extglob can be erroneously enabled in bash-5.2 through comsub nesting

[Kerin Millar]

Hi,

I am writing to report that the 5.2 release does not correctly address the 
regressions introduced by 5.2-rc3 (see 
https://lists.gnu.org/archive/html/bug-bash/2022-08/msg00104.html for the 
context). Given a sufficient degree of command substitution nesting, it remains 
possible for the extglob shell option to be switched on, without having 
instructed bash to do so.

$ declare -p BASH_VERSION
declare -- BASH_VERSION="5.2.0(1)-release"
$ BASH_COMPAT=50; shopt extglob; : $(: $(: $(:))); shopt extglob
extglob         off
extglob         on

When the bug occurs, all levels are affected, as is demonstrated by the 
attached script. See, also, the original bug report at 
https://bugs.gentoo.org/873931.

-- 
Kerin Millar

gentoo-bug-873931-reproducer-r1.bash
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