gnb@bby.oz (Gregory N. Bond) (11/14/89)
I'm-sure-this-has-been-hashed-to-death-before-but:
Is there some method of specifying varadic functions that is portable
to both old (varargs) and new (stdargs) implementations? Is there an
ANSI prototype for old varargs functions? Or do I have two prototyes
and two implementations surrounded by #if __STDC__? (My varargs is
the SunOs 3.5 one, in case there are many versions...)
Greg.
--
Gregory Bond, Burdett Buckeridge & Young Ltd, Melbourne, Australia
Internet: gnb@melba.bby.oz.au non-MX: gnb%melba.bby.oz@uunet.uu.net
Uucp: {uunet,pyramid,ubc-cs,ukc,mcvax,prlb2,nttlab...}!munnari!melba.bby.oz!gnbgwyn@smoke.BRL.MIL (Doug Gwyn) (11/14/89)
In article <GNB.89Nov14103800@baby.bby.oz> gnb@bby.oz (Gregory N. Bond) writes: >Is there some method of specifying varadic functions that is portable >to both old (varargs) and new (stdargs) implementations? The simple answer is that at some level you have to switch on __STDC__. >Is there an ANSI prototype for old varargs functions? No, such functions were not legal C although they happened to work in most implementations. Because of the widespread use of printf() in applications, it behooved implementors to figure out some solution. >Or do I have two prototyes and two implementations surrounded by >#if __STDC__? Some people use macros to make this a bit less painful, but in any event in the definition of the body of a variadic function you have to pick up the "fixed" arguments via va_arg() for varargs, but they're already accessible under stdarg.
maart@cs.vu.nl (Maarten Litmaath) (11/15/89)
How about this?
--
/*
* my_varargs.h
*/
#ifndef MY_VARARGS_H
#define MY_VARARGS_H
#ifdef __STDC__
#define EXTERN_VARARGS(type, f, args) extern type f args
#define VARARGS(type, f, args) type f args
#define VA_START(ap, type, start) va_start(ap, start)
#include <stdarg.h>
#else /* __STDC__ */
#define EXTERN_VARARGS(type, f, args) extern type f()
#define VARARGS(type, f, args) type f(va_alist) \
va_dcl
#define VA_START(ap, type, start) va_start(ap); \
start = va_arg(ap, type)
#include <varargs.h>
#endif /* __STDC__ */
#endif /* !MY_VARARGS_H */
--
In somefile.h:
--
EXTERN_VARARGS(void, error, (error_p_type error, ...));
--
In somefile.c:
--
/* VARARGS1 */
VARARGS(void, error, (error_p_type error_p, ...))
{
#ifndef __STDC__
error_p_type error_p;
#endif /* !__STDC__ */
va_list ap;
VA_START(ap, error_p_type, error_p);
vfprintf(stderr, error_p->message, ap);
va_end(ap);
exit(error_p->status);
}
--
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