Can anyone explain working of this code in brief and fix the code?

Question

https://code.sololearn.com/cpkLW5r1tSz2/?ref=app

Answer 1

Just include the header file stdlib.h to remove the implicit declaration warning

Answer 2

#include <stdio.h>
#include <stdlib.h> //add this

int main() {
char *a;

a = malloc(10); // it returns a void pointer since it is not type casted to any specific type. The malloc has allocated a chunk of memory with 10 blocks.

getFree(a); // function call

if(a==NULL) // now you should observe that both a and ptr were pointing to the same memory address but only ptr is made Null and there is no change occurred on a. So this line fails.

printf("null");
else
printf("not null"); // this is executed
return 0;
}
---------------------------------------------------------------
void getFree(void *ptr){ // a void pointer is now pointing to the same memory address as the 'a'.

if(ptr!=NULL){ // this line is true because there is some address pointed by ptr.

free(ptr); // memory deallocated

ptr=NULL; // ptr is now not pointing to any address.
}
return; // back to next line of call
}

Edit: the above explanation could be wrong because concepts of C have faded with time. I just tried.

Answer 3

If you return the pointer ptr from the function and assign it to 'a' then you would get the answer as null.

https://code.sololearn.com/c3ReE0s52M6c/?ref=app

Answer 4

For working of malloc, we have to include malloc.h file in c. You should include malloc.h file