Subj : Re: Can C++ local static objects be made thread safe?
To   : comp.programming.threads
From : SenderX
Date : Thu Jan 20 2005 12:48 pm

> #define MTSafeStatic( Type, Name, Initializer )         \
>     static Type * volatile x_ ## Name;                   \
>                                                          \
>     if ( ! x_ ## Name )                                  \
>     {                                                    \
>         Lock<Mutex>     l_lock( StaticInitializerMutex );\
>                                                          \
>         if ( ! x_ ## Name )                              \
>         {                                                \
>             static Type v_ ## Name Initializer;          \
>                                                          \
>             x_ ## Name = & v_ ## Name ;                  \
>         }                                                \
>     }                                                    \
>                                                          \
>     Type & Name = * x_ ## Name;                          \

Your totally breaking the producer/consumer relationship wrt memory 
visibility.




1:  static T volatile *shared = 0;

2:  T *local = shared;
3:  ac_cpu_mb_consumer_depends(); /* Sync with 10 */
4:  if ( ! local )
5:  {  ac_mutex_lock( &static_mutex );
6:     local = shared;
7:     ac_cpu_mb_consumer_depends(); /* Sync with 10 */
8:     if ( ! local )
9:     {  local = new T;
10:       ac_cpu_mb_producer(); /* Sync with 3 & 7 */
11:       shared = local; /* Make visible to 4 & 8 after sync */
12:    }
13:    ac_mutex_unlock( &static_mutex );
14: }
15: return local;


This must be compiled so the code sequence is executed in the "exact" order 
shown! All calls prefixed with 'ac_' are from my library.

.