va_arg(ap,char*) and strcat

[cmancre]

code:

// n = 2
void fun(int n, ...){
va_list ap;
int i;
char *arg1 = (char *) malloc(MAX * sizeof(char));
char *arg2 = (char *) malloc(MAX * sizeof(char));
va_start(ap, n);
memset(arg1,0,MAX);
memset(arg2,0,MAX);
arg1 =(char*)va_arg(ap,char*);
arg2 =(char*)va_arg(ap,char*);
fprintf(stdout,"%s",strcat(arg1,arg2);
va_end(ap);
}

problem: strcat dont concatenate the two arguments, help!!

 

[DaveSinkula]

You malloc to [tt]arg1[/tt] and [tt]arg2[/tt], then later assign these pointers elsewhere, leaking memory. The pointers are then pointing to the arguments passed to the function. If you can't concatenate them (if the pointers point to non-writeable string literals, for example), it may be because of these arguments.

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

void fun(int n, ...)
{
   char *arg1, *arg2, *arg;
   va_list ap;
   va_start(ap, n);
   arg1 = va_arg(ap, char*);
   arg2 = va_arg(ap, char*);
   va_end(ap);
   arg  = malloc(strlen(arg1) + strlen(arg2) + 1);
   if ( arg )
   {
      strcpy(arg, arg1);
      fprintf(stdout,"%s\n", strcat(arg, arg2));
      free(arg);
   }
}

int main()
{
   fun(2, "one", " two");
   return 0;
}

/* my output
one two
*/