12,358,339 members (70,227 online)
Rate this:
See more:
I m trying to learn C++; the problem comes with variable arguments the program is written as below:-

```#include<iostream>
#include"stdarg.h"
using namespace std;
int sum(int count,...)
{
if(count<=0)
return 0;
va_list arg_ptr;
va_start(arg_ptr,count);

int s=0;
for(int i=0;i<count;i++)

s+=va_arg(arg_ptr,int);

va_end(arg_ptr);
return s;

}

int main()

{
cout << sum(2,4,6) << endl;// runs fime as cout << sum(2,4) output is 6 fine but cout << sum(2,4,6) gives output 10
//which i suppose must be 12
cin.get();
cin.ignore();
}```
Posted 23-Jan-13 2:39am

Rate this:

## Solution 1

The output from `sum(2,4,6)` should be 10 not 12 ... your first parameter is a counter for the rest of the parameters. If you want the answer to be 12 you should call `sum(3,2,4,6)`
Mantu Singh 23-Jan-13 8:57am

Thanks a lot Got it!
One doubt pls
cout << sum(5,4,6) << endl; //5 -no of args still runs with
//junk value like4245556

Is there any clearer type safe way to do this like
param arrays in C#
Marcus Kramer 23-Jan-13 9:15am

In this case you are still pulling integer values from uninitialized memory space and getting whatever happens to be at that memory address.
CHill60 23-Jan-13 10:01am

Have a look at this article http://www.codeproject.com/Articles/7704/Arrays-in-C-CLI - might be of use
Marcus Kramer 23-Jan-13 9:14am

My 5.
Rate this:

## Solution 2

Hi.

For sum(2,4,6), 10 is correct result.
For sum(2,4), 6 is wrong.
The first argument (count) of the sum function tells how many numbers will follow, so ...

sum(2,4,6) tells to sum 2 numbers which values are 4 and 6, for a total of 10.
sum(2,4) tells to sum2 numbers, but the second is not provided, so it will be read from a wrong memory location (probably from the stack location where the first argument, currently 2, is stored).

sum(2,4) should be replaced with sum(1,4).

Regards,
Daniele.

Top Experts
Last 24hrsThis month
 OriginalGriff 270 Jochen Arndt 260 Sergey Alexandrovich Kryukov 210 Richard Deeming 205 Prava-MFS 205
 OriginalGriff 10,228 Dave Kreskowiak 3,384 ppolymorphe 2,507 Karthik Bangalore 2,411 Richard MacCutchan 2,369