-.PP
-The
-.B SOD_CAR
-macro accepts one or more arguments
-and expands to just its first argument,
-discarding the others.
-It is only defined if the C implementation
-advertises support for C99.
-It is used in the definitions of message convenience macros
-for messages which accept a variable number of arguments
-but no required arguments,
-and is exported because the author has found such a thing useful in
-other contexts.