug.
Alternatively, maybe just get rid? Who uses this anyway? 'redirect >&2'
takes four more keystrokes to type than 'exec >&2'.
- Make proper builtins out of the following scripting-related aliases, so
that 'unalias -a' does not eliminate them. If done correctly, this causes
no other change in behaviour. It would be good practice to 'unalias -a' in
a script to start with a clean slate, except ksh has always made that
impossible without losing these. Default aliases should be to facilitate
interactive use.
- autoload='typeset -fu'
- compound='typeset -C'
- float='typeset -lE'
- functions='typeset -f'
- integer='typeset -li'
- nameref='typeset -n'
- source='command .'
Keep these default aliases for the benefit of interactive shells:
+ history='hist -l'
+ r='hist -s'
+ stop='kill -s STOP'
+ suspend='kill -s STOP $$'
______
Fix currently known bugs affecting shell scripting. These are identified by
their modernish IDs. For exact details, see code/comments in:
https://github.com/modernish/modernish/tree/0.16/lib/modernish/cap/
- BUG_BRACQUOT: shell quoting within bracket patterns has no effect. This
bug means the '-' retains it special meaning of 'character range', and an
initial ! (and, on some shells, ^) retains the meaning of negation, even
in quoted strings within bracket patterns, including quoted variables.
- BUG_CMDEXPAN: if the 'command' command results from an expansion, it acts
like 'command -v', showing the path of the command instead of executing it.
For example:
v=command; "$v" ls
or
set -- command ls; "$@"
don't work.
See also: https://github.com/att/ast/issues/963
- BUG_CMDSPASGN: preceding a "special builtin"[*] with 'command' does not
stop preceding invocation-local variable assignments from becoming global.
[*] https://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#tag_18_14
- BUG_CMDSPEXIT: preceding a "special builtin"[*] (other than 'eval', 'exec',
'return' or 'exit') with 'command' does not always stop it from exiting
the shell if the builtin encounters error.
[*] https://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#tag_18_14
- BUG_CSUBSTDO: If standard output (file descriptor 1) is closed before
entering a $(command substitution), and any other file descriptors are
redirected within the command substitution, commands such as 'echo' will
not work within the command substitution, acting as if standard output is
still closed.
- BUG_IFSGLOBS: In glob pattern matching (as in case or parameter
substitution with # and %), if IFS starts with ? or * and the "$*"
parameter expansion inserts any IFS separator characters, those characters
are erroneously interpreted as wildcards when quoted "$*" is used as the
glob pattern.
- BUG_KUNSETIFS: ksh93: Can't unset IFS under very specific circumstances.
unset -v IFS is a known POSIX shell idiom to activate default field
splitting. With this bug, the unset builtin silently fails to unset IFS
(i.e. fails to activate field splitting) if we're executing an eval or a
trap and a number of specific conditions are met.
- BUG_LOOPRET2: If a 'return' command is given without a status argument
within the set of conditional commands in a 'while' or 'until' loop (i.e.,
between 'while'/'until' and 'do'), the exit status passed down from the
previous command is ignored and the function returns with status 0
instead.
- BUG_MULTIBIFS: We're on a UTF-8 locale and the shell supports UTF-8
characters in general (i.e. we don't have WRN_MULTIBYTE) however, using
multi-byte characters as IFS field delimiters still doesn't work. For
example, "$*" joins positional parameters on the first byte of IFS instead
of the first character.