Thread Specific Data vs Thread Local Storage

Question

I\'ve read Kerrisk\'s The Linux Programming Interface: A Linux and UNIX System Programming Handbook, Chapter 31 on Threads. The chapter include Thread Specific Data (Section

Answer 1

The pthread interfaces are POSIX standard, so they are more portable. Use them if you intend to use the code on something besides a linux system. On the other hand, if you are strictly on gcc/linux, then the __thread mechanism is certainly easier to use. Just be aware that it is a gcc specific extension, and not supported on all platforms.

Answer 2

The pthread_key_create and friends are much older, and thus supported on more systems.

The __thread is a relative newcomer, is generally much more convenient to use, and (according to Wikipedia) is supported on most POSIX systems that still matter: Solaris Studio C/C++, IBM XL C/C++, GNU C, Clang and Intel C++ Compiler (Linux systems).

The __thread also has a significant advantage that it is usable from signal handlers (with the exception of using __thread from dlopened shared library, see this bug), because its use does not involve malloc (with the same exception).