def _commandline_dep_string(cc_args, extra_postargs, pp_opts):
    """
    Return commandline representation used to determine if a file needs
    to be recompiled
    """
    cmdline = 'commandline: '
    cmdline += ' '.join(cc_args)
    cmdline += ' '.join(extra_postargs)
    cmdline += ' '.join(pp_opts) + '\n'
    return cmdline
