Re: [Boost-users] [interprocess]

From: Ion Gaztañaga (igaztanaga_at_[hidden])
Date: 2007-06-03 04:28:42

Aaron W. LaFramboise wrote:
  > In a multi-segment implementation, would an object like a vector be 
able
> to span multiple segments?  I think not, but I'm not sure.

No, because the memory must be contiguous. But other structures like 
deque/map-set/list could be implemented.

> If general growing of managed segments is too hard, maybe an easier 
> problem could be solved, like making shared memory containers that have 
> special support for growing.

I think you reach the same problem. You need to allocate more pages from 
the OS and map them atomically in every process sharing those pages.

> I agree with you about O_CREAT.  But what about on Windows, with 
> CreateFileMapping?   "If the object exists before the function call, the 
> function returns a handle to the existing object (with its current size, 
> not the specified size), and GetLastError returns ERROR_ALREADY_EXISTS."
> 
> It seems the API has a little bit of a POSIX bias. :)

It's not that I like POSIX, it's just it was easier to emulate POSIX for 
Windows than doing the inverse. Shmem had a Windows approach but shared 
memory lifetime was a real issue, so I changed to a POSIX-like approach. 
I've tried to be portable, but maybe I should add extensions for systems 
where the programmer can get more information.

Thanks for your comments,

Ion