unifdef(1) on FreeBSD
The text 664acadbffef, as FreeBSD 11.3-RELEASE shipped it.
remove preprocessor conditionals from code
Flags it lists
-
-B -
-D -
-I -
-K -
-M -
-S -
-U -
-V -
-b -
-c -
-d -
-e -
-f -
-h -
-iD -
-iU -
-k -
-m -
-n -
-o -
-s -
-t -
-x