When IFS is null, unquoted $* within an unquoted substitution (e.g.
${1+$*} or ${unset_var-$*}) joins the PPs together into one field, as if
either "$*" or the whole substitution were quoted.
POSIX says the unquoted substitution is supposed to generate one field
for each positional parameter, with further field splitting inactive due
to empty IFS.
Unquoted $* outside of a substitution does this correctly; the bug only
occurs within one.
Test:
bash -c 'IFS=; set "abc" "def ghi" "jkl";
set ${1+$*}; printf "[%s]\\n" "$#" "$@"'
Actual output:
[1]
[abcdef ghijkl]
Expected output (as produced by every other shell):
[3]
[abc]
[def ghi]
[jkl]
Bug confirmed on bash 3.2.57, 4.3.30, 4.4.12.
Bug confirmed *not* present on bash 2.05b.
Thanks,
- M.
