From: Eric Wong <normalperson@...>
Date: 2013-04-07T04:01:33+09:00
Subject: Re: C API version / functionality detection

William Fulton <lists@ruby-forum.com> wrote:
> Macros containing text such as RUBY_VERSION can't be usefully used by 
> the C preprocessor, but the numeric ones such as RUBY_API_VERSION_CODE 
> or the old RUBY_VERSION_CODE can be. However, they are in version.h 
> which poses two problems. First this file isn't always shipped (eg in 
> some Debian based system, such as ruby-1.9.0 on Ubuntu 10.04). Secondly 
> in order to get the macro one needs a '#include "version.h"' which is a 
> rather commonly named file name, so it may pick up some other version.h 
> file which is no good at all as our users are expected to use their own 
> code.

Instead of version.h, I suggest ruby/version.h
#include <ruby/version.h>

> Anyway, I've fixed the problem above as rb_respond_to changed in a 
> subtle way in 1.9 and the '== Qtrue' should be dropped to check for 
> success.

Using RTEST() should work reliably.