On Mar 13, 2014, at 4:08 PM, Jeff Hammond <[email protected]> wrote:

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It was not disallowed in MPI-2. I meant that we made a mistake in MPI-3 to disallow it since that is not backward compatible.

You told me two days ago it was at best undefined, which is no more useful than disallowed:

I’m not sure what you are referring to, but that was no my intention. Perhaps I misunderstood what you were asking. It think it’s pretty clear that it’s disallowed in MPI-3, not undefined.

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IMO, we should have kept the same semantics as MPI-2, but allowed the user to relax it with info arguments.

Well we broke backwards compatibility but made it almost impossible for anyone to notice and certainly didn't add an advice to users so we are clearly all jerks.

I like MPI-2’s approach. The data content is undefined, but not an error. — Pavan