output

$ ruby thread-rmagick.rb                                                              ruby-1.9.2-p0
thread-rmagick.rb:4: [BUG] Segmentation fault
ruby 1.9.2p0 (2010-08-18 revision 29036) [x86_64-darwin10.4.0]

-- control frame ----------
c:0004 p:---- s:0011 b:0011 l:000010 d:000010 CFUNC  :read
c:0003 p:0019 s:0007 b:0007 l:001598 d:000006 BLOCK  thread-rmagick.rb:4
c:0002 p:---- s:0004 b:0004 l:000003 d:000003 FINISH
c:0001 p:---- s:0002 b:0002 l:000001 d:000001 TOP   
---------------------------
-- Ruby level backtrace information ----------------------------------------
thread-rmagick.rb:4:in `block in <main>'
thread-rmagick.rb:4:in `read'

-- C level backtrace information -------------------------------------------

[NOTE]
You may have encountered a bug in the Ruby interpreter or extension libraries.
Bug reports are welcome.
For details: http://www.ruby-lang.org/bugreport.html

thread-rmagic.rb

require "RMagick"

Thread.new {
  i = Magick::Image.read("image.png")
}