CUDA version X complains about not supporting gcc version Y - what to do?

Question

_{The question is about a specific combination of versions but is relevant more generally.}

I've just dist-upgraded from Kubuntu 12.04 to 14.04. Now, when I want to compile CUDA code (with CUDA 6.5), I get:

#error -- unsupported GNU version! gcc 4.9 and up are not supported!

I installed gcc-4.8 (and 4.7), and tried to use the symlinks-in-/usr/local/cuda/bin solution suggested here:

CUDA incompatible with my gcc version

but this doesn't work. What should I do?

Answer 1

_{This solution is relevant to multiple combinations of CUDA and GCC versions.}

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You can tell CUDA's nvcc to use a specific version of gcc. So, suppose you want gcc 4.7 for use with CUDA 6. You run:

sudo apt-get install gcc-4.7 g++-4.7

and then add the following switch to your nvcc command-line:

nvcc --compiler-bindir /usr/bin/gcc-4.7  # rest of the command line here

If you're building with CMake, add an appropriate setting before looking for CUDA to your CMakeLists.txt, e.g.:

set(CUDA_HOST_COMPILER /usr/bin/gcc-4.7)  # -> ADD THIS LINE <-
find_package(CUDA)

Also, it seems clang can compile CUDA as well, maybe that's worth experimenting with (although you would have to build it appropriately).

Note: Some Linux (or other OS) distributions don't have packages for multiple versions of gcc (in the same release of the OS distribution). I would advise against trying to install a package from another release of the distribution on an older release, and consider building gcc instead. That's not entirely trivial but it is quite doable - and of course, it's your only option if you don't have root access to your machine.