Adjoint Smooth Sensitivities fails under WM_LABEL_SIZE=64

Summary

Running the tutorial: $FOAM_TUTORIALS/incompressible/adjointOptimisationFoam/sensitivityMaps/motorBike

With OpenFOAM compiled with label size 64 (instead of the default 32) leads to an MPI error.

The only modification to the tutorial is running in 2 processors rather than 20.

Steps to reproduce

Using OpenFOAM compiled with label size 64 (export WM_LABEL_SIZE=64), run the following tutorial: $FOAM_TUTORIALS/incompressible/adjointOptimisationFoam/sensitivityMaps/motorBike

I used only a 2 processor hierarchical decomposition:

numberOfSubdomains 2;
method          hierarchical;
coeffs
{
    n           (2 1 1);
}

What is the current bug behaviour?

MPI Error. The job does not finish.

What is the expected correct behavior?

Successful job with 64 label size

Relevant logs and/or images

I have attached the full log file: log.adjointOptimisationFoam

Environment information

• OpenFOAM version : v2112
• Operating system : centos 8
• Compiler : gcc 8.4.0

Possible fixes

The issue is somehow related to the inter-processor communication happening in the processorFaPatch.C

By changing the sender call

void Foam::processorFaPatch::initGeometry()
{
    if (Pstream::parRun())
    {
        OPstream toNeighbProc
        (
            Pstream::commsTypes::blocking,
            neighbProcNo() // ,
            // 3*(sizeof(label) + size()*sizeof(vector))  <- Use automatically computed message size
        );
    ...
    ...
}

And changing the recipient call

void Foam::processorFaPatch::calcGeometry()
{
    if (Pstream::parRun())
    {
        {
            IPstream fromNeighbProc
            (
                Pstream::commsTypes::blocking,
                neighbProcNo() //,
                // 3*(sizeof(label) + size()*sizeof(vector)) <- Use automatically computed message size
            );
    ...
    ...
}

Appears to fix the issue. However I think this is only hiding the issue.