Exercise: Variable Number Of Arguments

Questions for: Variable Number Of Arguments

Point out the error in the following program. 
#include<stdio.h>
#include<stdarg.h>
void display(char *s, ...);
void show(char *t, ...);

int main()
{
    display("Hello", 4, 12, 13, 14, 44);
    return 0;
}
void display(char *s, ...)
{
    show(s, ...);
}
void show(char *t, ...)
{
    int a;
    va_list ptr;
    va_start(ptr, s);
    a = va_arg(ptr, int);
    printf("%f", a);
}
A:
Error: invalid function display() call
B:
Error: invalid function show() call
C:
No error
D:
Error: Rvalue required for t
Answer: B
The call to show() is improper. This is not the way to pass variable argument list to a function.
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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: B
Use double instead of float in float c;
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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: C
We should have use va_start(ptr, num2);
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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: A
Using va_start(ptr, int);
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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: C
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