Date: Sun, 4 May 2008 04:01:39 -0700 (PDT) From: Unga <unga888@yahoo.com> To: Roland Smith <rsmith@xs4all.nl> Cc: freebsd-questions@freebsd.org Subject: Re: Variable arg function question Message-ID: <404840.88790.qm@web57007.mail.re3.yahoo.com> In-Reply-To: <20080504075517.GA46776@slackbox.xs4all.nl>
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--- Roland Smith <rsmith@xs4all.nl> wrote:
> On Sun, May 04, 2008 at 12:40:43AM -0700, Unga
> wrote:
> > Hi all
> >
> > I need to implement a variable argument function
> in C.
> > The number of args are not known but the type is
> > known, all are strings.
> >
> > Unfortunately va_arg() [stdarg(3)] does not return
> > NULL or any other suitable value after processing
> the
> > arg list, it just simply crashes once the arg list
> is
> > exhausted.
>
> It is _your_ task to properly close the argument
> list. E.g. by supplying
> a NULL pointer as the last argument.
>
Infact, I have implemented it in this way. I was
wondering if there is a better way. The issue I see
is, if someone forget to close the arg list with NULL
pointer, it crashes.
> > How do you guys implement variable arg function
> such
> > as f(str1, str2, str3, ..., strN)?
>
> you could use the same format as main: int foo(int
> num, char **args)
>
This is interesting. Who set the num? The compiler or
the user. If it is the user, its no better than above
NULL pointer method.
If this is possible, my problem is solved:
f(str1, str2, str3, ..., strN) is at compile time
expands to _f(int num, str1, str2, str3, ..., strN).
The num is set automatically by the compiler by
counting the args.
Is this possible?
Unga
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