Macro-fu to export C constants into Ruby

rb_const_macro.c

/*
 * Macro-fu to simplify the exporting C constants from a Ruby extension.
 */
#define EXPORT_RB_CONST(val, x)    \
do{ rb_define_const(val, #x, INT2NUM(x)); } while(0)

#define BAR 42

void
Init_foo(void)
{
        VALUE foo = rb_define_module("Foo"); 
        /* Now you can replace this:
         * rb_define_const(foo, "BAR", INT2NUM(BAR));
         * with:
         */
         EXPORT_RB_CONST(foo, BAR);
}