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cde/TODO
Martijn Dekker 952944197f Fix bugs in testing if a parameter is set
This fixes three related bugs:
1. Expansions like ${var+set} remained static when used within a
   'for', 'while' or 'until' loop; the expansions din't change
   along with the state of the variable, so they could not be used
   to check whether a variable is set within a loop if the state of
   that variable changed in the course of the loop. (BUG_ISSETLOOP)
2. ${IFS+s} always yielded 's', and [[ -v IFS ]] always yielded
   true, even if IFS is unset. (BUG_IFSISSET)
3. IFS was incorrectly exempt from '-u' ('-o nounset') checks.

src/cmd/ksh93/sh/macro.c: varsub():
- When getting a node pointer (np) to the parameter to test,
  special-case IFS by checking if it has a value and not setting
  the pointer if not. The node to IFS always exists, even after
  'unset -v IFS', so before this fix it always followed the code
  path for a parameter that is set. This fixes BUG_IFSISSET for
  ${IFS+s} and also fixes set -u (-o nounset) with IFS.
- Before using the 'nv_isnull' macro to check if a regular variable
  is set, call nv_optimize() if needed. This fixes BUG_ISSETLOOP.
  Idea from Kurtis Rader: https://github.com/att/ast/issues/1090
  Of course this only works if SHOPT_OPTIMIZE==1 (the default),
  but if not, then this bug is not triggered in the first place.
- Add some comments for future reference.

src/cmd/ksh93/bltins/test.c: test_unop():
- Fix BUG_IFSISSET for [[ -v IFS ]]. The nv_optimize() method
  doesn't seem to have any effect here, so the only way that I can
  figure out is to special-case IFS, nv_getval()'ing it to check if
  IFS has a value in the current scope.

src/cmd/ksh93/tests/variables.sh:
- Add regression tests for checking if a varariable is set within a
  loop, within and outside a function with that variable made local
  (to check if the scope is honoured). Repeat these tests for a
  regular variable and for IFS, for ${foo+set} and [[ -v foo ]].

(cherry picked from commit a2cf79cb98fa3e47eca85d9049d1d831636c9b16)
2020-06-12 01:45:14 +02:00

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TODO for AT&T ksh93, 93u+m bugfix branch
______
Fix or remove broken default aliases:
- Remove alias times='{ { time;} 2>&1;}' which does not produce POSIX-
compliant output; reimplement as a proper POSIX-compliant builtin.
In any case, implementing a standard utility as an alias is unacceptable
as 'unalias -a' (remove all aliases) should not remove standard utilities!
Backport the builtin from the abandoned Vashisht/Rader branch:
https://github.com/att/ast/pull/1332
- Remove alias command='command '. Continuing alias substitution after
'command' (due to the final space in the alias) is inherently broken, as
aliases may contain arbitrary shell grammar. For instance, when combining
this default alias with the default 'times' alias ('command times'), which
is perfectly valid per POSIX, you get a syntax error!
- Remove alias nohup='nohup '. Same reason as for 'command ' above.
- Remove pointless default aliases 'fc' and 'type'; these are already
implemented as normal shell builtins. Add man page entries for these.
______
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.
- 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 $(command substitution), and any other file descriptors are
redirected within the command substitution, commands such as 'echo' will
not work within the command substitution, acting as if standard output is
still closed.
- BUG_FNSUBSH: Function definitions within subshells (including command
substitutions) are ignored if a function by the same name exists in the
main shell, so the wrong function is executed. 'unset -f' is also silently
ignored. This only applies to non-forked subshells.
- BUG_IFSGLOBS: In glob pattern matching (as in case or parameter
substitution with # and %), if IFS starts with ? or * and the "$*"
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.
- BUG_TESTERR1A: test/[ exits with a non-error false status (1) if an
invalid argument is given to an operator.