[splint-discuss] Parse Error on Macro, help

[Richard A. O'Keefe]

I made two claims, one of which was wrong and one of which was right:

(1) defining a macro with () was not defined in C89 [wrong]. 
(2) invoking a macro with () was not defined in C89 [right].

Recall that
    > Allowing an empty argument list for a function-like macro was a
    > CHANGE from C89 to C99.  It was proposed by Fred J. Tydeman on 1995-01-09.

So we had the more than odd situation that apparently you were allowed
to define an argumentless function-like macro but you weren't allowed to
invoke it with no arguments.

Terry Colligan <terry-splint at tenberry.com>, who should
speak with authority, tries to have it both ways:

	It is (and was) clearly necessary to allow macros to replace
	functions, something which has been in C for a long time.
	
True, but not really relevant.  It was NOT necessary to allow an
argumentless DEFINITION to get that effect.  If empty arguments
had been legal, then

    #define foobar(dummy) (1+1)
    ...
	dummy()

would have been legal.

	  It *is* clearly in the X3.159-1989 standard, in section 3.8.3.
	 
Is there any way you could talk ANSI into making the old superseded standard
available on the web?  As I noted, I've spent several hundred dollars over
the years buying copies that have subsequently disappeared from my office,
so I can't check this for myself.

	> He was talking about empty *actual parameters*, but the two are related.
	> There is no point in writing
	>     #define FOO() ...
	> unless you mean to invoke it as
	>     ... FOO() ...
	
	  Yes! Exactly.
	
	> and the latter really was undefined behaviour caught by at least one
	> compiler.
	
(A)	  Then that compiler was not conforming to the 1989 standard.
	
	...	

(B)	  What C99 upgraded from a common extension to part of the standard was
	  the possiblility of empty actual arguments.

And that's where he tries to have it both ways.
(A) is a statement that "the latter" (that is, an INVOCATION of a macro
with an empty argument) conformed.
(B) is a statement that it didn't (it used to be a "common extension",
like three-argument main(), not "part of the standard").

	  The description is relentlessly and excessively terse, but that was one
	  of our goals -- to be as brief as possible so as to reduce the chance of
	  the standard being self-conflicting.  Personally, I think we went overboard
	  and made the standard much harder to read as a result.
	
The C89 standard wasn't a bad read.  In fact, compared with the C++
standard, it was an *excellent* read.  (Mind you, compared with
the C++ standard, what isn't?)

	> So it may be, but you still weren't allowed to do it in C89.
	
	  Yes, you were -- at least in any conforming compiler.
	
No, you have confirmed, in your statement

(B)	  What C99 upgraded from a common extension to part of the standard was
	  the possiblility of empty actual arguments.

that invoking a macro with empty actual parameters was *not* required of
conforming compilers.

Thank you for confirming that.