Re: [PATCH v2 05/10] Make gnulib's regcomp not abort()

[Paul Eggert]

It's not clear why this change is needed. POSIX says that for regerror 
"the application shall ensure is the last non-zero value returned by 
regcomp() or regexec() with the given value of preg". If an application 
violates a "shall" requirement, behavior is undefined so it's OK for 
regerror to abort in that case.