# File lib/phusion_passenger/platform_info/binary_compatibility.rb, line 110
        def self.cxx_binary_compatibility_id
                if os_name == "macosx"
                        # RUBY_PLATFORM gives us the kernel version, but we want
                        # the OS X version.
                        os_version_string = `sw_vers -productVersion`.strip
                        # sw_vers returns something like "10.6.2". We're only
                        # interested in the first two digits (MAJOR.MINOR) since
                        # tiny releases tend to be binary compatible with each
                        # other.
                        components = os_version_string.split(".")
                        os_version = "#{components[0]}.#{components[1]}"
                        os_runtime = os_version
                        
                        os_arch = cpu_architectures[0]
                        if os_version >= "10.5" && os_arch =~ /^i.86$/
                                # On Snow Leopard, 'uname -m' returns i386 but
                                # we *know* that everything is x86_64 by default.
                                os_arch = "x86_64"
                        end
                else
                        os_arch = cpu_architectures[0]
                        os_runtime = nil
                end
                
                return [os_arch, os_name, os_runtime].compact.join("-")
        end