Re: [boost] Regressions in your Boost libraries as of 2005-07-19

From: John Maddock (john_at_[hidden])
Date: 2005-07-22 04:45:24

> The problem only shows up on my dual-processor G5, and never seemed to
> happen on single-processor systems, so we have some kind of race
> condition. Looking more carefully at the Spirit source, I see this:
>
> #ifdef BOOST_SPIRIT_THREADSAFE
>                 static boost::mutex mutex;
>                 boost::mutex::scoped_lock lock(mutex);
> #endif
>
> I don't think that's valid, because two threads could try to initialize
> the static at the same time. We'd need to do some other kind of locking
> in here, then create the mutex on the heap.

Right that code absolutely will create a race condition in the mutex 
initialisation.

If it helps any regex has a static_mutex class that is initialised with a 
static initialiser list (so no race condition), I've been meaning to polish 
this off as a formal submission, but in the mean time the code is here: 
boost/regex/pending/static_mutex.hpp.

John.