Suddenly getting maxrregcount warnings and undefined reference errors when linking - c++

Question

I maintain the C+=-flavored CUDA API wrappers library. The library's current commit is relatively-well-tested, with some example programs and quite a few users. However, sometime very recently (can't say exactly when), and without committing anything new, I now get NVCC warnings during the "dlink" phase of my example programs, e.g.:
/path/to/nvcc /path/to/cuda-api-wrappers/examples/modified_cuda_samples/vectorAdd/vectorAdd.cu -dc -o /path/to/cuda-api-wrappers/CMakeFiles/vectorAdd.dir/examples/modified_cuda_samples/vectorAdd/./vectorAdd_generated_vectorAdd.cu.o -ccbin /opt/gcc-5.4.0/bin/gcc -m64 -gencode arch=compute_52,code=compute_52 --std=c++11 -Xcompiler -Wall -O3 -DNDEBUG -DNVCC -I/path/to/cuda/include -I/path/to/cuda-api-wrappers/src
/path/to/nvcc -gencode arch=compute_52,code=compute_52 --std=c++11 -Xcompiler -Wall -O3 -DNDEBUG -m64 -ccbin /opt/gcc-5.4.0/bin/gcc -dlink /export/path/to/cuda-api-wrappers/CMakeFiles/vectorAdd.dir/examples/modified_cuda_samples/vectorAdd/./vectorAdd_generated_vectorAdd.cu.o /path/to/cuda/lib64/libcublas_device.a -o /export/path/to/cuda-api-wrappers/CMakeFiles/vectorAdd.dir/./vectorAdd_intermediate_link.o
#O#ptxas info : 'device-function-maxrregcount' is a BETA feature
#O#ptxas info : 'device-function-maxrregcount' is a BETA feature
#O#ptxas info : 'device-function-maxrregcount' is a BETA feature
... this repeats many times ...
but the dlink face does conclude. This is already strange, since I haven't explicitly used any beta features.
/opt/gcc-5.4.0/bin/g++ -Wall -Wpedantic -O2 -DNDEBUG -L/path/to/cuda/lib64 -rdynamic CMakeFiles/vectorAdd.dir/examples/modified_cuda_samples/vectorAdd/vectorAdd_generated_vectorAdd.cu.o CMakeFiles/vectorAdd.dir/vectorAdd_intermediate_link.o -o examples/bin/vectorAdd lib/libcuda-api-wrappers.a -Wl,-Bstatic -lcudart_static -Wl,-Bdynamic -lpthread -ldl -lrt -lnvToolsExt -Wl,-Bstatic -lcudadevrt -Wl,-Bdynamic
CMakeFiles/vectorAdd.dir/vectorAdd_intermediate_link.o: In function `__cudaRegisterLinkedBinary_25_cublas_compute_70_cpp1_ii_f0559976':
link.stub:(.text+0xe0): undefined reference to `__fatbinwrap_25_cublas_compute_70_cpp1_ii_f0559976'
CMakeFiles/vectorAdd.dir/vectorAdd_intermediate_link.o: In function `__cudaRegisterLinkedBinary_25_xerbla_compute_70_cpp1_ii_cd7f3ad3':
link.stub:(.text+0x190): undefined reference to `__fatbinwrap_25_xerbla_compute_70_cpp1_ii_cd7f3ad3'
CMakeFiles/vectorAdd.dir/vectorAdd_intermediate_link.o: In function `__cudaRegisterLinkedBinary_23_nrm2_compute_70_cpp1_ii_8edbce95':
link.stub:(.text+0x240): undefined reference to `__fatbinwrap_23_nrm2_compute_70_cpp1_ii_8edbce95'
... more udnefined reference errors here ...
My question: Why would this happen and how do I circumvent/avoid/resolve it?
Notes:
I'm using separable compilation
I'm getting these specific errors with CUDA 9.1 and a SM 5.2 device (no 7.0).
The CMakeLists.txt is here.
I'm obviously clearing CMakeCache.txt before building.
This has happened to me both on a GNU/Linux Mint 18.3 and Fedora 26. On the first machine there have been some apt-get dist-upgrade's done, and now GCC is up to version 5.5.0, in case that matters. On the second machine - there really has been no change that I'm aware of; same compiler and CUDA version.

Answer 1

A partial answer / workaround:
This issue only seems to occur when libcublas is involved. If I remove /path/to/cuda/lib64/libcublas_device.a from the -dlink phase command-line, all warnings and errors go away (including from later stages). And in fact, my wrapper library is oblivious of cublas, not sure why CMake is adding it; it's not in $CUDA_LIBRARIES. See also:
Why does CMake force the use of libcublas with separable compilation?