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From: Stefan Seefeld (seefeld_at_[hidden])
Date: 2004-04-01 13:58:48

hi there,

we'v run into a problem with the boost_thread mutex class,
when used as a global object.

Imagine a singleton class as

class Singleton
    static Singleton *GetInstance();
    static void Destroy();

    struct Guard
      ~Guard() { Singleton::Destroy();}
    static Singleton *instance;
    static Guard guard;
    static boost::mutex mutex;

where the internal access to 'instance' is serialized by means of the
mutex (inside methods GetInstance() and Destroy()).

It is the Singleton::Guard destructor that is responsible to free
the instance (if it isn't destructed already). It, too, uses the
mutex to protect access.

In a specific context on windows xp it happened that the mutex
variable was destructed before the guard, leading to a global
application lock-up when the Singleton::Destroy() (called from
the guard destructor) attempts to aquire the lock.
Is there a way around this dilemma ?
During debugging I set the 'm_mutex' member of the mutex class
(which is a CRITICAL_SECTION) to zero right after deletion, which
worked, i.e. there was no lock-up. I'm not sure though that this
is the correct thing to do.

Any suggestions ?


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