Shalom, Monks. I've searched for an answer to this question, but my searches have come up empty. I've found a bug in my XML::Validator::Schema module and I think it's due to a limit in Perl's regular expression engine, but my attempts to confirm this have failed. XML::Validator::Schema uses regexes to validate XML Schema content models. I'm getting a failure when validating a file containing around 160,000 elements. The failure is happening on the 32,768th element, which is certainly a suspicious number indeed!

Inside XML::Validator::Schema, something like this is happening: 

   my $s = join('', (("<object>") x 160_000))
   die("Failed validation!") unless $s =~ /^(?:<object>)+$/;

[download]

I say "something like this" because it's a lot more complicated. The regex is dynamicly built and compliled with qr// and the string is built up from the incoming XML stream.

When I try to verify the limit by hand I can't get the same results: 

   $ perl -e '$s = join("", (("<object>") x 160_000)); print "ok\n" if
+ $s =~ /^(?:<object>)+$/'
   ok

[download]

What am I missing? Why does XML::Validator::Schema suffer from a limit of 32,768 repetitions on + when the same thing works on the command line?

Thanks,
-sam

PS: I'm working with Perl 5.6.1, if that makes a difference.

In reply to Is there a hard limit on + in a regex? by samtregar

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