taichi_core.so: undefined symbol: __cpu_model on Ubuntu 16.04

[janvorac]

Taichi won't import:

/home/janvorac/wheel/packages/taichi/taichi/python/taichi/core/load_core.py in <module>()
     29         sys.path.append(bin_dir)
     30         shutil.copy('libtaichi_core.so', 'taichi_core.so')
---> 31         import taichi_core as tc_core
     32 
     33         os.chdir(tmp_cwd)

ImportError: ./taichi_core.so: undefined symbol: __cpu_model

Installed using your wiki guide on XUbuntu 16.04.02. I am using Python 2.7.12 in virtual environment downloaded via mkvirtualenv (not compiled on my PC).
My gcc/g++ version is 5.4.0, cmake version is 3.5.1. Any help would be welcome!

[yuanming-hu]

This is really wired. I remember I also compiled Taichi on Ubuntu 16.04 with gcc5 and it worked, though I temporarily don't have access to that machine so I can't double check. Maybe a quick fix here is to compile with gcc 4, if you don't want to wait for my latency in fixing it. Sorry that I have several project deadlines...

If anyone would like to help on this, that greatly appreciated!

[janvorac]

Maybe a quick fix here is to compile with gcc 4

well, that was my first try with gcc 4 on XUbuntu 14. There, it wouldn't even compile with the -std=c++14 flag. I tried to change it everywhere to -std=c++1y which is understood by gcc4 and, I vaguely remember, that it compiled but couldn't import either. Not sure if the error was the same...

[yuanming-hu]

This was caused by an update of external/include/stb_image.h in commit yuanming-hu@259d620, since a bug of gcc5 was triggered:
https://bugs.launchpad.net/ubuntu/+source/gcc-5/+bug/1568899

See also,
baldurk/renderdoc#365
nothings/stb#280

[yuanming-hu]

As commented in those threads, upgrading to gcc-6 will probably fix it. Unfortunately I can not help much.

[yuanming-hu]

I think it's fixed. Please recompile with gcc-6. Sorry for the delay.

[yuanming-hu]

BTW I fixed it by updating stb_image, in the dev branch. I'll soon update the master branch.