My system is Kubuntu 20.04 (pre beta release) updated from Kubuntu 18.04.
I have gcc versions 7 and 9 installed (v10 was also originally installed but I uninstalled it).
If I compile Blender from master with CUDA binaries, it ends with an error related to “-- unsupported GNU version! gcc versions later than 8 are not supported!”. If I open CMakeCache.txt with cmake-gui, and I search for gcc, apparently it is trying to use gcc version 9. I replace 9 with 7 in all the related gcc, Configure, Generate and build, but the error of “-- unsupported GNU version! gcc versions later than 8 are not supported!” It is still happening.
Now, building without CUDA binaries for it to compile CUDA kernel dynamically… Opening blender and when rendering with GPU I get similar error related to gcc version not supported when it tries to compile CUDA kernel. So I run blender with:
CYCLES_CUDA_EXTRA_CFLAGS='-ccbin gcc-7' ./blender
This time Blender with GPU can dynamically compile the Kernel, and CUDA works when rendering with GPU only. But something strange happens, if I try to render with CPU+GPU, tiles corresponding to CPU are hung up and show only in black. If I press Esc key, GPU tile ends but CPU tiles are still hanging and black (Tasks manager shows CPU still in use) and I have to kill Blender process. Just mention that if I render on CPU only (not CPU+GPU) that problem does not occur, so GPU only and CPU only works correctly, but not CPU+GPU.
So, what would be the best solution for that gcc problem in my case? Is CPU+GPU problem also related to gcc version?
I tried with CUDA 10.1 from ubuntu repos and CUDA 10.2 from run file, the same problem with both
To test having only gcc7 installed on my system, I cannot do it because when trying to uninstall gcc9/g+±9 related packages from my system, it also tries to uninstall other fundamental packages from the distro.