Re: Perl 5.18 and Regexp::Grammars

On Fri, Jun 28, 2013 at 06:46:51AM +1000, Damian Conway wrote:
> Nicholas Clark queried:
> 
> > the code should still be able to work if 'use re eval' is added to
> > the scopes in which it it is used?
> 
> Should be able to work. But doesn't.

>         * The final problem that has arisen in 5.18 is that several
>           tests in R::G's suite changed from passing under 5.16 to
>           segfaulting under 5.18. That's a separate, and arguably far
>           more serious, problem in itself...and an indication that some
>           deep issue still lurks in the new mechanism. I have not yet
>           had the time to track this problem down more specifically.

Agree. It should not be possible to provoke SEGVs.
That suggests that (at least) one ugly bug remains. :-(

> Finally, please note that I am currently mired in final preparations for
> my annual speaking tour, which starts next week. As a result, my response-
> time will be poor, and I will not be able to properly perlbug this issue
> (i.e. boil Regexp::Grammars' 2500 lines of code down to minimal examples)
> for at least a month.
> 
> I appreciate everyone's concern over this issue, and apologize for the trouble
> it's causing.

Thanks for interrupting your preparations to provide the detailed summary of
issues.


On Tue, Jun 25, 2013 at 12:41:21AM -0700, Greg Lindahl wrote:
> Inspired by C-Reduce, perl-reduce takes a perl program that causes a
> bug in perl itself, such as a core-dump in the perl interpreter, and
> tries to reduce the program to the minimum program needed to cause the
> bug.
> 
> https://github.com/blekko/perl-reduce
> 
> I didn't have much luck finding buggy scripts to test this with; you
> guys are too clever at reducing scripts before you file bugs. I threw
> in some useful features like taint and valgrind based on one of the
> few examples that I did find.
> 
> Next time <someone> shows up with a 10,000 line crasher script and an
> attitude, send <them> to me. jk

Damian suggests that his test case is only 2500 lines. Is that an acceptable
challenge? Could you also wave the requirement to have an "attitude"? :-)

Nicholas Clark

• reducing perl-crashing scripts to a minimum reproducer by Greg Lindahl
• Re: Perl 5.18 and Regexp::Grammars by Nicholas Clark
• Re: reducing perl-crashing scripts to a minimum reproducer by Ed Avis