#error -- unsupported GNU version! gcc versions later than 6 are not supported!

[pgodwin]

Just a note for the docs, on Ubuntu 18 LTS I had to run the following:

sudo update-alternatives --install /usr/bin/g++ g++ /usr/bin/g++-6 10
sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-6 10

Otherwise I had the following errors running install.sh:

[  8%] Building NVCC (Device) object lib/THC/CMakeFiles/THC.dir/THC_generated_THCTensorCopy.cu.o
In file included from /usr/include/host_config.h:50:0,
                 from /usr/include/cuda_runtime.h:78,
                 from <command-line>:0:
/usr/include/crt/host_config.h:121:2: error: #error -- unsupported GNU version! gcc versions later than 6 are not supported!
 #error -- unsupported GNU version! gcc versions later than 6 are not supported!
  ^~~~~
In file included from /usr/include/host_config.h:50:0,
                 from /usr/include/cuda_runtime.h:78,
                 from <command-line>:0:
/usr/include/crt/host_config.h:121:2: error: #error -- unsupported GNU version! gcc versions later than 6 are not supported!
 #error -- unsupported GNU version! gcc versions later than 6 are not supported!
  ^~~~~
In file included from /usr/include/host_config.h:50:0,
                 from /usr/include/cuda_runtime.h:78,
                 from <command-line>:0:
/usr/include/crt/host_config.h:121:2: error: #error -- unsupported GNU version! gcc versions later than 6 are not supported!
 #error -- unsupported GNU version! gcc versions later than 6 are not supported!
  ^~~~~
In file included from /usr/include/host_config.h:50:0,
                 from /usr/include/cuda_runtime.h:78,
                 from <command-line>:0:
/usr/include/crt/host_config.h:121:2: error: #error -- unsupported GNU version! gcc versions later than 6 are not supported!
 #error -- unsupported GNU version! gcc versions later than 6 are not supported!
  ^~~~~
In file included from /usr/include/host_config.h:50:0,
                 from /usr/include/cuda_runtime.h:78,
                 from <command-line>:0:
/usr/include/crt/host_config.h:121:2: error: #error -- unsupported GNU version! gcc versions later than 6 are not supported!
 #error -- unsupported GNU version! gcc versions later than 6 are not supported!
  ^~~~~
In file included from /usr/include/host_config.h:50:0,
                 from /usr/include/cuda_runtime.h:78,
                 from <command-line>:0:
/usr/include/crt/host_config.h:121:2: error: #error -- unsupported GNU version! gcc versions later than 6 are not supported!
 #error -- unsupported GNU version! gcc versions later than 6 are not supported!
  ^~~~~
In file included from /usr/include/host_config.h:50:0,
                 from /usr/include/cuda_runtime.h:78,
                 from <command-line>:0:
/usr/include/crt/host_config.h:121:2: error: #error -- unsupported GNU version! gcc versions later than 6 are not supported!
 #error -- unsupported GNU version! gcc versions later than 6 are not supported!
  ^~~~~
In file included from /usr/include/host_config.h:50:0,
                 from /usr/include/cuda_runtime.h:78,
                 from <command-line>:0:
/usr/include/crt/host_config.h:121:2: error: #error -- unsupported GNU version! gcc versions later than 6 are not supported!
 #error -- unsupported GNU version! gcc versions later than 6 are not supported!
  ^~~~~
CMake Error at THC_generated_THCSleep.cu.o.cmake:207 (message):
  Error generating
  /home/pete/distro/extra/cutorch/build/lib/THC/CMakeFiles/THC.dir//./THC_generated_THCSleep.cu.o


lib/THC/CMakeFiles/THC.dir/build.make:77: recipe for target 'lib/THC/CMakeFiles/THC.dir/THC_generated_THCSleep.cu.o' failed
make[2]: *** [lib/THC/CMakeFiles/THC.dir/THC_generated_THCSleep.cu.o] Error 1
make[2]: *** Waiting for unfinished jobs....
CMake Error at THC_generated_THCBlas.cu.o.cmake:207 (message):
  Error generating
  /home/pete/distro/extra/cutorch/build/lib/THC/CMakeFiles/THC.dir//./THC_generated_THCBlas.cu.o


lib/THC/CMakeFiles/THC.dir/build.make:70: recipe for target 'lib/THC/CMakeFiles/THC.dir/THC_generated_THCBlas.cu.o' failed
make[2]: *** [lib/THC/CMakeFiles/THC.dir/THC_generated_THCBlas.cu.o] Error 1
CMake Error at THC_generated_THCTensor.cu.o.cmake:207 (message):
  Error generating
  /home/pete/distro/extra/cutorch/build/lib/THC/CMakeFiles/THC.dir//./THC_generated_THCTensor.cu.o


lib/THC/CMakeFiles/THC.dir/build.make:98: recipe for target 'lib/THC/CMakeFiles/THC.dir/THC_generated_THCTensor.cu.o' failed
make[2]: *** [lib/THC/CMakeFiles/THC.dir/THC_generated_THCTensor.cu.o] Error 1
CMake Error at THC_generated_THCTensorCopy.cu.o.cmake:207 (message):
  Error generating
  /home/pete/distro/extra/cutorch/build/lib/THC/CMakeFiles/THC.dir//./THC_generated_THCTensorCopy.cu.o


lib/THC/CMakeFiles/THC.dir/build.make:105: recipe for target 'lib/THC/CMakeFiles/THC.dir/THC_generated_THCTensorCopy.cu.o' failed
make[2]: *** [lib/THC/CMakeFiles/THC.dir/THC_generated_THCTensorCopy.cu.o] Error 1
CMake Error at THC_generated_THCStorageCopy.cu.o.cmake:207 (message):
  Error generating
  /home/pete/distro/extra/cutorch/build/lib/THC/CMakeFiles/THC.dir//./THC_generated_THCStorageCopy.cu.o


lib/THC/CMakeFiles/THC.dir/build.make:91: recipe for target 'lib/THC/CMakeFiles/THC.dir/THC_generated_THCStorageCopy.cu.o' failed
make[2]: *** [lib/THC/CMakeFiles/THC.dir/THC_generated_THCStorageCopy.cu.o] Error 1
CMake Error at THC_generated_THCReduceApplyUtils.cu.o.cmake:207 (message):
  Error generating
  /home/pete/distro/extra/cutorch/build/lib/THC/CMakeFiles/THC.dir//./THC_generated_THCReduceApplyUtils.cu.o


lib/THC/CMakeFiles/THC.dir/build.make:63: recipe for target 'lib/THC/CMakeFiles/THC.dir/THC_generated_THCReduceApplyUtils.cu.o' failed
make[2]: *** [lib/THC/CMakeFiles/THC.dir/THC_generated_THCReduceApplyUtils.cu.o] Error 1
CMake Error at THC_generated_THCHalf.cu.o.cmake:207 (message):
  Error generating
  /home/pete/distro/extra/cutorch/build/lib/THC/CMakeFiles/THC.dir//./THC_generated_THCHalf.cu.o


lib/THC/CMakeFiles/THC.dir/build.make:560: recipe for target 'lib/THC/CMakeFiles/THC.dir/THC_generated_THCHalf.cu.o' failed
make[2]: *** [lib/THC/CMakeFiles/THC.dir/THC_generated_THCHalf.cu.o] Error 1
CMake Error at THC_generated_THCStorage.cu.o.cmake:207 (message):
  Error generating
  /home/pete/distro/extra/cutorch/build/lib/THC/CMakeFiles/THC.dir//./THC_generated_THCStorage.cu.o


lib/THC/CMakeFiles/THC.dir/build.make:84: recipe for target 'lib/THC/CMakeFiles/THC.dir/THC_generated_THCStorage.cu.o' failed
make[2]: *** [lib/THC/CMakeFiles/THC.dir/THC_generated_THCStorage.cu.o] Error 1
CMakeFiles/Makefile2:172: recipe for target 'lib/THC/CMakeFiles/THC.dir/all' failed
make[1]: *** [lib/THC/CMakeFiles/THC.dir/all] Error 2
Makefile:129: recipe for target 'all' failed
make: *** [all] Error 2

Error: Build error: Failed building.

[nagadomi]

The supported gcc version depend on the CUDA version.
CUDA >= 10.1 supports gcc <= 8. See https://gist.github.com/ax3l/9489132
CUDA 9.2 in the Ubuntu official repository does not support gcc 7.4.0, but it is an Ubuntu issue.

[idanka]

• https://linuxconfig.org/how-to-install-cuda-on-ubuntu-20-04-focal-fossa-linux
• https://linuxconfig.org/how-to-switch-between-multiple-gcc-and-g-compiler-versions-on-ubuntu-20-04-lts-focal-fossa