[lug] variable args

[Ken Weinert]

#include<stdio.h>
#include<stdarg.h>


#define logMsg   printf

char* test1(char *fmt, ...)
{
  static char str[256];		/* some insanely large number? */
  va_list ap; 

  va_start(ap, fmt);

  vsprintf(str, fmt, ap);
  //  fprintf(stderr, str, va_arg( ap, va_list ) );   

  va_end(ap);

  return str;
}


void test(char *fmt, ...)
{
    va_list ap;
    va_start(ap, fmt);
    vprintf(fmt, ap);
    //    printf( fmt, va_arg( ap, va_list ) );
    va_end(ap);
}

int main (void)
{
    test("%d %d %d\n", 1, 2, 3);
    logMsg("%s", test1("%d %d %d\n", 4, 5, 6));
}

----------------
output
123
456

* Holshouser, David (dholshou at ball.com) [010504 20:10]:
> I cannot use [vf]printf for 2 reasons.
> I am working in a restricted environment (hardware&software. VxWorks rtos)
> and must (by mandate from above) use a function called logMsg to do any
> printing.
> 
> notice the 126 in the first output line. 
> if I change the magic number in the call to strncpy, that also changes.
> 
> output: 
> -------
> 1 126 44367872
> 2 44367872 431
> 
> 
> 
> void test(char *fmt, ...)
> {
>   char str[128];
>   va_list ap;
> 
>   str[0]='\0';
>   va_start(ap, fmt);
> 
>   strncpy(str, fmt, 126);
>   printf(str, va_arg( ap, va_list ) );
>   fprintf(stderr, str, va_arg( ap, va_list ) );
> 
>   va_end(ap);
> }
> 
> 
> 
> 
> 
> > -----Original Message-----
> > From: D. Stimits [mailto:stimits at idcomm.com]
> > Sent: Friday, May 04, 2001 1:51 PM
> > To: lug at lug.boulder.co.us
> > Subject: Re: [lug] variable args
> > 
> > 
> > Out of curiosity, I'm wondering what would happen if you did 
> > not buffer?
> > printf() buffers since it uses stdout, but if you instead try 
> > fprintf()
> > and print to stderr, buffering is removed. Buffering could be doing
> > something odd that stderr would not act odd with. I am also 
> > curious why
> > vprintf can't be used?
> > 
> > Also, you might want to temporarily alter the "test" function 
> > so that it
> > does not use the "fmt" argument directly; instead, strcpy (or strncpy)
> > fmt to a temporary buffer; I suggest this because for testing you want
> > to be guaranteed that "fmt" can't be changed to point at something
> > different as things go along, and a separate copy will guarantee the
> > variable argument setup does not change it.
> > 
> > D. Stimits, stimits at idcomm.com
> > 
> > "Holshouser, David" wrote:
> > > 
> > > FYI
> > > 
> > > Calling va_arg(ap, va_list) only seems to return the first 
> > argument in the
> > > original list.
> > > And it turns out that I can't use vprint (or printf for 
> > that matter).
> > > Back to the drawing board.
> > > 
> > > The following code produces:
> > > 1 2 3
> > > 1 1627655920 144
> > > 
> > > #include<stdio.h>
> > > #include<stdarg.h>
> > > 
> > > void test(char *fmt, ...)
> > > {
> > >     va_list ap;
> > >     va_start(ap, fmt);
> > >     vprintf(fmt, ap);
> > >     printf( fmt, va_arg( ap, va_list ) );
> > >     va_end(ap);
> > > }
> > > 
> > > int main (void)
> > > {
> > >     test("%d %d %d\n", 1, 2, 3);
> > > }
> > > 
> > > --
> > > David Holshouser
> > > Engineer I
> > > Ball Aerospace & Technologies Corp.
> > > (303)939-5085  dholshou at ball.com
> > > 
> > > _______________________________________________
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> > 
> _______________________________________________
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-- 
Ken Weinert   kenw at ihs.com 303-858-6956 (V) 303-705-4258 (F)
GnuPG KeyID: 9274F1CE           GnuPG available at http://www.gnupg.org/
GnuPG Key Fingerprint: 1D87 3720 BB77 4489 A928  79D6 F8EC DD76 9274 F1CE
If debugging is the process of removing bugs, then programming must be
the process of putting them in.

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