Can a C++ class determine whether it's on the stack or heap?

Question

I have

class Foo { .... } 

Is there a way for Foo to be able to separate out:

function blah() {   Foo foo; // on the stack } 

and

function blah() {   Foo foo* = new Foo(); // on the heap } 

I want Foo to be able to do different things depending on whether it's allocated on the Stack or the Heap.

Edit:

Alof of people have asked me "why do this?"

The answer:

I'm using a ref-counted GC right now. However, I want to have ability to run mark & sweep too. For this, I need to tag a set of "root" pointers -- these are the pointers on the stack. Thus, for each class, I'd like to know whether they're in the stack or in the heap.

Answer 1

A hacky way to do it:

struct Detect {    Detect() {       int i;       check(&i);    }  private:    void check(int *i) {       int j;       if ((i < &j) == ((void*)this < (void*)&j))          std::cout << "Stack" << std::endl;       else          std::cout << "Heap" << std::endl;    } }; 

If the object was created on the stack it must live somewhere in the direction of the outer functions stack variables. The heap usually grows from the other side, so that stack and heap would meet somewhere in the middle.

(There are for sure systems where this wouldn't work)