Re: Bug in cpp macro varargs extension

["Kaveh R. Ghazi" <ghazi at caip dot rutgers dot edu>]

 > From: Zack Weinberg <zack@rabi.columbia.edu>
 >  
 > On Tue, 2 Mar 1999 13:19:50 -0500 (EST), "Kaveh R. Ghazi" wrote:
 > >       Does anyone use gcc's macro varargs extension?  Is is
 > >considered usable?
 > >
 > >       I'm having several problems getting correct expansions.  I think
 > >it boils down to this test case:
 > >
 > > > #define error1(msg, args...) printf(msg, "foo", ## args)
 > > > #define error2(msg, args...) printf("foo", msg, ## args)
 > [...]
 >  
 > ## args, where args is an empty rest argument, deletes the `preceding
 > sequence of nonwhitespace characters', not the preceding token.  You
 > want
 >  
 > #define error1(msg, args...) printf(msg, "foo" , ## args)
 >  
 > Yes this is ugly.  It's done this way since cpp doesn't know what the
 > "preceding token" is.  cpp.info says that "we" may consider changing
 > it to the preceding token in the future.  Presumably this would
 > involve a token-based macro expander.  I've been thinking about that
 > idly.  The benefits are not clear, besides making it easier to
 > implement C89 Amendment 1 digraphs.
 >  
 > cpplib behaves identically.
 >  
 > zw


	Urg, my fault.  I didn't catch this when I read the docs
on macro varargs. 

		Thanks for your help. 
		--Kaveh
--
Kaveh R. Ghazi			Engagement Manager / Project Services
ghazi@caip.rutgers.edu		Qwest Internet Solutions