`LLJIT::addObjectFile` cannot work.

[lanistor]

When i try to run linked c++ function, error occured:

JIT session error: Unsupported file format
Failed to materialize symbols: { (0x7fdfb440b810, { _add, __mh_execute_header, _main }) }

Here are my code:
main.cpp

  InitLLVM X(argc, argv);
  InitializeNativeTarget();
  InitializeNativeTargetAsmPrinter();
  ThreadSafeContext context(std::make_unique<LLVMContext>());

  ExitOnError ExitOnErr;

  jitlink::InProcessMemoryManager MemMgr;

  auto JTMB = ExitOnErr(JITTargetMachineBuilder::detectHost());
  JTMB.setCodeModel(CodeModel::Small);

  auto jit =
      ExitOnErr(LLJITBuilder()
                    .setJITTargetMachineBuilder(std::move(JTMB))
                    .setObjectLinkingLayerCreator([&](ExecutionSession &ES, const Triple &TT) {
                      return std::make_unique<ObjectLinkingLayer>(ES, MemMgr);
                    })
                    .create());
  auto ffi = ExitOnErr(errorOrToExpected(MemoryBuffer::getFileAsStream("build/ffi")));
  jit->addObjectFile(std::move(ffi));

  char func_name[] = "add";
  // char file_path[] = "link.ll";
  auto add              = ExitOnErr(jit->lookup(func_name));
  int (*func)(int, int) = (int (*)(int, int))add.getAddress();
  int result            = func(111, 222);

ffi.cpp

extern "C" int add(int a, int b) {
  return a + b;
}

int main() {
  return 0;
}

(build/ffi is output object file of ffi.cpp)
When i run jit->lookup("add"), error occoured.

[lhames]

"build/ffi is output object file of ffi.cpp"

You will need to provide more information: What platform are you building on, and how are you building ffi from ffi.cpp?

[lanistor]

@lhames Thanks for reply.
My platform is MacOSX 10.14, and ffi file is build by clang++, used: clang++ ffi.cpp -o build/ffi.
Then Using nm -A build/ffi showing:

build/ffi: 0000000100000000 T __mh_execute_header
build/ffi: 0000000100000f70 T _add
build/ffi: 0000000100000f90 T _main
build/ffi:                  U dyld_stub_binder

[lhames]

clang++ ffi.cpp -o build/ffi

That command will produce an executable, not a relocatable object. That is the cause of the "unsupported file format" error. You want:

clang++ ffi.cpp -c -o build/ffi.o

You should also use MemoryBuffer::getFile rather than MemoryBuffer::getFileAsStream: The getFile method will use mmap under the hood for efficiency.

[lanistor]

@lhames Thanks, it works.
Bug what if ffi.cpp is using some libraries, such as

#include <iostream>

extern "C" int add(int a, int b) {
  std::cout << "add function run" << std::endl;
  return a + b;
}
int main() {
  return add(1, 2);
}

I had tested it, failed.

[lhames]

vifird: This sounds like a separate bug -- you should probably open a new issue for this. You will also need to provide more information: How does it fail? What is the output? What steps did you take to debug the failure?

[lanistor]

@lhames The reason should be(i guess): iostream isn't linked with ffi.o, so std::cout cannot be found, because we didn't link them(using -c).
The error is:

JIT session error: Symbols not found: { ___cxa_begin_catch, __ZNSt3__113basic_ostreamIcNS_11char_traitsIcEEE5flushEv, __Unwind_Resume, ___cxa_end_catch, __ZNSt3__113basic_ostreamIcNS_11char_traitsIcEEE6sentryD1Ev, __ZNSt3__18ios_base5clearEj, __ZNSt3__15ctypeIcE2idE, __ZNKSt3__16locale9use_facetERNS0_2idE, __ZSt9terminatev, __ZNSt3__112basic_stringIcNS_11char_traitsIcEENS_9allocatorIcEEED1Ev, __ZNSt3__14coutE, _memset, __ZNSt3__16localeD1Ev, _strlen, __ZNSt3__112basic_stringIcNS_11char_traitsIcEENS_9allocatorIcEEE6__initEmc, ___gxx_personality_v0, __ZNSt3__113basic_ostreamIcNS_11char_traitsIcEEE6sentryC1ERS3_, __ZNSt3__18ios_base33__set_badbit_and_consider_rethrowEv, ___cxa_call_unexpected, __ZNKSt3__18ios_base6getlocEv, __ZNSt3__113basic_ostreamIcNS_11char_traitsIcEEE3putEc }
Failed to materialize symbols: { (0x7fdb6440b810, { __ZNSt3__1lsINS_11char_traitsIcEEEERNS_13basic_ostreamIcT_EES6_PKc, __ZNSt3__124__put_character_sequenceIcNS_11char_traitsIcEEEERNS_13basic_ostreamIT_T0_EES7_PKS4_m, _link, __ZNSt3__116__pad_and_outputIcNS_11char_traitsIcEEEENS_19ostreambuf_iteratorIT_T0_EES6_PKS4_S8_S8_RNS_8ios_baseES4_, ___clang_call_terminate, _add, __ZNSt3__111char_traitsIcE3eofEv, __ZNSt3__111char_traitsIcE11eq_int_typeEii, _main, __ZNSt3__111char_traitsIcE6lengthEPKc }) }

[lhames]

Yep -- this is a distinct problem. Please file a separate issue for this.

[lanistor]

OK, thanks