Fred Bertsch <fred.bertsch@gmail.com> writes:
This is a fairly minor point, in my opinion, and I don't think I can say which way is better for shmem, but I'll try to explain it a bit better.
For example, named_shared_object can only be created through its default constructor. Once created this way, you probably can't actually use your named_shared_object. Instead, you can complete the construction of the object by using open, create, or one of the other methods that "construct" the object. An error is indicated by the return value of these member functions. I don't actually know the name of this technique, and I suspect my point would be clearer if I knew its name.
If I'm understanding you correctly, that's known as "two-phase construction" and it's generally a very bad idea, because it weakens the class invariants and -- consequently -- the assumptions that code can make about the object's state. It oftne means that the class has a special "zombie" state that you always have to check for before operating on it. The opposite of this technique is RAII.
The alternative technique is to have several constructors or static member functions in named_shared_object. These would create an opened or created named_shared_object if nothing bad happened, and they would throw an exception if an error came up.
I mostly brought this up because few things in boost use the first technique, so someone might have a strong opinion about it.
I'm surprised this hasn't drawn more fire. I'll be happy to condemn it -- even before I've seen the details of the code -- and risk that I've completely misinterpreted this in which case I'll have to apologize. -- Dave Abrahams Boost Consulting www.boost-consulting.com