Re: [boost] Which libs need multithreading?

From: John Maddock (john_at_[hidden])
Date: 2005-08-12 05:06:30

> If serialization depends upon BOOST_HAS_THREADS its totally unintentional 
> on my part.   I don't know where such a dependency would come from unless 
> its shared_ptr which I only recently started to depend upon.  I would like 
> to see more information on this topic.

I just did a quick search for BOOST_HAS_THREADS: shared_count_132.hpp 
changes the ABI of sp_counted_base depending on whether it's defined or not. 
Whether that's an issue in practice I can't say, it depends on how that 
class is used.

As for shared_ptr, it would indeed be useful to have more information, for 
example can I link a multithreaded lib that contains an API returning 
shared_ptr<foo> to a single threaded app?  Looking at the source, it appears 
that for most platforms the answer is "yes": as long as shared_ptr 
recognises the platform and can use atomic increment/decrement operations, 
then those operations will always be used (and the internal ABI's remain 
unchanged as well).  However it looks like there may be some platforms that 
rely on BOOST_HAS_THREADS / BOOST_HAS_PTHREADS, and I'm guessing that their 
ABI's will change.  I'm not sure that this is the definitive answer 
though...

John.