BOLT default options

BOLT has a large number of command line options. I would like to tweak them to see if I can improve the result of the optimization, but I can’t tell what the default values are for the options, which makes this hard (e.g., I may uselessly try -icf=1 but this may already be the default).

Is there a way to show the default option values without spelunking the source?

Are there any options whose default behavior cannot be obtained by an explicit value for that flag on the command line, but only by leaving it off?

I don’t think this is possible with the current command line infrastructure (though it might nice to have).