LLVM: "Export" class - class

Question

I'd like to call this code from my program using LLVM:
#include <string>
#include <iostream>
extern "C" void hello() {
std::cout << "hello" << std::endl;
}
class Hello {
public:
Hello() {
std::cout <<"Hello::Hello()" << std::endl;
};
int hello() {
std::cout<< "Hello::hello()" << std::endl;
return 99;
};
};
I compiled this code to llvm byte code using clang++ -emit-llvm -c -o hello.bc hello.cpp and then I want to call it from this program:
#include <llvm/ExecutionEngine/ExecutionEngine.h>
#include <llvm/ExecutionEngine/GenericValue.h>
#include <llvm/ExecutionEngine/JIT.h>
#include <llvm/LLVMContext.h>
#include <llvm/Module.h>
#include <llvm/Target/TargetSelect.h>
#include <llvm/Support/MemoryBuffer.h>
#include <llvm/Support/IRReader.h>
#include <string>
#include <iostream>
#include <vector>
using namespace std;
using namespace llvm;
void callFunction(string file, string function) {
InitializeNativeTarget();
LLVMContext context;
string error;
MemoryBuffer* buff = MemoryBuffer::getFile(file);
assert(buff);
Module* m = getLazyBitcodeModule(buff, context, &error);
ExecutionEngine* engine = ExecutionEngine::create(m);
Function* func = m->getFunction(function);
vector<GenericValue> args(0);
engine->runFunction(func, args);
func = m->getFunction("Hello::Hello");
engine->runFunction(func, args);
}
int main() {
callFunction("hello.bc", "hello");
}
(compiled using g++ -g main.cpp 'llvm-config --cppflags --ldflags --libs core jit native bitreader')
I can call the hello() function without any problems.
My question is: how can I create a new instance of the Hello class using LLVM?
I'm getting a segmentation fault when I call Hello::Hello()
Thanks for any hints!!
Manuel

Answer 1

Running clang++ -emit-llvm on the given source won't emit Hello::Hello, and m->getFunction("Hello::Hello") wouldn't find it even if it were emitted. I would guess it's crashing because func is null.
Trying to directly call functions which aren't extern "C" from the LLVM JIT is generally not recommended... I'd suggest writing a wrapper like the following, and compiling it with clang (or using the clang API, depending on what you're doing):
extern "C" Hello* Hello_construct() {
return new Hello;
}