If a memory allocation failure occurs during bracket expression
parsing in regcomp, a double-free error may result.
Reported-by: Anastasia Belova <abelova@astralinux.ru>
Co-authored-by: Paul Eggert <eggert@cs.ucla.edu>
Reviewed-by: Andreas K. Huettel <dilfridge@gentoo.org>
(cherry picked from commit 7ea06e9940)