C Programming - Variable Number of Arguments

Exercise :: Variable Number of Arguments - Point Out Errors

1. 

Point out the error in the following program.

#include<stdio.h>
#include<stdarg.h>
fun(...);

int main()
{
    fun(3, 7, -11.2, 0.66);
    return 0;
}
fun(...)
{
    va_list ptr;
    int num;
    va_start(ptr, n);
    num = va_arg(ptr, int);
    printf("%d", num);
}

A. Error: fun() needs return type
B. Error: ptr Lvalue required
C. Error: Invalid declaration of fun(...)
D. No error

Answer: Option C

Explanation:

There is no fixed argument in the definition fun()

2. 

Point out the error if any in the following program (Turbo C).

#include<stdio.h>
#include<stdarg.h>
void display(int num, ...);

int main()
{
    display(4, 'A', 'a', 'b', 'c');
    return 0;
}
void display(int num, ...)
{
    char c; int j;
    va_list ptr;
    va_start(ptr, num);
    for(j=1; j<=num; j++)
    {
        c = va_arg(ptr, char);
        printf("%c", c);
    }
}

A. Error: unknown variable ptr
B. Error: Lvalue required for parameter
C. No error and print A a b c
D. No error and print 4 A a b c

Answer: Option C

Explanation:

No answer description available for this question. Let us discuss.

3. 

Point out the error in the following program.

#include<stdio.h>
#include<stdarg.h>
void varfun(int n, ...);

int main()
{
    varfun(3, 7, -11, 0);
    return 0;
}
void varfun(int n, ...)
{
    va_list ptr;
    int num;
    num = va_arg(ptr, int);
    printf("%d", num);
}

A. Error: ptr has to be set at begining
B. Error: ptr must be type of va_list
C. Error: invalid access to list member
D. No error

Answer: Option A

Explanation:

Using va_start(ptr, int);

4. 

Point out the error in the following program.

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

int main()
{
    void display(char *s, int num1, int num2, ...);
    display("Hello", 4, 2, 12.5, 13.5, 14.5, 44.0);
    return 0;
}
void display(char *s, int num1, int num2, ...)
{
    double c;
    char s;
    va_list ptr;
    va_start(ptr, s);
    c = va_arg(ptr, double);
    printf("%f", c);
}

A. Error: invalid arguments in function display()
B. Error: too many parameters
C. Error: in va_start(ptr, s);
D. No error

Answer: Option C

Explanation:

We should have use va_start(ptr, num2);

5. 

Point out the error in the following program.

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

int main()
{
    void display(int num, ...);
    display(4, 12.5, 13.5, 14.5, 44.3);
    return 0;
}
void display(int num, ...)
{
    float c; int j;
    va_list ptr;
    va_start(ptr, num);
    for(j=1; j<=num; j++)
    {
        c = va_arg(ptr, float);
        printf("%f", c);
    }
}

A. Error: invalid va_list declaration
B. Error: var c data type mismatch
C. No error
D. No error and Nothing will print

Answer: Option B

Explanation:

Use double instead of float in float c;