Issue with overlapping vector datatype

[bosilca]

As reported by the DKRZ folks, creating a datatype with overlapping capabilities (legal for all send communications) leads to data corruption, as the packing and unpacking function will fail to compute the correct memory layout.

A simple example of such datatype is:

MPI_Type_vector(3, 1, 0, MPI_INT, &btypes[0]);
MPI_Type_indexed(1, (int[]){1}, (int[]){0}, MPI_INT, &btypes[1]);

MPI_Type_create_struct(2, (int[]){1,1}, (MPI_Aint[]){0,12}, btypes, &dt);

All Open MPI versions are affected. However, it has been decided during the weekly call to only fix it in every release after 3.0 and obviously master.

[gpaulsen]

George has a patch that's coming.

[jsquyres]

Discussed on 2018-09-11 webex; @bosilca mentioned that he has a patch but he hasn't tested it properly with all the other datatype tests. Stay tuned.

[gpaulsen]

Discussed at the RM meeting today, and will bring up again on tomorrow's Web-ex.