On 2023-04-03 05:07, Koen Claessen wrote:
BTW, if you are interested, I could do a larger more targeted effort stress
testing grep like this and possibly find more test cases with unexpected
behavior. I would need some guidance on where to put most effort in order
to be as useful as this can be. I could find a MSc student to help out with
that. Let me know if this sounds like an interesting thing to do!
Any help like this would be most welcome.
Unfortunately (or perhaps fortunately for your student, who will learn a
lot!), none of the current maintainers of the glibc regex code really
understand it. The code's original author is no longer available to
answer questions, and the code is tricky as it attempts to implement
POSIX regular expressions (which are worst-case exponential) efficiently
in the usual cases.
The main guidance I can give you is to look at the existing bug reports
against glibc regex[1] and against grep[2], as well as at the grep
source code itself[3].
[1]:
https://sourceware.org/bugzilla/buglist.cgi?component=regex&product=glibc
[2]: https://debbugs.gnu.org/cgi/pkgreport.cgi?package=grep
[3]: https://savannah.gnu.org/projects/grep
