Re: How to best cope with variadic input

[Maximilian Schneider <king@greatfreeworld.org>]

On Tue, 2011-03-01 at 08:59 +0000, Jonathan Wakely wrote:
> On 1 March 2011 05:11,  <richardcavell@mail.com> wrote:
> > Hi everyone.  I've decided to learn C99, and so I'm passing -std=c99 to gcc.
> >  I've decided to write a Wikipedia bot in C (don't laugh).
> >
> > Owing partly to obsessive tendencies and partly due to the need for the bot
> > to be robust in working unattended at high speed, I want to wrap printf in a
> > wrapper that automatically detects when printf has failed and tells the
> > user.  The idea is that it is called like this:
> >
> > int res = safeprint ( __FILE__ , __LINE__ , "Blah" ) ;
> > if ( res < 0 ) // uh oh
> >
> >  But printf has variadic input.  I am scratching my head wondering what is
> > my best option:
> >
> > 1.  Make safeprint a variadic function  (I don't know how to do this)
> 
> Use va_list, va_start, va_arg and va_end, defined by:
> #include <stdarg.h>
> 
> On GNU/Linux you should be able to say "man stdarg.h" to see usage examples.
> 
> > 2.  Turn on C++ and overload safeprint with different combinations of
> > arguments
> 
> A better option would be to use a C++ variadic template.
> 
> > 3.  Create multiple safeprint functions with different names, that take
> > different combinations of arguments
> 
> That would be inconvenient to use.

I would have to agree with Jonathan here. In my experience with c++ (Qt)
overloading has only caused me trouble.

the va_list method is straight forward. Note that printf() even comes in
a va_list compatible form. vprintf()

Max S.