How to programmatically tell if two variables are on the same stack? (in Windows)

Question

I'm in a thread. I have an address. Is that address from a variable on the same stack that I'm using?

static int *address;

void A()
{
    int x;
    atomic::CAS(address, 0, &x); // ie address = &x
    // ...
}

void B()
{
   int y;
   int * addr = atomic::read(address); // ie addr = address
   if (addr && on_same_stack(&y, addr))
   {
      // B() called from A()
   }
   else
   {
      // B() called from different thread than A()
   }
}

I need to implement on_same_stack(addr1, addr2). I know that the stack(s) on Windows grow as needed, but I also know that there is a limit to the growth, and that (in debug at least) there is stack-overflow-checking code on every function call. So I think it can be done.

Now, I also know that I could/should use thread IDs, etc. But I'm trying to implement some tricky lock-free coding here, and I don't really have the room to store the thread IDs, just a single pointer. (I'm hoping to avoid CMPXCH16). Please trust me that I somewhat know what I'm doing :-).

This is for Windows-only for now. But the more portable the better. (NT/XP/7/CE?)

P.S. this site is called "stackoverflow" so it should be the right place to ask, shouldn't it? :-)

EDIT: adding context, since everyone is asking. I'm implementing a custom call_once similar to pthread_once or boost.threads call_once. I'm attempting to check for recursion. I am very limited with what I have to work with. I can't add function parameters. I can't make assumptions about what the rest of the program is doing, like how much TLS they are already using. Etc. I can only code inside my one function, and make no changes or assumptions about anything outside of that.

Thanks for your questions/answers.

Answer 1

How about something crazy like (untested):

declspec(__thread) void* stackBottom;

void Thread1Routine(void* arg)
{
  volatile int bottom;
  stackBottom = ⊥

  ... (do stuff which ends up calling on_same_stack()) ...
}


bool on_same_stack(void* p)
{
  volatile int top;
  return ((LONG_PTR)p >= (LONG_PTR)&top) && ((LONG_PTR)p <= (LONG_PTR)stackBottom);
}

(edited to remove theoretical register-based arg passing issues)

Answer 2

Using Win32 Thread Information Block

These examples use the main thread but actually it must work on in any thread.

Example #1:

#include <iostream>
#include <windows.h>
#include <winnt.h>
#include <intrin.h>

inline size_t get_thread_top_stack_size()
{
    NT_TIB *s = (NT_TIB*)getTib();
    return (size_t)s->StackBase ;
}

int global_var;

int main () 
{
    size_t sp_value = 0; 
    _asm { mov [sp_value], esp } 
    size_t thread_top_stack = get_thread_top_stack_size();

    int my_local_var;
    size_t my_local_var_addr = (size_t)&my_local_var;
    if (my_local_var_addr  < thread_top_stack && my_local_var_addr > sp_value  ) {
        std::cout << "Yes, on the thread stack";
    } else {
        std::cout << "No, not on the thread stack";
    }

    size_t my_global_var_addr = (size_t)&global_var;
    if (my_global_var_addr < thread_top_stack && my_global_var_addr> sp_value  ) {
        std::cout << "Yes, on the thread stack";
    } else {
        std::cout << "No, not on the thread stack";
    }
    return 0;
}

Example #2:

#include <windows.h>
#include <winnt.h>
#include <intrin.h>

inline NT_TIB* getTib()
{
    return (NT_TIB*)__readfsdword( 0x18 );
}

inline bool is_var_on_the_thread_stack(void* ptr)
{
    NT_TIB *nt_tib = getTib();
    return (nt_tib->StackBase >= ptr) &&  (nt_tib->StackLimit <= ptr );
}

int my_global_var;

int main () 
{
    int my_thread_var;
    if (is_var_on_the_thread_stack(&my_thread_var)) {
        std::cout << "Yes, on the thread stack" << std::endl;
    } else {
        std::cout << "No, not on the thread stack" << std::endl;
    }
    if (is_var_on_the_thread_stack(&my_global_var)) {
        std::cout << "Yes, on the thread stack" << std::endl;
    } else {
        std::cout << "No, not on the thread stack" << std::endl;
    }
    return 0;
}

Answer 3

from your comment B() called from A(), can't you just pass an argument to B() and set it to a specific value when called from A() ?? (with a default argument value, that would not require a big change)

your sample is not very complete, so here is another attempt making A LOT of assumptions about your problem... what about:

void A()
{
    B_lockfree();
}

void B()
{
    // acquire a lock here
    B_lockfree();
    // release your lock here
}

void B_lockfree()
{
    // do whatever you want here
}

(well, i can think of a lot of ways, but without knowing the big picture, they may all be completely wrong...)