Expose c-library functionality to node

Question

I have been working on using a c library in my node project. After little bit investigation I found node-gyp.

I was successfully able to execute example but when I am trying to using third party c library functions in the code it was giving me linking error on run time.

Library can be found here http://bibutils.refbase.org/bibutils_3.40_src.tgz

I compiled the library independently to have *.a objects

I am using following example https://github.com/nodejs/node-addon-examples/tree/master/5_function_factory/node_0.12

So I have following questions as I can infer

• Shall I convert bibutils from make to gyp?
• Shall I convert each source file to work with V8? I don't know how to do this.
• How can I easily link this project to work with node-gyp with less noise?

Details related to script can be found below. bibutils folder is placed along with addon.cc

binding.gyp looks like

{
  "targets": [
    {
      "target_name": "addon",
      "sources": [ "addon.cc" ],
      "include_dirs": ["bibutils/lib"],
      "library_dirs": ["bibutils/lib/libbibutil.a","bibutils/lib/libbibprogs.a"]
    }
  ]
}

modified addon.cc

#include <node.h>
#include "bibutils.h"
#include "bibprogs.h"

using namespace v8;

void MyFunction(const FunctionCallbackInfo<Value>& args) {
  Isolate* isolate = Isolate::GetCurrent();
  HandleScope scope(isolate);
      /****This is not production code just to check the execution***/
      bibl b;   
      bibl_init( &b );
      bibl_free( &b );
      /**************************************************************/
  args.GetReturnValue().Set(String::NewFromUtf8(isolate, "hello world"));
}

void CreateFunction(const FunctionCallbackInfo<Value>& args) {
  Isolate* isolate = Isolate::GetCurrent();
  HandleScope scope(isolate);

  Local<FunctionTemplate> tpl = FunctionTemplate::New(isolate, MyFunction);
  Local<Function> fn = tpl->GetFunction();

  // omit this to make it anonymous
  fn->SetName(String::NewFromUtf8(isolate, "theFunction"));

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

Compilation Result

user1@ubuntu:~/node-addon-examples/5_function_factory/node_0.12$ npm install

> function_factory@0.0.0 install /home/user1/node-addon-examples/5_function_factory/node_0.12
> node-gyp rebuild

make: Entering directory `/home/user1/node-addon-examples/5_function_factory/node_0.12/build'
  CXX(target) Release/obj.target/addon/addon.o
  SOLINK_MODULE(target) Release/obj.target/addon.node
  COPY Release/addon.node
make: Leaving directory `/home/user1/node-addon-examples/5_function_factory/node_0.12/build'

On Execution

user1@ubuntu:~/node-addon-examples/5_function_factory/node_0.12$ node addon.js
node: symbol lookup error: /home/user1/node-addon-examples/5_function_factory/node_0.12/build/Release/addon.node: undefined symbol: _Z9bibl_initP4bibl

Debug Info:

user1@ubuntu:~/node-addon-examples/5_function_factory/node_0.12$ nm -C build/Release/addon.node | grep bibl_init
                 U bibl_init(bibl*)

Answer 1

The problem was communication between C++ and C. In above case a C header file was included in C++ code. Compile was expecting the C++ code. So on compiling linker was got choked due to mismatch in compiled code.

So I used the extern "C" directive to tell the compiler about C header files by following code.

extern "C" {
    #include "bibutils.h"
    #include "bibprogs.h"
}