Hi

In C extension code, what's the canonical way to test whether the ruby 
being compiled against is 1.8 or 1.9?

I've been using ways like

#ifdef RUBY_RUBY_H
... 1.9 code
#endif

But this seems accidental. However I didn't find a RUBY_VERSION constant 
in the headers anywhere.

I'd like to submit a patch to SWIG to fix problems it has with the 
latest 1.9.1-preview, and wish to use the authoritative way.

thanks
a