Paul Eggert wrote:
It's a bug in the glibc regular expression matcher, and as such will need a glibc fix. I plan to propose a patch there.
I created glibc bug report BZ#18986 about this, and put in a pointer to the Gnulib patch. Hope that's enough to get it fixed in glibc, eventually.
https://sourceware.org/bugzilla/show_bug.cgi?id=18986
