# File src/ruby_supportlib/phusion_passenger/platform_info/binary_compatibility.rb, line 111
    def self.cxx_binary_compatibility_id
      if os_name_simple == "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_simple, os_runtime].compact.join("-")
    end