GATE Overflow Test Series | Programming | Test 1 | Question: 21

Question

What will be the output of the following C program?

#include <stdlib.h>
int* fun();
int main()
{
    int a = 5;
    int *p = &a;
    p = fun();
    printf("%d",*p);
    return 0;
}
int* fun()
{
    int *a =(int*) malloc(sizeof(int));
    *a = 1;
    return a;
}

Answer 1

hope this will help it out.

Answer 2

p = fun();

Here, fun() returns a pointer which is having heap memory (have lifetime scope). So, $*p = 1$ which is assigned inside fun.

Correct Answer: $1$

Comments

I have a question: @Deepak Poonia sir.

when the fun() ends: the memory allocated to ‘a’ is also destroyed.

So ‘p’ will point to a memory in the heap which is not present.

 

Is it concept valid only when something is stored in a stack, not in heap?

@Arjun sir

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@Udhay_Brahmi yes. Because memory allocation in heap gets cleaned only after a process exits or when we explicitly calls the free function. There's no automatic garbage collector in C. 

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@Arjun if we don’t write return a then answer would be 5?

Can I say that this works in dynamic memory allocation only, if 'a' was local variable then can we write return a or not?