[llvm-dev] Orc JIT vs. STL

[Geoff Levner via llvm-dev]

On Tue, Aug 27, 2019 at 4:56 PM Praveen Velliengiri
<praveenvelliengiri at gmail.com> wrote:
>
> HI
> Did you run the static constructor and destructor? How did you make your process symbols visible to ORC jit?

Yes. It's the constructor that generates the undefined symbol error.
We use DynamicLibrary::LoadLibraryPermanently(nullptr) to add process
symbols.

> Could you please share us the for what symbols you get undefined references :-)

Certainly! Mangled:

    _ZNSi4swapERSi
    _ZNSt13basic_filebufIcSt11char_traitsIcEE4swapERS2_

And unmangled:

    std::basic_istream<char, std::char_traits<char>
>::swap(std::basic_istream<char, std::char_traits<char> >&)
    std::basic_filebuf<char, std::char_traits<char>
>::swap(std::basic_filebuf<char, std::char_traits<char> >&)

Incidentally, if I call that STL swap() function in the application,
to ensure it is in the process symbols, the second symbol is found,
but the first is still undefined.


>
> On Aug 27, 2019 8:18 PM, "Geoff Levner via llvm-dev" <llvm-dev at lists.llvm.org> wrote:
>>
>> Greetings, LLVM wizards.
>>
>> We are using 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().
>>
>> The problem we have run into recently is when a module calls a function from the STL -- in particular this swap() function for input streams:
>>
>> #include <fstream>
>> std::ifstream stream1, stream2;
>> stream1.swap(stream2);
>>
>> When we run the constructors for the module, we get two undefined symbols. And explicitly adding libstdc++ doesn't help. It turns out that the missing symbols are defined not in the runtime DSO but in an archive file:
>>
>> /opt/rh/devtoolset-6/root/usr/lib/gcc/x86_64-redhat-linux/6.3.1/libstdc++.a
>>
>> So my questions are:
>>
>> 1. Is there a simple way to get access to all symbols defined in the STL? Intuitively, it seems like we should not need to know about such compiler magic.
>>
>> 2. If there is no magical solution, is there a way to explicitly add symbols from an archive?
>>
>> Thanks,
>> Geoff
>>
>>
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