Re: [Boost-users] [interprocess] Segment existance check

From: Ion Gaztañaga (igaztanaga_at_[hidden])
Date: 2006-10-17 01:04:03

Hi,

> I don't know if I'm just missing it or if this feature doesn't exist, but is
> there a feature in interprocess to check that a segment exists prior to
> attempting to find or construct a variable in that segment? If it doesn't
> exist this would be an extremely useful feature so that when an application
> goes to create an object in shared memory where the shared memory segment
> has not been created the program doesn't just segfault but gives the
> application at least a small chance of exiting gracefully (i.e. a thrown
> exception).

If you hold a reference to a managed_shared_memory the segment always 
exists, since in Interprocess, the processes is detached from the 
segment in the destructor of the managed_shared_memory. This is 
different from Shmem, where you could call "close()". No other processes 
can destroy the segment while you have a opened/created 
managed_shared_memory. At best, in UNIX, it will unlink it, so new 
processes won't be able to find it, but old processes attached to the 
segment will continue working fine.

I don't know if I have responded correctly to your question, so could 
you show me an example of what do you want to achieve?

Regards,

Ion