__thread

Interesante, siempre me pregunté para que %$")%$"%/(&·)&·()%· servía eso de TLS. Matt Dillon lo sabe explicar de una manera bastante comprensible:

TLS stands for 'thread local storage'. It is a way of abstracting global variable declarations that you want to be 'per thread' storage rather then common storage.

so, e.g. in a threaded environment, if you declare a global variable:

int Fubar;

Then that global variable will represent the same storage across all threads.
But if you declare it:

__thread int Fubar;

Then each thread will be given *different* storage for Fubar.

This feature could be used by, well, just about every library. For example, it would allow us to clean up how 'errno' works in a threaded environment. It would allow standard libc calls such as ctime() and localtime() work properly in a threaded environment, and it would greatly simplify the job of writing threaded library code.