FYI on some changes that may be needed for gfortran version 10

[billsacks]

I inadvertently updated to gfortran version 10 on my Mac and ran into some build issues. I spent some time figuring out how to resolve them, so thought I'd share that knowledge in case others run into similar issues. I'm opening an issue for this just as somewhere to record this, but I guess I'll just close it immediately, because I don't think anything needs to be done right now.

I ran into two issues:

(1) I got a weird compilation error in some share code indicating a type mismatch between the actual argument to one mpi_bcast call and the actual argument to a different mpi_bcast call in that same module. I found similar issues from some google searches (Unidata/netcdf-fortran#212, GlobalArrays/ga#157, https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91731), including a suggestion that this may be due to a problem in mpich (which is the mpi library I am using on my mac). The workaround is to add the compilation flag -fallow-argument-mismatch.

(2) When building a case that includes CTSM, I got an error about the non-standard use of a BOZ literal constant; I suspect this may appear in other components as well. See ESCOMP/CTSM#1270, with the fix here ESCOMP/CTSM#1271. Until that fix is in place in all components, a workaround is to add the flag -fallow-invalid-boz

[billsacks]

Closing this, since I only opened it for informational purposes.

[billsacks]

See also ESCOMP/CDEPS#38