It is, however, according to Charlie Savage, possible to mix code built from newer compilers into it .
That being said it would appear that you need to also avoid the /MD compiler directive in MS compilers, as well .
Also, users may need to download a redistributable for the version of C compiler you used.
However, it should work.
Note that for distributing gems, you can use Luis Lavena's "rake compiler" to build your binaries for you .
 http://github.com/luislavena/rake-compiler/tree/master ex: