[Boost-users] Threading a Shared Model with pointers

Subject: [Boost-users] Threading a Shared Model with pointers
From: pcunite_at_[hidden]
Date: 2011-03-04 18:40:00

Threading a Shared Model with pointers

I have a vector of pointers to objects created with new. Multiple threads access this vector in a safe manner with get/set. However, a thread may delete one of the objects, in which case another thread's pointer to the object is no longer valid. How can a method know if the pointer is valid? I have to examples that work and would like your thoughts.

Test for pointer validity:

1.
Use integers instead of pointers. A hash (std::map) checks to see if the pointer is still valid. Public methods look like get(size_t iKey), etc.
Insde the method it does:
if((it = mMap.find(iKey)) != mMap.end())
{
    TMyType * pMyType = it->second;
    // do something with know good pointer.
}

2.
Have a vector of shared_ptr. Each thread tries to call lock() on its weak_ptr. If the returned shared_ptr is null we know someone deleted it while we were waiting. Public methods look like get(boost::weak_ptr<TMyType> pMyType), etc.
Insde the method it does:
boost::shared_ptr<TMyType> pGOOD = pMyType.lock();
if (pGOOD  == NULL)
{
    // null, bad pointer do something
    return;
} 

3.
Test for null on plain raw pointers? Is this possible? Public methods look like get(TMyType * pMyType), etc.

Option 1 and 2 actually seem to work well. I don't know how they will scale. What is the best approach? Is there a portable version 3?