CODEWITHSUNDEEP
cfor-loopparametersvariadic-functions
ESM
ESM

Reputation: 185

C function with variable number of arguments returns unexpected output when called with fewer number of arguments

I'm learning C, and I created a simple addNumbers(int num, ...) function, that takes any number of int arguments, and returns the sum of them.

This issue is that when I get the output of addNumbers(4, 2), the output is 14823901. Which is obviously incorrect.

When I call the function addNumbers(4, 2, 4, 7, 10), it outputs 23, which is also incorrect because it should be 27, but at least it's closer.

Here's my code:

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

// Functions with variable number of arguments
int addNumbers(int num, ...)
{
    int i;
    int sum = 0;

    // List to hold variable amount of parameters
    va_list parameters;

    // Initialize "parameters" list with arguments
    va_start(parameters, num);

    for(i = 0; i < num; i++)
    {
        // Adds each "int" argument from "parameters" to sum
        sum += va_arg(parameters, int);
    }

    // Cleans memory
    va_end(parameters);

    return sum;
}

int main()
{
    printf("%i", addNumbers(4, 2, 4, 7, 10));
    return 0;
}

Should I not be using va_list, va_arg, etc...?

What's the best way to be able to take in a variable number of arguments?

Upvotes: 0

Views: 94

Answers (1)

bari barix
bari barix

Reputation: 68

for addNumber(4, 2) you are using the first parameter as counter which there are 4 parameter to addup but your giving just 1, so the for loop continue reading from the memory expecting more parameter and just pick up ramdom values and add them up.

Upvotes: 1

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