Programming Windows®, Fifth Edition

Thread Local Storage

Global variables in a multithreaded program, as well as any allocated memory, are shared among all the threads in the program. Local static variables in a function are also shared among all threads using that function. Local automatic variables in a function are unique to each thread because they are stored on the stack and each thread has its own stack.

It might be necessary to have persistent storage that is unique to each thread. For example, the C strtok function I mentioned earlier in this chapter requires this type of storage. Unfortunately, the C language does not support such a variable. But Windows includes four functions that implement a mechanism to do it, and the Microsoft extensions to C also support it. As we’ve ...