[GitHub] [incubator-mxnet] aws-taylor commented on issue #17589: OSError: /tmp/makepkg/sl1-mxnet-git/src/build/libmxnet.so.1.5.1: undefined symbol: _ZN4dmlc14RecordIOReader10NextRecordEPSs

[GitBox <gi...@apache.org>]

aws-taylor commented on issue #17589:
URL: https://github.com/apache/incubator-mxnet/issues/17589#issuecomment-680287164


   ```_ZN4dmlc14RecordIOReader10NextRecordEPSs``` corresponds to  ```dmlc::RecordIOReader::NextRecord(std::basic_string<char, std::char_traits<char>, std::allocator<char> >*)```
   
   I ran into this problem because I was compiling MxNet with GCC 8 but linking to a 4.9 libstdc++. Somewhere between 4.9 and 8, there was an ABI change to std::string in order to comply with C++11 requirements that resulted in std::string being moved into the **std::__cxx11** namespace. You can see this below (T ~= 'defined', 'U' ~= missing):
   
   ```
   >> nm -C libmxnet.so | grep 'dmlc::RecordIOReader::NextRecord'
   
   000000000471cc60 T dmlc::RecordIOReader::NextRecord(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >*)
   0000000000cd897c t dmlc::RecordIOReader::NextRecord(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >*) [clone .cold.54]
                    U dmlc::RecordIOReader::NextRecord(std::string*)
   ```
   
   If you look in libmxnet.so, you'll find tons of similarly missing symbols. For whatever reason, NextRecord(...) just happens to be the first in the compilation.
   
   Normally it is possible to force GCC to compile using the old, pre-C++11 namespace by compiling with ```-D_GLIBCXX_USE_CXX11_ABI=0```, however there appears to have been a bug in MxNet that didn't forward CXX_FLAGS to the build correctly. I haven't tracked down precisely which commit fixed the problem, but if you run into this issue, try using a newer commit or make sure that your GCC and libstdc++ versions are compatible.


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