[LLVMdev] using external functions from llvm

Alec Benzer alecbenzer at gmail.com
Thu Aug 19 17:24:03 PDT 2010

Ok, so calling lle_X_FUNCTIONNAME instead of FUNCTIONNAME works (is there
any reason the post used the lle_X_ prefix other than convention? was it
once possible to call external functions as I was originally trying, or, why
did the blog post think it was possible?)

I'm now running into trouble when trying to access arguments however.
printing args.size() from the function yields 12105250188025543488. The
generated call to it looks like:

%object_tmp = call %object_structure* @lle_X_create_number_object(double
5.000000e+00) ; <%object_structure*> [#uses=1]

On Thu, Aug 19, 2010 at 6:56 PM, Alec Benzer <alecbenzer at gmail.com> wrote:

> The blog post I linked to implied that adding a symbol in the form
> lle_X_FUNCTIONNAME would allow you to call a function called FUNCTIONNAME.
> Is this not the case?
> On Thu, Aug 19, 2010 at 6:46 PM, <o.j.sivart at gmail.com> wrote:
>> You are adding the symbol as "lle_X_create_number_object" yet your error
>> message implies you have tried to lookup and use "create_number_object". Can
>> you provide the code for the lookup?
>> On 20/08/2010, at 8:07 AM, Alec Benzer wrote:
>> Is there documentation somewhere on how to call external functions from
>> llvm? The only guide I found was this:
>> http://www.gearleaf.com/blog/post/44, and it doesn't seem to be working
>> for me.
>> I have a function:
>> llvm::GenericValue lle_X_create_number_object(llvm::FunctionType* ft,
>> const std::vector<llvm::GenericValue>& args)
>> {
>>   llvm_object_structure* result = new llvm_object_structure;
>>   result->typeIdx = TypeSystem::number;
>>   result->data = reinterpret_cast<unsigned char*>(new
>> double(args[0].DoubleVal));
>>   llvm::GenericValue gv;
>>   gv.PointerVal = reinterpret_cast<void*>(result);
>>   return gv;
>> }
>> defined in an extern "C" block. I add it as a symbol with:
>> llvm::sys::DynamicLibrary::AddSymbol("lle_X_create_number_object",(void*)lle_X_create_number_object);
>> yet when attempting to call it I still get: "LLVM ERROR: Program used
>> external function 'create_number_object' which could not be resolved!"
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