Accessing extern variable in Ruby DLL

[Jordan Miner]

Hello,

I recently wrote a binding to Ruby’s extension API , and today finished writing a simple extension using it. But I ran into something strange. (I also had a problem compiling the DLL since I use Tango, but searching the newsgroup yielded the solution.)

Ruby’s API has rb_cObject, rb_cString, etc. as global variables that it sets to the Object class, String class etc. In ruby.h, they are defined as

extern unsigned long rb_cObject;

so in my binding I have

extern uint rb_cObject;

But when I try to use rb_cObject from my extension, it is not the right value... I think rb_cObject should equal rb_eval_string("Object"), but it does not. (Using the wrong value causes an access violation.)

I produced an OMF import library for Ruby’s runtime DLL by using coff2omf on the COFF import library that ships with it. I'm linking my extension with this import library.

If I remove the extern from my binding, I get a multiple definition error, so I must be linking with the variable in the DLL? But it seems the value is wrong. I’ve worked around this by calling rb_eval_string("Object") instead, but I’m really curious what could be happening here. Using rb_cObject is the usual way of referring to the Object class in C extensions, and I want to make sure my binding is correct. Could it be because the DLL was compiled with Visual Studio and my extension is in D?

Any ideas?