Subj : Re: Can C++ local static objects be made thread safe?
To   : comp.programming.threads
From : Alexander Terekhov
Date : Tue Feb 15 2005 09:06 pm


David Schwartz wrote:
[...]
>     Another implementation does the magic in the page mapping. Each thread
> gets the same address for the thread local variable, but a different page is
> mapped into that address in each thread.

That would preclude sharing and brake POSIX and C/C++ process/
program object model with shareable objects and unique per-object 
addresses (within a process). 

__thread storage duration is nothing but syntactical sugar for 
accesses via pthread_getspecific() with "statically intialized" keys 
and (GCC aside for a moment) object ctors and dtors thrown into the 
mix. 

The mappings (key/value bindings) can be held in per-thread "MMU 
state" (see POSIX Rationale), but associated objects must have
unique addresses within a process and must be accessible from 
other threads.

Otherwise it's totally brain-dead.

regards,
alexander.

.