Question

Is there any difference between the two functions below isn’t in both cases the address of local variable returned, but the using the f1() fn returns the correct value 4 but not f2(). Also in third case am I right about this that string constant are not stored in stack so when we return the pointer it will work fine. Also then where are string constant are stored?

int* f1()
{
  int* a=(int*)4;
  return a;
}

int* f2()
{
  int a=4;
  return &a;
}

char* f3()
{
  char* p="abcd";
  return p;
}

Answer 1

There are differences between all of them:

1. The first returns an int * with the value 4, note that it doesn’t point to a variable with the value 4, but to the address 4.
2. The second returns a pointer to a variable that holds 4, but actually, this pointer is not valid, as it points to a local variable of an already returned function, and any usage of it will result in undefined behavior.
3. The third returns a pointer to char (by definition), but actually this is a pointer to a string literal (by implementation). The problem with it, is that as the function return char * and not const char *, one may try to modify the return buffer, which will, again result in undefined behavior.