GATE Overflow Test Series | Mock GATE | Test 5 | Question: 40

Question

Consider the following C program:

#include<stdio.h>
int (*foo(int (*f)(int,int))) (int, int)
{
    return f+1;
}
int fun1(int x,int y)
{
    return x+y;
}
int fun2(int x,int y)
{
    return x*y;
}
int main()
{
    int (*fun_ptr[2])(int,int);
    int x,y;
    fun_ptr[0]=fun1;
    x=fun_ptr[0](4,5);
    fun_ptr[1]=fun2;
    fun_ptr[0] = foo(fun_ptr[0]);
    y=fun_ptr[0](4,5);
    printf("%d %d",x,y);
    return 0;
}

What will be the output when the above program is executed?

• A. $4\;\; 5$
• B. $20\;\; 9$
• C. $9\;\; 20$
• D. None of these

Answer 1

Here foo is a function which accepts a function pointer and returns its increment. But this increment value need not point to a valid function address. So, the below line can cause possible runtime error.

y=fun_ptr[0](4,5);

Correct answer: D.

Comments

Sir what could be the correct approach for making the function pointer point to next function without any error??

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No way here with an increment operation unless the address of array is passed in which case we can increment and then dereference.

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@gatecse @Sachin Mittal 1 @Deepak Poonia sir 

here f is pointing to fun1 so if we increment f+1 then it is not necessary that it points to fun2 because fun_ptr is array but fun1 and fun2 are 2 functions which can be created any where need not be contiguous.