bug in unset in POSIX mode

[Eric Blake]

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Configuration Information:
Machine: i686
OS: cygwin
Compiler: gcc
Compilation CFLAGS:  -DPROGRAM='bash.exe' -DCONF_HOSTTYPE='i686'
- -DCONF_OSTYPE='cygwin' -DCONF_MACHTYPE='i686-pc-cygwin' -DCONF_VENDOR='pc'
- -DLOCALEDIR='/usr/local/share/locale' -DPACKAGE='bash' -DSHELL
- -DHAVE_CONFIG_H -DRECYCLES_PIDS  -I.  -I. -I./include -I./lib   -g -O2
uname output: CYGWIN_NT-5.1 LOUNGE 1.5.16(0.128/4/2) 2005-04-25 20:26 i686
unknown unknown Cygwin
Machine Type: i686-pc-cygwin

Bash Version: 3.0
Patch Level: 16
Release Status: release

Description:
  POSIX XCU 2.9.1 requires that for all simple commands (special built-ins
or otherwise), variables be set in the current environment BEFORE
executing the command.  Therefore, both of the two special built-ins that
can unset variables (unset and .) should end up with foo not set in the
environment after completion, but with bar remaining set.  The trace shows
that unset is buggy.

See my report to the austin group,
https://www.opengroup.org/sophocles/show_mail.tpl?source=L&listname=austin-group-l&id=8356



Repeat-By:

$ set -o posix
$ echo unset foo > dot
$ unset foo bar
$ foo=bar bar=blah unset foo      # BUG - foo should be unset
$ echo ${foo-unset} ${bar-unset}
bar blah
$ unset foo bar
$ foo=bar bar=blah . ./dot        # Correct - only bar remains set
$ echo ${foo-unset} ${bar-unset}
unset blah
$

- --
Life is short - so eat dessert first!

Eric Blake             ebb9@byu.net
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