[openib-general] makiing ibverb.h transport neutral -- 2nd draft

[Caitlin Bestler]

> 
> I don't have an issue with how post_send/post_recv would 
> work; just pointing out that type checking is lost, which can 
> lead to accessing invalid memory. 
>   For example, an application cannot just define struct 
> rdma_wc and then call rdma_poll_cq() and have it work.  This 
> would result in stack corruption, yet matches the defined API.
> 
> - Sean
> 

So would you favor changing the signature to match the largest
size, with  comment to the effect that you *could* use a cast
and a smaller object but only if you are sure.

I can see the danger of someone just using 'rdma_wc', so flipping
the naming convention would definitely make sense.

As to the size. Is there a size smaller than 256 that crosses
over into a significantly safer stack allocation but is still
*very* safe in terms of 'sure to be big enough'? Keep in mind
that 'struct sockaddr' has problems precisely because 'biggest
possible address' turned out to be too small.