# Dl/win32 EnumWindows loops correctly then segfaults **URL:** \ **Category:** Ruby\ **Created:** [April 12, 2006, 8:12am UTC](https://www.ruby-forum.com/t/dl-win32-enumwindows-loops-correctly-then-segfaults/93859 "2006-04-12T08:12:31Z")\ **Posts on this page:** 1\ **Page:** 1
**Author:** ![david](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/aeb1de/32.png) [@david](https://www.ruby-forum.com/u/david)\ **Post date:** [April 12, 2006, 8:12am UTC](https://www.ruby-forum.com/t/dl-win32-enumwindows-loops-correctly-then-segfaults/93859/1 "2006-04-12T08:12:31Z")
Hi All, Googling for “ruby win32api EnumWindows” led me to this four-year-old post from “Shusaku”: [http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-talk/54587](http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-talk/54587) What I want to do (for now) is list all of the windows currently open on the system, with their captions. (Ultimately I want to write an script that will save and restore the positions of various windows on the desktop, such as positioning my IM client so that it looks “docked”.) When I run this script, it seems to run just fine, listing 148 open windows, about 1/3 of which have captions. Then it crashes with this message: * * * ./scratch.rb:23: [BUG] Segmentation fault ruby 1.8.4 (2005-12-24) [i386-cygwin] ## Aborted (core dumped) Any ideas? As the message indicates, this is ruby 1.8.4 running in Cygwin. This is on a Windows XP Media Center Edition laptop with an AMD 64 Turion, if that matters. When I run Shusaku’s original code, it closes all open IE windows… and then segfaults. So I’m thinking maybe the EnumWindows loop isn’t terminating correctly, or I’m simply using this code wrong. Help? Here’s the script: * * * #!/usr/bin/env ruby # list all windows on the machine and their captions… require ‘dl’ User32 = DL.dlopen(‘user32’) enum\_windows = User32[‘EnumWindows’, ‘IPL’] post\_message = User32[‘PostMessage’, ‘ILILL’] get\_class\_name = User32[‘GetClassName’, ‘ILpI’] get\_window\_text = User32[‘GetWindowText’, ‘ILpI’] BUF\_SIZE = 250 TRUE = 1 buff = " " \* BUF\_SIZE ## enum\_windows\_proc = DL.callback(‘ILL’) {|hwnd,lparam| r,rs = get\_window\_text.call(hwnd, buff, buff.size) puts “#{sprintf(‘0x%08x’, hwnd)}: #{rs[1].to\_s}” TRUE } r,rs = enum\_windows.call( enum\_windows\_proc, 0) -dB