bug#34140: AddressSanitizer reported heap-buffer-overflow when ignoring case

[Paul Eggert]

Thanks for the bug report. I tracked it down to a read buffer overrun in glibc's 
regexec.c and filed a bug report with a fix here:

https://sourceware.org/bugzilla/show_bug.cgi?id=24114
glibc is frozen right now (it's just before the glibc 2.29 release), so most 
likely the bug fix will appear in glibc 2.30. I plan to propagate the fix into 
Gnulib (and therefore into grep) shortly after glibc 2.29 is released.