Re: [boost] singleton and thread safety

From: Alexander Terekhov (terekhov_at_[hidden])
Date: 2005-08-03 05:45:05

Jonathan Wakely wrote:
> 
> Jonathan Turkanis wrote:
> 
> > Pavel Vozenilek wrote:
> > > "Jason Hise" wrote:
> > >
> > >>> http://www.boost.org/doc/html/call_once.html?
> > >>>
> > >> Why does it require that the function which is called once not be
> > >> allowed to throw?  I am not sure that I can meet this requirement,
> > >> as I may need to dynamically allocate memory.
> > >>
> > > Possibly because of internal implementation.
> >
> > I think it's a pthreads requirement.
> 
> Pthreads knows nothing about exceptions, 

That's not true.

http://www.opengroup.org/onlinepubs/009695399/functions/pthread_once.html

"The pthread_once() function is not a cancellation point. However, if 
 init_routine is a cancellation point and is canceled, the effect on 
 once_control shall be as if pthread_once() was never called."

http://www.opengroup.org/onlinepubs/009695399/functions/pthread_cleanup_push.html

"Note that the specified cleanup handling mechanism is especially tied 
 to the C language and, while the requirement for a uniform mechanism 
 for expressing cleanup is language-independent, the mechanism used in 
 other languages may be quite different. In addition, this mechanism 
 is really only necessary due to the lack of a real exception 
 mechanism in the C language, which would be the ideal solution."

http://www.opengroup.org/onlinepubs/009695399/xrat/xsh_chap02.html#tag_03_02_09_20

"...it is an explicit goal of IEEE Std 1003.1-2001 to be compatible 
 with existing exception facilities and languages having exceptions."

regards,
alexander.

P.S. http://groups.google.de/group/comp.std.c++/msg/20a156f0b068c9e1