C++/C object->isOnStack()

Question

I would like to be able to determine if a pointer is on the stack or not at runtime for a number of reasons. Like if I pass it into a function call, I can determine whether I need to clone it or not. or whether I need to delete it.

In Microsft C (VC 6,7,8) is there a way to bounds check a pointer to see if it in on the stack or not? I am only concerned with determining this on the thread that owns the stack the object was placed on.

something like

static const int __stack_size and __stack_top

???? Thanks!

Answer 1

Knowing whether an object is on the stack or heap isn't going to tell you whether it should be cloned or deleted by the called function. After all, you can clone either type, and while you shouldn't try to delete a stack-allocated function you shouldn't try to delete all heap pointers either.

Having a function that will make some arcane check to see whether it should delete a passed pointer or not is going to cause confusion down the line. You don't want a situation where you may or may not be able to refer to fields in an object you passed, depending on context. Nor do you want to risk a mistake that will result in trying to free a stack object.

There isn't any standard way to tell what a pointer points to, and any nonstandard way is likely to break. You can't count on stack contiguity, particularly in multithreaded applications (and somebody could easily add a thread to an application without realizing the consequences).

The only safe ways are to have a calling convention that the called function will or will not delete a passed object, or to pass some sort of smart pointer. Anything else is asking for trouble.