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variable arguments           Overview          variable arguments




The ANSI  Standard mandates the creation of a  set of routines to
help implement  functions, such as pprriinnttff and  ssccaannff, that take a
variable  number of  arguments.  These  routines are  called from
within another function to help it handle its arguments.

These routines  are declared or  defined in the  header ssttddaarrgg.hh,
and are as follows:


     vvaa_aarrgg()  Return pointer to next argument in argument list
     vvaa_eenndd()  Tidy up after an argument list has been traversed
     vvaa_ssttaarrtt()Initialize object that holds function arguments


vvaa_aarrgg and vvaa_ssttaarrtt must be implemented as macros; vvaa_eenndd must be
implemented  as a  library function.  All  three use  the special
type vvaa_lliisstt, which is an  object that holds the arguments to the
function being implemented.

***** Example *****

The following example concatenates multiple strings into a common
allocated string and returns the string's address.


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



char *
multcat(numargs)
int numargs;
{
          va_list argptr;
          char *result;
          int i, siz;



          /* get size required */
          va_start(argptr, numargs);
          for(siz = i = 0; i < numargs; i++)
          siz += strlen(va_arg(argptr, char *));



          if ((result = calloc(siz + 1, 1)) == NULL) {
          fprintf(stderr, "Out of space\n");
          exit(EXIT_FAILURE);
          }
          va_end(argptr);


COHERENT Lexicon                                           Page 1




variable arguments           Overview          variable arguments






          va_start(argptr, numargs);
          for(i = 0; i < numargs; i++)
          strcat(result, va_arg(argptr, char *));
          va_end(argptr);
          return(result);
}



int
main(void)
{
          printf(multcat(5, "One ", "two ", "three ",
          "testing", ".\n"));
}


***** See Also *****

lliibbrraarriieess, ssttddaarrgg.hh


































COHERENT Lexicon                                           Page 2

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