MPI_UNPACK bug

[jsquyres]

There is a bug in MPI_UNPACK that is causing many MTT tests to fail. The bug appears to be on v2.0.x and v2.x, but not master.

#3060 (v2.1.x) and #3061 (v2.0.x) have been proposed to fix the issue. @ggouaillardet seems to think that there should be a different fix.

Filing this issue to track the problem.

@hppritcha v2.1.0 or v2.1.1? Tentatively marked as v2.1.0 because it's causing a lot of MTT failures, and the fix appears straightforward / isolated / low risk.

[hppritcha]

I think this is a reasonable fix to go into a 2.1.0rc2 tarball.

[hppritcha]

Why are we just now detecting this in MTT?

[jsquyres]

I don't have a good answer, other than: perhaps we weren't looking at MTT close enough...?

[jsquyres]

This is now closed; MTT shows all these issues are fixed.