Thread-Local Storage (TLS) is a class of static storage that, like the stack, is private to each thread of execution. Each thread in a process is given a location where it can store thread-specific data. Variables are allocated so that there is one instance of the variable for each existing thread.

Before each thread terminates, it releases its dynamic memory and any pointers to thread-local variables in that thread become invalid.

See __declspec(thread) in the Compiler Reference Guide.