Bug #5038: Ruby 1.9.2 stops on some Regular Expressions

Your regular expression is exponential, with a repeater (+) inside a repeater (*). It requires the regex engine to do a ton of backtracking, creating the seemingly endless loop. A lot of languages would choke on an expression like that.

• Status changed from Open to Rejected

It is limitation of the spec which uses NFA regexp engine. see also http://swtch.com/~rsc/regexp/regexp1.html

I put #{} into your Issue and got nil n = 50 st = "Phone" + " "#{*n} + "Fax" st.match(/(.+\s)*email/i) ----- Original Message ----- From: "Yui NARUSE" <[e-mail]> To: [e-mail] Sent: Sunday, July 17, 2011 10:47:13 AM Subject: [ruby-core:38142] [Ruby 1.9 - Bug #5038][Rejected] Ruby 1.9.2 stops on some Regular Expressions Issue #5038 has been updated by Yui NARUSE. Status changed from Open to Rejected It is limitation of the spec which uses NFA regexp engine. see also http://swtch.com/~rsc/regexp/regexp1.html ---------------------------------------- Bug #5038: Ruby 1.9.2 stops on some Regular Expressions http://redmine.ruby-lang.org/issues/5038 Author: Bob Ambartsumov Status: Rejected Priority: Normal Assignee: Category: Target version: ruby -v: ruby 1.9.2p290 (2011-07-09 revision 32553) [i686-linux] # Code to reproduce: n = 50 st = "Phone" + " "*n + "Fax" st.match(/(.+\s)*email/i) nil is expected The execution stops on match, or enters some endless loop. CPU load is high. Works as expected when not using /i (case-insensitive) Works as expected on smaller n (<20) Takes about 5 seconds to execute on n=30 -- http://redmine.ruby-lang.org