NVHPC (NVIDIA) cannot build `select rank`

[marshallward]

Describe the bug
nvfortran does not yet support the select rank block, so we cannot build the latest FMS. It reports a syntax error.

mpifort -DPACKAGE_NAME=\"FMS\" -DPACKAGE_TARNAME=\"fms\" -DPACKAGE_VERSION=\"\ \" -DPACKAGE_STRING=\"FMS\ \ \" -DPACKAGE_BUGREPORT=\"https://github.com/NOAA-GFDL/FMS/issues\" -DPACKAGE_URL=\"\" -DHAVE_MPI=1 -DHAVE_SCHED_GETAFFINITY=1 -DHAVE_MPI=1 -Duse_libMPI=1 -DSTDC_HEADERS=1 -DHAVE_SYS_TYPES_H=1 -DHAVE_SYS_STAT_H=1 -DHAVE_STDLIB_H=1 -DHAVE_STRING_H=1 -DHAVE_MEMORY_H=1 -DHAVE_STRINGS_H=1 -DHAVE_INTTYPES_H=1 -DHAVE_STDINT_H=1 -DHAVE_UNISTD_H=1 -DHAVE_NETCDF_H=1 -Duse_netCDF=1 -I/scratch/cimes/mw0089/include -I/scratch/cimes/mw0089//include -r8   -I../src/include -I../src/mpp/include -c ../src/mpp/mpp_domains.F90
NVFORTRAN-S-0034-Syntax error at or near identifier rank (../src/mpp/include/mpp_pack.fh: 56)
NVFORTRAN-S-0034-Syntax error at or near end of line (../src/mpp/include/mpp_pack.fh: 57)
NVFORTRAN-S-0034-Syntax error at or near end of line (../src/mpp/include/mpp_pack.fh: 59)
NVFORTRAN-S-0034-Syntax error at or near end of line (../src/mpp/include/mpp_pack.fh: 61)
NVFORTRAN-S-0034-Syntax error at or near end of line (../src/mpp/include/mpp_pack.fh: 63)
  0 inform,   0 warnings,   5 severes, 0 fatal for arr2vec_r8

(&c...)

To Reproduce
Build main (or at least 377b5e8) with any newer nvfortran compiler.

Expected behavior
It should build.

System Environment
Describe the system environment, include:

• OS:

  $ uname -a
  Linux stellar-amd.princeton.edu 4.18.0-553.117.1.el8_10.x86_64 #1 SMP Fri Mar 27 18:49:45 EDT 2026 x86_64 x86_64 x86_64 GNU/Linux
  

• Compiler(s): Type and version [e.g. Intel 19.1]

   $ nvfortran --version
  
   nvfortran 26.1-0 64-bit target on x86-64 Linux -tp znver2 
  

• MPI type, and version (e.g. MPICH, Cray MPI, openMPI)

  $ mpirun --version
  mpirun (Open MPI) 4.1.9a1
  

• netCDF Version: For both C and Fortran

  $ nc-config --version
  netCDF 4.9.2
  $ nf-config --version
  netCDF-Fortran 4.6.1
  

• Configure options: Any additional flags, or macros passed to configure

  See above

Additional context
I didn't test older compiler versions.

[rem1776]

@marshallward I can work on a fix for this, I think we should be able to get around it by using the built in rank() function and a select case.

[marshallward]

Thank you @rem1776, we were hopeful that this might work as a solution. Let me know if you need us to do additional testing.