Re: Thread safe, thread-local variable

(please ignore previous post).

I am writing a class which is an analytic engine that traverses a MxN
matrix space and makes calculations at each point in the matrix. The
calculations involve calling "exposed" functions via callbacks.

In a nutshell, I need to be able to pass the current position in the grid
to the callback function, so I have somehing like this:

//'global' vars
namespace
{
    Point mypoint ;
}

class MyEngine
{
public:
    void WriteCurrentPointValue();
    //...
};

//"registered" functions
int foo()
{
   Point point = ReadCurrentPointValue();
   return DoSomething(point);
}

However, this soln is not thread safe in that if I have multiple instances
of the engine running in different threads, all bets are off. My question
is this:

How can I provide threadsafe, threadlocal 'global' variable for use as
discussed above?