GATE CSE 2016 Set 1 | Question: 12

Question

Consider the following "C" program.

void f(int, short);
void main()
{
    int i = 100;
    short s = 12;
    short *p = &s;
    ____________;  // call to f()
}

 Which one of the following expressions , when placed in the blank above, will NOT result in a type checking error?

• A. $f(s, *s)$
• B. $i = f(i,s)$
• C. $f(i, *s)$
• D. $f(i, *p)$

Comments

.

Answer 1

• A. $f(s, *s) - 1^{\text{st}}$ argument is short whereas the function expects an int. But in C language short gets implicitly converted to int during a function call and so this won’t be a type error. But second argument is a pointer (can be $64$ bits on a $\textsf{x64}$ machine) where as the function expects a short (can be even $16$ bits). So this will generate a type error. So, WRONG.
• B. $i = f(i,s)$ - return type is not void. So, WRONG.
• C. $f(i, \ast s) - 1^{\text{st}}$ argument is int, second is again syntax error. So, WRONG
• D. $f(i, \ast p)$ - Both the arguments and return type match. $p$ is a pointer to short, so $\ast p$ is value of short. So, D is ANSWER.

Comments

@Vicky rix... question seems to be correct as we are passing values of i and *p in the calling function instead of address.

---

@Vicky rix I also thought the same thing but here in this question we are passing *p , because we have derefernced p and then passed to it will not show any error the ultimate values that are going to be passed are (100 and 12 only), if in option D it is is f(i,p) then it is wrong that time we send an address of short and for catching it we placed a short varible so .. correct option is D only

 

---

in C it must be semantic error , as it is a type mismatch. but syntax is correct there.

Answer 2

By option elimination method:
Options A & C are wrong because *s is an invalid argument as s is not a pointer

Option B is incorrect because the f function return type is void while in option it shows of type int implicitly.

Option D is correct because f(100,12) is a valid function call for f(int, short).

Comments

What if it would be (i,&s) ??

---

Then it will return f(100,2000) as per previous comment assumptions. Therefore it would give error as short is a variable holding a value not address.

Correct me if I'm wrong

---

explain something in  Option B which is incorrect because of the f function return type is void while in option it shown of type int implicitly.