two (and a half) more crashes in regex module

Hello, Prompted by the recent bug reports, I decided to do some targeted fuzzing on gnulib's regex module using afl. So far I found two obscure bugs, and one pathological case. Can be easily reproduced with: $ echo 1 | grep -E "(\'|^)(\1|)" grep: regexec.c:1375: pop_fail_stack: Assertio

two more crashes in regex module

Hello, Prompted by the recent bug reports, I decided to do some targeted fuzzing on gnulib's regex module using afl. So far I found two (obscure) bugs. Can be easily reproduced with: $ echo 1 | grep -E "(\'|^)(\1|)" grep: regexec.c:1375: pop_fail_stack: Assertion `num >= 0' failed. Ab