npm addon unresolved external symbol

Question

I am trying to create my first npm addon, but I keep getting an unresolved external symbol.

> node-gyp configure build
> error LNK2001: unresolved external symbol DeliverMessage

The error is telling me that the header file is not being linked to the library file. I know the binding.gyp file finds the library file because it is not throwing a "cannot open input file". Everything seems correct and I am not really sure what to check next.

using: node v8.0.0

node-gyp v3.6.2

---

project structure:

 - example
  - myLibrary.h
  - myLibrary.lib
  - example.cc
  - binding.gyp

---

// myLibrary.h

#ifndef EXAMPLE_H
#define EXAMPLE_H

int Send(char *Address1, unsigned short SaveLoad, char *Address2);

---

// example.cc

#include "myLibrary.h"
#include <node.h>


using v8::Exception;
using v8::FunctionCallbackInfo;
using v8::Isolate;
using v8::Local;
using v8::Number;
using v8::Object;
using v8::String;
using v8::Value;


void SendMessage (const FunctionCallbackInfo<Value>& args) {

    char *a = "AAAAAA";
    char *c = "CCCCCC";

    int result = DeliverMessage(a, 0, c);


  args.GetReturnValue().Set(result);
}

void Init(Local<Object> exports) {
  NODE_SET_METHOD(exports, "sendMessage", SendMessage);
}

NODE_MODULE(addon, Init)

---

// binding.gyp

{
  "targets": [
    {
      "target_name": "exampleBuild",
      "link_settings": {
        "libraries": [
          "../myLibrary.lib",
        ]
      },
      "sources": [ "example.cc" ],
      "include_dirs": [
        "<!(node -e \"require('nan')\")",
      ]
    }
  ]
}

Answer 1

After a lot of time of troubleshooting and researching, I found that I had two problems:

(1) The .lib file is written in C. So I needed to encapsulate my header file like so:

// myLibrary.h

#ifndef EXAMPLE_H
#define EXAMPLE_H

extern "C" {
    int Send(char *Address1, unsigned short SaveLoad, char *Address2);
}

(2) The .lib was 32-bit and my version of node was 64-bit. I had to install 32-bit node.

When the addon was built, it created a bindings.sln file. This file was extremely helpful in figuring out the problem. I opened it in Visual Studio, which offered some warnings and errors.

Answer 2

So DeliverMessage is part of your library? As you noticed its a linker error, if the relative path is correct did you try it with an absolute path to your .lib? And why ../myLibrary, should be ./ if the .lib file is in the same directory as your bindings.gyp.