[GitHub] [incubator-mxnet] aws-taylor edited a comment 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 edited a comment 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.
   
   It is possible to force GCC to compile using the old, pre-C++11 namespace and functionality by compiling with ```-D_GLIBCXX_USE_CXX11_ABI=0```. It appears you can configure MxNet to build with ```ADD_CFLAGS=-D_GLIBCXX_USE_CXX11_ABI=0``` to add this to your build.


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