Building an ELF shared library with static libstdc++ dependency

Question

Currently I am trying to implement an ELF shared library, built with -static-libstdc++ and -static-libgcc options. This shared library MUST be built with C++11 and it has some legacy code, besides, it has a very specific design.

If some application links this shared library, their C++ utilities MUST NOT interfere with each other. For example, std::cout-related, and hence, std::ios_base::Init::Init() (_ZNSt8ios_base4InitC1Ev), are awaited to be present in two independent implementations, one static for this specific shared library, and another shared one for the application and it's other shared libraries. However, LD_DEBUG=all usage shows that there this specific shared library's C++ utility symbols, like std::ios_base::Init::Init(), get bound to the symbols, defined in libstdc++, which I try to avoid...

Can such logic be implemented or at least worked around somehow? In any case, I DO NEED separate C++ utility. Thanks in advance!

Answer 1

Currently I am trying to implement an ELF shared library, built with -static-libstdc++ and -static-libgcc options.

Your best bet is to not do that -- link your library "normally" (so it depends on libstdc++.so.6 and libgcc_s.so.1), and most of your problems would disappear. (See also http://xyproblem.info -- why do you want to link libstdc++ statically?)

However, LD_DEBUG=all usage shows that there this specific shared library's C++ utility symbols, like std::ios_base::Init::Init(), get bound to the symbols, defined in libstdc++

This statement is meaningless when you have two copies of libstdc++ -- one inside your library, and one "outside" (presumably libstdc++.so.6).

What you probably mean is that references to std::ios_base::Init::Init() from your library get bound to definitions inside libstdc++.so.6.

You can avoid this by making all symbols inside your library hidden, and only exposing the "official" interface from it, using linker script. See this answer.

Note:

• Controlling the ABI of a C++ shared library is much harder than for a pure-C one
• If you "hide" libstdc++ inside your shared library, and pass C++ objects through the interface (e.g. a std::string or std::map), you can expect all kinds of ~impossible to debug issues due to ABI incompatibility between the "hidden" libstdc++.a and the external libstdc++.so.6.