The following macro in cbson.c is incorrect:

// rubinius compatibility
#ifndef RREGEXP_OPTIONS
#define RREGEXP_OPTIONS(r) RREGEXP(value)>ptr>options
#endif

The "r" parameter is not used and the macro incorrectly reverences "value". The only reason this works in the code is by chance the value passed in for "r" happens to be "value". "value" should be replaced with "r" in the macro.