[llvm-dev] Orc JIT vs. devtoolset-6

[Geoff Levner via llvm-dev]

[I am reposting this with a different title and other changes, because I am
fairly confident our problem is related to Red Hat's developer toolset.]

Greetings, LLVM wizards.

We have an application that uses Clang and Orc JIT (v1) to compile and
execute C++ code on the fly. If a C++ module calls functions from external
libraries, we add them via DynamicLibrary::LoadLibraryPermanently().

Recently we moved to gcc 6.3.1 to build our application, using Red Hat's
devtoolset-6 on CentOS, and this seems to create problems when a module
calls functions from the STL. If a module calls this swap() function for
input streams, for example:

    #include <fstream>
    std::ifstream stream1, stream2;
    stream1.swap(stream2);

When we run the constructors for the module, we get undefined STL symbols.
It turns out that the missing symbols are defined not in the runtime DSO
(in /usr/lib64) but in an archive file installed with the developer toolset:


/opt/rh/devtoolset-6/root/usr/lib/gcc/x86_64-redhat-linux/6.3.1/libstdc++.a

Apparently the linker performs some magic allowing an application compiled
and linked with gcc 6.3.1 to run on a system with an older version of the
STL (from gcc 4.8.5), augmenting the old DSO with stuff that is linked in
statically.

SO my question is: is there any way to reproduce that magical behavior in
an Orc JIT compiler, so that code can link properly with the STL?

Thanks,
Geoff
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