Dear maintainer,
I tried to debug this a bit with
$ strace -f darktable-cltest -d opencl
and found that the reason is that the library "libnvidia-nvvm.so.4" was
not found for the compilation. Darktable searches
/usr/lib/x86_64-linux-gnu/glibc-hwcaps/x86-64-v3/libnvidia-nvvm.so.4
/usr/lib/x86_64-linux-gnu/glibc-hwcaps/x86-64-v2/libnvidia-nvvm.so.4
/usr/lib/x86_64-linux-gnu/tls/haswell/x86_64/libnvidia-nvvm.so.4
/usr/lib/x86_64-linux-gnu/tls/haswell/libnvidia-nvvm.so.4
/usr/lib/x86_64-linux-gnu/tls/x86_64/libnvidia-nvvm.so.4
/usr/lib/x86_64-linux-gnu/tls/libnvidia-nvvm.so.4
/usr/lib/x86_64-linux-gnu/haswell/x86_64/libnvidia-nvvm.so.4
/usr/lib/x86_64-linux-gnu/haswell/libnvidia-nvvm.so.4
/usr/lib/x86_64-linux-gnu/x86_64/libnvidia-nvvm.so.4
/usr/lib/x86_64-linux-gnu/libnvidia-nvvm.so.4
/usr/lib/x86_64-linux-gnu/libnvidia-nvvm.so.525.85.12
(and also on more places outside of /usr/lib/x86_64-linux-gnu/).
The installed driver libnvidia-nvvm4 however puts them under
/usr/lib/x86_64-linux-gnu/nvidia/current/libnvidia-nvvm.so.4
/usr/lib/x86_64-linux-gnu/nvidia/current/libnvidia-nvvm.so.525.85.12
which is *not* searched. Pragmatically creating a symlink
libnvidia-nvvm.so.4 -> nvidia/current/libnvidia-nvvm.so.4
in /usr/lib/x86_64-linux-gnu/ resolves this; the darktable-cltest
succeeds and darktable runs with OpenCL support.
I have no idea whether this syslink was forgotten in the libnvidia-nvvm4
package or darktable should be adjusted to search in the new places.
However, with this hint the problem should be resolvable in one of the
packages.
Cheers
Ole
