[msarnoff]

That's been my primary usage of them. Another is to create a list of config file options (or command line arguments) like

  X(foo,      int,         "set the number of foos")
  X(filename, std::string, "input filename")
  X(verbose,  bool,        "verbose logging")

which can then be used to (a) generate the fields of a config struct, define the mapping from string to field (using the stringifying macro operators), define what functions to use for parsing each field, create the help message, etc. Basically like `argparse` or `clap` but much hackier.

As gross as they are, the ability to define one table of data that's used multiple ways in multiple places is handy.