Link errors with crayclanggpu target on frontier

[philipwjones]

When trying to build omega for gpu on frontier, I get some link errors like:

ld.lld: error: undefined symbol: __cray_sset_detect

referenced by pio_rearrange.c
pio_rearrange.c.o:(define_iodesc_datatypes) in archive ../external/scorpio/src/clib/libpioc.a
referenced by pio_rearrange.c
pio_rearrange.c.o:(compute_counts) in archive ../external/scorpio/src/clib/libpioc.a
referenced by pio_rearrange.c
pio_rearrange.c.o:(compute_counts) in archive ../external/scorpio/src/clib/libpioc.a
referenced 45 more times
clang-15: error: linker command failed with exit code 1 (use -v to see invocation)

Poking around a bit online, it seems like people who see this with other libs seem to point to the cray wrappers (CC) as a potential source - is scorpio not being built with CC? The crayclang cpu option works fine. It only fails with a gpu build.

This was using omega_build.sh after the Cmake invocation:
cmake -DOMEGA_CIME_MACHINE=frontier -DOMEGA_CIME_COMPILER=crayclanggpu -DOMEGA_ARCH=HIP -DOMEGA_PARMETIS_ROOT=${PARMETIS_ROOT} -DOMEGA_BUILD_TEST=ON ..

[grnydawn]

@philipwjones , Scorpio is being built with CC cray compiler wrapper, but testDecomp.exe is compiled and linked with hipcc when OMEGA_ARCH is set to HIP.
I think what happened was that the hipcc just could not find the symbols of : __cray_sset_detect and __cray_dset_detect during linking testDecomp.exe because it is not a cray wrapper.

After some tries, I found that adding C language support in "$E3SM/compoinets/omega/CMakeLists.txt" fixed the issue in my test cases:

BEFORE:
project(${OMEGA_PROJECT_NAME}
LANGUAGES CXX
)
AFTER:
project(${OMEGA_PROJECT_NAME}
LANGUAGES C CXX
)

Adding C language support seems to configure several language-specific cmake-internal variables such as MPI flags, additional library for linking, etc. While it is not clear to me why the change fixed this issue, so far all the tests that I have done were passed on Frontier.

[philipwjones]

Interesting...thanks for tracking it down.