Subj : Re: double-checked locking in C
To   : comp.programming.threads
From : Joe Seigh
Date : Thu Jul 07 2005 02:15 pm

Alexander Terekhov wrote:
> Joe Seigh wrote:
> [...]
> 
>>memcpy() of a static pthread_once_t initialized with PTHREAD_ONCE_INIT
>>for pthread_once_init().  
> 
> 
> Undefined behavior (as soon as you call pthread_once() on a "cloned" 
> thing). Because pthread_once_t is noncopyable, just like any other 
> synchronization objects.
> 
> "The behavior of pthread_once() is undefined if once_control has 
>  automatic storage duration or is not initialized by 
>  PTHREAD_ONCE_INIT."
> 
So what kind of value could PTHREAD_ONCE_INIT have that couldn't be
memcpy'd from an initialized pthread_once_t object never otherwise
used?

> 
>>I don't even know what pthread_once_reset() even means.
> 
> 
> Effect is the same as pthread_once_destroy()+pthread_once_init()
> (with pthread_once_destroy() invoking optional destructor function)
> except that it is throw()-nothing operation (vs pthread_once_init() 
> that can throw).
> 
If C had exceptions.


-- 
Joe Seigh

When you get lemons, you make lemonade.
When you get hardware, you make software.

.