Symbols are not loading on dynamic linking of wfdb library using node-gyp on macOS High Sierra

Question

i am trying to create a dynamic library having dependency on WFDB library ( https://www.physionet.org/physiotools/wfdb.shtml ). My c++ code looks as:

#include <stdio.h>
#include <iostream>
#include <vector>
#include <vector>
extern "C" {
    #include <wfdb/wfdb.h>
}

#include "./sample_wfdb.h"

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

int read(){
    int i, nsig;
    WFDB_Siginfo* siarray;
    WFDB_Sample* v;
    nsig = isigopen("/data/100s", NULL, 0);
    if (nsig < 1)
        exit(1);
    siarray = (WFDB_Siginfo*)malloc(nsig * sizeof(WFDB_Siginfo));
    nsig = isigopen("data/100s", siarray, nsig);
    for (i = 0; i < nsig; i++)

        v = (WFDB_Sample*)malloc(nsig * sizeof(WFDB_Sample));

    if (v == NULL) {
        fprintf(stderr,"%s: insufficient memory\n");
        exit(2);
    }
    std::vector<int> signal1, signal2;
    for (int i = 0; i < siarray[0].nsamp; i++) {
        if (getvec(v) < 0)
            break;
        for (int j = 0; j < nsig; j++) {
            if (j == 0) {
                signal1.push_back(v[j]);
            }
            if (j == 1) {
                signal2.push_back(v[j]);
            }
        }
    }
    int sig_size = signal1.size();
    std::cout << sig_size << std::endl;
    return sig_size;
}

the header file for this goes as

#ifdef __linux__
  extern "C" int read();
  extern "C" int add(int x, int y);
#elif _WIN32
  extern "C" __declspec(dllexport) extern "C" int read();
  extern "C" __declspec(dllexport) int add(int x, int y);
#elif __APPLE__
  extern "C" int read();
  extern "C" int add(int x, int y);
#endif

The binding. gyp is

{
  "targets": [
    {
      "target_name": "wfdb-test",
      "type": "shared_library",
      "libraries": [ "/usr/local/lib/libwfdb.10.6.0.dylib"] ,
      "sources": [ "sample_wfdb.cpp -lwfdb" ],
      "cflags!": [ "-fno-exceptions" ],
      "cflags": [ "-std=c++11" ],
      "cflags_cc!": [ "-fno-exceptions" ]
    }
  ]
}

Upon running the project with node-gyp rebuild. I get the following output.

gyp info it worked if it ends with ok
gyp info using [email protected]
gyp info using [email protected] | darwin | x64
gyp info spawn /usr/local/bin/python2
gyp info spawn args [ '/usr/local/lib/node_modules/node-gyp/gyp/gyp_main.py',
gyp info spawn args   'binding.gyp',
gyp info spawn args   '-f',
gyp info spawn args   'make',
gyp info spawn args   '-I',gyp info spawn args   '/Users/abhinashkumarjha/Desktop/cpp-codes/build/config.gypi',
gyp info spawn args   '-I',gyp info spawn args   '/usr/local/lib/node_modules/node-gyp/addon.gypi',
gyp info spawn args   '-I',
gyp info spawn args   '/Users/abhinashkumarjha/.node-gyp/8.11.3/include/node/common.gypi',
gyp info spawn args   '-Dlibrary=shared_library',
gyp info spawn args   '-Dvisibility=default',
gyp info spawn args   '-Dnode_root_dir=/Users/abhinashkumarjha/.node-gyp/8.11.3',
gyp info spawn args   '-Dnode_gyp_dir=/usr/local/lib/node_modules/node-gyp',
gyp info spawn args   '-Dnode_lib_file=/Users/abhinashkumarjha/.node-gyp/8.11.3/<(target_arch)/nod
e.lib',
gyp info spawn args   '-Dmodule_root_dir=/Users/abhinashkumarjha/Desktop/cpp-codes',
gyp info spawn args   '-Dnode_engine=v8',
gyp info spawn args   '--depth=.',
gyp info spawn args   '--no-parallel',
gyp info spawn args   '--generator-output',
gyp info spawn args   'build',
gyp info spawn args   '-Goutput_dir=.' ]
gyp info spawn make
gyp info spawn args [ 'BUILDTYPE=Release', '-C', 'build' ]
  SOLINK(target) Release/wfdb-test.dylib
gyp info ok

And a dynamic library is generated under ./build/Release/wfdb-test.dylib

Upon looking for symbols inside the generated dylib file by:

nm -a build/Release/wfdb-test.dylib

i get

U dyld_stub_binder

which is the default cpp symbol( i am expecting more symbols here.). Can anyone please help me where i am going wrong.

The development environment details are:

os: mac OS High Sierra ( v10.13.6 )
node: v8.11.3
node-gyp: v3.8.0

Rectrix

Answer 1

Please forgive me if this seems silly, but where is the main() function? Is there another entry point to the code?

Is it possible to write a program without using main() function?

Also, with cflags! and cflags_cc! set to -fno-exceptions, is it possible that the compiling is going all the way through without throwing the proper exceptions?

https://blog.mozilla.org/nnethercote/2011/01/18/the-dangers-of-fno-exceptions/

Continually

Hi, I am trying to build a shared library. main is not required in it as an entry point to the whole program . Please go through sysleaf.com/nodejs-ffi as it has a simpler demonstration of what i am trying to achieve. – Rectrix

Answer 2

If you creating project via Cmake, you should check your CMakeLists.txt. Somewhere should be this line:

target_link_libraries(your_project_name wfdb)

Jabez