Error when Linking CXX executable caffe

[Jiaxu Zhu]

I met some errors when compiling caffe

CMakeFiles/caffe.bin.dir/caffe.cpp.o: In function `std::string* google::MakeCheckOpString<cudaError, cudaError>(cudaError const&, cudaError const&, char const*)':

caffe.cpp:(.text._ZN6google17MakeCheckOpStringI9cudaErrorS1_EEPSsRKT_RKT0_PKc[_ZN6google17MakeCheckOpStringI9cudaErrorS1_EEPSsRKT_RKT0_PKc]+0x50): undefined reference to `google::base::CheckOpMessageBuilder::NewString()'

CMakeFiles/caffe.bin.dir/caffe.cpp.o: In function `std::string* google::MakeCheckOpString<unsigned long, int>(unsigned long const&, int const&, char const*)':

caffe.cpp:(.text._ZN6google17MakeCheckOpStringImiEEPSsRKT_RKT0_PKc[_ZN6google17MakeCheckOpStringImiEEPSsRKT_RKT0_PKc]+0x50): undefined reference to `google::base::CheckOpMessageBuilder::NewString()'

CMakeFiles/caffe.bin.dir/caffe.cpp.o: In function `main':

caffe.cpp:(.text.startup+0x50): undefined reference to `google::SetUsageMessage(std::string const&)'

../lib/libcaffe.so: undefined reference to `leveldb::DB::Open(leveldb::Options const&, std::string const&, leveldb::DB**)'

../lib/libcaffe.so: undefined reference to `leveldb::Status::ToString() const'

collect2: error: ld returned 1 exit status

tools/CMakeFiles/caffe.bin.dir/build.make:120: recipe for target 'tools/caffe' failed

make[2]: *** [tools/caffe] Error 1

CMakeFiles/Makefile2:406: recipe for target 'tools/CMakeFiles/caffe.bin.dir/all' failed

make[1]: *** [tools/CMakeFiles/caffe.bin.dir/all] Error 2

Makefile:116: recipe for target 'all' failed

make: *** [all] Error 2

This error is kind of rare and I cannot solve it bymyself

I have all dependencies installed and the platform is Ubuntu 15.10 (since my pc motherboard is Z170) 

Thanks!

[Piotr Koncewicz]

Well I had the same trouble :) The solution is:
change your gcc and c++ to 4.9

sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-5 10
sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-4.9 20

sudo update-alternatives --install /usr/bin/g++ g++ /usr/bin/g++-5 10
sudo update-alternatives --install /usr/bin/g++ g++ /usr/bin/g++-4.9 20

sudo update-alternatives --install /usr/bin/cc cc /usr/bin/gcc 30
sudo update-alternatives --set cc /usr/bin/gcc

sudo update-alternatives --install /usr/bin/c++ c++ /usr/bin/g++ 30
sudo update-alternatives --set c++ /usr/bin/g++

sudo update-alternatives --config gcc
sudo update-alternatives --config g++

download other leveldb version, like this https://github.com/chirino/leveldb (if you compile it before changing gcc, the problem will still appear, but shorter, without leveldb errors)
clean and recompile protobuf, glog, leveldb and gflags
Goodluck!