AMDG Fabien Niñoles <fabien.ninoles <at> gmail.com> writes:
You're perfectly right on this issue: only the second_lock is necessary, and pInstance must also be volatile (I never write such code myself, I always used Loki implementation when I need a singleton). As for instanciation, the standard ensure that a local static variable will only be initialized once, before entrance to the block scope. How this is handled in multi-thread program? I guess it's depend on your threaded platform. As for where the mutexes is defined... Well, that's also depends on the class policy (and what's the mutex implementation permits).
The zero-initialization (8.5) of all local objects with static storage duration (3.7.1) is performed before any other initialization takes place. (6.7/4) A mutex is overkill. In this case a volatile class static with a trivial constructor and a volatile boolean flag is enough. In Christ, Steven Watanabe