[LLVMdev] jit with external functions

[Chris Lattner]

On Sat, 9 Dec 2006, Ram Bhamidipaty wrote:
> Will it also handle symbols that are in shared libraries loaded into
> the process?

I'm not sure, but I thought so.

> I am creating a python module that has the llvm functionality. This
> module is loaded
> into the process as a shared library. I want to generate llvm assembler that has
> calls to functions in this shared library.
>
> I just tried an experiment and I got this back:
>
> ERROR: Program used external function 'rtcg_callback' which could not
> be resolved!
> Aborted

Guess not :).  Are you sure that rtcg_callback isn't marked static and 
isn't hidden by an export map?

> It looks like the additional shared libraries might not be searched. I 
> plan on looking at the code to see if I can modify it to handle my case. 
> Any suggestions on how or where I should make the change?

see llvm/lib/ExecutionEngine/JIT/Intercept.cpp: 
JIT::getPointerToNamedFunction.  It ends up calling:

   // If it's an external function, look it up in the process image...
   void *Ptr = sys::DynamicLibrary::SearchForAddressOfSymbol(NameStr);
   if (Ptr) return Ptr;

It also prepends a _ to the symbol name and tries that.  Alternatively, 
you can use the ExecutionEngine::addGlobalMapping to say that specific 
functions/globals are at specific addresses.

-Chris

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