c++ - _GLIBCXX_USE_CXX11_ABI, GCC 4.8 and ABI compatibility

Question

We received some libraries (.a) compiled for linux (probably compiled with GCC 6.x).

We are using GCC 4.8 and we are getting the error of the type: undefined reference to std::__cxx11::basic_string when trying to link.

Normally this could be fixed by making sure all units have been compiled with the same _GLIBCXX_USE_CXX11_ABI flag. However if I understood correctly, this was introduced by GCC 5.1 and on.

1. Is there a way to make this work with GCC 4.8 or do we need to ask the people to recompile the libraries with a different _GLIBCXX_USE_CXX11_ABI?
2. I guess if we are able to switch to GCC >= 5.1 we can make this work?

Thanks!

Answer 1

It's possible to use the C++11 ABI with gcc 4.8.2, but it's a dangerous hack; you would be far better off if at all possible to ask your vendors to ship libraries compiled with the C++03 ABI (-D_GLIBCXX_USE_CXX11_ABI=0) or to upgrade to GCC 5 or above.

You would need to download and install gcc 5 so that you can use its libstdc++ headers and libraries, then direct gcc 4.8 to use those in preference to its own. In addition, because gcc 4.8 is missing some intrinsics required by the libstdc++ shipped with gcc 5, you would need to hack out their usage.

For example, to compile a simple single-file application that includes <string>:

/usr/local/gcc-4.8.2/bin/g++ 
   -std=c++11 
   -D_GLIBCXX_USE_CXX11_ABI=1 
   -D'__is_trivially_copyable(...)=0' 
   -D'__is_trivially_constructible(...)=0' 
   -D'__is_trivially_assignable(...)=0' 
   -nostdinc++ 
   -isystem /usr/local/gcc-5.4.0/include/c++/5.4.0/ 
   -isystem /usr/local/gcc-5.4.0/include/c++/5.4.0/x86_64-unknown-linux-gnu 
   -L /usr/local/gcc-5.4.0/lib64
   a.cpp

This is dangerous because the gcc 5.4 libstdc++ is not designed to work with gcc 4.8, and redefining the intrinsics used (__is_trivially_copyable etc.) could change the layout of structures or otherwise cause binary incompatibility between your programs and the vendor's libraries.

In order to run the resulting executable, you would also need to ensure that the dynamic linker finds a compatible libstdc++, for example by adding /usr/local/gcc-5.4.0/lib64 to /etc/ld.so.conf, or using -Wl,-rpath /usr/local/gcc-5.4.0/lib64.