#defines with variable # arguments

[Richard A. O'Keefe]

In article <2886 at phoenix.Princeton.EDU>, lgy at pupthy2.PRINCETON.EDU (Larry Yaffe) writes:
> In article <2633 at tekcrl.TEK.COM> terryl at tekcrl.tek.com writes:
>  >In article <2855 at phoenix.Princeton.EDU+ (lgy at pupthy2.PRINCETON.EDU) I wrote:
>  >+    Are there any versions of cpp which allow one to define macros which
>  >+accept variable numbers of arguments?>  >     I came across this kludge years ago, hope it helps:
>  >     The TRICK is to ADD an extra level of parentheses, using it like thus:
>  >		sprintf( (buffer,"<what-ever-string-you-want>",<varargs>) );
>  >This makes cpp THINK there is only one argument to the macro; I know you
>  >don't want to muck with the sources and just want to put in the #define
>     A number of people suggested variants of the above.

Just a wild heretical suggestion, but there is *another* macro processor
which comes standard with UNIX.  System V has it and BSD has it, and there
is a rather nice public domain version.  I refer, of course, to m4.

What I suggest is a one-time conversion:
	sprintf(S,F)		-> sprintf0(S,F)
	sprintf(S,F,A)		-> sprintf1(S,F,A)
	...
	sprintf(S,F,A,B,C,D,E,F)-> sprintf6(S,F,A,B,C,D,E,F)
however many you need.  This is easy enough to do with m4.  Then you write
your cpp macros for each sprintfN, which is a bit of a pain, but means you
don't have to keep using m4.

It is precisely because m4 is there to fall back on when you need REAL
macro-power that cpp can be so weak.