From: Conrad Schneiker/Austin/Contr/IBM <schneik@...>
Date: 2000-11-13T17:53:30+09:00
Subject: [ruby-talk:6305] Re: Regular expression puzzle: user error or bug?

FWIW, I still get the same error when compiling with the added "-O 
-qmaxmen=8192" (optimization flags for the AIX vac and xlc C compilers), 
both under AIX 4.3 and AIX 5.0.

It looks like configure only tries to do optimized compiles when using 
gcc; can the above flags be added for the AIX cc compilers?

FWIW, I found a somewhat simpler case (#2 below) that produces the regexp 
stack overflow problem, and what seems to be an equivalent case (#1 below) 
that doesn't. (Am I missing some subtly of /x mode?)

=====================
#!/usr/bin/env ruby

puts "----case 1----"
p = Regexp.new(
  " 
    ^(.*/)*(((?:[^.]|[.](?=[^.]*[.]))*))$
  ",'x')
m = p.match("myfile.txt.sav")
m.to_a.each { |x| puts x }

puts "----case 2----"
p = Regexp.new("^(.*/)*(((?:[^.]|[.](?=[^.]*[.]))*))$",'x')
m = p.match("myfile.txt.sav")
m.to_a.each { |x| puts x }
=====================

ruby 1.6.2 (2000-11-10) [rs6000-aix4.3.2.0]

=====================
# ./re_bug.rb
----case 1----
----case 2----
./re_bug.rb:13:in `match': Stack overflow in regexp matcher: 
/^(.*\/)*(((?:[^.\/]|[.](?=[^.\/]*[.]))*))$/i (RegexpError)
        from ./re_bug.rb:13
=====================

Conrad Schneiker
(This note is unofficial and subject to improvement without notice.)