XCode 2.2.1 attaching to ruby process for debugging

Hi,

I am developing an extension for Ruby and wish to debug it using
XCode.

I used mkmf.rb to generate the Makefile to compile the bundle.

The extension works fine, I am adding more complicated features and
would like to use XCode to debug the more complicated bits.

I was able to start irb to exercise the extension and I was able to
attach to the irb process from XCode.

But it does not seems to be honour the breakpoints I set in the
source code.

As a comparison, I am able to attach to the ruby process on Windows
using Visual Studio and when I load and run my extension, it does stop
at the break points I set.

Is there some addition compiler/linker flag I need to set in my
extconf.rb file for XCode to play well with irb? Given that OSX(BSD)
and Linux have similarity, I am wondering if anyone is using an IDE to
debug Ruby extension on Linux, e.g. Eclipse?

BTW, I am writing my extension using C++.

Cheers