Warnings squash for icx compiler

[abrooks98]

Pull Request Description

Starting with oneAPI version 2022.0.1, new warnings are showing up when using icx, for which this PR addresses:

adio/common/p2p_aggregation.c:150:9: warning: variable 'totalAmountDataReceived' set but not used [-Wunused-but-set-variable]
    int totalAmountDataReceived = 0;
        ^

mpiexec/pmiserv_utils.c:252:22: warning: variable 'total_filler_processes' set but not used [-Wunused-but-set-variable]
    int proxy_count, total_filler_processes, total_core_count;
                     ^

src/mpi/datatype/datatype_impl.c:27:46: warning: performing pointer subtraction with a null pointer has undefined behavior [-Wnull-pointer-subtraction]
    *address = (MPI_Aint) ((char *) location - (char *) MPI_BOTTOM);
                                             ^ ~~~~~~~~~~~~~~~~~~~

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[abrooks98]

@hzhou there is an additional warning showing up for which I am unsure how to address:

src/mpi/datatype/datatype_impl.c:27:46: warning: performing pointer subtraction with a null pointer has undefined behavior [-Wnull-pointer-subtraction]
    *address = (MPI_Aint) ((char *) location - (char *) MPI_BOTTOM);
                                             ^ ~~~~~~~~~~~~~~~~~~~

Based on the comments to the corresponding code, the intention is to subtract a null pointer from location, which this warning is complaining about.

[hzhou]

@hzhou there is an additional warning showing up for which I am unsure how to address:

src/mpi/datatype/datatype_impl.c:27:46: warning: performing pointer subtraction with a null pointer has undefined behavior [-Wnull-pointer-subtraction]
    *address = (MPI_Aint) ((char *) location - (char *) MPI_BOTTOM);
                                             ^ ~~~~~~~~~~~~~~~~~~~

Based on the comments to the corresponding code, the intention is to subtract a null pointer from location, which this warning is complaining about.

This is strictly standard-compliant and we are as explicit in our intention with the cast as we can. So IMO it's the compiler's fault to warn about. You can try the direct casting branch to see if the compiler like it better.

[abrooks98]

This is strictly standard-compliant and we are as explicit in our intention with the cast as we can. So IMO it's the compiler's fault to warn about. You can try the direct casting branch to see if the compiler like it better.

Taking the direct casting branch for icx seems to resolve the warning on our side. I've added a commit for this, but let me know if you had something else in mind regarding how to do this. I'll also reach out to someone on the compiler team to discuss standard compliance regarding this warning